Sample records for stm

  1. SSE software test management STM capability: Using STM in the Ground Systems Development Environment (GSDE)

    NASA Technical Reports Server (NTRS)

    Church, Victor E.; Long, D.; Hartenstein, Ray; Perez-Davila, Alfredo

    1992-01-01

    This report is one of a series discussing configuration management (CM) topics for Space Station ground systems software development. It provides a description of the Software Support Environment (SSE)-developed Software Test Management (STM) capability, and discusses the possible use of this capability for management of developed software during testing performed on target platforms. This is intended to supplement the formal documentation of STM provided by the SEE Project. How STM can be used to integrate contractor CM and formal CM for software before delivery to operations is described. STM provides a level of control that is flexible enough to support integration and debugging, but sufficiently rigorous to insure the integrity of the testing process.

  2. LT-STM/STS studies of clean armchair edge

    NASA Astrophysics Data System (ADS)

    Ju, Zheng; Zhang, Wenhan; Wu, Weida; Weida Wu Team

    It was predicted and observed that the passivated zigzag edges of graphene host highly localized edge state. This edge state is predicted to be spin-polarized, which is appealing for spintronic applications. In contrast, no edge state was expected at passivated armchair graphene edge. Here we report low temperature scanning tunneling microscopy and spectroscopy (STM/STS) studies of electronic properties of clean monoatomic step edges on cleaved surface of HOPG. Most of step edges are armchair edges, in agreement with previous STM results. We observed only (√{ 3} ×√{ 3}) R30° superstructure near armchair edges, which has been reported in previous STM studies. On the other hand, no honeycomb superstructure was observed in our STM data. In addition, our STM results reveal an intriguing localized electronic state at clean armchair edges. Spectroscopic and spatial evolution of this edge state will be presented. This work is supported by NSF DMR-1506618.

  3. Restructuring STM (Science, Technology, and Mathematics) Education for Entrepreneurship

    ERIC Educational Resources Information Center

    Ezeudu, F. O.; Ofoegbu, T. O.; Anyaegbunnam, N. J.

    2013-01-01

    This paper discussed the need to restructure STM (science, technology, and mathematics) education to reflect entrepreneurship. This is because the present STM education has not achieved its aim of making graduates self-reliant. Entrepreneurship education if introduced in the STM education will produce graduate who can effectively manage their…

  4. Fingerprints of single nuclear spin energy levels using STM - ENDOR

    NASA Astrophysics Data System (ADS)

    Manassen, Yishay; Averbukh, Michael; Jbara, Moamen; Siebenhofer, Bernhard; Shnirman, Alexander; Horovitz, Baruch

    2018-04-01

    We performed STM-ENDOR experiments where the intensity of one of the hyperfine components detected in ESR-STM is recorded while an rf power is irradiated into the tunneling junction and its frequency is swept. When the latter frequency is near a nuclear transition a dip in ESR-STM signal is observed. This experiment was performed in three different systems: near surface SiC vacancies where the electron spin is coupled to a next nearest neighbor 29Si nucleus; Cu deposited on Si(111)7x7 surface, where the unpaired electron of the Cu atom is coupled to the Cu nucleus (63Cu, 65Cu) and on Tempo molecules adsorbed on Au(111), where the unpaired electron is coupled to a Nitrogen nucleus (14N). While some of the hyperfine values are unresolved in the ESR-STM data due to linewidth we find that they are accurately determined in the STM-ENDOR data including those from remote nuclei, which are not detected in the ESR-STM spectrum. Furthermore, STM-ENDOR can measure single nuclear Zeeman frequencies, distinguish between isotopes through their different nuclear magnetic moments and detect quadrupole spectra. We also develop and solve a Bloch type equation for the coupled electron-nuclear system that facilitates interpretation of the data. The improved spectral resolution of STM - ENDOR opens many possibilities for nanometric scale chemical analysis.

  5. The Sounds of Nanoscience: Acoustic STM Analogues

    ERIC Educational Resources Information Center

    Euler, Manfred

    2013-01-01

    A hands-on model of scanning tunnelling microscopy (STM) is presented. It uses near-field imaging with sound and computer assisted visualization to create acoustic mappings of resonator arrangements. Due to the (partial) analogy of matter and sound waves the images closely resemble STM scans of atoms. Moreover, the method can be extended to build…

  6. Fingerprints of single nuclear spin energy levels using STM - ENDOR.

    PubMed

    Manassen, Yishay; Averbukh, Michael; Jbara, Moamen; Siebenhofer, Bernhard; Shnirman, Alexander; Horovitz, Baruch

    2018-04-01

    We performed STM-ENDOR experiments where the intensity of one of the hyperfine components detected in ESR-STM is recorded while an rf power is irradiated into the tunneling junction and its frequency is swept. When the latter frequency is near a nuclear transition a dip in ESR-STM signal is observed. This experiment was performed in three different systems: near surface SiC vacancies where the electron spin is coupled to a next nearest neighbor 29 Si nucleus; Cu deposited on Si(111)7x7 surface, where the unpaired electron of the Cu atom is coupled to the Cu nucleus ( 63 Cu, 65 Cu) and on Tempo molecules adsorbed on Au(111), where the unpaired electron is coupled to a Nitrogen nucleus ( 14 N). While some of the hyperfine values are unresolved in the ESR-STM data due to linewidth we find that they are accurately determined in the STM-ENDOR data including those from remote nuclei, which are not detected in the ESR-STM spectrum. Furthermore, STM-ENDOR can measure single nuclear Zeeman frequencies, distinguish between isotopes through their different nuclear magnetic moments and detect quadrupole spectra. We also develop and solve a Bloch type equation for the coupled electron-nuclear system that facilitates interpretation of the data. The improved spectral resolution of STM - ENDOR opens many possibilities for nanometric scale chemical analysis. Copyright © 2018 Elsevier Inc. All rights reserved.

  7. Type-specific proactive interference in patients with semantic and phonological STM deficits.

    PubMed

    Harris, Lara; Olson, Andrew; Humphreys, Glyn

    2014-01-01

    Prior neuropsychological evidence suggests that semantic and phonological components of short-term memory (STM) are functionally and neurologically distinct. The current paper examines proactive interference (PI) from semantic and phonological information in two STM-impaired patients, DS (semantic STM deficit) and AK (phonological STM deficit). In Experiment 1 probe recognition tasks with open and closed sets of stimuli were used. Phonological PI was assessed using nonword items, and semantic and phonological PI was assessed using words. In Experiment 2 phonological and semantic PI was elicited by an item recognition probe test with stimuli that bore phonological and semantic relations to the probes. The data suggested heightened phonological PI for the semantic STM patient, and exaggerated effects of semantic PI in the phonological STM case. The findings are consistent with an account of extremely rapid decay of activated type-specific representations in cases of severely impaired phonological and semantic STM.

  8. Strong correlation effects in theoretical STM studies of magnetic adatoms

    NASA Astrophysics Data System (ADS)

    Dang, Hung T.; dos Santos Dias, Manuel; Liebsch, Ansgar; Lounis, Samir

    2016-03-01

    We present a theoretical study for the scanning tunneling microscopy (STM) spectra of surface-supported magnetic nanostructures, incorporating strong correlation effects. As concrete examples, we study Co and Mn adatoms on the Cu(111) surface, which are expected to represent the opposite limits of Kondo physics and local moment behavior, using a combination of density functional theory and both quantum Monte Carlo and exact diagonalization impurity solvers. We examine in detail the effects of temperature T , correlation strength U , and impurity d electron occupancy Nd on the local density of states. We also study the effective coherence energy scale, i.e., the Kondo temperature TK, which can be extracted from the STM spectra. Theoretical STM spectra are computed as a function of STM tip position relative to each adatom. Because of the multiorbital nature of the adatoms, the STM spectra are shown to consist of a complicated superposition of orbital contributions, with different orbital symmetries, self-energies, and Kondo temperatures. For a Mn adatom, which is close to half-filling, the STM spectra are featureless near the Fermi level. On the other hand, the quasiparticle peak for a Co adatom gives rise to strongly position-dependent Fano line shapes.

  9. University of Maryland MRSEC - Facilities: SEM/STM/AFM

    Science.gov Websites

    MRSEC Templates Opportunities Search Home » Facilities » SEM/STM/AFM Shared Experimental Facilities conducting and non conducting samples. The sample stage permits electronic device imaging under operational Specifications: Image Modes - STM, STS, MFM, EFM, SKPM, contact- and non-contact AFM Three Sample Contacts 0.1 nm

  10. Chemical contrast in STM imaging of transition metal aluminides

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

    Duguet, T.; Thiel, Patricia A.

    2012-08-01

    The present manuscript reviews recent scanning tunnelling microscopy (STM) studies of transition metal (TM) aluminide surfaces. It provides a general perspective on the contrast between Al atoms and TM atoms in STM imaging. A general trend is the much stronger bias dependence of TM atoms, or TM-rich regions of the surface. This dependence can be attenuated by the local chemical arrangements and environments. Al atoms can show a stronger bias dependence when their chemical environment, such as their immediate subsurface, is populated with TM. All this is well explained in light of combined results of STM and both theoretical andmore » experimental electronic and crystallographic structure determinations. Since STM probes the Fermi surface, the electronic structure in the vicinity of the Fermi level (EF) is essential for understanding contrast and bias dependence. Hence, partial density of states provides information about the TM d band position and width, s–p–d hybridization or interactions, or charge transfer between constituent elements. In addition, recent developments in STM image simulations are very interesting for elucidating chemical contrast at Al–TM alloy surfaces, and allow direct atomic identification, when the surface does not show too much disorder. Overall, we show that chemically-specific imaging is often possible at these surfaces.« less

  11. Near-Field Imaging with Sound: An Acoustic STM Model

    ERIC Educational Resources Information Center

    Euler, Manfred

    2012-01-01

    The invention of scanning tunneling microscopy (STM) 30 years ago opened up a visual window to the nano-world and sparked off a bunch of new methods for investigating and controlling matter and its transformations at the atomic and molecular level. However, an adequate theoretical understanding of the method is demanding; STM images can be…

  12. Laser-assisted electron tunneling in a STM junction

    NASA Astrophysics Data System (ADS)

    Chang, Shunhua Thomas

    2000-10-01

    Since its introduction in 1981, the Nobel prize-winning scanning tunneling microscope (STM) has been developed into a powerful yet conceptually simple instrument, replacing traditional scanning and transmission electron microscopes (SEM/TEM) in many of the microscopic surface phenomenon studies. The strength of the STM stems from the sensitive tunneling current-potential barrier width relationship of the electron tunneling process, and has been used to re-examine the frequency-mixing and harmonic generation properties of an non-linear metal- oxide-metal (MOM) tunneling junction. In this research, electron-tunneling events under polarized laser radiation at 514.5-nm argon and 10.6-μm carbon dioxide laser wavelengths were investigated. The objective is to understand the underlying interactive mechanisms between the tunneling junction and the external laser excitation. A commercial scanning tunneling microscope head and controller were incorporated into the experimental setup. Operation characteristics and the electrical properties of the STM junction were determined. Tunneling current and distance responses with respect to different laser polarization, modulation frequency, incident power, and tunneling distance were also conducted. From the experimental results it is shown that thermal expansion effect was the dominant source of response for laser modulation frequency up to about 100 kHz, in quantitative agreement with theoretical calculations. Different laser polarizations as the experiments demonstrated did not contribute significantly to the STM response in the investigated frequency range. The electric field induced by the laser beam was calculated to be one to two order of magnitudes lower than the field required to initiate field emission where the tunneling junction I- V curve is most non-linear. Also, the electrical coupling of the incident laser at the STM junction was determined to be non-critical at visible laser wavelength, and the reflected laser

  13. Spectroscopic properties and STM images of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Rubio, A.

    We present a theoretical study of the role of the local environment in the electronic properties of carbon nanotubes: isolated single- and multi-wall nanotubes, nanotube ropes, tubes supported on gold and cut to finite length. Interaction with the substrate or with other tubes does not alter the scanning tunneling microscopy patterns (STM) observed for isolated tubes. A finite-length nanotube shows standing-wave patterns that can be completely characterized by a set of four different three-dimensional shapes. These patterns are understood in terms of a simple π-electron tight-binding (TB) model. STM-topographic images of topological defects ani (pentagon/heptagon pair) and tube caps have also been studied. In both cases the image obtained depends on the sign of the applied voltage and can be described in terms of the previous catalog of STM images (interference between electronic waves scattered by the defect). We have also computed the electronic density of states for isolated tubes with different chiralities and radii, confirming a correlation between the peak structure in the DOS and nanotube diameter. However, the metallic plateau in the DOS also depends on the nanotube chirality. Furthermore the conduction an valence band structures are not fully symmetrical to one another. This anisotropy shows up in the DOS and indicates the limitations of the π-TB model in describing spectroscopic data. In contrast to STM images, here the interaction with the substrate does modify the energy levels of the nanotube. We observe opening of small pseudogaps around the Fermi level and broadening of the sharp van Hove singularities of the isolated single-walled nanotubes that can be used to extract useful information about the tube structure and bonding. The combination of STM and spectroscopic studies provides a new way to address the electronic and structural properties of carbon and composite nanotubes.

  14. Mergers, Acquisitions, and Access: STM Publishing Today

    NASA Astrophysics Data System (ADS)

    Robertson, Kathleen

    Electronic publishing is changing the fundamentals of the entire printing/delivery/archive system that has served as the distribution mechanism for scientific research over the last century and a half. The merger-mania of the last 20 years, preprint pools, and publishers' licensing and journals-bundling plans are among the phenomena impacting the scientific information field. Science-Technology-Medical (STM) publishing is experiencing a period of intense consolidation and reorganization. This paper gives an overview of the economic factors fueling these trends, the major STM publishers, and the government regulatory bodies that referee this industry in Europe, Canada, and the USA.

  15. Haptic-STM: a human-in-the-loop interface to a scanning tunneling microscope.

    PubMed

    Perdigão, Luís M A; Saywell, Alex

    2011-07-01

    The operation of a haptic device interfaced with a scanning tunneling microscope (STM) is presented here. The user moves the STM tip in three dimensions by means of a stylus attached to the haptic instrument. The tunneling current measured by the STM is converted to a vertical force, applied to the stylus and felt by the user, with the user being incorporated into the feedback loop that controls the tip-surface distance. A haptic-STM interface of this nature allows the user to feel atomic features on the surface and facilitates the tactile manipulation of the adsorbate/substrate system. The operation of this device is demonstrated via the room temperature STM imaging of C(60) molecules adsorbed on an Au(111) surface in ultra-high vacuum.

  16. Physical Modeling of Contact Processes on the Cutting Tools Surfaces of STM When Turning

    NASA Astrophysics Data System (ADS)

    Belozerov, V. A.; Uteshev, M. H.

    2016-08-01

    This article describes how to create an optimization model of the process of fine turning of superalloys and steel tools from STM on CNC machines, flexible manufacturing units (GPM), machining centers. Creation of the optimization model allows you to link (unite) contact processes simultaneously on the front and back surfaces of the tool from STM to manage contact processes and the dynamic strength of the cutting tool at the top of the STM. Established optimization model of management of the dynamic strength of the incisors of the STM in the process of fine turning is based on a previously developed thermomechanical (physical, heat) model, which allows the system thermomechanical approach to choosing brands STM (domestic and foreign) for cutting tools from STM designed for fine turning of heat resistant alloys and steels.

  17. X-ray STM: Nanoscale elemental analysis & Observation of atomic track.

    PubMed

    Saito, Akira; Furudate, Y; Kusui, Y; Saito, T; Akai-Kasaya, M; Tanaka, Y; Tamasaku, K; Kohmura, Y; Ishikawa, T; Kuwahara, Y; Aono, M

    2014-11-01

    Scanning tunneling microscopy (STM) combined with brilliant X-rays from synchrotron radiation (SR) can provide various possibilities of original and important applications, such as the elemental analysis on solid surfaces at an atomic scale. The principle of the elemental analysis is based on the inner-shell excitation of an element-specific energy level "under STM observation". A key to obtain an atomic locality is to extract the element-specific modulation of the local tunneling current (not emission that can damage the spatial resolution), which is derived from the inner-shell excitation [1]. On this purpose, we developed a special SR-STM system and smart tip. To surmount a tiny core-excitation efficiency by hard X-rays, we focused two-dimensionally an incident beam having the highest photon density at the SPring-8.After successes in the elemental analyses by SR-STM [1,2] on a semiconductor hetero-interface (Ge on Si) and metal-semiconductor interface (Cu on Ge), we succeeded in obtaining the elemental contrast between Co nano-islands and Au substrate. The results on the metallic substrate suggest the generality of the method and give some important implications on the principle of contrast. For all cases of three samples, the spatial resolution of the analysis was estimated to be ∼1 nm or less, and it is worth noting that the measured surface domains had a deposition thickness of less than one atomic layer (Fig. 1, left and center).jmicro;63/suppl_1/i14-a/DFU045F1F1DFU045F1Fig. 1.(left) Topographic image and (center) beam-induced tip current image of Ge(111)-Cu (-2V, 0.2 nA). (right) X-ray- induced atomic motion tracks on Ge(111) that were newly imaged by the Xray-STM. On the other hand, we found that the "X-ray induced atomic motion" can be observed directly with atomic scale using the SR-STM system effectively under the incident photon density of ∼2 x10(15) photon/sec/mm(2) [3]. SR-STM visualized successfully the track of the atomic motion (Fig. 1, right

  18. Mechanical stress contributes to the expression of the STM homeobox gene in Arabidopsis shoot meristems

    PubMed Central

    Landrein, Benoît; Kiss, Annamaria; Sassi, Massimiliano; Chauvet, Aurélie; Das, Pradeep; Cortizo, Millan; Laufs, Patrick; Takeda, Seiji; Aida, Mitsuhiro; Traas, Jan; Vernoux, Teva; Boudaoud, Arezki; Hamant, Olivier

    2015-01-01

    The role of mechanical signals in cell identity determination remains poorly explored in tissues. Furthermore, because mechanical stress is widespread, mechanical signals are difficult to uncouple from biochemical-based transduction pathways. Here we focus on the homeobox gene SHOOT MERISTEMLESS (STM), a master regulator and marker of meristematic identity in Arabidopsis. We found that STM expression is quantitatively correlated to curvature in the saddle-shaped boundary domain of the shoot apical meristem. As tissue folding reflects the presence of mechanical stress, we test and demonstrate that STM expression is induced after micromechanical perturbations. We also show that STM expression in the boundary domain is required for organ separation. While STM expression correlates with auxin depletion in this domain, auxin distribution and STM expression can also be uncoupled. STM expression and boundary identity are thus strengthened through a synergy between auxin depletion and an auxin-independent mechanotransduction pathway at the shoot apical meristem. DOI: http://dx.doi.org/10.7554/eLife.07811.001 PMID:26623515

  19. STM/STS studies of Ca-intercalated bilayer graphene

    NASA Astrophysics Data System (ADS)

    Shimizu, Ryota; Sugawara, Katsuaki; Kanetani, Kohei; Iwaya, Katsuya; Sato, Takafumi; Takahashi, Takashi; Hitosugi, Taro

    2013-03-01

    We have performed low temperature scanning tunneling microscopy/spectroscopy (STM/STS) measurements on a two-dimensional Ca-intercalated bilayer graphene epitaxially grown on a 6H-SiC(0001) substrate. The STM topographic images clearly resolve each intercalated Ca atom with graphene-based honeycomb lattice. Furthermore, we found a clear ×2.5 modulation in the topography, implying charge density wave or Moiré pattern originated from the interaction with the SiC substrate. Comparison with ARPES measurements provided us of further insight into the Fermi surface deduced from STS.

  20. Adsorption configurations and scanning voltage determined STM images of small hydrogen clusters on bilayer graphene.

    PubMed

    Cao, Teng Fei; Huang, Liang Feng; Zheng, Xiao Hong; Zhou, Wang Huai; Zeng, Zhi

    2013-11-21

    By density functional theory calculations, the scanning tunneling microscopy (STM) images of various hydrogen clusters adsorbed on bilayer-graphene are systematically simulated. The hydrogen configurations of the STM images observed in the experiments have been thoroughly figured out. In particular, two kinds of hydrogen dimers (ortho-dimer, para-dimer) and two kinds of tetramers (tetramer-A, -B) are determined to be the hydrogen configurations corresponding to the ellipsoidal-like STM images with different structures and sizes. One particular hexamer (hexamer-B) is the hydrogen configuration generating the star-like STM images. For each hydrogen cluster, the simulated STM images show unique voltage-dependent features, which provides a feasible way to determine hydrogen adsorption states on graphene or graphite surface in the experiments by varying-voltage measurements. Stability analysis proves that the above determined hydrogen configurations are quite stable on graphene, hence they are likely to be detected in the STM experiments. Consequently, through systematic analysis of the STM images and the stability of hydrogen clusters on bilayer graphene, many experimental observations have been consistently explained.

  1. Prototyping the HPDP Chip on STM 65 NM Process

    NASA Astrophysics Data System (ADS)

    Papadas, C.; Dramitinos, G.; Syed, M.; Helfers, T.; Dedes, G.; Schoellkopf, J.-P.; Dugoujon, L.

    2011-08-01

    Currently Astrium GmbH is involved in the of the High Performance Data Processor (HPDP) development programme for telecommunication applications under a DLR contract. The HPDP project targets the implementation of the commercially available reconfigurable array processor IP (XPP from the company PACT XPP Technologies) in a radiation hardened technology.In the current complementary development phase funded under the Greek Industry Incentive scheme, it is planned to prototype the HPDP chip in commercial STM 65 nm technology. In addition it is also planned to utilise the preliminary radiation hardened components of this library wherever possible.This abstract gives an overview of the HPDP chip architecture, the basic details of the STM 65 nm process and the design flow foreseen for the prototyping. The paper will discuss the development and integration issues involved in using the STM 65 nm process (also including the available preliminary radiation hardened components) for designs targeted to be used in space applications.

  2. UHV LT-STM system with Sample and Tip Exchange

    NASA Astrophysics Data System (ADS)

    Dreyer, Michael; Lee, Jonghee; Wang, Hui; Sullivan, Dan; Barker, Barry

    2006-03-01

    We developed and built a low temperature scanning tunneling microscope system with ultra high vacuum sample and tip preparation capabilities. The STM is mounted inside an UHV can which is submerged in a He bath cryostat. The cryostat is equipped with two superconducting magnets allowing a maximum in plane field of 2 T and a maximum out of plane field of 9 T. The two fields can be combined to a 1 T vector field. The vacuum can is connected to an UHV system at room temperature consisting of two chambers: One dedicated to transferring samples and tips to the STM, and the other chamber used for tip/sample preparation. It is equipped with two electron beam evaporators, an argon ion sputter gun as well as sample heaters. The whole system is supported by an optical table to decouple the STM from building vibrations. The system was successfully used to study standing electron waves on gold (111) as well as vortices on NbSe2. Details of the microscope, sample and tip handling system, as well as the UHV system will be presented.

  3. Identification of surface terminations of iron pnictides with low-temperature STM/STS

    NASA Astrophysics Data System (ADS)

    Wang, Jihui; Li, Ang; Ma, Jihua; Wu, Zheng; Yin, Jiaxin; Lv, Bing; Chu, C. W.; Sefat, A.; McGuire, M.; Sales, B.; Mandrus, D.; Zhang, Chenglin; Dai, Pengcheng; Jin, Rongying; Zhang, Jiandi; Plummer, E. W.; Chen, Genfu; Ding, Hong; Pan, Shuheng H.

    2013-03-01

    The alkaline-earth metal iron pnictide superconductor AEFe2As2 (AE =Ca, Sr, Ba) have been studied extensively with modern surface techniques, such as scanning tunneling microscopy/spectroscopy (STM/STS) and Angle Resolved Photoemission Spectroscopy (ARPES). Yet the surface termination upon cleaving is still controversial. Hence, the interpretation of those results of STM/STS and reconcile with results of other surface techniques tend to be challenging. We have performed a systematic low-temperature STM/STS study on a series of (Ca,Na)Fe2As2, (Ba,K)Fe2As2, Ba(Fe,Co)2As2, and BaFe2(As,P)2. We found that, with cryogenic cleaving method, all three crystalline atomic layers can be revealed and identified. We will discuss their identities and their implications.

  4. High-quality draft genome sequence of Rhizobium mesoamericanum strain STM6155, a Mimosa pudica microsymbiont from New Caledonia

    DOE PAGES

    Klonowska, Agnieszka; López-López, Aline; Moulin, Lionel; ...

    2017-01-17

    Rhizobium mesoamericanum STM6155 (INSCD=ATYY01000000) is an aerobic, motile, Gram-negative, non-spore-forming rod that can exist as a soil saprophyte or as an effective nitrogen fixing microsymbiont of the legume Mimosa pudica L.. STM6155 was isolated in 2009 from a nodule of the trap host M. pudica grown in nickel-rich soil collected near Mont Dore, New Caledonia. R. mesoamericanum STM6155 was selected as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) genome sequencing project. Here we describe the symbiotic properties of R. mesoamericanum STM6155, together with its genome sequence information and annotation. Themore » 6,927,906bp high-quality draft genome is arranged into 147 scaffolds of 152 contigs containing 6855 protein-coding genes and 71 RNA-only encoding genes. Strain STM6155 forms an ANI clique (ID 2435) with the sequenced R. mesoamericanum strain STM3625, and the nodulation genes are highly conserved in these strains and the type strain of Rhizobium grahamii CCGE501 T . Within the STM6155 genome, we have identified a chr chromate efflux gene cluster of six genes arranged into two putative operons and we postulate that this cluster is important for the survival of STM6155 in ultramafic soils containing high concentrations of chromate.« less

  5. High-quality draft genome sequence of Rhizobium mesoamericanum strain STM6155, a Mimosa pudica microsymbiont from New Caledonia

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

    Klonowska, Agnieszka; López-López, Aline; Moulin, Lionel

    Rhizobium mesoamericanum STM6155 (INSCD=ATYY01000000) is an aerobic, motile, Gram-negative, non-spore-forming rod that can exist as a soil saprophyte or as an effective nitrogen fixing microsymbiont of the legume Mimosa pudica L.. STM6155 was isolated in 2009 from a nodule of the trap host M. pudica grown in nickel-rich soil collected near Mont Dore, New Caledonia. R. mesoamericanum STM6155 was selected as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) genome sequencing project. Here we describe the symbiotic properties of R. mesoamericanum STM6155, together with its genome sequence information and annotation. Themore » 6,927,906bp high-quality draft genome is arranged into 147 scaffolds of 152 contigs containing 6855 protein-coding genes and 71 RNA-only encoding genes. Strain STM6155 forms an ANI clique (ID 2435) with the sequenced R. mesoamericanum strain STM3625, and the nodulation genes are highly conserved in these strains and the type strain of Rhizobium grahamii CCGE501 T . Within the STM6155 genome, we have identified a chr chromate efflux gene cluster of six genes arranged into two putative operons and we postulate that this cluster is important for the survival of STM6155 in ultramafic soils containing high concentrations of chromate.« less

  6. STM-electroluminescence from clustered C3N4 nanodomains synthesized via green chemistry process.

    PubMed

    Andrade, E P; Costa, B B A; Chaves, C R; de Paula, A M; Cury, L A; Malachias, A; Safar, G A M

    2018-01-01

    A Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and synchrotron X-ray diffraction study on clustered C 3 N 4 nanoparticles (nanoflakes) is conducted on green-chemistry synthesized samples obtained from chitosan through high power sonication. Morphological aspects and the electronic characteristics are investigated. The observed bandgap of the nanoflakes reveals the presence of different phases in the material. Combining STM morphology, STS spectra and X-ray diffraction (XRD) results one finds that the most abundant phase is graphitic C 3 N 4 . A high density of defects is inferred from the XRD measurements. Additionally, STM-electroluminescence (STMEL) is detected in C 3 N 4 nanoflakes deposited on a gold substrate. The tunneling current creates photons that are three times more energetic than the tunneling electrons of the STM sample. We ponder about the two most probable models to explain the observed photon emission energy: either a nonlinear optical phenomenon or a localized state emission. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Cryogenic STM in 3D vector magnetic fields realized through a rotatable insert.

    PubMed

    Trainer, C; Yim, C M; McLaren, M; Wahl, P

    2017-09-01

    Spin-polarized scanning tunneling microscopy (SP-STM) performed in vector magnetic fields promises atomic scale imaging of magnetic structure, providing complete information on the local spin texture of a sample in three dimensions. Here, we have designed and constructed a turntable system for a low temperature STM which in combination with a 2D vector magnet provides magnetic fields of up to 5 T in any direction relative to the tip-sample geometry. This enables STM imaging and spectroscopy to be performed at the same atomic-scale location and field-of-view on the sample, and most importantly, without experiencing any change on the tip apex before and after field switching. Combined with a ferromagnetic tip, this enables us to study the magnetization of complex magnetic orders in all three spatial directions.

  8. A convenient method for large-scale STM mapping of freestanding atomically thin conductive membranes

    NASA Astrophysics Data System (ADS)

    Uder, B.; Hartmann, U.

    2017-06-01

    Two-dimensional atomically flat sheets with a high flexibility are very attractive as ultrathin membranes but are also inherently challenging for microscopic investigations. We report on a method using Scanning Tunneling Microscopy (STM) under ultra-high vacuum conditions for large-scale mapping of several-micrometer-sized freestanding single and multilayer graphene membranes. This is achieved by operating the STM at unusual parameters. We found that large-scale scanning on atomically thin membranes delivers valuable results using very high tip-scan speeds combined with high feedback-loop gain and low tunneling currents. The method ultimately relies on the particular behavior of the freestanding membrane in the STM which is much different from that of a solid substrate.

  9. Two-probe STM experiments at the atomic level.

    PubMed

    Kolmer, Marek; Olszowski, Piotr; Zuzak, Rafal; Godlewski, Szymon; Joachim, Christian; Szymonski, Marek

    2017-11-08

    Direct characterization of planar atomic or molecular scale devices and circuits on a supporting surface by multi-probe measurements requires unprecedented stability of single atom contacts and manipulation of scanning probes over large, nanometer scale area with atomic precision. In this work, we describe the full methodology behind atomically defined two-probe scanning tunneling microscopy (STM) experiments performed on a model system: dangling bond dimer wire supported on a hydrogenated germanium (0 0 1) surface. We show that 70 nm long atomic wire can be simultaneously approached by two independent STM scanners with exact probe to probe distance reaching down to 30 nm. This allows direct wire characterization by two-probe I-V characteristics at distances below 50 nm. Our technical results presented in this work open a new area for multi-probe research, which can be now performed with precision so far accessible only by single-probe scanning probe microscopy (SPM) experiments.

  10. Simultaneous noncontact AFM and STM of Ag:Si(111)-(3×3)R30∘

    NASA Astrophysics Data System (ADS)

    Sweetman, Adam; Stannard, Andrew; Sugimoto, Yoshiaki; Abe, Masayuki; Morita, Seizo; Moriarty, Philip

    2013-02-01

    The Ag:Si(111)-(3×3)R30∘ surface structure has attracted considerable debate concerning interpretation of scanning tunneling microscope (STM) and noncontact atomic force microscope (NC-AFM) images. In particular, the accepted interpretation of atomic resolution images in NC-AFM has been questioned by theoretical and STM studies. In this paper, we use combined NC-AFM and STM to conclusively show that the inequivalent trimer (IET) configuration best describes the surface ground state. Thermal-averaging effects result in a honeycomb-chained-trimer (HCT) appearance at room temperature, in contrast to studies suggesting that the IET configuration remains stable at higher temperatures [Zhang, Gustafsson, and Johansson, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.74.201304 74, 201304(R) (2006) and J. Phys.: Conf. Ser.1742-658810.1088/1742-6596/61/1/264 61, 1336 (2007)]. We also comment on results obtained at an intermediate temperature that suggest an intriguing difference between the imaging mechanisms of NC-AFM and STM on structurally fluctuating samples.

  11. STM images and STS for a rectangular quantum corral constructed with δ-function barriers and the effect of an adsorbed atom on STM images and STS

    NASA Astrophysics Data System (ADS)

    Mitsuoka, Shigenori; Tamura, Akira

    2012-04-01

    Assuming that an electron confined by double δ-function barriers is in a quasi-stationary state, we derived eigenfunctions and eigenenergies of the electron. Applying this point of view to the electron confined in a rectangular quantum corral (QC), we obtained scanning tunneling microscopic (STM) images and scanning tunneling spectrum (STS). Our results are consistent with experimental ones, which confirms validity of the present model. Comparing with the treatment in which the corral potential is chosen to be of square-barrier type, the present treatment has an advantage that the eigenvalue equations are simple and the number of parameters that specify the potential barrier is only one except the bottom of the potential well. On the basis of a Dyson equation for the Green function we calculated STM images and STS of the QC having an adsorbed atom inside. Our results are consistent with experimental STM images and STS. In contrast to a previous viewpoint that the STS profile is reversed with that of the empty QC, we concluded the STS peaks of the adsorbed QC are shifted downward from those of the empty QC.

  12. Analysis of STM images with pure and CO-functionalized tips: A first-principles and experimental study

    NASA Astrophysics Data System (ADS)

    Gustafsson, Alexander; Okabayashi, Norio; Peronio, Angelo; Giessibl, Franz J.; Paulsson, Magnus

    2017-08-01

    We describe a first-principles method to calculate scanning tunneling microscopy (STM) images, and compare the results to well-characterized experiments combining STM with atomic force microscopy (AFM). The theory is based on density functional theory with a localized basis set, where the wave functions in the vacuum gap are computed by propagating the localized-basis wave functions into the gap using a real-space grid. Constant-height STM images are computed using Bardeen's approximation method, including averaging over the reciprocal space. We consider copper adatoms and single CO molecules adsorbed on Cu(111), scanned with a single-atom copper tip with and without CO functionalization. The calculated images agree with state-of-the-art experiments, where the atomic structure of the tip apex is determined by AFM. The comparison further allows for detailed interpretation of the STM images.

  13. Nano-scale Stripe Structures on FeTe Observed by Low-temperature STM/STS

    NASA Astrophysics Data System (ADS)

    Sugimoto, A.; Ukita, R.; Ekino, T.

    We have investigated the nano-scale stripe structures on a parent compound of the iron chalcogenide superconductor Fe1+dTe (d=0.033) by using low-temperature scanning tunneling microscopy (STM). The STM topographies and the dI/dV maps show clear stripe structures with the period of twice as large as the Te-Te atomic displacement (~0.76 nm = 2a0, a0 is lattice constant), in addition to weak modulation with the same period of lattice constant (~0.38 nm). The bias-voltage dependence of both STM topographies and dI/dV maps show the several kinds of the stripe structures. The 2a0 modulations are similar to the bicollinear spin order of the parent compound FeTe, indicating the possibility of the coupling with spin density wave and electronic structures.

  14. Upgrade of the Surface Spectrometer at NEPOMUC for PAES, XPS and STM Investigations

    NASA Astrophysics Data System (ADS)

    Zimnik, S.; Lippert, F.; Hugenschmidt, C.

    2014-04-01

    The characterization of the elemental composition of surfaces is of great importance for the understanding of many surface processes, such as surface segregation or oxidation. Positron-annihilation-induced Auger Electron Spectroscopy (PAES) is a powerful technique for gathering information about the elemental composition of only the topmost atomic layer of a sample. The upgraded surface spectrometer at NEPOMUC (NEtron induced POsitron source MUniCh) enables a comprehensive surface analysis with the complementary techniques STM, XPS and PAES. A new X-ray source for X-ray induced photoelectron spectroscopy (XPS) was installed to gather additional information on oxidation states. A new scanning tunneling microscope (STM) is used as a complementary method to investigate with atomic resolution the surface electron density. The combination of PAES, XPS and STM allows the characterization of both the elemental composition, and the surface topology.

  15. Key Role of M.G. Nakhodkin’s Insight and Inspiration in Development of UHV STM-Related Techniques and Methods

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

    Lyubinetsky, Igor

    2015-02-15

    In this contribution I briefly describe my joint efforts and experiences with M.G. Nakhodkin in the field of scanning tunneling microscopy (STM) including a construction of the home-built microscopes, application of this technique in various scientific endevours, as well as fruitfull and enlightening discusions. Our co-operation was focused on the novel aspects of STM probes preparation and conditioning, coupling the STM junction with laser irradiation, STM-based nanolithography, and also on collaboration at the international scale with M.G. Nakhodkin and members of his scientific group.

  16. STM/STS study of ridges on epitaxial graphene/SiC

    NASA Astrophysics Data System (ADS)

    Li, Y. Y.; Liu, Y.; Weinert, M.; Li, L.

    2012-02-01

    The graphitization of hexagonal SiC surfaces provides a viable alternative for the synthesis of wafer-sized graphene for mass device production. During later stages of growth, ridges are often observed on the graphene layers as a result of bending and buckling to relieve the strain between the graphene and SiC substrate. In this work, we show, by atomic resolution STM/STS, that these ridges are in fact bulged regions of the graphene layer, forming one-dimentional (nanowire) and zero-dimentional (quantum dot) nanostructures. We further show that their structures can be manipulated by the pressure exerted by the STM tip during imaging. These results and their impact on the electronic properties of epitaxial graphene on SiC(0001) will be presented at the meeting.

  17. STM investigations of Au(1 1 1) electrodes coated with vitamin B 12 derivatives

    NASA Astrophysics Data System (ADS)

    Szőcs, E.; Durrer, L.; Luginbühl, R.; Simic, N.; Viana, A. S.; Abrantes, L. M.; Keese, R.; Siegenthaler, H.

    2006-01-01

    Vitamin B 12 derivatives immobilized at flame-annealed Au(1 1 1) electrode surfaces have been investigated in close correlation with their structural properties and spatial arrangement at the electrode substrate by scanning tunneling microscopy (STM) in air and in aqueous 0.1 M NaClO 4 solution. The investigated compounds were symmetrical (B 12C 10S-SC 10B 12) and nonsymmetrical (B 12C 10S-SC 10) dialkyl disulfide derivatives of vitamin B 12, attached to the electrode surfaces by the S-Au bond. The ex situ and in situ STM experiments show the formation of a surface layer, whose packing density and structure is presumably controlled by the spatial arrangement of the large cobyrinate head groups. In presence of the symmetrical B 12 compound, a disordered surface layer is observed. Voltammetric investigations show that, in 0.1 M NaClO 4, this layer becomes unstable at potentials approximately ⩽ -1000 mV vs. MSE and is almost completely removed at more negative potentials. The STM imaging properties of the nonsymmetrical B 12 surface layer show a significant dependence on the tunneling distance. In particular, at small tunneling distances, a highly regular hexagonal surface pattern is observed that suggests strongly the presence of an ordered surface assembly. Modeling of the B 12 head group has been performed to provide information for a structure-related interpretation of the high-resolution STM images. The investigations are first STM results obtained at such B 12 modified electrodes.

  18. Fabrication and characterization of CNT-based smart tips for synchrotron assisted STM

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

    Yan, Hui; Cummings, Marvin; Camino, Fernando

    Determination of chemical composition along with imaging at the atomic level provides critical information towards fundamental understanding of the surface of materials and, hence, yields the capability to design new materials by tailoring their ultimate functionalities. Synchrotron X-ray assisted scanning tunneling microscopy (SX-STM) is a promising new technique to achieve real space chemically specific atomic mapping. Chemical sensitivity of SX-STM relies on excitation of core electrons by incident X-rays when their energy is tuned to an absorption edge of a particular element. However, along with core-level electrons, photoelectrons are also excited, which yield additional current and interfere with the tunnelingmore » current. To reduce the background photoelectron current and to improve ultimate resolution of SX-STM, we have developed and fabricated multiwalled carbon nanotubes (MWCNT) based “smart tips” using plasma enhanced chemical vapor deposition and focused ion beam milling. As a result, the newly developed CNT-based smart tips, characterized step by step by scanning electron microscopy (SEM) during the fabrication process, demonstrate good performance and provide opportunity for realizing atomic chemical mapping.« less

  19. Fabrication and characterization of CNT-based smart tips for synchrotron assisted STM

    DOE PAGES

    Yan, Hui; Cummings, Marvin; Camino, Fernando; ...

    2015-08-05

    Determination of chemical composition along with imaging at the atomic level provides critical information towards fundamental understanding of the surface of materials and, hence, yields the capability to design new materials by tailoring their ultimate functionalities. Synchrotron X-ray assisted scanning tunneling microscopy (SX-STM) is a promising new technique to achieve real space chemically specific atomic mapping. Chemical sensitivity of SX-STM relies on excitation of core electrons by incident X-rays when their energy is tuned to an absorption edge of a particular element. However, along with core-level electrons, photoelectrons are also excited, which yield additional current and interfere with the tunnelingmore » current. To reduce the background photoelectron current and to improve ultimate resolution of SX-STM, we have developed and fabricated multiwalled carbon nanotubes (MWCNT) based “smart tips” using plasma enhanced chemical vapor deposition and focused ion beam milling. As a result, the newly developed CNT-based smart tips, characterized step by step by scanning electron microscopy (SEM) during the fabrication process, demonstrate good performance and provide opportunity for realizing atomic chemical mapping.« less

  20. Electronic structure and simulated STM images of non-honeycomb phosphorene allotropes

    NASA Astrophysics Data System (ADS)

    Kaur, Sumandeep; Kumar, Ashok; Srivastava, Sunita; Tankeshwar, K.

    2018-04-01

    We have investigated the electronic structure and simulated STM images of various non-honeycomb allotropes of phosphorene namely ɛ - P, ζ - P, η - P and θ - P, within combined density functional theory and Tersoff-Hamman approach. All these allotropes are found to be energetically stable and electronically semiconductingwith bandgap ranging between 0.5-1.2 eV. Simulated STM images show distinctly different features in terms of the topography. Different maximas in the distance-height profile indicates the difference in buckling of atoms in these allotropes. Distinctly different images obtained in this study may be useful to differentiate various allotropes that can serve as fingerprints to identify various allotropes during the synthesis of phosphorene.

  1. STM, SECPM, AFM and Electrochemistry on Single Crystalline Surfaces

    PubMed Central

    Wolfschmidt, Holger; Baier, Claudia; Gsell, Stefan; Fischer, Martin; Schreck, Matthias; Stimming, Ulrich

    2010-01-01

    Scanning probe microscopy (SPM) techniques have had a great impact on research fields of surface science and nanotechnology during the last decades. They are used to investigate surfaces with scanning ranges between several 100 μm down to atomic resolution. Depending on experimental conditions, and the interaction forces between probe and sample, different SPM techniques allow mapping of different surface properties. In this work, scanning tunneling microscopy (STM) in air and under electrochemical conditions (EC-STM), atomic force microscopy (AFM) in air and scanning electrochemical potential microscopy (SECPM) under electrochemical conditions, were used to study different single crystalline surfaces in electrochemistry. Especially SECPM offers potentially new insights into the solid-liquid interface by providing the possibility to image the potential distribution of the surface, with a resolution that is comparable to STM. In electrocatalysis, nanostructured catalysts supported on different electrode materials often show behavior different from their bulk electrodes. This was experimentally and theoretically shown for several combinations and recently on Pt on Au(111) towards fuel cell relevant reactions. For these investigations single crystals often provide accurate and well defined reference and support systems. We will show heteroepitaxially grown Ru, Ir and Rh single crystalline surface films and bulk Au single crystals with different orientations under electrochemical conditions. Image studies from all three different SPM methods will be presented and compared to electrochemical data obtained by cyclic voltammetry in acidic media. The quality of the single crystalline supports will be verified by the SPM images and the cyclic voltammograms. Furthermore, an outlook will be presented on how such supports can be used in electrocatalytic studies. PMID:28883327

  2. STM/STS Observation on Layered Nitride Superconductor α-(DDA)xTiNCl

    NASA Astrophysics Data System (ADS)

    Sugimoto, Akira; Ukita, Ryuichi; Ekino, Toshikazu; Zheng, Zhanfeng; Yamanaka, Shoji

    2012-12-01

    Scanning tunneling microscopy/spectroscopy (STM/STS) measurements on α-(DDA)xTiNCl (DDA=H2N-(CH2)10-NH2, Tc=16 K) have been carried out. The STM topography exhibits simple rectangular shaped atomic lattice with the periods of |a|=0.38 nm and |b| =0.33 nm. The averaged dI / dV spectrum shows the gap value of Δ ~ 9 meV, giving an unusual large gap ratio 2Δ/kBTc ≃ 13. The STS results show the bar-shaped domain structures along the b-axis direction in the bias range of V = +5 ~ +15 mV, demonstrating the possible existence of intercalated molecules.

  3. Oxygen adsorption on the Al₉Co₂(001) surface: first-principles and STM study.

    PubMed

    Villaseca, S Alarcón; Loli, L N Serkovic; Ledieu, J; Fournée, V; Gille, P; Dubois, J-M; Gaudry, E

    2013-09-04

    Atomic oxygen adsorption on a pure aluminum terminated Al9Co2(001) surface is studied by first-principle calculations coupled with STM measurements. Relative adsorption energies of oxygen atoms have been calculated on different surface sites along with the associated STM images. The local electronic structure of the most favourable adsorption site is described. The preferential adsorption site is identified as a 'bridge' type site between the cluster entities exposed at the (001) surface termination. The Al-O bonding between the adsorbate and the substrate presents a covalent character, with s-p hybridization occurring between the states of the adsorbed oxygen atom and the aluminum atoms of the surface. The simulated STM image of the preferential adsorption site is in agreement with experimental observations. This work shows that oxygen adsorption generates important atomic relaxations of the topmost surface layer and that sub-surface cobalt atoms strongly influence the values of the adsorption energies. The calculated Al-O distances are in agreement with those reported in Al2O and Al2O3 oxides and for oxygen adsorption on Al(111).

  4. Automated extraction of single H atoms with STM: tip state dependency

    NASA Astrophysics Data System (ADS)

    Møller, Morten; Jarvis, Samuel P.; Guérinet, Laurent; Sharp, Peter; Woolley, Richard; Rahe, Philipp; Moriarty, Philip

    2017-02-01

    The atomistic structure of the tip apex plays a crucial role in performing reliable atomic-scale surface and adsorbate manipulation using scanning probe techniques. We have developed an automated extraction routine for controlled removal of single hydrogen atoms from the H:Si(100) surface. The set of atomic extraction protocols detect a variety of desorption events during scanning tunneling microscope (STM)-induced modification of the hydrogen-passivated surface. The influence of the tip state on the probability for hydrogen removal was examined by comparing the desorption efficiency for various classifications of STM topographs (rows, dimers, atoms, etc). We find that dimer-row-resolving tip apices extract hydrogen atoms most readily and reliably (and with least spurious desorption), while tip states which provide atomic resolution counter-intuitively have a lower probability for single H atom removal.

  5. Functional group selective STM Imaging in self-assembled monolayers: Benzeneselenol on Au(111)

    NASA Astrophysics Data System (ADS)

    Azzam, Waleed; Zharnikov, Michael; Rohwerde, Michael; Bashir, Asif

    2018-01-01

    Benzeneselenol (PSe) self-assembled monolayers (SAMs) formed on Au(111) substrate by the immersion procedure with an immersion time of 24 h and 4 weeks were studied by high-resolution scanning tunneling microscopy (STM). The short molecular rows, which have been previously attributed to irregular translational domains, were found to be regularly repeated within a single domain in the SAMs fabricated upon the immersion for 4 weeks, forming adlayer structure with a very large unit cell. This structure could be assigned as a (27 × 5) superlattice (α phase) containing 36 molecules in the oblique unit cell. This phase coexisted with a different phase having a commensurate (8√{ 3 } × 4) superstructure (β phase) containing 28 protrusions per rectangular unit cell. Analysis of the STM images suggested that each PSe molecule in the β phase was imaged not as one but as a pair of protrusions, which were attributed to the benzene ring and the selenium headgroup of the PSe molecule. At the given molecular length, the spacing between the protrusions defined the molecular tilt, allowing us to derive the orientation of the SAM constituents directly from the STM image.

  6. Single-layer ZnS supported on Au(111): A combined XPS, LEED, STM and DFT study

    DOE PAGES

    Deng, Xingyi; Sorescu, Dan C.; Lee, Junseok

    2016-12-31

    Single-layer of ZnS, consisting of one atomic layer of ZnS(111) plane, has been grown on Au(111) and characterized using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). While the LEED measurement indicates a coincidence structure of ZnS-(3×3)/Au(111)-(4×4), high resolution STM images reveal hexagonal unit cells of 6.7×6.7 Å 2 and 11.6×11.6 Å 2, corresponding to √3 and 3 times the unit cell of the ideal zincblende ZnS-(1×1), respectively, depending on the tunneling conditions. Calculations based on density functional theory (DFT) indicate a significantly reconstructed non-planar structure of ZnS single-layer on Au(111) with 2/3 ofmore » the S anions being located nearly in the plane of the Zn cations and the rest 1/3 of the S anions protruding above the Zn plane. In conclusion, the calculated STM image shows similar characteristics to those of the experimental STM image. Additionally, the DFT calculations reveal the different bonding nature of the S anions in ZnS single-layer supported on Au(111).« less

  7. STM/STS on proximity-coupled superconducting graphene

    NASA Astrophysics Data System (ADS)

    Ovadia, Maoz; Ji, Yu; Lee, Gil-Ho; Fang, Wenjing; Hoffman, Jennifer; Jarillo-Herrero, Pablo; Kong, Jing; Kim, Philip

    Graphene in good electrical contact with a superconductor has been observed to have an enhanced proximity effect. Application of a magnetic field is expected to generate an Abrikosov lattice of superconducting vortices, each containing Andreev bound states in its core. With our versatile, homebuilt, low temperature scanning tunneling force microscope (STM/SFM), we investigate the electronic properties of graphene on superconducting NbSe2 in a magnetic field and search for signatures of these vortex core states. This work was supported by the STC Center for Integrated Quantum Materials, NSF Grant No. DMR-1231319.

  8. STM/STS on proximity-coupled superconducting graphene

    NASA Astrophysics Data System (ADS)

    Ovadia, Maoz; Ji, Yu; Hoffman, Jennifer; Wang, Joel I.-Jan; Jarillo-Herrero, Pablo

    2015-03-01

    Graphene in good electrical contact with a superconductor has been observed to have an enhanced proximity effect. Application of a magnetic field is expected to generate an Abrikosov lattice of superconducting vortices, each containing Andreev bound states in its core. With our versatile, homebuilt, low temperature scanning tunneling force microscope (STM/SFM), we investigate the electronic properties of graphene on superconducting NbSe2 in a magnetic field and search for signatures of these vortex core states. This work was supported by the STC Center for Integrated Quantum Materials, NSF Grant No. DMR-1231319.

  9. In situ STM imaging of the structures of pentacene molecules adsorbed on Au(111).

    PubMed

    Pong, Ifan; Yau, Shuehlin; Huang, Peng-Yi; Chen, Ming-Chou; Hu, Tarng-Shiang; Yang, Yawchia; Lee, Yuh-Lang

    2009-09-01

    In situ scanning tunneling microscope (STM) was used to examine the spatial structures of pentacene molecules adsorbed onto a Au(111) single-crystal electrode from a benzene dosing solution containing 16-400 microM pentacene. Molecular-resolution STM imaging conducted in 0.1 M HClO(4) revealed highly ordered pentacene structures of ( radical31 x radical31)R8.9 degrees , (3 x 10), ( radical31 x 10), and ( radical7 x 2 radical7)R19.1 degrees adsorbed on the reconstructed Au(111) electrode dosed with different pentacene solutions. These pentacene structures and the reconstructed Au(111) substrate were stable between 0.2 and 0.8 V [vs reversible hydrogen electrode, RHE]. Increasing the potential to E > 0.8 V lifted the reconstructed Au(111) surface and disrupted the ordered pentacene adlattices simultaneously. Ordered pentacene structures could be restored by applying potentials negative enough to reinforce the reconstructed Au(111). At potentials negative of 0.2 V, the adsorption of protons became increasingly important to displace adsorbed pentacene admolecules. Although the reconstructed Au(111) structure was not essential to produce ordered pentacene adlayers, it seemed to help the adsorption of pentacene molecules in a long-range ordered pattern. At room temperature (25 degrees C), approximately 100 pentacene molecules seen in STM images could rotate and align themselves to a neighboring domain in 10 s, suggesting that pentacene admolecules could be mobile on Au(111) under the STM imaging conditions of -150 mV in bias voltage and 1 nA in feedback current.

  10. Nanoscale Decoration of Electrode Surfaces with an STM

    DTIC Science & Technology

    1999-05-30

    covered gold electrode surfaces at predetermined positions. First, metal is deposited electrochemically onto the STM tip, then the clusters are formed by a...onto the tip, the jump-to-contact occurs in the opposite direction leaving holes in the gold surface. The stability of the metal clusters against anodic...deposition, clusters, a surprisingly high stability of the small Ag Hg/HgSO4 for Ag deposition and a Pt wire for Ni clusters on gold against anodic

  11. Simulation of STM technique for electron transport through boron-nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Ganji, M. D.; Mohammadi-nejad, A.

    2008-06-01

    We report first-principles calculations on the electrical transport properties of boron-nitrid nanotubes (BNNTs). We consider a single walled (5,0) boron-nitrid nanotube sandwiched between an Au(1 0 0) substrate and a monatomic Au scanning tunneling microscope (STM) tip. Lateral motion of the tip over the nanotube wall cause it to change from one conformation class to the others and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity these Au/BNNT/Au nanowires are shown to be a convenient switch. Experiments with a conventional STM are proposed to test these predictions. The projection of the density of states (PDOS) and the transmission coefficients T(E) of the two-probe systems at zero bias are analyzed, and it suggests that the variation of the coupling between the wire and the electrodes leads to switching behaviour.

  12. Techniques Use by Science, Technology and Mathematics (STM) Teachers for Controlling Undesirable Classroom Behaviours in Anambra State Secondary Schools

    ERIC Educational Resources Information Center

    Chinelo, Okigbo Ebele; Nwanneka, Okoli Josephine

    2016-01-01

    This study investigated the techniques used by secondary school Science Technology and Mathematics (STM) teachers in controlling undesirable behaviours in their classrooms. It adopted descriptive survey design in which 178 Anambra State teachers teaching STM subjects in senior secondary were involved in the research. Two sections of questionnaire…

  13. Genomic structure and expression of STM2, the chromosome 1 familial Alzheimer disease gene.

    PubMed

    Levy-Lahad, E; Poorkaj, P; Wang, K; Fu, Y H; Oshima, J; Mulligan, J; Schellenberg, G D

    1996-06-01

    Mutations in the gene STM2 result in autosomal dominant familial Alzheimer disease. To screen for mutations and to identify regulatory elements for this gene, the genomic DNA sequence and intron-exon structure were determined. Twelve exons including 10 coding exons were identified in a genomic region spanning 23,737 bp. The first 2 exons encode the 5'-untranslated region. Expression analysis of STM2 indicates that two transcripts of 2.4 and 2.8 kb are found in skeletal muscle, pancreas, and heart. In addition, a splice variant of the 2.4-kb transcript was identified that is the result of the use of an alternative splice acceptor site located in exon 10. The use of this site results in a transcript lacking a single glutamate. The promotor for this gene and the alternatively spliced exons leading to the 2.8-kb form of the gene remain to be identified. Expression of STM2 was high in skeletal muscle and pancreas, with comparatively low levels observed in brain. This expression pattern is intriguing since in Alzheimer disease, pathology and degeneration are observed only in the central nervous system.

  14. Using Ab-Initio Calculations to Appraise Stm-Based - and Kink-Formation Energies

    NASA Astrophysics Data System (ADS)

    Feibelman, Peter J.

    2001-03-01

    Ab-initio total energies can and should be used to test the typically model-dependent results of interpreting STM morphologies. The benefits of such tests are illustrated here by ab-initio energies of step- and kink-formation on Pb and Pt(111) which show that the STM-based values of the kink energies must be revised. On Pt(111), the computed kink-energies for (100)- and (111)-microfacet steps are about 0.25 and 0.18 eV. These results imply a specific ratio of formation energies for the two step types, namely 1.14, in excellent agreement with experiment. If kink-formation actually cost the same energy on the two step types, an inference drawn from scanning probe observations of step wandering,(M. Giesen et al., Surf. Sci. 366, 229(1996).) this ratio ought to be 1. In the case of Pb(111), though computed energies to form (100)- and (111)-microfacet steps agree with measurement, the ab-initio kink-formation energies for the two step types, 41 and 60 meV, are 40-50% below experimental values drawn from STM images.(K. Arenhold et al., Surf. Sci. 424, 271(1999).) The discrepancy results from interpreting the images with a step-stiffness vs. kink-energy relation appropriate to (100) but not (111) surfaces. Good agreement is found when proper account of the trigonal symmetry of Pb(111) is taken in reinterpreting the step-stiffness data.

  15. A previously uncharacterized gene stm0551 plays a repressive role in the regulation of type 1 fimbriae in Salmonella enterica serotype Typhimurium

    PubMed Central

    2012-01-01

    Background Salmonella enterica serotype Typhimurium produces surface-associated fimbriae that facilitate adherence of the bacteria to a variety of cells and tissues. Type 1 fimbriae with binding specificity to mannose residues are the most commonly found fimbrial type. In vitro, static-broth culture favors the growth of S. Typhimurium with type 1 fimbriae, whereas non-type 1 fimbriate bacteria are obtained by culture on solid-agar media. Previous studies demonstrated that the phenotypic expression of type 1 fimbriae is the result of the interaction and cooperation of the regulatory genes fimZ, fimY, fimW, and fimU within the fim gene cluster. Genome sequencing revealed a novel gene, stm0551, located between fimY and fimW that encodes an 11.4-kDa putative phosphodiesterase specific for the bacterial second messenger cyclic-diguanylate monophosphate (c-di-GMP). The role of stm0551 in the regulation of type 1 fimbriae in S. Typhimurium remains unclear. Results A stm0551-deleted stain constructed by allelic exchange constitutively produced type 1 fimbriae in both static-broth and solid-agar medium conditions. Quantative RT-PCR revealed that expression of the fimbrial major subunit gene, fimA, and one of the regulatory genes, fimZ, were comparably increased in the stm0551-deleted strain compared with those of the parental strain when grown on the solid-agar medium, a condition that normally inhibits expression of type 1 fimbriae. Following transformation with a plasmid possessing the coding sequence of stm0551, expression of fimA and fimZ decreased in the stm0551 mutant strain in both culture conditions, whereas transformation with the control vector pACYC184 relieved this repression. A purified STM0551 protein exhibited a phosphodiesterase activity in vitro while a point mutation in the putative EAL domain, substituting glutamic acid (E) with alanine (A), of STM0551 or a FimY protein abolished this activity. Conclusions The finding that the stm0551 gene plays a

  16. Structure Determination of Au on Pt(111) Surface: LEED, STM and DFT Study

    PubMed Central

    Krupski, Katarzyna; Moors, Marco; Jóźwik, Paweł; Kobiela, Tomasz; Krupski, Aleksander

    2015-01-01

    Low-energy electron diffraction (LEED), scanning tunneling microscopy (STM) and density functional theory (DFT) calculations have been used to investigate the atomic and electronic structure of gold deposited (between 0.8 and 1.0 monolayer) on the Pt(111) face in ultrahigh vacuum at room temperature. The analysis of LEED and STM measurements indicates two-dimensional growth of the first Au monolayer. Change of the measured surface lattice constant equal to 2.80 Å after Au adsorption was not observed. Based on DFT, the distance between the nearest atoms in the case of bare Pt(111) and Au/Pt(111) surface is equal to 2.83 Å, which gives 1% difference in comparison with STM values. The first and second interlayer spacing of the clean Pt(111) surface are expanded by +0.87% and contracted by −0.43%, respectively. The adsorption energy of the Au atom on the Pt(111) surface is dependent on the adsorption position, and there is a preference for a hollow fcc site. For the Au/Pt(111) surface, the top interlayer spacing is expanded by +2.16% with respect to the ideal bulk value. Changes in the electronic properties of the Au/Pt(111) system below the Fermi level connected to the interaction of Au atoms with Pt(111) surface are observed.

  17. S182 and STM2 gene missense mutations in sporadic alzheimer disease

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

    Higuchi, Susumu; Matsushita, Sachio; Hasegawa, Yoshio

    1996-07-26

    The linkage of genes S182 and STM2 to early-onset or late-onset sporadic Alzheimer disease (AD) was not found in a group of 97 clinically-diagnosed AD patients and 46 autopsy-confirmed AD cases, using PCR-RFLP methods. 7 refs.

  18. Genomic structure and expression of STM2, the chromosome 1 familial Alzheimer disease gene

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

    Levy-Lahad, E.; Wang, Kai; Fu, Ying Hui

    1996-06-01

    Mutations in the gene STM2 result in autosomal dominant familial Alzheimer disease. To screen for mutations and to identify regulatory elements for this gene, the genomic DNA sequence and intron-exon structure were determined. Twelve exons including 10 coding exons were identified in a genomic region spanning 23, 737 bp. The first 2 exons encode the 5{prime}-untranslated region. Expression analysis of STM2 indicates that two transcripts of 2.4 and 2.8 kb are found in skeletal muscle, pancreas, and heart. In addition, a splice variant of the 2.4-kb transcript was identified that is the result of the use of an alternative splicemore » acceptor site located in exon 10. The use of this site results in a transcript lacking a single glutamate. The promotor for this gene and the alternatively spliced exons leading to the 2.8-kb form of the gene remain to be identified. Expression of STM2 was high in skeletal muscle and pancreas, with comparatively low levels observed in brain. This expression pattern is intriguing since in Alzheimer disease, pathology and degeneration are observed only in the central nervous system. 19 refs., 2 figs., 3 tabs.« less

  19. Adaptation of Acoustic Model Experiments of STM via Smartphones and Tablets

    ERIC Educational Resources Information Center

    Thees, Michael; Hochberg, Katrin; Kuhn, Jochen; Aeschlimann, Martin

    2017-01-01

    The importance of Scanning Tunneling Microscopy (STM) in today's research and industry leads to the question of how to include such a key technology in physics education. Manfred Euler has developed an acoustic model experiment to illustrate the fundamental measuring principles based on an analogy between quantum mechanics and acoustics. Based on…

  20. Effect of dissolved LiCl on the ionic liquid-Au(111) interface: an in situ STM study

    NASA Astrophysics Data System (ADS)

    Borisenko, Natalia; Atkin, Rob; Lahiri, Abhishek; Zein El Abedin, Sherif; Endres, Frank

    2014-07-01

    The structure of the electrolyte/electrode interface plays a significant role in electrochemical processes. To date, most studies are focusing on understanding the interfacial structure in pure ionic liquids. In this paper in situ scanning tunnelling microscopy (STM) has been employed to elucidate the structure of the charged Au(111)-ionic liquid (1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate, [Py1,4]FAP) interface in the presence of 0.1 M LiCl. The addition of the Li salt to the ionic liquid has a strong influence on the interfacial structure. In the first STM scan in situ measurements reveal that Au(111) undergoes the (22 \\times \\surd 3) ‘herringbone’ reconstruction in a certain potential regime, and there is strong evidence that the gold surface dissolves at negative electrode potentials in [Py1,4]FAP containing LiCl. Bulk deposition of Li is obtained at -2.9 V in the second STM scan.

  1. An effect of couterion in STM imaging process of DNA on Cu(111)

    NASA Astrophysics Data System (ADS)

    Furukawa, Masashi; Nishimura, Makoto; Tanaka, Hiroyuki; Kawai, Tomoji

    2002-03-01

    In order to elucidate electrical conduction mechanism of DNA, which is still under debate over the last decade, we have performed local electronic structure measurement of single- and double-stranded DNA molecules adsorbed onto Cu(111) surfaces using scanning tunneling microscope (STM). Bias-voltage-dependent STM images (from -5 V to +5 V) have shown that the molecular corrugation height in STM increases gradually at positive bias voltage region (empty state). Despite the theoretical assumption in which their 1st-LUMO states are localized at π plane of DNA bases, one cannot conclude its origin as the existence of their LUMO states, based on the results of relevant control measurements, DNA base molecules/Cu(111) [1] and NaCl/Cu(111). In fact, we found almost identical bias dependencies in the latter case (NaCl/Cu(111)), indicating that the feature of π* states of DNA bases should be buried in an additional channel that opens up by the onset of its unoccupied overlayer state in the tunneling process [2]. This study implies a potential difficulty in direct comparison of the obtained data with those characterized by XAS, in which π* states is located at ca. -1 eV relative to the Fermi level [3]. [1]M. Furukawa et al., submitted to Surf. Sci. [2] J. Kliewer et al., Surf. Sci. 477 (2001) 250.; A. Carlsson et al., Phys. Rev. B. 56 (1997) 1593. [3] M. Furukawa et al., submitted to Phys. Rev. B.

  2. STM study of the Ga thin films grown on Si(111) surface

    NASA Astrophysics Data System (ADS)

    Tao, Min-Long; Tu, Yu-Bing; Sun, Kai; Ye, Juan; Hao, Shao-Jie; Xiao, Hua-Fang; Wang, Ya-Li; Xie, Zheng-Bo; Wang, Jun-Zhong

    2017-09-01

    Structural evolution of Ga thin films grown on the Si(111)-√{ 3 } × √{ 3 } -Ga template have been investigated with a low-temperature scanning tunneling microscopy (STM). The first Ga layer exhibits a stripe structure along the base vectors of Si(111) lattices. Individual Ga dimers have been directly visualized from the high-resolution STM images of the first Ga layer. The second Ga layer reveals a pseudo 1×1 structure with respect to the Si(111). A new 5×5 phase has been found in the second Ga layer when annealing the sample to 120 ℃. Further annealing to 150 ℃ leads to the formation of 6.3×6.3 phase, which is more stable than the 5×5 phase. The existences of a variety of superstructures of Ga films demonstrates the delicate balance between the interactions of Si(111)-Ga and Ga-Ga. These results shed important light on the epitaxial growth mechanism of Ga films on semiconductor surfaces.

  3. WUS and STM-based reporter genes for studying meristem development in poplar

    USDA-ARS?s Scientific Manuscript database

    We describe the development of a reporter system for monitoring meristem initiation in poplar using promoters of poplar homologs to the meristem-active regulatory genes WUSCHEL (WUS) and SHOOTMERISTEMLESS (STM). When ~3 kb of the 5’ flanking regions of close homologs were used to drive expression o...

  4. STM/STS investigation of edge structure in epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Ridene, M.; Girard, J. C.; Travers, L.; David, C.; Ouerghi, A.

    2012-08-01

    In this paper, we have used low temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS) to study zigzag or armchair edges of epitaxial graphene on 6H-SiC (0001). The monolayer carbon structures exhibit occasionally one-dimensional ridge (1D) in close vicinity to step edge. This ridge exhibits different edges orientations in armchair-zigzag transition which give rise to different local density of states (LDOS) along this 1D structure. This ridge formation is likely explained by residual compressive in-plane stresses.

  5. Non-magnetic impurity effects in LiFeAs studied by STM/STS

    NASA Astrophysics Data System (ADS)

    Hanaguri, T.; Khim, Seung Hyun; Lee, Bumsung; Kim, Kee Hoon; Kitagawa, K.; Matsubayashi, K.; Mazaki, Y.; Uwatoko, Y.; Takigawa, M.; Takagi, H.

    2012-02-01

    Detecting the possible sign reversal of the superconducting gap in iron-based superconductors is highly non-trivial. Here we use non-magnetic impurity as a sign indicator. If the sign of the superconducting gap is positive everywhere in momentum space, in-gap bound state should not be observed near the impurity site unless it is magnetic. On the other hand, if there is a sign-reversal in the gap, even non-magnetic impurity may create in-gap bound state [1]. We performed STM/STS experiments on self-flux and Sn-flux grown LiFeAs crystals and examined the effects of Sn impurity. In STM images of Sn-flux grown samples, we found a ring-like object which may represent Sn. Tunneling spectrum taken at this defect site exhibits in-gap bound state. Together with flat-bottom superconducting gap observed far from the defects, sign-reversing s-wave gap is the most plausible gap structure in LiFeAs. [1] T. Kariyado and M. Ogata, JPSJ 79, 083704 (2010).

  6. Cysteine Catabolism and Cysteine Desulfhydrase (CdsH/STM0458) in Salmonella enterica Serovar Typhimurium

    PubMed Central

    Oguri, Tamiko; Schneider, Barbara

    2012-01-01

    Cysteine is potentially toxic and can affect diverse functions such as oxidative stress, antibiotic resistance, and swarming motility. The contribution of cysteine catabolism in modulating responses to cysteine has not been examined, in part because the genes have not been identified and mutants lacking these genes have not been isolated or characterized. We identified the gene for a previously described cysteine desulfhydrase, which we designated cdsH (formerly STM0458). We also identified a divergently transcribed gene that regulates cdsH expression, which we designated cutR (formerly ybaO, or STM0459). CdsH appears to be the major cysteine-degrading and sulfide-producing enzyme aerobically but not anaerobically. Mutants with deletions of cdsH and ybaO exhibited increased sensitivity to cysteine toxicity and altered swarming motility but unaltered cysteine-enhanced antibiotic resistance and survival in macrophages. PMID:22685283

  7. Computational simulation of subatomic-resolution AFM and STM images for graphene/hexagonal boron nitride heterostructures with intercalated defects

    NASA Astrophysics Data System (ADS)

    Lee, Junsu; Kim, Minjung; Chelikowsky, James R.; Kim, Gunn

    2016-07-01

    Using ab initio density functional calculations, we predict subatomic-resolution atomic force microscopy (AFM) and scanning tunneling microscopy (STM) images of vertical heterostructures of graphene/hexagonal boron nitride (h-BN) with an intercalated metal atom (Li, K, Cr, Mn, Co, or Cu), and study the effects of the extrinsic metal defect on the interfacial coupling. We find that the structural deformation of the graphene/h-BN layer caused by the metal defect strongly affects the AFM images, whereas orbital hybridization between the metal defect and the graphene/h-BN layer characterizes the STM images.

  8. The Impact of Pointing on the Short-Term Memory (STM) of Heterophonic Homographs

    ERIC Educational Resources Information Center

    Vaknin-Nusbaum, Vered; Miller, Paul

    2014-01-01

    This study entailed two short-term memory (STM) experiments investigating the importance of vowel diacritics for the temporary retention of three distinct Hebrew word list types: heterophonic homographs, non-homographs and homophonic homographs. Eighty university students participated in each experiment, with half of them tested with word lists…

  9. Whey protein isolate improves acid and bile tolerances of Streptococcus thermophilus ST-M5 and Lactobacillus delbrueckii ssp. bulgaricus LB-12.

    PubMed

    Vargas, Luis A; Olson, Douglas W; Aryana, Kayanush J

    2015-04-01

    Acid tolerance and bile tolerance are important probiotic characteristics. Whey proteins contain branched-chain amino acids, which play a role in muscle building and are popular among athletes. Increasing emphasis is being placed on diets containing less carbohydrate, less fat, and more protein. The effect of incremental additions of whey protein isolate (WPI) on probiotic characteristics of pure cultures is not known. The objective of this study was to determine the influence of added WPI on acid tolerance and bile tolerance of pure cultures of Streptococcus thermophilus ST-M5 and Lactobacillus bulgaricus LB-12. The WPI was used at 0 (control), 1, 2 and 3% (wt/vol). Assessment of acid tolerance was conducted on pure cultures at 30-min intervals for 2h of acid exposure and bile tolerance at 1-h intervals for 5h of bile exposure. Use of 1, 2, and 3% WPI improved acid tolerance of Strep. thermophilus ST-M5 and Lb. bulgaricus LB-12. The highest counts for acid tolerance of Strep. thermophilus ST-M5 and Lb. bulgaricus LB-12 were obtained when 3% WPI was used. Use of 2 and 3% WPI improved bile tolerance of Strep. thermophilus ST-M5 and Lb. bulgaricus LB-12 over 5h of bile exposure. The use of WPI is recommended to improve acid and bile tolerance of the yogurt culture bacteria Strep. thermophilus ST-M5 and Lb. bulgaricus LB-12. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  10. Ultrathin TiO(x) films on Pt(111): a LEED, XPS, and STM investigation.

    PubMed

    Sedona, Francesco; Rizzi, Gian Andrea; Agnoli, Stefano; Llabrés i Xamena, Francesc X; Papageorgiou, Anthoula; Ostermann, Dieter; Sambi, Mauro; Finetti, Paola; Schierbaum, Klaus; Granozzi, Gaetano

    2005-12-29

    Ultrathin ordered titanium oxide films on Pt(111) surface are prepared by reactive evaporation of Ti in oxygen. By varying the Ti dose and the annealing conditions (i.e., temperature and oxygen pressure), six different long-range ordered phases are obtained. They are characterized by means of low-energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS), and scanning tunneling microscopy (STM). By careful optimization of the preparative parameters, we find conditions where predominantly single phases of TiO(x), revealing distinct LEED pattern and STM images, are produced. XPS binding energy and photoelectron diffraction (XPD) data indicate that all the phases, except one (the stoichiometric rect-TiO2), are one monolayer thick and composed of a Ti-O bilayer with interfacial Ti. Atomically resolved STM images confirm that these TiO(x) phases wet the Pt surface, in contrast to rect-TiO2. This indicates their interface stabilization. At a low Ti dose (0.4 monolayer equivalents, MLE), an incommensurate kagomé-like low-density phase (k-TiO(x) phase) is observed where hexagons are sharing their vertexes. At a higher Ti dose (0.8 MLE), two denser phases are found, both characterized by a zigzag motif (z- and z'-TiO(x) phases), but with distinct rectangular unit cells. Among them, z'-TiO(x), which is obtained by annealing in ultrahigh vacuum (UHV), shows a larger unit cell. When the postannealing of the 0.8 MLE deposit is carried out at high temperatures and high oxygen partial pressures, the incommensurate nonwetting, fully oxidized rect-TiO2 is found The symmetry and lattice dimensions are almost identical with rect-VO2, observed in the system VO(x)/Pd(111). At a higher coverage (1.2 MLE), two commensurate hexagonal phases are formed, namely the w- [(square root(43) x square root(43)) R 7.6 degrees] and w'-TiO(x) phase [(7 x 7) R 21.8 degrees]. They show wagon-wheel-like structures and have slightly different lattice dimensions. Larger Ti deposits

  11. Influence of the State of the Tungsten Tip on STM Topographic Images of SnSe Surfaces

    NASA Astrophysics Data System (ADS)

    Ly, Trinh Thi; Kim, Jungdae

    2018-03-01

    Tin selenide (SnSe) has recently attracted significant attention because of its excellent thermoelectric properties with a figure of merit (ZT) of 2.6. Previous scanning tunneling microscopy (STM) studies of SnSe surfaces showed that only Sn atoms are resolved in topographic images due to the dominant contribution of the Sn 5 p z states in tunneling. However, when the state of the tungsten (W) tip changes from a typical four-lobe d state such as d xy or {d_{{x^2} - {y^2}}} to a two-lobe {d_{{z^2}}} state, the atomic features observed on the SnSe surface in STM topography can be dramatically altered. In this report, we present the results of a systematic study on the influence of the W tip's states on the STM images of SnSe surfaces. Sn atoms are observed with much stronger corrugation amplitude and smaller apparent radius when the tip is in a {d_{{z^2}}} state. In addition, the atomic features of the Se atoms become visible because of the sharply focused shape of the W {d_{{z^2}}} state. We expect our results to provide important information for establishing a better understanding of the microscopic nature of SnSe surfaces.

  12. Initial stages of Lutetium growth on Si (111)-7 × 7 probed by STM and core-level photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Smykalla, Lars; Shukrynau, Pavel; Hietschold, Michael

    2017-09-01

    The interaction of small amounts of Lutetium with the Si (111)-7 × 7 reconstructed surface was investigated in detail using a combination of Scanning Tunneling Microscopy (STM) and Photoelectron Spectroscopy (XPS and UPS). Various immobile and also fastly moving atoms and nanocluster were found in the initial growth of the Lu/Si interface. Density functional theory calculations and photoelectron spectroscopy results suggest that the most attractive adsorption sites for the Lu atoms are basins around Si rest-atoms and there is no strong interaction between Lu and Si at the initial steps of film growth. However Lu nanocluster could also be found on other adsorption sites which results in a different voltage dependence in STM. Coverage-dependent STM images reveal the growth of a closed Lu metal overlayer by joining of the clusters. The existence of a stoichiometric Lu silicide compound was not detected on the surface in the initial growth for deposition at room temperature.

  13. STM contrast of a CO dimer on a Cu(1 1 1) surface: a wave-function analysis.

    PubMed

    Gustafsson, Alexander; Paulsson, Magnus

    2017-12-20

    We present a method used to intuitively interpret the scanning tunneling microscopy (STM) contrast by investigating individual wave functions originating from the substrate and tip side. We use localized basis orbital density functional theory, and propagate the wave functions into the vacuum region at a real-space grid, including averaging over the lateral reciprocal space. Optimization by means of the method of Lagrange multipliers is implemented to perform a unitary transformation of the wave functions in the middle of the vacuum region. The method enables (i) reduction of the number of contributing tip-substrate wave function combinations used in the corresponding transmission matrix, and (ii) to bundle up wave functions with similar symmetry in the lateral plane, so that (iii) an intuitive understanding of the STM contrast can be achieved. The theory is applied to a CO dimer adsorbed on a Cu(1 1 1) surface scanned by a single-atom Cu tip, whose STM image is discussed in detail by the outlined method.

  14. STM contrast of a CO dimer on a Cu(1 1 1) surface: a wave-function analysis

    NASA Astrophysics Data System (ADS)

    Gustafsson, Alexander; Paulsson, Magnus

    2017-12-01

    We present a method used to intuitively interpret the scanning tunneling microscopy (STM) contrast by investigating individual wave functions originating from the substrate and tip side. We use localized basis orbital density functional theory, and propagate the wave functions into the vacuum region at a real-space grid, including averaging over the lateral reciprocal space. Optimization by means of the method of Lagrange multipliers is implemented to perform a unitary transformation of the wave functions in the middle of the vacuum region. The method enables (i) reduction of the number of contributing tip-substrate wave function combinations used in the corresponding transmission matrix, and (ii) to bundle up wave functions with similar symmetry in the lateral plane, so that (iii) an intuitive understanding of the STM contrast can be achieved. The theory is applied to a CO dimer adsorbed on a Cu(1 1 1) surface scanned by a single-atom Cu tip, whose STM image is discussed in detail by the outlined method.

  15. The combinatorial effect of different Equex STM paste concentrations, cryoprotectants and the straw-freezing methods on the post-thaw boar semen quality.

    PubMed

    Wu, T-W; Cheng, F-P; Chen, I-H; Yang, C-H; Tsai, M-Y; Chang, M-H; Wang, J-H; Wu, J-T

    2013-02-01

    This study was to evaluate the combinatorial effect (14 treatments, A-N) of different Equex STM paste concentrations, cryoprotectants and the straw-freezing method on the post-thaw boar semen quality. Two ejaculates were collected from each of nine boars (three boars from each of three breeds). Semen was diluted in extenders with different concentrations of Equex STM paste and different cryoprotectants [glycerol or dimethylacetamide (DMA)] before cryopreserving via liquid nitrogen or dry ice. Motility, viability, percentage of spermatozoa with intense acrosomal staining and with normal morphology of post-thaw sperm were evaluated. The qualities of thawed semen were best preserved in treatment H (extender with 0.5% Equex STM paste and 5% glycerol and freezing by dry ice) and were worst in treatment B (extender with 0% Equex STM paste and 5% DMA and freezing by dry ice). Significant difference (p < 0.05) was present in post-thawed sperm motility (63% vs 27%), sperm viability (70% vs 33%) and sperm acrosomal integrity rate (68% vs 29%) between treatments H and B. However, sperm proportion with normal morphology showed no significant difference among treatments (66% vs 66%; p > 0.05). Moreover, statistical analysis suggests that no significant difference was present in semen quality among breed or individual donors (p > 0.05). These findings suggest that Equex STM paste improved the cryosurvival efficiency of boar sperm, and the favourable straw-freezing method changes between glycerol and DMA. © 2012 Blackwell Verlag GmbH.

  16. STM/BP-Like KNOXI Is Uncoupled from ARP in the Regulation of Compound Leaf Development in Medicago truncatula[C][W][OPEN

    PubMed Central

    Zhou, Chuanen; Han, Lu; Li, Guifen; Chai, Maofeng; Fu, Chunxiang; Cheng, Xiaofei; Wen, Jiangqi; Tang, Yuhong; Wang, Zeng-Yu

    2014-01-01

    Class I KNOTTED-like homeobox (KNOXI) genes are critical for the maintenance of the shoot apical meristem. The expression domain of KNOXI is regulated by ASYMMETRIC LEAVES1/ROUGHSHEATH2/PHANTASTICA (ARP) genes, which are associated with leaf morphology. In the inverted repeat-lacking clade (IRLC) of Fabaceae, the orthologs of LEAFY (LFY) function in place of KNOXI to regulate compound leaf development. Here, we characterized loss-of-function mutants of ARP (PHAN) and SHOOTMERISTEMLESS (STM)- and BREVIPEDICELLUS (BP)-like KNOXI in the model IRLC legume species Medicago truncatula. The function of ARP genes is species specific. The repression of STM/BP-like KNOXI genes in leaves is not mediated by PHAN, and no suppression of PHAN by STM/BP-like KNOXI genes was observed either, indicating that STM/BP-like KNOXI genes are uncoupled from PHAN in M. truncatula. Furthermore, comparative analyses of phenotypic output in response to ectopic expression of KNOXI and the M. truncatula LFY ortholog, SINGLE LEAFLET1 (SGL1), reveal that KNOXI and SGL1 regulate parallel pathways in leaf development. We propose that SGL1 probably functions in a stage-specific manner in the regulation of the indeterminate state of developing leaves in M. truncatula. PMID:24781113

  17. Performance mapping of the STM4-120 kinematic Stirling engine using a statistical design of experiments method

    NASA Astrophysics Data System (ADS)

    Powell, M. A.; Rawlinson, K. S.

    A kinetic Stirling cycle engine, the Stirling Thermal Motors (STM) STM4-120, was tested at the Sandia National Laboratories Engine Test Facility (ETF) from March 1989-August 1992. Sandia is interested in determining this engine's potential for solar-thermal-electric applications. The last round of testing was conducted from July-August 1992 using Sandia-designed gas-fired heat pipe evaporators as the heat input system to the engine. The STM4-120 was performance mapped over a range of sodium vapor temperatures, cooling water temperatures, and cycle pressures. The resulting shaft power output levels ranged from 5-9 kW. The engine demonstrated high conversion efficiency (24-31%) even though the power output level was less than 40% of the rated output of 25 kW. The engine had been previously derated from 25 kW to 10 kW shaft power due to mechanical limitations that were identified by STM during parallel testing at their facility in Ann Arbor, MI. A statistical method was used to design the experiment, to choose the experimental points, and to generate correlation equations describing the engine performance given the operating parameters. The testing was truncated due to a failure of the heat pipe system caused by entrainment of liquid sodium in the condenser section of the heat pipes. Enough data was gathered to generate the correlations and to demonstrate the experimental technique. The correlation is accurate in the experimental space and is simple enough for use in hand calculations and spreadsheet-based system models. Use of this method can simplify the construction of accurate performance and economic models of systems in which the engine is a component. The purpose of this paper is to present the method used to design the experiments and to analyze the performance data.

  18. Space simulation techniques and facilities for SAX STM test campaign

    NASA Technical Reports Server (NTRS)

    Giordano, Pietro; Raimondo, Giacomo; Messidoro, Piero

    1994-01-01

    SAX is a satellite for X-Ray astronomy. It is a major element of the overall basic Science Program of the Italian Space Agency (ASI) and is being developed with the contribution of the Netherlands Agency for Aerospace Programs (NIVR). The scientific objectives of SAX are to carry out systematic and comprehensive observations of celestial X-Ray sources over the 0.1 - 300 KeV energy range with special emphasis on spectral and timing measurements. The satellite will also monitor the X-Ray sky to investigate long-term source variability and to permit localization and study of X-Ray transients. Alenia Spazio is developing the satellite that is intended for launch in the second half of 1995 in a low, near-equatorial Earth orbit. At system level a Structural Thermal Model (STM) has been conceived to verify the environmental requirements by validating the mechanical and thermal analytical models and qualifying satellite structure and thermal control. In particular, the following tests have been carried out in Alenia Spazio, CEA/CESTA and ESTEC facilities: Modal Survey, Centrifuge, Acoustic, Sinusoidal/Random Vibration and Thermal Balance. The paper, after a short introduction of the SAX satellite, summarizes the environmental qualification program performed on the SAX STM. It presents test objectives, methodologies and relevant test configurations. Peculiar aspects of the test campaign are highlighted. Problems encountered and solutions adopted in performing the tests are described as well. Furthermore, test results are presented and assessed.

  19. Ethylene dissociation on flat and stepped Ni(1 1 1): A combined STM and DFT study

    NASA Astrophysics Data System (ADS)

    Vang, Ronnie T.; Honkala, Karoliina; Dahl, Søren; Vestergaard, Ebbe K.; Schnadt, Joachim; Lægsgaard, Erik; Clausen, Bjerne S.; Nørskov, Jens K.; Besenbacher, Flemming

    2006-01-01

    The dissociative adsorption of ethylene (C 2H 4) on Ni(1 1 1) was studied by scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The STM studies reveal that ethylene decomposes exclusively at the step edges at room temperature. However, the step edge sites are poisoned by the reaction products and thus only a small brim of decomposed ethylene is formed. At 500 K decomposition on the (1 1 1) facets leads to a continuous growth of carbidic islands, which nucleate along the step edges. DFT calculations were performed for several intermediate steps in the decomposition of ethylene on both Ni(1 1 1) and the stepped Ni(2 1 1) surface. In general the Ni(2 1 1) surface is found to have a higher reactivity than the Ni(1 1 1) surface. Furthermore, the calculations show that the influence of step edge atoms is very different for the different reaction pathways. In particular the barrier for dissociation is lowered significantly more than the barrier for dehydrogenation, and this is of great importance for the bond-breaking selectivity of Ni surfaces. The influence of step edges was also probed by evaporating Ag onto the Ni(1 1 1) surface. STM shows that the room temperature evaporation leads to a step flow growth of Ag islands, and a subsequent annealing at 800 K causes the Ag atoms to completely wet the step edges of Ni(1 1 1). The blocking of the step edges is shown to prevent all decomposition of ethylene at room temperature, whereas the terrace site decomposition at 500 K is confirmed to be unaffected by the Ag atoms. Finally a high surface area NiAg alloy catalyst supported on MgAl 2O 4 was synthesized and tested in flow reactor measurements. The NiAg catalyst has a much lower activity for ethane hydrogenolysis than a similar Ni catalyst, which can be rationalized by the STM and DFT results.

  20. Monolayer-by-monolayer compositional analysis of InAs/InAsSb superlattices with cross-sectional STM

    DOE PAGES

    Wood, M. R.; Kanedy, K.; Lopez, F.; ...

    2015-02-23

    In this paper, we use cross-sectional scanning tunneling microscopy (STM) to reconstruct the monolayer-by-monolayer composition profile across a representative subset of MBE-grown InAs/InAsSb superlattice layers and find that antimony segregation frustrates the intended compositional discontinuities across both antimonide-on-arsenide and arsenide-on-antimonide heterojunctions. Graded, rather than abrupt, interfaces are formed in either case. We likewise find that the incorporated antimony per superlattice period varies measurably from beginning to end of the multilayer stack. Finally, although the intended antimony discontinuities predict significant discrepancies with respect to the experimentally observed high-resolution x-ray diffraction spectrum, dynamical simulations based on the STM-derived profiles provide an excellentmore » quantitative match to all important aspects of the x-ray data.« less

  1. STM study on the surface structures and defects of SnSe

    NASA Astrophysics Data System (ADS)

    Kim, Jungdae; Duvjir, Ganbat; Ly, Trinh Thi; Min, Taewon; Kim, Taehoon; Kim, Sang Hwa; Duong, Anh-Tuan; Rhim, S. H.; Cho, Sunglae; Lee, Jaekwang

    Tin selenide (SnSe) is a IV-VI semiconductor with a band gap of 1.0 eV, and also one of layered chalcogenide materials (LCMs) where each layer is coupled by weak van der Waals interactions. SnSe has been widely studied due to its many potential applications that take advantage of its excellent thermoelectric, photovoltaic, and optoelectronic properties. However, experimental investigations into the microscopic structure of SnSe remain largely unexplored. The atomic and electronic structures of SnSe surfaces are studied by a home-built low temperature scanning tunneling microscope (STM). The cleaved surface of SnSe is comprised of covalently bonded Se and Sn atoms in zigzag patterns. However, rectangular periodicity was observed in the atomic images of SnSe surfaces for filled and empty state probing. Detailed atomic structures are analyzed by density functional theory (DFT) calculations, indicating that the bright extrusions of both filled and empty state images are mostly located at the positions of Sn atoms. We also report the origin of p-type behavior in SnSe by investigating three dominant intrinsic defects (Sn, Se, and Se-Sn-Se vacancies) using STM and DFT calculations. This work was supported by the National Research Foundation of Korea (NRF-2015R1D1A1A01057271, NRF-2009-0093818, and NRF-2014R1A4A1071686).

  2. Expression patterns of STM-like KNOX and Histone H4 genes in shoot development of the dissected-leaved basal eudicot plants Chelidonium majus and Eschscholzia californica (Papaveraceae).

    PubMed

    Groot, Edwin P; Sinha, Neelima; Gleissberg, Stefan

    2005-06-01

    Knotted-like homeobox (KNOX) genes encode important regulators of shoot development in flowering plants. In Arabidopsis, class I KNOX genes are part of a regulatory system that contributes to indeterminacy of shoot development, delimitation of leaf primordia and internode development. In other species, class I KNOX genes have also been recruited in the control of marginal blastozone fractionation during dissected leaf development. Here we report the isolation of class I KNOX genes from two species of the basal eudicot family Papaveraceae, Chelidonium majus and Eschscholzia californica. Sequence comparisons and expression patterns indicate that these genes are orthologs of SHOOTMERISTEMLESS (STM), a class I KNOX gene from Arabidopsis. Both genes are expressed in the center of vegetative and floral shoot apical meristems (SAM), but downregulated at leaf or floral organ initiating sites. While Eschscholzia californica STM (EcSTM) is again upregulated during acropetal pinna formation, in situ hybridization could not detect Chelidonium majus STM (CmSTM) transcripts at any stage of basipetal leaf development, indicating divergent evolution of STM gene function in leaves within Papaveraceae. Immunolocalization of KNOX proteins indicate that other gene family members may control leaf dissection in both species. The contrasting direction of pinna initiation in the two species was also investigated using Histone H4 expression. Leaves at early stages of development did not reveal notable differences in cell division activity of the elongating leaf axis, suggesting that differential meristematic growth may not play a role in determining the observed dissection patterns.

  3. Recoding between Two Types of STM Representation Revealed by the Dynamics of Memory Search

    ERIC Educational Resources Information Center

    Leszczynski, Marcin; Myers, Nicholas E.; Akyurek, Elkan G.; Schubo, Anna

    2012-01-01

    Visual STM (VSTM) is thought to be related to visual attention in several ways. Attention controls access to VSTM during memory encoding and plays a role in the maintenance of stored information by strengthening memorized content. We investigated the involvement of visual attention in recall from VSTM. In two experiments, we measured…

  4. In-Situ TEM-STM Observations of SWCNT Ropes/Tubular Transformations

    NASA Technical Reports Server (NTRS)

    Sola, F.; Lebron-Colon, M.; Ferreira, P. J.; Fonseca, L. F.; Meador, M. A.; Marin, C.

    2010-01-01

    Single-walled carbon nanotubes (SWCNTs) prepared by the HiPco process were purified using a modified gas phase purification technique. A TEM-STM holder was used to study the morphological changes of SWCNT ropes as a function of applied voltage. Kink formation, buckling behavior, tubular transformation and eventual breakdown of the system were observed. The tubular formation was attributed to a transformation from SWCNT ropes to multi-walled carbon nanotube (MWCNT) structures. It is likely mediated by the patching and tearing mechanism which is promoted primarily by the mobile vacancies generated due to current-induced heating and, to some extent, by electron irradiation.

  5. Deducing 2D crystal structure at the liquid/solid interface with atomic resolution: a combined STM and SFG study.

    PubMed

    McClelland, Arthur A; Ahn, Seokhoon; Matzger, Adam J; Chen, Zhan

    2009-11-17

    Sum frequency generation vibrational spectroscopy (SFG) has been applied to study two-dimensional (2D) crystals formed by an isophthalic acid diester on the surface of highly oriented pyrolytic graphite, providing complementary measurements to scanning tunneling microscopy (STM) and computational modeling. SFG results indicate that both aromatic and C=O groups in the 2D crystal tilt from the surface. This study demonstrates that a combination of SFG and STM techniques can be used to gain a more complete picture of 2D crystal structure, and it is necessary to consider solvent-2D crystal interactions and dynamics in the computer models to achieve an accurate representation of interfacial structure.

  6. Effect of Fe-doping on CDW state in 1T-TaS2 investigated by STM/STS

    NASA Astrophysics Data System (ADS)

    Fujisawa, Y.; Shimabukuro, T.; Kojima, H.; Kobayashi, K.; Demura, S.; Sakata, H.

    2017-07-01

    1T-TaS2 has been known to undergo Mott transition from nearly commensurate charge density wave (CDW) state to commensurate CDW state at about 200 K. Recently, Fe doping was found to suppress the Mott transition and induce superconductivity. In this study, we report on the scanning tunneling microscopy (STM) and spectroscopy (STS) study on Fe doped 1T-TaS2 with different Fe concentration. STM observations reveal that the CDW superlattice becomes irregular as increasing Fe concentration. STS measurements uncover the spatial change in the local density of state (LDOS). We find two types of David-star: one has symmetric LDOS with respect to Fermi energy, and the other has asymmetric one. We identify that the asymmetric spectrum is due to an Fe dopant.

  7. Release from PI in Running Memory: What Does This Tell Us about Developmental STM?

    ERIC Educational Resources Information Center

    Cohen, Ronald L.; Griffiths, Karen

    1987-01-01

    To study age-related improvements in information processing, a release from proactive interference (PI) procedure was used with 144 children in conjunction with a running memory task. For class of item and acoustic similarity, evidence was found for PI release with age, but there was no evidence of a relationship between short-term memory (STM)…

  8. Variable electronic stripe structures of the parent iron-chalcogenide superconductor Fe1 +dTe observed by STM-STS

    NASA Astrophysics Data System (ADS)

    Sugimoto, Akira; Ekino, Toshikazu; Gabovich, Alexander M.

    2014-12-01

    Nanoscale stripe structures of the parent iron-11 superconductor Fe1.033Te were investigated using low-temperature scanning tunnel microscopy-scanning tunnel spectroscopy (STM-STS). STM topographies and d I /d V maps show clear stripe structures with the bias-dependent multiple periods 2 ×a0 and a0, where a0 is the lattice constant ˜0.38 nm. The form of the stripe structures seen on d I /d V maps strongly depends on the bias voltage. Varying stripe structures are apparently driven by magnetic order appearing below the transition temperature Ts˜72 K, that is defined by the noticeable drop in the temperature dependence of resistivity, and are strongly influenced by the underlying excess Fe.

  9. Experimental Investigation of the Electronic Properties of Twisted Bilayer Graphene by STM and STS

    NASA Astrophysics Data System (ADS)

    Yin, Longjing; Qiao, Jiabin; Wang, Wenxiao; Zuo, Weijie; He, Lin

    The electronic properties of graphene multilayers depend sensitively on their stacking order. A twisted angle is treated as a unique degree of freedom to tune the electronic properties of graphene system. Here we study electronic structures of the twisted bilayers by scanning tunneling microscopy (STM) and spectroscopy (STS). We demonstrate that the interlayer coupling strength affects both the Van Hove singularities and the Fermi velocity of twisted bilayers dramatically. This removes the discrepancy about the Fermi velocity renormalization in the twisted bilayers and provides a consistent interpretation of all current data. Moreover, we report the experimental evidence for non-Abelian gauge potentials in twisted graphene bilayers by STM and STS. At a magic twisted angle, about 1.11°, a pronounced sharp peak is observed in the tunnelling spectra due to the action of the non-Abelian gauge fields. Because of the effective non-Abelian gauge fields, the rotation angle could transfer the charge carriers in the twisted bilayers from massless Dirac fermions into well localized electrons, or vice versa, efficiently. This provides a new route to tune the electronic properties of graphene systems, which will be essential in future graphene nanoelectronics.

  10. Adaptation of acoustic model experiments of STM via smartphones and tablets

    NASA Astrophysics Data System (ADS)

    Thees, Michael; Hochberg, Katrin; Kuhn, Jochen; Aeschlimann, Martin

    2017-10-01

    The importance of Scanning Tunneling Microscopy (STM) in today's research and industry leads to the question of how to include such a key technology in physics education. Manfred Euler has developed an acoustic model experiment to illustrate the fundamental measuring principles based on an analogy between quantum mechanics and acoustics. Based on earlier work we applied mobile devices such as smartphones and tablets instead of using a computer to record and display the experimental data and thus converted Euler's experimental setup into a low-cost experiment that is easy to build and handle by students themselves.

  11. STM/STS Study of the Sb (111) Surface

    NASA Astrophysics Data System (ADS)

    Chekmazov, S. V.; Bozhko, S. I.; Smirnov, A. A.; Ionov, A. M.; Kapustin, A. A.

    An Sb crystal is a Peierls insulator. Formation of double layers in the Sb structure is due to the shift of atomic planes (111) next but one along the C3 axis. Atomic layers inside the double layer are connected by covalent bonds. The interaction between double layers is determined mainly by Van der Waals forces. The cleave of an Sb single crystal used to be via break of Van der Waals bonds. However, using scanning tunneling microscopy (STM) and spectroscopy (STS) we demonstrated that apart from islands equal in thickness to the double layer, steps of one atomic layer in height also exist on the cleaved Sb (111) surface. Formation of "unpaired" (111) planes on the surface leads to a local break of conditions of Peierls transition. STS experiment reveals higher local density of states (LDOS) measured for "unpaired" (111) planes in comparison with those for the double layer.

  12. pSTM6-275, a Conjugative IncHI2 Plasmid of Salmonella enterica That Confers Antibiotic and Heavy-Metal Resistance under Changing Physiological Conditions.

    PubMed

    Billman-Jacobe, Helen; Liu, Yuhong; Haites, Ruth; Weaver, Tom; Robinson, Lily; Marenda, Marc; Dyall-Smith, Mike

    2018-05-01

    Detailed annotation of an IncHI2 plasmid, pSTM6-275, from Salmonella enterica serotype 1,4,5,12:i:- strain TW-Stm6 revealed a composite structure, including antimicrobial resistance genes on mobile genetic elements. The plasmid was thermosensitive for transfer to Escherichia coli and conferred reduced susceptibility to antibiotics, copper sulfate, and silver nitrate. Metal ion susceptibility was dependent on physiological conditions, giving an insight into the environments where this trait might confer a fitness advantage. Copyright © 2018 Billman-Jacobe et al.

  13. STM/STS Study of LixCoO2 Single Crystals

    NASA Astrophysics Data System (ADS)

    Iwaya, Katsuya; Minato, Taketoshi; Miyoshi, Kiyotaka; Takeuchi, Jun; Kim, Yousoo; Hitosugi, Taro

    2012-02-01

    We have performed low temperature scanning tunneling microscopy/spectroscopy (STM/STS) measurements on LixCoO2 (x=0.66) single crystal surfaces. A (1x1) hexagonal lattice was clearly observed and found to be moved by changing bias-voltage polarity, indicating that this could be associated with Li ions on the surface. Under the (1x1) hexagonal lattice, we imaged almost randomly distributed bright dots that were strongly dependent on bias-voltage, with insulating spectroscopic features. Different area on the surface showed a (2x2) hexagonal lattice that could be related to an ordering of Co^3+ and Co^4+ ions. These results suggest the electronic structure of LixCoO2 surface is inhomogeneous possibly due to segregation of Li ions.

  14. Effects of Orthographic and Phonological Word Length on Memory for Lists Shown at RSVP and STM Rates

    ERIC Educational Resources Information Center

    Coltheart, Veronika; Mondy, Stephen; Dux, Paul E.; Stephenson, Lisa

    2004-01-01

    This article reports 3 experiments in which effects of orthographic and phonological word length on memory were examined for short lists shown at rapid serial visual presentation (RSVP) and short-term memory (STM) rates. Only visual-orthographic length reduced RSVP serial recall, whereas both orthographic and phonological length lowered recall for…

  15. New sub-family of lysozyme-like proteins shows no catalytic activity: crystallographic and biochemical study of STM3605 protein from Salmonella Typhimurium

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

    Michalska, Karolina; Brown, Roslyn N.; Li, Hui

    Phage viruses that infect prokaryotes integrate their genome into the host chromosome; thus, microbial genomes typically contain genetic remnants of both recent and ancient phage infections. Often phage genes occur in clusters of atypical G+C content that reflect integration of the foreign DNA. However, some phage genes occur in isolation without other phage gene neighbors, probably resulting from horizontal gene transfer. In these cases, the phage gene product is unlikely to function as a component of a mature phage particle, and instead may have been co-opted by the host for its own benefit. The product of one such gene frommore » Salmonella enterica serovar Typhimurium, STM3605, encodes a protein with modest sequence similarity to phage-like lysozyme (N-acetylmuramidase) but appears to lack essential catalytic residues that are strictly conserved in all lysozymes. Close homologs in other bacteria share this characteristic. The structure of the STM3605 protein was characterized by X-ray crystallography, and functional assays showed that it is a stable, folded protein whose structure closely resembles lysozyme. However, this protein is unlikely to hydrolyze peptidoglycan. Instead, STM3605 is presumed to have evolved an alternative function because it shows some lytic activity and partitions to micelles.« less

  16. STM imaging ortho- and para-fluorothiophenol self-assembled monolayers on Au(111).

    PubMed

    Jiang, Peng; Deng, Ke; Fichou, Denis; Xie, Si-Shen; Nion, Aymeric; Wang, Chen

    2009-05-05

    Self-assembled monolayers (SAMs) of para- and ortho-fluorothiophenol (p- and o-FTP) spontaneously formed on Au(111) substrate have been contrasted through investigation by a scanning tunneling microscope (STM) at room temperature. High-resolution STM imaging reveals that p-FTP adopts a 6 x radical3R30 degrees molecule arrangement containing six molecules. Two different kinds of p-FTP molecule dimer line structures have been formed on Au(111) by intermolecular pi-pi stacking along 112 substrate directions, besides a single p-FTP molecule line. In contrast, o-FTP molecules self-assemble into a much looser wave-like SAM, which can be described as a 5 x 3 radical3R30 degrees structure containing two molecules. Periodic density functional theory (DFT) calculations for the two systems suggest that these kinds of FTP molecules preferentially take the asymmetrical positions between 3-fold face-centered cubic (fcc) hollow and bridge sites on Au(111), tilting from the substrate surface. Theoretical simulation gives apparent average tilted angles of 58 degrees and 68 degrees for p-FTP and o-FTP with respect to the surface normal, respectively. This simulation shows that o-FTP is more inclined to lie down toward the Au(111) surface compared to p-FTP. The difference between p-FTP and o-FTP SAM structures can be qualitatively understood in terms of the variation of intermolecular dipole-dipole orientation. This suggests that, besides well-known Au-S and pi-pi interactions, electrostatic interactions including dipole-dipole, quadrupole-quadrupole, and dipole-quadrupole interactions might also play an important role in influencing the SAM structures formed by aromatic thiols with a permanent dipole moment.

  17. Exploring routes to tailor the physical and chemical properties of oxides via doping: an STM study

    NASA Astrophysics Data System (ADS)

    Nilius, Niklas

    2015-08-01

    Doping opens fascinating possibilities for tailoring the electronic, optical, magnetic, and chemical properties of oxides. The dopants perturb the intrinsic behavior of the material by generating charge centers for electron transfer into adsorbates, by inducing new energy levels for electronic and optical excitations, and by altering the surface morphology and hence the adsorption and reactivity pattern. Despite a vivid scientific interest, knowledge on doped oxides is limited when compared to semiconductors, which reflects the higher complexity and the insulating nature of many oxides. In fact, atomic-scale studies, aiming at a mechanistic understanding of dopant-related processes, are still scarce. In this article, we review our scanning tunneling microscopy (STM) experiments on thin, crystalline oxide films with a defined doping level. We demonstrate how the impurities alter the surface morphology and produce cationic/anionic vacancies in order to keep the system charge neutral. We discuss how individual dopants can be visualized in the lattice, even if they reside in subsurface layers. By means of STM-conductance and x-ray photoelectron spectroscopy, we determine the electronic impact of dopants, including the energies of their eigen states and local band-bending effects in the host oxide. Electronic transitions between dopant-induced gap states give rise to new optical modes, as detected with STM luminescence spectroscopy. From a chemical perspective, dopants are introduced to improve the redox potential of oxide materials. Electron transfer from Mo-donors, for example, alters the growth behavior of gold and activates O2 molecules on a wide-gap CaO surface. Such results demonstrate the enormous potential of doped oxides in heterogeneous catalysis. Our experiments address the issue of doping from a fundamental viewpoint, posing questions on the lattice position, charge state, and electron-transfer potential of the impurity ions. Whether doped oxides are

  18. Deducing 2D Crystal Structure at the Solid/Liquid Interface with Atomic Resolution by Combined STM and SFG Study

    NASA Astrophysics Data System (ADS)

    McClelland, Arthur; Ahn, Seokhoon; Matzger, Adam J.; Chen, Zhan

    2009-03-01

    Supplemented by computed models, Scanning Tunneling Microscopy (STM) can provide detailed structure of 2D crystals formed at the liquid/solid interface with atomic resolution. However, some structural information such as functional group orientations in such 2D crystals needs to be tested experimentally to ensure the accuracy of the deduced structures. Due to the limited sensitivity, many other experimental techniques such as Raman and infrared spectroscopy have not been allowed to provide such structural information of 2D crystals. Here we showed that Sum Frequency Generation Vibrational Spectroscopy (SFG) can measure average orientation of functional groups in such 2D crystals, or physisorbed monolayers, providing key experimental data to aid in the modeling and interpretation of the STM images. The usefulness of combining these two techniques is demonstrated with a phthalate diesters monolayer formed at the 1-phenyloctane/ highly oriented pyrolytic graphite (HOPG) interface. The spatial orientation of the ester C=O of the monolayer was successfully determined using SFG.

  19. The spatial distributions of large gap-like structure on Fe(Se,Te) single crystals observed by STM/STS

    NASA Astrophysics Data System (ADS)

    Sugimoto, Akira; Sakai, Yuta; Nagasaka, Kouhei; Ekino, Toshikazu

    2015-11-01

    The nanoscale spatial distributions of large gap-like structure on superconducting FeSe1-xTex were investigated by scanning tunneling microscopy/spectroscopy (STM/STS). The STM topography shows regular atomic lattice arrangements with the lattice spacing ∼0.38 nm, together with the randomly distributed large spots due to the excess Fe atoms. From the STS measurements, the small gap structures of Δ ∼ 7 meV were partly observed. On the other hand, the high-bias dI/dV curves exhibit the broad peak structures at the negative biases of VPG = -200 to -400 mV in the measured whole surface area. The average of these large gaps is |VPGave| ∼ 305 mV with the standard deviation of σ ∼ 48 mV. The spatial distributions of the VPG exhibit the domain structures consisting of the relatively smaller gaps (<250 meV), which correspond to the excess Fe positions. The small gap Δ ∼ 7 meV is also observed at those positions, suggesting that the excess Fe affects the electronic structures of FeSe1-xTex.

  20. Structure of the orthorhombic Al13Co4(100) surface using LEED, STM, and ab initio studies

    NASA Astrophysics Data System (ADS)

    Shin, Heekeun; Pussi, K.; Gaudry, É.; Ledieu, J.; Fournée, V.; Alarcón Villaseca, S.; Dubois, J.-M.; Grin, Yu.; Gille, P.; Moritz, W.; Diehl, R. D.

    2011-08-01

    In a combined scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and density functional theory (DFT) study of the surface of Al13Co4(100), all techniques have found that after annealing to 1165 K, the surface structure is consistent with a dense Al-rich plane with surface Co atom depletion. Various structure models were considered, and in the LEED study, the best agreement was found with a model that consists of Al-rich terminating planes with no Co atoms, and otherwise a structure similar to the bulk puckered layers. This structure was also found to be stable in the DFT study. The best-fit structural parameters are presented for the two domains of this structure, which contain bipentagons that can be related to the pentagonal bipyramidal structures in the bulk, plus additional glue atoms between them. These domains are not strictly related to each other by symmetry, as they have different surface relaxations. The STM study found significant differences in the surfaces of samples grown by different methods and is able to explain a different interpretation made in an earlier study.

  1. A new recipe for preparing oxidized TiO2(1 1 0) surfaces: An STM study

    NASA Astrophysics Data System (ADS)

    Hansen, Jonas Ø.; Matthiesen, Jesper; Lira, Estephania; Lammich, Lutz; Wendt, Stefan

    2017-12-01

    Using high-resolution scanning tunneling microscopy (STM), we have studied the oxidation of rutile TiO2(1 1 0)-(1 × 1) surfaces with Had species at room temperature. We followed the evolution of various stable species as function of the O2 exposure, and the nature of the ultimately dominating species in the Ti troughs is described. When O2 saturation was accomplished using a glass-capillary array doser, we found that on-top O (Oot) adatoms are the predominant surface species. In contrast, when O2 was supplied via backfilling of the chamber the predominant surface species are tentatively assigned to terminal OH groups. We argue that unintended reactions with the chamber walls have a strong influence on the formed surface species, explaining scattered results in the literature. On the basis of our STM data we propose an alternative, easy way of preparing oxidized TiO2(1 1 0) surfaces with Oot adatoms (o-TiO2). It is certain that o-TiO2(1 1 0) surfaces prepared according to this recipe do not have any residual surface O vacancies. This contradicts the situation when oxidizing reduced TiO2(1 1 0) surfaces with O vacancies, where some O vacancies persist.

  2. Diffusion of anthracene derivatives on Cu(111) studied by STM and DFT

    NASA Astrophysics Data System (ADS)

    Wyrick, Jonathan; Bartels, Ludwig; Einstein, Theodore

    2014-03-01

    Substituted anthracenes have drawn attention due to their ability to diffuse uniaxially on a Cu(111) surface. We compare anthracene to three of its derivatives whose 9,10 hydrogens are replaced by elements of the chalcogen group that act as linkers binding the molecules to a Cu(111) substrate. DFT calculations shed light on STM imaging and diffusion studies on the three substituted species. We present an analysis of the DFT results in which energetic contributions to the diffusion barriers are partitioned among the Kohn-Sham orbitals, allowing us to make assignments as to how each orbital affects diffusion for each species and draw comparisons between them. Present address: Center for Nanoscale Science and Technology, NIST, Gaithersburg, MD.

  3. New Pt/Alumina model catalysts for STM and in situ XPS studies

    NASA Astrophysics Data System (ADS)

    Nartova, Anna V.; Gharachorlou, Amir; Bukhtiyarov, Andrey V.; Kvon, Ren I.; Bukhtiyarov, Valerii I.

    2017-04-01

    The new Pt/alumina model catalysts for STM and in situ XPS studies based on thin alumina film formed over the conductive substrate are proposed. Procedure of platinum deposition developed for porous alumina was adapted for the model alumina support. The set of Pt/AlOx-film samples with the different mean platinum particle size was prepared. Capabilities of in situ XPS investigations of the proposed catalysts were demonstrated in study of NO decomposition on platinum nanoparticles. It is shown that proposed model catalysts behave similarly to Pt/γ-Al2O3 and provide the new opportunities for the instrumental studies of platinum catalysts due to resolving several issues (charging, heating, screening) that are typical for the investigation of the porous oxide supported catalysts.

  4. FI-STM study of hydrogen adsorption on Si(100) surface

    NASA Astrophysics Data System (ADS)

    Hua, Lu; Xiang-dong, Wang; Motai, K.; Hashizume, T.; Sakurai, T.

    1992-11-01

    Chemisorption of atomic hydrogen on the Si(100)2 × 1 surface has been investigated in detail by using a field ion-scanning tunneling microscope (FI-STM). The results showed that the adsorption geometry changed from the 2 × 1 monohydride phase to the 1 × 1 dihydride phase with increasing exposure of hydrogen. The data of desorption of the hydrogen-saturated Si surface showed that on annealing at 670 K the surface becomes highly disordered: the 1 × 1 dihydride structure is eliminated and the 2 × 1 reconstructed monohydride is also hardly to identify. When the temperature rises to as high as 730 K, the surface is dominated by the 2 × 1 structure with missing dimer rows, and some adatom chains occur on the Si substrate terraces. We attribute the formation of these atomic chains to an epitaxial growth of Si atoms which are formed by the dissociation of SiHx (x = 1, 2, 3 or 4) compounds on the Si surface.

  5. Single Crystal Synthesis and STM Studies of High Temperature Superconductors

    NASA Technical Reports Server (NTRS)

    Barrientos, Alfonso

    1997-01-01

    This is a final report for the work initiated in September of 1994 under the grant NAG8-1085 - NASA/OMU, on the fabrication of bulk and single crystal synthesis, specific heat measuring and STM studies of high temperature superconductors. Efforts were made to fabricate bulk and single crystals of mercury based superconducting material. A systematic thermal analysis on the precursors for the corresponding oxides and carbonates were carried out to synthesized bulk samples. Bulk material was used as seed in an attempt to grow single crystals by a two-step self flux process. On the other hand bulk samples were characterized by x-ray diffraction, electrical resistivity and magnetic susceptibility, We studied the specific heat behavior in the range from 80 to 300 K. Some preliminary attempts were made to study the atomic morphology of our samples. As part of our efforts we built an ac susceptibility apparatus for measuring the transition temperature of our sintered samples.

  6. Acquisition and diversification of tendrilled leaves in Bignonieae (Bignoniaceae) involved changes in expression patterns of SHOOTMERISTEMLESS (STM), LEAFY/FLORICAULA (LFY/FLO), and PHANTASTICA (PHAN).

    PubMed

    Sousa-Baena, Mariane Silveira; Lohmann, Lúcia G; Rossi, Magdalena; Sinha, Neelima R

    2014-02-01

    Leaves have undergone structural modifications over evolutionary time, and presently exist in many forms. For instance, in Fabaceae and Bignoniaceae, leaf parts can be modified into tendrils. Currently, no data are available on genic control of tendrilled leaf development outside Fabaceae. Here, we conducted a detailed study of three representatives of Bignonieae: Amphilophium buccinatorium, Dolichandra unguis-cati, and Bignonia callistegioides, bearing multifid, trifid, and simple-tendrilled leaves, respectively. We investigated the structure of their petioles, petiolules, leaflets, and tendrils through histological analyses. Additionally, the expression of SHOOTMERISTEMLESS (STM), PHANTASTICA (PHAN), and LEAFY/FLORICAULA (LFY/FLO) during leaf development was analyzed by in situ hybridizations. Tendrils share some anatomical similarities with leaflets, but not with other leaf parts. Transcripts of both STM and LFY/FLO were detected in leaf primordia, associated with regions from which leaflets and tendril branches originate. PHAN expression was found to be polarized in branched tendrils, but not in simple tendrils. In Bignonieae, tendrils are modified leaflets that, as a result of premature completion of development, become bladeless organs. Bignonieae leaves develop differently from those of peas, as both LFY/FLO and STM are expressed in developing leaves of Bignonieae. Moreover, PHAN is probably involved in tendril diversification in Bignonieae, as it has distinct expression patterns in different leaf types. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  7. Phase transition on the Si(001) clean surface prepared in UHV MBE chamber: a study by high-resolution STM and in situ RHEED

    PubMed Central

    2011-01-01

    The Si(001) surface deoxidized by short annealing at T ~ 925°C in the ultrahigh vacuum molecuar beam epitaxy chamber has been in situ investigated using high-resolution scanning tunneling microscopy (STM)and redegreesected high-energy electron diffraction (RHEED. RHEED patterns corresponding to (2 × 1) and (4 × 4) structures were observed during sample treatment. The (4 × 4) reconstruction arose at T ≲ 600°C after annealing. The reconstruction was observed to be reversible: the (4 × 4) structure turned into the (2 × 1) one at T ≳ 600°C, the (4 × 4) structure appeared again at recurring cooling. The c(8 × 8) reconstruction was revealed by STM at room temperature on the same samples. A fraction of the surface area covered by the c(8 × 8) structure decreased, as the sample cooling rate was reduced. The (2 × 1) structure was observed on the surface free of the c(8 × 8) one. The c(8 × 8) structure has been evidenced to manifest itself as the (4 × 4) one in the RHEED patterns. A model of the c(8 × 8) structure formation has been built on the basis of the STM data. Origin of the high-order structure on the Si(001) surface and its connection with the epinucleation phenomenon are discussed. PACS 68.35.B-·68.37.Ef·68.49.Jk·68.47.Fg PMID:21711733

  8. STM/STS study of graphene directly grown on h-BN films on Cu foils

    NASA Astrophysics Data System (ADS)

    Jang, Won-Jun; Wang, Min; Jang, Seong-Gyu; Kim, Minwoo; Park, Seong-Yong; Kim, Sang-Woo; Kahng, Se-Jong; Choi, Jae-Young; Song, Young; Lee, Sungjoo; Sanit Collaboration; Department Of Physics, Korea University Collaboration; Graphene Research Center, Samsung Advanced Institute Of Technology Collaboration

    2013-03-01

    Graphene-based devices on standard SiO2 substrate commonly exhibit inferior characteristics relative to the expected intrinsic properties of graphene, due to the disorder existing at graphene-SiO2 interface. Recently, it has been shown that exfoliated and chemical vapor deposition (CVD) graphene transferred onto hexagonal boron nitride (h-BN) possesses significantly reduced charge inhomogeneity, and yields improved device performance. Here we report the scanning tunneling microscopy (STM) and spectroscopy (STS) results obtained from a graphene layer directly grown on h-BN insulating films on Cu foils. STS measurements illustrate that graphene/h-BN film is charge neutral without electronic perturbation from h-BN/Cu substrate. Corresponding Author

  9. Transcriptomic profiling of Burkholderia phymatum STM815, Cupriavidus taiwanensis LMG19424 and Rhizobium mesoamericanum STM3625 in response to Mimosa pudica root exudates illuminates the molecular basis of their nodulation competitiveness and symbiotic evolutionary history.

    PubMed

    Klonowska, Agnieszka; Melkonian, Rémy; Miché, Lucie; Tisseyre, Pierre; Moulin, Lionel

    2018-01-30

    Rhizobial symbionts belong to the classes Alphaproteobacteria and Betaproteobacteria (called "alpha" and "beta"-rhizobia). Most knowledge on the genetic basis of symbiosis is based on model strains belonging to alpha-rhizobia. Mimosa pudica is a legume that offers an excellent opportunity to study the adaptation toward symbiotic nitrogen fixation in beta-rhizobia compared to alpha-rhizobia. In a previous study (Melkonian et al., Environ Microbiol 16:2099-111, 2014) we described the symbiotic competitiveness of M. pudica symbionts belonging to Burkholderia, Cupriavidus and Rhizobium species. In this article we present a comparative analysis of the transcriptomes (by RNAseq) of B. phymatum STM815 (BP), C. taiwanensis LMG19424 (CT) and R. mesoamericanum STM3625 (RM) in conditions mimicking the early steps of symbiosis (i.e. perception of root exudates). BP exhibited the strongest transcriptome shift both quantitatively and qualitatively, which mirrors its high competitiveness in the early steps of symbiosis and its ancient evolutionary history as a symbiont, while CT had a minimal response which correlates with its status as a younger symbiont (probably via acquisition of symbiotic genes from a Burkholderia ancestor) and RM had a typical response of Alphaproteobacterial rhizospheric bacteria. Interestingly, the upregulation of nodulation genes was the only common response among the three strains; the exception was an up-regulated gene encoding a putative fatty acid hydroxylase, which appears to be a novel symbiotic gene specific to Mimosa symbionts. The transcriptional response to root exudates was correlated to each strain nodulation competitiveness, with Burkholderia phymatum appearing as the best specialised symbiont of Mimosa pudica.

  10. Self-assembled organic radicals on Au(111) surfaces: a combined ToF-SIMS, STM, and ESR study.

    PubMed

    Mannini, Matteo; Sorace, Lorenzo; Gorini, Lapo; Piras, Federica M; Caneschi, Andrea; Magnani, Agnese; Menichetti, Stefano; Gatteschi, Dante

    2007-02-27

    Electron spin resonance (ESR), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and scanning tunneling microscopy (STM) have been used in parallel to characterize the deposition on gold surface of a series of nitronyl nitroxide radicals. These compounds have been specifically synthesized with methyl-thio linking groups suitable to interact with the gold surface to form self-assembled monolayers (SAMs), which can be considered relevant in the research for molecular-based spintronics devices, as suggested in recent papers. The degree of the expected ordering on the surface of these SAMs has been tuned by varying the chemical structure of synthesized radicals. ToF-SIMS has been used to support the evidence of the occurrence of the deposition process. STM has shown the different qualities of the obtained SAMs, with the degree of local order increasing as the degree of freedom of the molecules on the surface is decreased. Finally, ESR has confirmed that the deposition process does not affect the paramagnetic characteristics of radicals and that it affords a complete single-layered coverage of the surface. Further, the absence of angular dependence in the spectra indicates that the small regions of local ordering do not give rise to a long-range order and suggests a quite large mobility of the radical on the surface, probably due to the weak interaction with gold provided by the methyl-thio linking group.

  11. Investigation of local tunneling current noise spectra on the silicon crystal surfaces by means of STM/STS

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

    Mantsevich, V. N., E-mail: vmantsev@spmlab.phys.msu.su; Maslova, N. S.; Cao, G. Y.

    We report on a careful analysis of the local tunneling conductivity by means of ultra-high vacuum scanning tunneling microscopy/spectroscopy (STM/STS) technique in the vicinity of low-dimensional structures on the Si(111)–(7 × 7) and Si(110)–(16 × 2) surfaces. The power-law exponent α of low-frequency tunneling current noise spectra is investigated for different values of the tunneling contact parameters: relaxation rates, the localized state coupling, and the tunneling barrier width and height.

  12. Investigation of local tunneling current noise spectra on the silicon crystal surfaces by means of STM/STS

    NASA Astrophysics Data System (ADS)

    Mantsevich, V. N.; Maslova, N. S.; Cao, G. Y.

    2015-08-01

    We report on a careful analysis of the local tunneling conductivity by means of ultra-high vacuum scanning tunneling microscopy/spectroscopy (STM/STS) technique in the vicinity of low-dimensional structures on the Si(111)-(7 × 7) and Si(110)-(16 × 2) surfaces. The power-law exponent α of low-frequency tunneling current noise spectra is investigated for different values of the tunneling contact parameters: relaxation rates, the localized state coupling, and the tunneling barrier width and height.

  13. Ordering of Zn-centered porphyrin and phthalocyanine on TiO2(011): STM studies

    PubMed Central

    Godlewski, Szymon; Such, Bartosz; Pawlak, Rémy; Hinaut, Antoine; Jöhr, Res; Glatzel, Thilo; Meyer, Ernst; Szymonski, Marek

    2017-01-01

    Zn(II)phthalocyanine molecules (ZnPc) were thermally deposited on a rutile TiO2(011) surface and on Zn(II)meso-tetraphenylporphyrin (ZnTPP) wetting layers at room temperature and after elevated temperature thermal processing. The molecular homo- and heterostructures were characterized by high-resolution scanning tunneling microscopy (STM) at room temperature and their geometrical arrangement and degree of ordering are compared with the previously studied copper phthalocyanine (CuPc) and ZnTPP heterostructures. It was found that the central metal atom may play some role in ordering and growth of phthalocyanine/ZnTPP heterostructures, causing differences in stability of upright standing ZnPc versus CuPc molecular chains at given thermal annealing conditions. PMID:28144569

  14. Measurements of auditory-verbal STM span in aphasia: effects of item, task, and lexical impairment.

    PubMed

    Martin, Nadine; Ayala, Jennifer

    2004-06-01

    In the first part of this study, we investigated effects of item and task type on span performance in a group of aphasic individuals with word processing and STM deficits. Group analyses revealed significant effects of item on span performance with span being greater for digits than for words. We also investigated associations between subjects' lexical-semantic and phonological processing abilities and performance on four measures of verbal span (digit and word span, each varied for type of response, verbal vs. pointing) as well as one measure of nonverbal span. We predicted and found that the patterns of association between verbal span tasks and lexical abilities reflected the integrity of language processes and representations deployed in each paradigm used to assess span. Performance on the pointing span task, which engages both lexical-semantic and phonological processes, correlated with measures of both lexical-semantic and phonological abilities. Performance on repetition span, which engages primarily input and output phonological processes, correlated with measures of phonological abilities but not measures of lexical-semantic abilities. However, when partial correlations were performed for two subject groups based on their relative preservation of lexical-semantic ability (less or more than phonological ability), repetition span correlated with lexical-semantic measures only in the subgroup with relatively impaired lexical-semantics. Additionally, performance on the nonverbal span task correlated with measures of phonological abilities, suggesting either a general cognitive deficit affecting verbal and nonverbal STM or possibly, the use of a verbal strategy to perform this task. Our discussion focuses on the interpretation of span measurements in clinical practice and research, as well as the implications of these data for theories of short-term memory and word processing.

  15. Two-color field enhancement at an STM junction for spatiotemporally resolved photoemission

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

    Meng, Xiang; Jin, Wencan; Yang, Hao

    Here, we report measurements and numerical simulations of ultrafast laser-excited carrier flow across a scanning tunneling microscope (STM) junction. The current from a nanoscopic tungsten tip across a ~1 nm vacuum gap to a silver surface is driven by a two-color excitation scheme that uses an optical delay-modulation technique to extract the two-color signal from background contributions. The role of optical field enhancements in driving the current is investigated using density functional theory and full three-dimensional finite-difference time-domain computations. We find that simulated field-enhanced two-photon photoemission (2PPE) currents are in excellent agreement with the observed exponential decay of the two-colormore » photoexcited current with increasing tip–surface separation, as well as its optical-delay dependence. The results suggest an approach to 2PPE with simultaneous subpicosecond temporal and nanometer spatial resolution.« less

  16. Two-color field enhancement at an STM junction for spatiotemporally resolved photoemission

    DOE PAGES

    Meng, Xiang; Jin, Wencan; Yang, Hao; ...

    2017-06-30

    Here, we report measurements and numerical simulations of ultrafast laser-excited carrier flow across a scanning tunneling microscope (STM) junction. The current from a nanoscopic tungsten tip across a ~1 nm vacuum gap to a silver surface is driven by a two-color excitation scheme that uses an optical delay-modulation technique to extract the two-color signal from background contributions. The role of optical field enhancements in driving the current is investigated using density functional theory and full three-dimensional finite-difference time-domain computations. We find that simulated field-enhanced two-photon photoemission (2PPE) currents are in excellent agreement with the observed exponential decay of the two-colormore » photoexcited current with increasing tip–surface separation, as well as its optical-delay dependence. The results suggest an approach to 2PPE with simultaneous subpicosecond temporal and nanometer spatial resolution.« less

  17. A Safe Vaccine (DV-STM-07) against Salmonella Infection Prevents Abortion and Confers Protective Immunity to the Pregnant and New Born Mice

    PubMed Central

    Negi, Vidya Devi; Nagarajan, Arvindhan G.; Chakravortty, Dipshikha

    2010-01-01

    Pregnancy is a transient immuno-compromised condition which has evolved to avoid the immune rejection of the fetus by the maternal immune system. The altered immune response of the pregnant female leads to increased susceptibility to invading pathogens, resulting in abortion and congenital defects of the fetus and a subnormal response to vaccination. Active vaccination during pregnancy may lead to abortion induced by heightened cell mediated immune response. In this study, we have administered the highly attenuated vaccine strain ΔpmrG-HM-D (DV-STM-07) in female mice before the onset of pregnancy and followed the immune reaction against challenge with virulent S. Typhimurium in pregnant mice. Here we demonstrate that DV-STM-07 vaccine gives protection against Salmonella in pregnant mice and also prevents Salmonella induced abortion. This protection is conferred by directing the immune response towards Th2 activation and Th1 suppression. The low Th1 response prevents abortion. The use of live attenuated vaccine just before pregnancy carries the risk of transmission to the fetus. We have shown that this vaccine is safe as the vaccine strain is quickly eliminated from the mother and is not transmitted to the fetus. This vaccine also confers immunity to the new born mice of vaccinated mothers. Since there is no evidence of the vaccine candidate reaching the new born mice, we hypothesize that it may be due to trans-colostral transfer of protective anti-Salmonella antibodies. These results suggest that our vaccine DV-STM-07 can be very useful in preventing abortion in the pregnant individuals and confer immunity to the new born. Since there are no such vaccine candidates which can be given to the new born and to the pregnant women, this vaccine holds a very bright future to combat Salmonella induced pregnancy loss. PMID:20161765

  18. Template growth of Au, Ni and Ni–Au nanoclusters on hexagonal boron nitride/Rh(111): a combined STM, TPD and AES study

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

    Wu, Fanglue; Huang, Dali; Yue, Yuan

    In this study, the template growth of Au, Ni, and Ni–Au bimetallic nanoclusters on hexagonal boron nitride/Rh(111), i.e. h-BN/Rh(111), was investigated via scanning tunneling microscopy (STM), temperature programmed-desorption (TPD), and Auger electron spectroscopy (AES). STM study shows that template growth of Au clusters on h-BN/Rh(111) forms mainly well-dispersed monolayer clusters. In contrast, Ni forms large multilayer clusters showing a relatively high diffusivity on h-BN/Rh(111) substrate. Ni–Au bimetallic clusters are effectively formed first by Au deposition followed by Ni deposition, with the Au clusters functioning as nucleation sites for the subsequently deposited Ni. Further structural analysis was carried out via TPDmore » and AES. The resulting TPD and AES data show the surface composition and charge transfer between Au and Ni of the bimetallic clusters. These results suggest that the h-BN/Rh(111) substrate represents a unique candidate for supporting Ni–Au bimetallic clusters in further catalytic reactions.« less

  19. Template growth of Au, Ni and Ni–Au nanoclusters on hexagonal boron nitride/Rh(111): a combined STM, TPD and AES study

    DOE PAGES

    Wu, Fanglue; Huang, Dali; Yue, Yuan; ...

    2017-09-12

    In this study, the template growth of Au, Ni, and Ni–Au bimetallic nanoclusters on hexagonal boron nitride/Rh(111), i.e. h-BN/Rh(111), was investigated via scanning tunneling microscopy (STM), temperature programmed-desorption (TPD), and Auger electron spectroscopy (AES). STM study shows that template growth of Au clusters on h-BN/Rh(111) forms mainly well-dispersed monolayer clusters. In contrast, Ni forms large multilayer clusters showing a relatively high diffusivity on h-BN/Rh(111) substrate. Ni–Au bimetallic clusters are effectively formed first by Au deposition followed by Ni deposition, with the Au clusters functioning as nucleation sites for the subsequently deposited Ni. Further structural analysis was carried out via TPDmore » and AES. The resulting TPD and AES data show the surface composition and charge transfer between Au and Ni of the bimetallic clusters. These results suggest that the h-BN/Rh(111) substrate represents a unique candidate for supporting Ni–Au bimetallic clusters in further catalytic reactions.« less

  20. Design of PID temperature control system based on STM32

    NASA Astrophysics Data System (ADS)

    Zhang, Jianxin; Li, Hailin; Ma, Kai; Xue, Liang; Han, Bianhua; Dong, Yuemeng; Tan, Yue; Gu, Chengru

    2018-03-01

    A rapid and high-accuracy temperature control system was designed using proportional-integral-derivative (PID) control algorithm with STM32 as micro-controller unit (MCU). The temperature control system can be applied in the fields which have high requirements on the response speed and accuracy of temperature control. The temperature acquisition circuit in system adopted Pt1000 resistance thermometer as temperature sensor. Through this acquisition circuit, the monitoring actual temperature signal could be converted into voltage signal and transmitted into MCU. A TLP521-1 photoelectric coupler was matched with BD237 power transistor to drive the thermoelectric cooler (TEC) in FTA951 module. The effective electric power of TEC was controlled by the pulse width modulation (PWM) signals which generated by MCU. The PWM signal parameters could be adjusted timely by PID algorithm according to the difference between monitoring actual temperature and set temperature. The upper computer was used to input the set temperature and monitor the system running state via serial port. The application experiment results show that the temperature control system is featured by simple structure, rapid response speed, good stability and high temperature control accuracy with the error less than ±0.5°C.

  1. Thermally oxidized Inconel 600 and 690 nickel-based alloys characterizations by combination of global photoelectrochemistry and local near-field microscopy techniques (STM, STS, AFM, SKPFM)

    NASA Astrophysics Data System (ADS)

    Mechehoud, F.; Benaioun, N. E.; Hakiki, N. E.; Khelil, A.; Simon, L.; Bubendorff, J. L.

    2018-03-01

    Thermally oxidized nickel-based alloys are studied by scanning tunnelling microscopy (STM), scanning tunnelling spectroscopy (STS), atomic force microscopy (AFM), scanning kelvin probe force microscopy (SKPFM) and photoelectro-chemical techniques as a function of oxidation time at a fixed temperature of 623 K. By photoelectrochemistry measurements we identify the formation of three oxides NiO, Fe2O3, Cr2O3 and determine the corresponding gap values. We use these values as parameter for imaging the surface at high bias voltage by STM allowing the spatial localization and identification of both NiO, Fe2O3 oxide phases using STS measurements. Associated to Kelvin probe measurements we show also that STS allow to distinguished NiO from Cr2O3 and confirm that the Cr2O3 is not visible at the surface and localized at the oxide/steel interface.

  2. Superconducting states of topological surface states in β-PdBi2 investigated by STM/STS

    NASA Astrophysics Data System (ADS)

    Iwaya, Katsuya; Okawa, Kenjiro; Hanaguri, Tetsuo; Kohsaka, Yuhki; Machida, Tadashi; Sasagawa, Takao

    We investigate superconducting (SC) states of topological surface states in β-PdBi2 using very low temperature STM. Characteristic quasiparticle interference patterns strongly support the existence of the spin-polarized surface states at the Fermi level in the normal state. A fully-opened SC gap well described by the conventional BCS model is observed, indicating the SC gap opening at the spin-polarized Fermi surfaces. Considering a possible mixing of odd- and even parity orbital functions in C4v group symmetry lowered from D4h near the surface, we suggest that the SC gap consists of the mixture of s- and p-wave SC gap functions in the two-dimensional state.

  3. Surface induced selective deposition of Dysprosium Polyoxometalate on HOPG surface studied by STM and STS

    NASA Astrophysics Data System (ADS)

    Costa Milan, David; Pinilla Cienfuegos, Elena; Cardona Serra, Salvador; Coronado Miralles, Eugenio; Untiedt Lecuona, Carlos

    2013-03-01

    Scanning Tunneling Microscope (STM) and scanning Tunnelling spectroscopy (STS) techniques have been used to study the Preyssler type Polyoxometalate K12[DyP5W30O110] molecules deposited on Highly Oriented Pyrolytic Graphite surface (HOPG). Chainlike arrangements of clusters containing two or three molecules, as well as different cluster sizes are observed. As many structural artifacts are present on the graphite surface, like Moiré patterns, that could look like the molecular deposits, we have studied their STS and size to ensure the presence of the POM molecules on the surface. This article shows the possibility of addressing POMs on a flat surface to obtain their electronic properties through STS.

  4. Thermomyces lanuginosus STm: a source of thermostable hydrolytic enzymes for novel application in extraction of high-quality natural rubber from Taraxacum kok-saghyz (rubber dandelion)

    USDA-ARS?s Scientific Manuscript database

    Hydrolytic enzymes from a newly isolated strain of the thermophilic fungus Thermomyces lanuginosus were used to extract rubber from Taraxacum kok-saghyz commonly known as rubber (or Russian or Kazak(h)) dandelion. The fungus was isolated from garden soil and identified as Thermomyces lanuginosus STm...

  5. Tunneling STM/STS and break-junction spectroscopy of the layered nitro-chloride superconductors MNCl (M = Ti, Hf, Zr)

    NASA Astrophysics Data System (ADS)

    Ekino, Toshikazu; Sugimoto, Akira; Gabovich, Alexander M.; Zheng, Zhanfeng; Zhang, Shuai; Yamanaka, Shoji

    2014-05-01

    The layered superconductors β-MNCl with the critical temperatures Tc = 14 K (M = Zr) - 25 K (M = Hf) were investigated by means of scanning-tunneling microscopy/spectroscopy and break-junction tunneling spectroscopy. The STM/STS was used to investigate the surface electronic structures in nanometer length scale, while the BJTS was employed to precisely determine the gap characteristics. Both techniques consistently clarified the unusually large size of the superconducting gap. Wide gap distributions with large-scale maximum gap values were also revealed in α-KyTiNCl with a different crystal structure.

  6. Observation of the Gap Distribution on Multi-layered Cuprate Superconductor Ba2Ca4Cu5O10(O1-x, Fx)2 by STM/STS

    NASA Astrophysics Data System (ADS)

    Sugimoto, Akira; Ekino, Toshikazu; Tanaka, Katsuhiro; Mineta, Kyohei; Tanabe, Kenji; Tokiwa, Kazuyasu

    The nano-scale spatial gap distributions on apical-fluorine multi-layered cuprate superconductors Ba2Ca4Cu5O10(O1-x, Fx) (F0245, Tc = 70 K) are investigated by scanning tunneling microscopy/spectroscopy (STM/STS). The STM image shows randomly-distributed bright spot structures, which are assigned to the non-replaced apical oxygen. The dI/dV tunnel spectra show the coexistence of two kinds of the gap structures. The magnitudes of these gaps at 4.9 K are about ΔS ∼25 meV and ΔL ∼78 meV, respectively. The ΔL map shows the inhomogeneous distribution with the characteristic length of ∼1 nm. The smaller ΔL gap regions tend to locate at the bright-spot positions, indicating that the apical oxygen causes reduction of ΔL. These results are consistent with the well known relation between the carrier doping level and macroscopically observed gap size.

  7. Dy uniform film morphologies on graphene studied with SPA-LEED and STM

    DOE PAGES

    McDougall, D.; Hattab, H.; Hershberger, M. T.; ...

    2016-07-01

    The use of graphene for microelectronics and spintronic applications requires strategies for metals to wet graphene and to grow layer-by-layer. This is especially important when metals will be used as electrical contacts or as spin filters. Extensive work in the literature so far has shown that this is very challenging, since practically all metals grow 3D, with multi-height islands forming easily. Reasons for the 3D morphology are the much weaker metal carbon bond when compared to the metal cohesive energy and the role of Coulomb repulsion of the poorly screened charges at the metal graphene interface. We employed the complementarymore » techniques of SPA-LEED and STM to study the growth of Dy on graphene. It was found that under kinetic limitations it is possible to fully cover graphene with a bilayer Dy film, by growing well below room temperature in stepwise deposition experiments. Lastly, the Dy film, however, is amorphous but ways to crystallize it within the 2D morphology are possible, since long range order improves at higher growth temperature.« less

  8. Spatially Resolved Nano-Scale Characterization of Electronic States in SrTiO3(001) Surfaces by STM/STS

    NASA Astrophysics Data System (ADS)

    Iwaya, Katsuya; Ohsawa, Takeo; Shimizu, Ryota; Hashizume, Tomihiro; Hitosugi, Taro

    2012-02-01

    We have performed low temperature scanning tunneling microscopy/spectroscopy (STM/STS) measurements on TiO2-terminated SrTiO3(001) thin film surfaces. The conductance map exhibited electronic modulations that were completely different from the surface structure. We also found that the electronic modulations were strongly dependent on temperature and the density of atomic defects associated with oxygen vacancies. These results suggest the existence of strongly correlated two-dimensional electronic states near the SrTiO3 surface, implying the importance of electron correlation at the interfaces of SrTiO3-related heterostructures.

  9. The Sentinel-3 Surface Topography Mission (S-3 STM): Level 2 SAR Ocean Retracker

    NASA Astrophysics Data System (ADS)

    Dinardo, S.; Lucas, B.; Benveniste, J.

    2015-12-01

    The SRAL Radar Altimeter, on board of the ESA Mission Sentinel-3 (S-3), has the capacity to operate either in the Pulse-Limited Mode (also known as LRM) or in the novel Synthetic Aperture Radar (SAR) mode. Thanks to the initial results from SAR Altimetry obtained exploiting CryoSat-2 data, lately the interest by the scientific community in this new technology has significantly increased and consequently the definition of accurate processing methodologies (along with validation strategies) has now assumed a capital importance. In this paper, we present the algorithm proposed to retrieve from S-3 STM SAR return waveforms the standard ocean geophysical parameters (ocean topography, wave height and sigma nought) and the validation results that have been so far achieved exploiting the CryoSat-2 data as well as the simulated data. The inversion method (retracking) to extract from the return waveform the geophysical information is a curve best-fitting scheme based on the bounded Levenberg-Marquardt Least-Squares Estimation Method (LEVMAR-LSE). The S-3 STM SAR Ocean retracking algorithm adopts, as return waveform’s model, the “SAMOSA” model [Ray et al, 2014], named after the R&D project SAMOSA (led by Satoc and funded by ESA), in which it has been initially developed. The SAMOSA model is a physically-based model that offers a complete description of a SAR Altimeter return waveform from ocean surface, expressed in the form of maps of reflected power in Delay-Doppler space (also known as stack) or expressed as multilooked echoes. SAMOSA is able to account for an elliptical antenna pattern, mispointing errors in roll and yaw, surface scattering pattern, non-linear ocean wave statistics and spherical Earth surface effects. In spite of its truly comprehensive character, the SAMOSA model comes with a compact analytical formulation expressed in term of Modified Bessel functions. The specifications of the retracking algorithm have been gathered in a technical document (DPM

  10. A comprehensive study of catalytic, morphological and electronic properties of ligand-protected gold nanoclusters using XPS, STM, XAFS, and TPD techniques

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

    Wu, Qiyuan; Cen, Jiajie; Zhao, Yue

    Ultra-small gold nanoclusters were synthesized via a ligand exchange method and deposited onto different TiO2 supports to study their properties. STM imaging revealed that the as-synthesized gold nanoclusters had 2-D morphology consisting of monolayers of gold atoms. In conclusion, subsequent XPS, XAFS, and CO oxidation TPD results indicated that heat treatments of gold clusters at different temperatures significantly altered their electronic and catalytic properties due to ligand deprotection and cluster agglomeration.

  11. Modeling of the Magnetization Behavior of Realistic Self-Organized InAs/GaAs Quantum Craters as Observed with Cross-Sectional STM

    NASA Astrophysics Data System (ADS)

    Fomin, V. M.; Gladilin, V. N.; Devreese, J. T.; Offermans, P.; Koenraad, P. M.; Wolter, J. H.; García, J. M.; Granados, D.

    2005-06-01

    Recently, using cross-sectional scanning-tunneling microscopy (X-STM), it was shown that self-organized ring-like InAs quantum dots are much smaller in diameter than it is expected from atomic force microscopy measurements and, moreover, that they possess a depression rather than an opening in the central region. For those quantum craters, we analyze the possibility to reveal the electronic properties (like the Aharonov-Bohm oscillations) peculiar to doubly connected geometry of quantum rings.

  12. A comprehensive study of catalytic, morphological and electronic properties of ligand-protected gold nanoclusters using XPS, STM, XAFS, and TPD techniques

    DOE PAGES

    Wu, Qiyuan; Cen, Jiajie; Zhao, Yue; ...

    2017-12-08

    Ultra-small gold nanoclusters were synthesized via a ligand exchange method and deposited onto different TiO2 supports to study their properties. STM imaging revealed that the as-synthesized gold nanoclusters had 2-D morphology consisting of monolayers of gold atoms. In conclusion, subsequent XPS, XAFS, and CO oxidation TPD results indicated that heat treatments of gold clusters at different temperatures significantly altered their electronic and catalytic properties due to ligand deprotection and cluster agglomeration.

  13. [Research on the High Efficiency Data Communication Repeater Based on STM32F103].

    PubMed

    Zhang, Yahui; Li, Zheng; Chen, Guangfei

    2015-11-01

    To improve the radio frequency (RF) transmission distance of the wireless terminal of the medical internet of things (LOT), to realize the real-time and efficient data communication, the intelligent relay system based on STM32F103 single chip microcomputer (SCM) is proposed. The system used nRF905 chip to achieve the collection, of medical and health information of patients in the 433 MHz band, used SCM to control the serial port to Wi-Fi module to transmit information from 433 MHz to 2.4 GHz wireless Wi-Fi band, and used table look-up algorithm of ready list to improve the efficiency of data communications. The design can realize real-time and efficient data communication. The relay which is easy to use with high practical value can extend the distance and mode of data transmission and achieve real-time transmission of data.

  14. STM/STS Study of Surface Modification Effect on Bandgap Structure of Ti2C with -OH, -F, and -H

    NASA Astrophysics Data System (ADS)

    Jung, Seong Jun; Lai, Shen; Jeong, Taehwan; Lee, Sungjoo; Song, Young Jae

    In this presentation, we present Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) study of bandgap structures of surface-modified Ti2C with -OH, -F, and -O in atomic scale. Since the discovery of new two dimensional (2D) materials like graphene, various 2D materials including transition metal dichalcogenide (TMD) have been intensively investigated. There are, however, still scientific issues to apply them to the device fabrications for controlling the appropriate bandgap structure with high field effect mobility. Recently another 2D materials of transition metal carbide (TMC), Ti2CTx with modifiable surface group Tx(-OH, -F, and -O) was suggested. [S. Lai et. al, Nanoscale (2015), DOI: 10.1039/C5NR06513E]. This 2D material shows that the mobility at room temperature is less sensitive to the measured transport bandgap, which can imply that Ti2CTx can be a strong candidate of 2D TMC for application to the future electronic devices. Surface modification on the electronic structure of Ti2C by -OH, -F, and -O is, therefore, investigated by STM and STS in atomic scale. More scientific results will be further discussed in the presentation. This research was supported by Basic Science Research Program through the National Research Foundation of Korea funded by the Korean government (Grant Numbers: 2015R1A1A1A05027585, 2011­0030046, IBS- R011­D1, 2014M3C1A3053024 and 2015M3A7B4050455).

  15. Anisotropic superconductivity in β-(BDA-TTP)2SbF6: STM spectroscopy

    NASA Astrophysics Data System (ADS)

    Nomura, K.; Muraoka, R.; Matsunaga, N.; Ichimura, K.; Yamada, J.

    2009-03-01

    We have investigated the gap symmetry in the superconducting phase of β-(BDA-TTP)2SbF6 with use of the scanning tunneling microscope (STM). The tunneling spectra obtained on the conducting surface show a clear superconducting gap structure. Its functional form is of V-shaped similarly to κ-(BEDT-TTF)2X and suggests the anisotropic superconducting gap with line nodes. For lateral surfaces the shape of tunneling spectra varies from the U-shape with relatively large gap to the V-shape with small gap depending on the tunneling direction alternately twice between directional angle 0 and π. From the analysis of conductance curve taking the k dependence of the tunneling probability into account, it is found that the gap has maximum near the a* and c* axes and the nodes appear along near a*+c* and the a-c* directions. These indicate that the d like superconducting pair is formed in this system as the case of κ-(BEDT-TTF)2X. This node direction is consistent with the theoretical prediction based on the spin fluctuation mechanism. However, the zero-bias conductance peak has not been observed yet.

  16. STM images of carbon-nanotube quantum dots: Seeing a Wigner molecule of correlated electrons

    NASA Astrophysics Data System (ADS)

    Secchi, Andrea; Rontani, Massimo

    2011-03-01

    The paradigm of few-electron complexes in quantum dots (QDs) relies on the idea that the lowest quantized levels are filled according to Pauli's exclusion principle. If Coulomb repulsion is sufficiently strong to overcome the kinetic energy cost of localization, a different scenario is predicted: a ``Wigner'' molecule (WM) forms, made of electrons frozen in space according to a geometrical pattern. Despite considerable experimental effort, evidence of the WM in semiconductor QDs has been elusive so far. Here we demonstrate theoretically that WMs occur in gate-defined QDs embedded in typical semiconducting carbon nanotubes (CNTs). The unambiguous signatures of the WM state must be searched in the scanning tunneling microscopy (STM) images of the electrons. Through exact diagonalisation (ED) calculations, we unveil the inherent features of the electron molecular states. We show that, like nuclei in a usual molecule, electrons have localized wave functions and hence negligible exchange interactions. ED results for single and double QDs provide a simple interpretation for transport experiments in ultraclean CNTs.

  17. Electrodeposition of Al in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquids: in situ STM and EQCM studies.

    PubMed

    Moustafa, E M; El Abedin, S Zein; Shkurankov, A; Zschippang, E; Saad, A Y; Bund, A; Endres, F

    2007-05-10

    In the present paper, the electrodeposition of Al on flame-annealed Au(111) and polycrystalline Au substrates in two air- and water-stable ionic liquids namely, 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide, [Py(1,4)]Tf(2)N, and 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide, [EMIm]Tf(2)N, has been investigated by in situ scanning tunneling microscopy (STM), electrochemical quartz crystal microbalance (EQCM), and cyclic voltammetry. The cyclic voltammogram of aluminum deposition and stripping on Au(111) in the upper phase of the biphasic mixture of AlCl(3)/[EMIm]Tf(2)N at room temperature (25 degrees C) shows that the electrodeposition process is completely reversible as also evidenced by in situ STM and EQCM studies. Additionally, a cathodic peak at an electrode potential of about 0.55 V vs Al/Al(III) is correlated to the aluminum UPD process that was evidenced by in situ STM. A surface alloying of Al with Au at the early stage of deposition occurs. It has been found that the Au(111) surface is subject to a restructuring/reconstruction in the upper phase of the biphasic mixture of AlCl(3)/[Py(1,4)]Tf(2)N at room temperature (25 degrees C) and that the deposition is not fully reversible. Furthermore, the underpotential deposition of Al in [Py(1,4)]Tf(2)N is not as clear as in [EMIm]Tf(2)N. The frequency shift in the EQCM experiments in [Py(1,4)]Tf(2)N shows a surprising result as an increase in frequency and a decrease in damping with bulk aluminum deposition at potentials more negative than -1.8 V was observed at room temperature. However, at 100 degrees C there is a frequency decrease with ongoing Al deposition. At -2.0 V vs Al/Al(III), a bulk aluminum deposition sets in.

  18. Influence of twin boundaries on superconducting gap nodes in FeSe single crystal studied by STM/STS

    NASA Astrophysics Data System (ADS)

    Watashige, T.; Hanaguri, T.; Kohsaka, Y.; Iwaya, K.; Fu, Y.; Kasahara, S.; Watanabe, D.; Mizukami, Y.; Mikami, T.; Kawamoto, Y.; Kurata, S.; Shibauchi, T.; Matsuda, Y.; Böhmer, A. E.; Wolf, T.; Meingast, C.; Löhneysen, H. V.

    2014-03-01

    We performed scanning tunneling microscopy (STM) and spectroscopy (STS) measurements on high-quality FeSe single crystals grown by vapor transport technique to examine the superconducting-gap structure. In MBE-grown FeSe thin films, based on the V-shaped tunneling spectra, nodal superconductivity is suggested. It is interesting to investigate how the nodes are affected by various kinds of defects. We found that twin boundaries bring about drastic effects on the gap nodes. With approaching to the twin boundary, V-shaped spectra gradually change to U-shaped ones. Interestingly, in the area between the twin boundaries separated by about 30 nm, the gap node is completely lifted and there appears a finite gap over +/-0.4 meV. This unusual twin-boundary effect will give us a hint to elucidate the superconducting-gap structure.

  19. Dimer formation and surface alloying: a STM study of lead on Cu(211)

    NASA Astrophysics Data System (ADS)

    Bartels, L.; Zöphel, S.; Meyer, G.; Henze, E.; Rieder, K.-H.

    1997-02-01

    We present a STM investigation of Pb adsorption on the Cu(211) surface in the temperature range between 30 K and room temperature. We observe three different kinds of ordered 1D Pb and PbCu chains (nanowires) located at the intrinsic step edges of the Cu(211) surface. On room temperature prepared samples, Pb is found to be incorporated into the step edges of the (211) surface. The first ordered structure consists of CuPb chains at the step edges (p(2 × disorder)) and is followed with increasing coverage by a close packed row of Pb-atoms (p(4 × disorder)). Preparation at low temperature yields Pb-dimers, and the first ordered structure is a row of Pb-dimers at the step edge (p(3 × disorder)) followed with increased coverage by a structure as described above. By systematic manipulation with the tunneling tip, we could get additional insight into the structural elements of the PbCu layer on the atomic scale. Furthermore, by measuring the threshold resistance to detach atoms from different ad-sites, we can approximately determine the binding energy and gain some insight into the thermodynamical parameters involved.

  20. Surface science approach to Pt/carbon model catalysts: XPS, STM and microreactor studies

    NASA Astrophysics Data System (ADS)

    Motin, Abdul Md.; Haunold, Thomas; Bukhtiyarov, Andrey V.; Bera, Abhijit; Rameshan, Christoph; Rupprechter, Günther

    2018-05-01

    Pt nanoparticles supported on carbon are an important technological catalyst. A corresponding model catalyst was prepared by physical vapor deposition (PVD) of Pt on sputtered HOPG (highly oriented pyrolytic graphite). The carbon substrate before and after sputtering as well as the Pt/HOPG system before and after Pt deposition and annealing were examined by XPS and STM. This yielded information on the surface density of defects, which serve as nucleation centres for Pt, and on the size distribution (mean size/height) of the Pt nanoparticles. Two different model catalysts were prepared with mean sizes of 2.0 and 3.6 nm, both turned out to be stable upon UHV-annealing to 300 °C. After transfer into a UHV-compatible flow microreactor and subsequent cleaning in UHV and under mbar pressure, the catalytic activity of the Pt/HOPG model system for ethylene hydrogenation was examined under atmospheric pressure flow conditions. This enabled to determine temperature-dependent conversion rates, turnover frequencies (TOFs) and activation energies. The catalytic results obtained are in line with the characteristics of technological Pt/C, demonstrating the validity of the current surface science based model catalyst approach.

  1. Electronic states of domain structure in 1T-TaS2-x Se x observed by STM/STS

    NASA Astrophysics Data System (ADS)

    Fujii, D.; Iwasaki, T.; Akiyama, K.; Fujisawa, Y.; Demura, S.; Sakata, H.

    2018-03-01

    We report on a systematic scanning tunneling microscopy and spectroscopy (STM/STS) study on 1T–TaS2-x Se x (x = 0, 0.3, 1.0) at 4.2 K. While the compounds with x = 0 and 0.3, which undergoes the Mott transition, showed the commensurate charge density wave (CDW) with the period of \\sqrt{13}{a}0× \\sqrt{13}{a}0 (a 0 is in-plane lattice constant), the compound with x=1, which shows superconductivity at 3.5 K, exhibits anomalous domain structure: The domain structure consists of regions with regular array of David-stars divided by bright contrasted walls at positive bias voltage. We found the domain wall showed the different electronic state from that of the domain.

  2. STM Studies of Spin-­Orbit Coupled Phases in Real-­ and Momentum-­Space

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

    Madhavan, Vidya

    The recently discovered class of spin-orbit coupled materials with interesting topological character are fascinating both from fundamental as well as application point of view. Two striking examples are 3D topological insulators (TIs) and topological crystalline insulators (TCIs). These materials host linearly dispersing (Dirac like) surface states with an odd number of Dirac nodes and are predicted to carry a quantized half-integer value of the axion field. The non-trivial topological properties of TIs and TCIs arise from strong spin-orbit coupling leading to an inverted band structure; which also leads to the chiral spin texture in momentum space. In this project wemore » used low temperature scanning tunneling microscopy (STM) and spectroscopy (STS) to study materials with topological phases in real- and momentum-space. We studied both single crystals and thin films of topological materials which are susceptible to being tuned by doping, strain or gating, allowing us to explore their physical properties in the most interesting regimes and set the stage for future technological applications. .« less

  3. STM/STS study of the superconducting gap in SmFeAsO1-xFx

    NASA Astrophysics Data System (ADS)

    Kawashima, Yuki; Ichimura, Koichi; Katono, Kazuhiro; Kurosawa, Tohru; Oda, Migaku; Tanda, Satoshi; Kamihara, Yoichi; Hosono, Hideo

    2015-02-01

    We report an electron tunneling study of SmFeAsO1-xFx in the low doping region (x=0, 0.045, 0.046, 0.069) by low temperature UHV-STM/STS. Superconducting gaps are observed for each superconducting sample x=0.045 (Tc=12.9 K), x=0.046 (Tc=32.9 K) and x=0.069 (Tc=46.9 K). We obtained corresponding superconducting gap size of ΔSC = 9.5 ± 0.5 meV, 9.75±0.25 meV and 11±1 meV. While Tc increases, ΔSC is kept the same. This suggests that the effective attractive interaction is the same and that there is some mechanism that suppresses the superconductivity in the low doping region. On the other hand, similar gap structures were found in a non-superconducting sample with x=0 at 7.8 K. The obtained gap size was ΔN = 8.5 ± 1.5 meV, which is almost the same as the superconducting gap in the superconducting samples (x=0.045, 0.046, 0.069).

  4. Characterizing the electronic ground states of single-layer NbSe2 via STM/STS

    NASA Astrophysics Data System (ADS)

    Chen, Yi; Ugeda, Miguel; Bradley, Aaron; Zhang, Yi; Onishi, Seita; Ruan, Wei; Ojeda-Aristizabal, Claudia; Ryu, Hyejin; Edmonds, Mark; Tsai, Hsin-Zon; Riss, Alexander; Mo, Sung-Kwan; Lee, Dunghai; Zettl, Alex; Hussain, Zahid; Shen, Zhi-Xun; Crommie, Michael

    Layered transition metal dichalcogenides (TMDs) are ideal systems for exploring collective electronic phases such as charge density wave (CDW) order and superconductivity. In bulk NbSe2 the CDW sets in at TCDW = 33K and superconductivity sets in at Tc = 7.2K. Below Tc these electronic states coexist but their microscopic formation mechanisms remain controversial. Here we present an electronic characterization study of a single 2D layer of NbSe2 by means of low temperature scanning tunneling microscopy/spectroscopy (STM/STS), angle-resolved photoemission spectroscopy (ARPES), and electrical transport measurements. We demonstrate that the CDW order remains intact in 2D and exhibits a robust 3 x 3 superlattice. Superconductivity also still occurs but its onset is depressed to 1.6K. Our STS measurements at 5K reveal a CDW gap of Δ = 4 meV at the Fermi energy, which is accessible via STS due to the removal of bands crossing the Fermi surface in the 2D limit. Our observations are consistent with the predicted simplified (compared to bulk) electronic structure of single-layer NbSe2, thus providing new insight into CDW formation and superconductivity in this model strongly-correlated system.

  5. Investigations of Topological Surface States in Sb (111) Ultrathin Films by STM/STS Experiments and DFT Calculations

    NASA Astrophysics Data System (ADS)

    Luo, Ziyu; Yao, Guanggeng; Xu, Wentao; Feng, Yuanping; Wang, Xue-Sen

    2014-03-01

    Bulk Sb was regarded as a semimetal with a nontrivial topological order. It is worth exploring whether the Sb ultrathin film has the potential to be an elementary topological insulator. In the presence of quantum confinement effect, we investigated the evolution of topological surface states in Sb (111) ultrathin films with different thickness by the scanning tunneling microscopy/ spectroscopy (STM/STS) experiments and density functional theory (DFT) calculations. By comparing the quasiparticle interference (QPI) patterns obtained from Fourier-transform scanning tunneling spectroscopy (FT-STS) and from DFT calculations, we successfully derive the spin properties of topological surface states on Sb (111) ultrathin films. In addition, based on the DFT calculations, the 8BL Sb (111) ultrathin film was proved to possess up to 30% spinseparated topological surface states within the bandgap. Therefore, the highquality 8BL Sb (111) ultrathin film could be regarded as an elementary topological insulator.

  6. STM experiment and atomistic modelling hand in hand: individual molecules on semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Briggs, G. A. D.; Fisher, A. J.

    When the scanning tunnelling microscope was invented, the world was amazed at the atomic resolution images of surfaces which could be obtained. It soon became apparent that it was one thing to obtain an image, and quite another to understand the structure that was seen. Happily the developments in real space experimental techniques for studying surfaces have been accompanied by developments in real space theoretical techniques for modelling electronic structure and bonding at surfaces. The aim of this review is to describe how and why STM experiments and atomistic modelling should be combined and what they can then be expected to tell us. A summary is given of the experimental methods for theorists and vice versa, and their relationship is illustrated using a number of case studies where they have been used together. To give the review a coherent focus the examples are confined to studies of adsorbed molecules on semiconductor surfaces, in particular Si(001) and GaAs(001). Questions thus addressed include: How are experimental images and structural modelling linked by tunnelling theory? What can they tell us together that we could not learn from experiment or theory alone? What can we learn about atomic positions and bonding at semiconductor surfaces with and without adsorbed molecules? How many different ways are there to relate images to calculations?

  7. Intermolecular vs molecule–substrate interactions: A combined STM and theoretical study of supramolecular phases on graphene/Ru(0001)

    PubMed Central

    Roos, Michael; Uhl, Benedikt; Künzel, Daniela; Hoster, Harry E; Groß, Axel

    2011-01-01

    Summary The competition between intermolecular interactions and long-range lateral variations in the substrate–adsorbate interaction was studied by scanning tunnelling microscopy (STM) and force field based calculations, by comparing the phase formation of (sub-) monolayers of the organic molecules (i) 2-phenyl-4,6-bis(6-(pyridin-3-yl)-4-(pyridin-3-yl)pyridin-2-yl)pyrimidine (3,3'-BTP) and (ii) 3,4,9,10-perylene tetracarboxylic-dianhydride (PTCDA) on graphene/Ru(0001). For PTCDA adsorption, a 2D adlayer phase was formed, which extended over large areas, while for 3,3'-BTP adsorption linear or ring like structures were formed, which exclusively populated the areas between the maxima of the moiré structure of the buckled graphene layer. The consequences for the competing intermolecular interactions and corrugation in the adsorption potential are discussed and compared with the theoretical results. PMID:22003444

  8. Complete Genome sequence of Burkholderia phymatum STM815, a broad host range and efficient nitrogen-fixing symbiont of Mimosa species

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

    Moulin, Lionel; Klonowska, Agnieszka; Caroline, Bournaud

    Burkholderia phymatum is a soil bacterium able to develop a nitrogen-fixing symbiosis with species of the legume genus Mimosa, and is frequently found associated specifically with Mimosa pudica. The type strain of the species, STM 815T, was isolated from a root nodule in French Guiana in 2000. The strain is an aerobic, motile, non-spore forming, Gram-negative rod, and is a highly competitive strain for nodulation compared to other Mimosa symbionts, as it also nodulates a broad range of other legume genera and species. The 8,676,562 bp genome is composed of two chromosomes (3,479,187 and 2,697,374 bp), a megaplasmid (1,904,893 bp)more » and a plasmid hosting the symbiotic functions (595,108 bp).« less

  9. Complete Genome sequence of Burkholderia phymatum STM815T, a broad host range and efficient nitrogen-fixing symbiont of Mimosa species

    PubMed Central

    Moulin, Lionel; Klonowska, Agnieszka; Caroline, Bournaud; Booth, Kristina; Vriezen, Jan A.C.; Melkonian, Rémy; James, Euan K.; Young, J. Peter W.; Bena, Gilles; Hauser, Loren; Land, Miriam; Kyrpides, Nikos; Bruce, David; Chain, Patrick; Copeland, Alex; Pitluck, Sam; Woyke, Tanja; Lizotte-Waniewski, Michelle; Bristow, Jim; Riley, Margaret

    2014-01-01

    Burkholderia phymatum is a soil bacterium able to develop a nitrogen-fixing symbiosis with species of the legume genus Mimosa, and is frequently found associated specifically with Mimosa pudica. The type strain of the species, STM 815T, was isolated from a root nodule in French Guiana in 2000. The strain is an aerobic, motile, non-spore forming, Gram-negative rod, and is a highly competitive strain for nodulation compared to other Mimosa symbionts, as it also nodulates a broad range of other legume genera and species. The 8,676,562 bp genome is composed of two chromosomes (3,479,187 and 2,697,374 bp), a megaplasmid (1,904,893 bp) and a plasmid hosting the symbiotic functions (595,108 bp). PMID:25197461

  10. Tantalum induced butterfly-like clusters on Si (111)-7 × 7 surface: STM/STS study at low coverage

    NASA Astrophysics Data System (ADS)

    Shukrynau, Pavel; Mutombo, Pingo; Švec, Martin; Hietschold, Michael; Cháb, Vladimír

    2012-02-01

    The adsorption of the small amounts of tantalum on Si (111)-7 × 7 reconstructed surface is investigated systematically using scanning tunneling microscopy and tunneling spectroscopy combined with first-principles density functional theory calculations. We find out that the moderate annealing of the Ta covered surface results in the formation of clusters of the butterfly-like shape. The clusters are sporadically distributed over the surface and their density is metal coverage dependent. Filled and empty state STM images of the clusters differ strongly suggesting the existence of covalent bonds within the cluster. Tunneling spectroscopy measurements reveal small energy gap, showing semiconductor-like behavior of the constituent atoms. The cluster model based on experimental images and theoretical calculations has been proposed and discussed. Presented results show that Ta joins the family of adsorbates, that are known to form magic clusters on Si (111)-7 × 7, but its magic cluster has the structural and electronic properties that are different from those reported before.

  11. Pump-probe STM light emission spectroscopy for detection of photo-induced semiconductor-metal phase transition of VO2

    NASA Astrophysics Data System (ADS)

    Sakai, Joe; Katano, Satoshi; Kuwahara, Masashi; Uehara, Yoichi

    2017-10-01

    We attempted to observe pump-probe scanning tunneling microscopy (STM)-light emission (LE) from a VO2 thin film grown on a rutile TiO2(0 0 1) substrate, with an Ag tip fixed over a semiconducting domain. Laser pulses from a Ti:sapphire laser (wavelength 920 nm pulse width less than 1.5 ps) irradiated the tip-sample gap as pump and probe light sources. With a photon energy of 2.7 eV, suggesting phase transition from semiconducting monoclinic (M) to metallic rutile (R) phases in relation to the electronic band structure, faint LE was observed roughly 30 ps after the irradiation of the pump pulse, followed by retention for roughly 20 ps. The incident energy fluence of the pump pulse at the gap was five orders of magnitude lower than the threshold value for reported photo-induced M-R phase transition. The mechanism that makes it possible to reduce the threshold fluence is discussed.

  12. Pump-probe STM light emission spectroscopy for detection of photo-induced semiconductor-metal phase transition of VO2.

    PubMed

    Sakai, Joe; Katano, Satoshi; Kuwahara, Masashi; Uehara, Yoichi

    2017-10-11

    We attempted to observe pump-probe scanning tunneling microscopy (STM)-light emission (LE) from a VO 2 thin film grown on a rutile TiO 2 (0 0 1) substrate, with an Ag tip fixed over a semiconducting domain. Laser pulses from a Ti:sapphire laser (wavelength 920 nm; pulse width less than 1.5 ps) irradiated the tip-sample gap as pump and probe light sources. With a photon energy of 2.7 eV, suggesting phase transition from semiconducting monoclinic (M) to metallic rutile (R) phases in relation to the electronic band structure, faint LE was observed roughly 30 ps after the irradiation of the pump pulse, followed by retention for roughly 20 ps. The incident energy fluence of the pump pulse at the gap was five orders of magnitude lower than the threshold value for reported photo-induced M-R phase transition. The mechanism that makes it possible to reduce the threshold fluence is discussed.

  13. Surface Confined Metallosupramolecular Architectures: Formation and STM Characterization

    PubMed Central

    Li, Shan-Shan; Northrop, Brian H.; Yuan, Qun-Hui; Wan, Li-Jun; Stang, Peter J.

    2009-01-01

    CONSPECTUS Metallosupramolecular compounds have attracted a great deal of attention over the past two decades largely because of their unique, highly-complex structural characteristics, the fact that they can be prepared with relative ease using coordination-driven self-assembly techniques, and their potential electronic, magnetic, optical, and catalytic properties. In particular, the use of electron-poor square planar Pt(II) transition metals in conjunction with rigid, electron-rich pyridyl donors had enabled the spontaneous self-assembly of a rich library of 2D metallacyclic and 3D metallacage assemblies via the directional-bonding approach. With the tremendous progress that has been made in the preparation and characterization of metallosupramolecules, much attention is now being turned toward fully exploring and developing their materials properties. Assembling metallosupramolecular compounds on solid supports represents a vitally important step toward developing their materials properties. Surfaces provide a means of uniformly aligning and orienting these highly symmetric metallacycles and metallacages, which increases the level of coherence between molecules above that which can be achieved in the solution phase and affords a means of integrating adlayers into a solid-state materials setting. The dynamic nature of kinetically labile Pt(II)-N coordination bonds, however, requires that deposition and imaging conditions be appropriate to retain the assemblies' stability. Toward these aims it is imperative to understand the factors that govern surface self-assembly and the interactions that influence the structure and stability of the resulting adlayer. Such insight can be obtained from Scanning Tunneling Microscopy (STM), which has emerged as a powerful technique for the imaging and characterization of self-assembled adlayers. This account describes the means by which 2D rectangular and square metallacycles and 3D trigonal bipyrimidal and chiral trigonal prism

  14. Recoding between two types of STM representation revealed by the dynamics of memory search.

    PubMed

    Leszczyński, Marcin; Myers, Nicholas E; Akyürek, Elkan G; Schubö, Anna

    2012-03-01

    Visual STM (VSTM) is thought to be related to visual attention in several ways. Attention controls access to VSTM during memory encoding and plays a role in the maintenance of stored information by strengthening memorized content. We investigated the involvement of visual attention in recall from VSTM. In two experiments, we measured electrophysiological markers of attention in a memory search task with varying intervals between VSTM encoding and recall, and so we were able to track recoding of representations in memory. Results confirmed the involvement of attention in VSTM recall. However, the amplitude of the N2pc and N3rs components, which mark orienting of attention and search within VSTM, decreased as a function of delay. Conversely, the amplitude of the P3 and sustained posterior contralateral negativity components increased as a function of delay, effectively the opposite of the N2pc and N3rs modulations. These effects were only observed when verbal memory was not taxed. Thus, the results suggested that gradual recoding from visuospatial orienting of attention into verbal recall mechanisms takes place from short to long retention intervals. Interestingly, recall at longer delays was faster than at short delays, indicating that verbal representation is coupled with faster responses. These results extend the orienting-of-attention hypothesis by including an account of representational recoding during short-term consolidation and its consequences for recall from VSTM.

  15. A combined optical, SEM and STM study of growth spirals on the polytypic cadmium iodide crystals

    NASA Astrophysics Data System (ADS)

    Singh, Rajendra; Samanta, S. B.; Narlikar, A. V.; Trigunayat, G. C.

    2000-05-01

    Some novel results of a combined sequential study of growth spirals on the basal surface of the richly polytypic CdI 2 crystals by optical microscopy, scanning electron microscopy (SEM) and scanning tunneling microscopy (STM) are presented and discussed. Under the high resolution and magnification achieved in the scanning electron microscope, the growth steps of large heights seen in the optical micrographs are found to have a large number of additional steps of smaller heights existing between any two adjacent large height growth steps. When further seen by a scanning tunneling microscope, which provides still higher resolution, sequences of unit substeps, each of height equal to the unit cell height of the underlying polytype, are revealed to exist on the surface. Several large steps also lie between the unit steps, with heights equal to an integral multiple of either the unit cell height of the underlying polytype or the thickness of a molecular sheet I-Cd-I. It is suggested that initially a giant screw dislocation may form by brittle fracture of the crystal platelet, which may gradually decompose into numerous unit dislocations during subsequent crystal growth.

  16. A two-step dilution tris-egg yolk extender containing Equex STM significantly improves sperm cryopreservation in the African wild dog (Lycaon pictus).

    PubMed

    Van den Berghe, Femke; Paris, Monique Christina Johanna; Briggs, Michael Brent; Farstad, Wenche Kristin; Paris, Damien Boyd Bertrand Paul

    2018-02-01

    Conservation management of endangered African wild dogs (AWD; Lycaon pictus) can benefit greatly from development of sperm freezing and artificial insemination. Previous freezing attempts yielded nearly 0% motile sperm within 2 h of thawing. In this study, two canine freezing protocols were tested: Protocol 1: a one-step dilution in TRIS-20% egg yolk containing 8% glycerol; and Protocol 2: a two-step dilution in TRIS-20% egg yolk containing a final extender concentration of 5% glycerol and 0.5% Equex STM, coupled with a TRIS-citrate-fructose thawing solution. Semen was collected by electroejaculation from n = 24 AWDs, of which eight ejaculates of sufficient quality (four good quality with initial sperm motility of 75.0 ± 4.4% and four poor quality; showing rapid decrease in sperm motility to 3.3 ± 3.3% prior to freezing) were frozen. For good quality samples, motility and sperm motility index persisted for up to 8 h for Protocol 2, and was higher between 2 and 6 h after thawing with a decrease from 4 h of incubation. Motility dropped to nearly 0% after 2 h incubation for Protocol 1. Viability was higher for Protocol 2 throughout the 8 h of incubation, with a decrease after 6 h, compared to 4 h for Protocol 1. Acrosome integrity was higher for Protocol 2 throughout post-thaw incubation, with a decrease after 2 h for both protocols. Protocols did not differ in normal sperm morphology or DNA integrity. Poor quality samples yielded similar results, except for acrosome integrity, which declined for Protocol 2. In conclusion, a two-step dilution in TRIS-egg yolk-glycerol extender containing Equex STM yields significantly improved post-thaw quality and longevity of AWD spermatozoa, making it suitable for sperm banking and artificial insemination initiatives. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

  17. Simulated structure and imaging of NTCDI on Si(1 1 1)-7 × 7 : a combined STM, NC-AFM and DFT study

    NASA Astrophysics Data System (ADS)

    Jarvis, S. P.; Sweetman, A. M.; Lekkas, I.; Champness, N. R.; Kantorovich, L.; Moriarty, P.

    2015-02-01

    The adsorption of naphthalene tetracarboxylic diimide (NTCDI) on Si(1 1 1)-7 × 7 is investigated through a combination of scanning tunnelling microscopy (STM), noncontact atomic force microscopy (NC-AFM) and density functional theory (DFT) calculations. We show that NTCDI adopts multiple planar adsorption geometries on the Si(1 1 1)-7 × 7 surface which can be imaged with intramolecular bond resolution using NC-AFM. DFT calculations reveal adsorption is dominated by covalent bond formation between the molecular oxygen atoms and the surface silicon adatoms. The chemisorption of the molecule is found to induce subtle distortions to the molecular structure, which are observed in NC-AFM images.

  18. Evolution of Ge nanoislands on Si(110)-'16 × 2' surface under thermal annealing studied using STM

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, Subhashis; Yoshimura, Masamichi; Ueda, Kazuyuki

    2009-11-01

    The initial nucleation of Ge nanoclusters on Si(110) at room temperature (RT), annealing-induced surface roughening and the evolution of three-dimensional Ge nanoislands have been investigated using scanning tunneling microscopy (STM). A few monolayers (ML) of Ge deposited at room temperature lead to the formation of Ge clusters which are homogeneously distributed across the surface. The stripe-like patterns, characteristic of the Si(110)-'16 × 2' surface reconstruction are also retained. Increasing annealing temperatures, however, lead to significant surface diffusion and thus, disruption of the underlying '16 × 2' reconstruction. The annealing-induced removal of the stripe structures (originated from '16 × 2' reconstruction) starts at approximately 300 °C, whereas the terrace structures of Si(110) are thermally stable up to 500 °C. At approximately 650 °C, shallow Ge islands of pyramidal shape with (15,17,1) side facets start to form. Annealing at even higher temperatures enhances Ge island formation. Our findings are explained in terms of partial dewetting of the metastable Ge wetting layer (WL) (formed at room temperature) as well as partial relaxation of lattice strain through three-dimensional (3D) island growth.

  19. Supramolecular order and structural dynamics: A STM study of 2H-tetraphenylporphycene on Cu(111)

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

    Stark, Michael; Träg, Johannes; Ditze, Stefanie

    2015-03-14

    The adsorption of 2H-tetraphenylporphycene (2HTPPc) on Cu(111) was investigated by scanning tunneling microscopy (STM). At medium coverages, supramolecular ordered islands are observed. The individual 2HTPPc molecules appear as two pairs of intense protrusions which are separated by an elongated depression. In the islands, the molecules are organized in rows oriented along one of the close packed Cu(111) substrate rows; the structure is stabilized by T-type interactions of the phenyl substituents of neighboring molecules. Two types of rows are observed, namely, highly ordered rows in which all molecules exhibit the same orientation, and less ordered rows in which the molecules exhibitmore » two perpendicular orientations. Altogether, three different azimuthal orientations of 2HTPPc are observed within one domain, all of them rotated by 15° ± 1° relative to one closed packed Cu direction. The highly ordered rows are always separated by either one or two less ordered rows, with the latter structure being the thermodynamically more stable one. The situation in the islands is highly dynamic, such that molecules in the less ordered rows occasionally change orientation, also complete highly ordered rows can move. The supramolecular order and structural dynamics are discussed on the basis of the specific molecule-substrate and molecule-molecule interactions.« less

  20. STM/STS study of superconducting properties in Ca10(Pt4As8)(Fe2As2)5

    NASA Astrophysics Data System (ADS)

    Kim, Jisun; Nam, Hyoungdo; Li, Guorong; Karki, Amar; Shih, Chih-Kang; Zhang, Jiandi; Jin, Rongying; Plummer, E. W.

    2014-03-01

    Newly discovered iron-based superconductor, Ca10(Pt4As8)(Fe2As2)5 (Tc = 34 K) is studied using scanning tunneling microscopy/spectroscopy (STM/S). Given the symmetry of the crystal structure, several surface terminations are expected with roughly same probability: 1) Ca or partial Ca layer on top Fe2As2; 2) Ca or partial Ca layer on top Pt4As8 layer; 3) A Fe2As2 layer, and; 4) A Pt4As8layer.Surprisingly,Fe2As2 related layers (1 & 3) are rarely observed (less than 1%). Instead, we observe Pt4As8 layers separated by unit-cell-high (~ 1 nm) steps accompanied with Ca or partial Ca layer on top Pt4As8 layer (1 - 2 Å step height). Scanning tunneling spectroscopy reveals different spectra for each surface, with superconducting coherence peaks seen only on Ca layers. We argue that intermediary layers are proximity-coupled to superconducting Fe2As2 layers. The results from Ca10(Pt4As8)(Fe2As2)5 are discussed with the properties observed in other iron-based superconductors. Funded by NSF

  1. Electrodeposition of copper on a Pt(111) electrode in sulfuric acid containing poly(ethylene glycol) and chloride ions as probed by in situ STM.

    PubMed

    Fu, YunLin; Pao, Te; Chen, Sih-Zih; Yau, ShuehLin; Dow, Wei-Ping; Lee, Yuh-Lang

    2012-07-03

    This study employed real-time in situ STM imaging to examine the adsorption of PEG molecules on Pt(111) modified by a monolayer of copper adatoms and the subsequent bulk Cu deposition in 1 M H(2)SO(4) + 1 mM CuSO(4)+ 1 mM KCl + 88 μM PEG. At the end of Cu underpotential deposition (~0.35 V vs Ag/AgCl), a highly ordered Pt(111)-(√3 × √7)-Cu + HSO(4)(-) structure was observed in 1 M H(2)SO(4) + 1 mM CuSO(4). This adlattice restructured upon the introduction of poly(ethylene glycol) (PEG, molecular weight 200) and chloride anions. At the onset potential for bulk Cu deposition (~0 V), a Pt(111)-(√3 × √3)R30°-Cu + Cl(-) structure was imaged with a tunneling current of 0.5 nA and a bias voltage of 100 mV. Lowering the tunneling current to 0.2 nA yielded a (4 × 4) structure, presumably because of adsorbed PEG200 molecules. The subsequent nucleation and deposition processes of Cu in solution containing PEG and Cl(-) were examined, revealing the nucleation of 2- to 3-nm-wide CuCl clusters on an atomically smooth Pt(111) surface at overpotentials of less than 50 mV. With larger overpotential (η > 150 mV), Cu deposition seemed to bypass the production of CuCl species, leading to layered Cu deposition, starting preferentially at step defects, followed by lateral growth to cover the entire Pt electrode surface. These processes were observed with both PEG200 and 4000, although the former tended to produce more CuCl nanoclusters. Raising [H(2)SO(4)] to 1 M substantiates the suppressing effect of PEG on Cu deposition. This STM study provided atomic- or molecular-level insight into the effect of PEG additives on the deposition of Cu.

  2. Transmission measurement based on STM observation to detect the penetration depth of low-energy heavy ions in botanic samples.

    PubMed

    Liu, Feng; Wang, Yugang; Xue, Jianming; Wang, Sixue; Du, Guanhua; Zhao, Weijiang

    2003-02-01

    The penetration depth of low-energy heavy ions in botanic samples was detected with a new transmission measurement. In the measurement, highly oriented pyrolytic graphite (HOPG) pieces were placed behind the botanic samples with certain thickness. During the irradiation of heavy ions with energy of tens of keV, the energetic particles transmitted from those samples were received by the HOPG pieces. After irradiation, scanning tunneling microscope (STM) was applied to observe protrusion-like damage induced by these transmitted ions on the surface of the HOPG. The statistical average number density of protrusions and the minimum transmission rate of the low-energy heavy ions can be obtained. The detection efficiency of the new method for low-energy heavy ions was about 0.1-1 and the background in the measurement can be reduced to as low as 1.0 x 10(8) protrusions/cm2. With this method, the penetration depth of the energetic particles was detected to be no less than 60 micrometers in kidney bean slices when the slices were irradiated by 100 keVAr+ ion at the fluence of 5 x 10(16) ions/cm2. c2002 Elsevier Science Ltd. All rights reserved.

  3. Transmission measurement based on STM observation to detect the penetration depth of low-energy heavy ions in botanic samples

    NASA Technical Reports Server (NTRS)

    Liu, Feng; Wang, Yugang; Xue, Jianming; Wang, Sixue; Du, Guanhua; Zhao, Weijiang

    2003-01-01

    The penetration depth of low-energy heavy ions in botanic samples was detected with a new transmission measurement. In the measurement, highly oriented pyrolytic graphite (HOPG) pieces were placed behind the botanic samples with certain thickness. During the irradiation of heavy ions with energy of tens of keV, the energetic particles transmitted from those samples were received by the HOPG pieces. After irradiation, scanning tunneling microscope (STM) was applied to observe protrusion-like damage induced by these transmitted ions on the surface of the HOPG. The statistical average number density of protrusions and the minimum transmission rate of the low-energy heavy ions can be obtained. The detection efficiency of the new method for low-energy heavy ions was about 0.1-1 and the background in the measurement can be reduced to as low as 1.0 x 10(8) protrusions/cm2. With this method, the penetration depth of the energetic particles was detected to be no less than 60 micrometers in kidney bean slices when the slices were irradiated by 100 keVAr+ ion at the fluence of 5 x 10(16) ions/cm2. c2002 Elsevier Science Ltd. All rights reserved.

  4. Observation of van Hove singularity and quasiparticle interference in KFe2 As2 superconductors revealed by STM/STS measurements

    NASA Astrophysics Data System (ADS)

    Wen, Hai-Hu; Fang, Delong; Du, Zengyi; Wang, Zhenyu; Yang, Huan; Ding, Xiaxin

    2015-03-01

    We have conducted STM/STS investigations on the KFe2As2 superconducting single crystals down to 0.45 K under magnetic field. Clear electronic standing waves have been observed allowing us to investigate the quasiparticle interference (QPI). Interestingly we observed a sharp peak of local density of states (LDOS) near the Fermi energy showing evidence of strongly enhanced DOS both below and above Tc. We demonstrate that this is induced by a van Hove singularity with the saddle point locating only 4 meV below the Fermi energy. Below Tc it is found that only 20% of the normal state DOS is gapped away by superconductivity, with the major part of DOS due to VHS ungapped. Combing with the ARPES data, we find that the VHS points locate on the (π,0) point, which gives strong constraint on the gap function and pairing mechanism. In the mixed state we clearly observed the mixture of vortices and the standing waves due to quasiparticle interference, giving support to above picture. In collaboration with X. Shi, P. Richard, T. Qian and H. Ding et al. in Institute of Physics, CAS.

  5. STM/STS studies for interplane disorder effects on the electronic states of the Cu-O plane in Bi2201

    NASA Astrophysics Data System (ADS)

    Kurosawa, T.; Hatta, G.; Miyazaki, H.; Yamaji, J.; Yoshikawa, K.; Nakagawa, Y.; Shibata, Y.; Yoshida, H.; Oda, M.; Ido, M.; Takeyama, K.; Momono, N.

    2015-08-01

    STM/STS experiments have been performed in Bi2Sr1.7R0.3CuO6+δ (R-Bi2201) systems with R = La and Eu, which are of a nearly optimal doping level po but have different Tc values, 35 K and 20 K, respectively, to examine interplane disorder effects on the superconducting (SC) gap and the pseudogap (PG) that is accompanied by a checkerboard-type charge order (CCO). We report that as interplane disorders are strengthened by replacing La with Eu in optimal Bi2201, the antinodal PG size Δ∗ increases from ˜ 30meV to ˜ 60meV, which is comparable to the value for an underdoping level p/po ˜ 0.5 in La-Bi2201. On the other hand, the period of CCO in optimal Eu-Bi2201 is the same as in optimal La-Bi2201, about five times lattice constant ˜ 5a along the Cu-O bond directions; it remains unchanged even if the PG develops markedly to the same degree as for p/po ˜ 0.5 in La-Bi2201, whose period is ˜ 4a.

  6. STM/STS study on electronic superstructures in the superconducting state of high-Tc cuprate Bi2Sr2CaCu2O8+δ

    NASA Astrophysics Data System (ADS)

    Mizuta, S.; Kurosawa, T.; Takeyama, K.; Momono, N.; Ishii, Y.; Yoshida, H.; Oda, M.; Ido, M.

    2018-03-01

    We report STM/STS measurements at 8 K in underdoped Bi2Sr2CaCu2O8+δ crystals (T c = 76 K and hole-doping level p ∼ 0.12) whose energy spectra around the Fermi level are characterized by a two-gap structure consisting of spatially inhomogeneous pseudogap (PG) and comparatively homogeneous superconducting gap (SCG). Two electronic superstructures, checkerboard modulation (CBM) and Cu-O-Cu bond-centered modulation (BCM), are observed with mapping spectral weights at low energies within the SCG and the ratio of spectral weights at ±ΔPG (PG energy), respectively. On the basis of the present findings, we suggest that the lower-energy scale CBM is an intrinsic property of Cu-O planes and can coexist with the BCM whose characteristic energy is ∼ΔPG in identical regions in real space.

  7. STM studies of an atomic-scale gate electrode formed by a single charged vacancy in GaAs

    NASA Astrophysics Data System (ADS)

    Lee, Donghun; Daughton, David; Gupta, Jay

    2009-03-01

    Electric-field control of spin-spin interactions at the atomic level is desirable for the realization of spintronics and spin-based quantum computation. Here we demonstrate the realization of an atomic-scale gate electrode formed by a single charged vacancy on the GaAs(110) surface[1]. We can position these vacancies with atomic precision using the tip of a home-built, low temperature STM. Tunneling spectroscopy of single Mn acceptors is used to quantify the electrostatic field as a function of distance from the vacancy. Single Mn acceptors are formed by substituting Mn adatoms for Ga atoms in the first layer of the p-GaAs(110) surface[2]. Depending on the distance, the in-gap resonance of single Mn acceptors can shift as much as 200meV. Our data indicate that the electrostatic field decays according to a screened Coulomb potential. The charge state of the vacancy can be switched to neutral, as evidenced by the Mn resonance returning to its unperturbed position. Reversible control of the local electric field as well as charged states of defects in semiconductors can open new insights such as realizing an atomic-scale gate control and studying spin-spin interactions in semiconductors. http://www.physics.ohio-state.edu/sim jgupta [1] D. Lee and J.A. Gupta (in preparation) [2] D. Kitchen et al., Nature 442, 436-439 (2006)

  8. Features of Superconducting Gaps Revealed by STM/STS in Iron Based Superconductors With and Without Hole Pockets

    NASA Astrophysics Data System (ADS)

    Wen, Hai-Hu; Hai-Hu Wen Team

    The pairing mechanism and gap structure in iron based superconductors (IBS) remains unresolved. We have conducted extensive STM/STS study on the Na(Fe1-xTx) As (T =Co, Cu, Mn), Ba1-xKxFe2As2KFe2As2, and Li1-xFexOHFeSe single crystals. We found the clear evidence of the in-gap quasi-particle states induced by the non-magnetic Cu impurities in Na(Fe0.97- x Co0.03Cux) As, giving strong evidence of the S+/- pairing. Furthermore, we show the presence of the bosonic mode with the energy identical to that of the neutron resonance and a simple linear relation Ω/kBTc ~ 4.3, being explained a consequence of the S+/-pairing. The STS spectrum in Li1-x FexOHFeSe clearly indicates the presence of double superconducting gaps with Δ1 ~ 14.3 meV and Δ2 ~ 8.6 meV. Further analysis based on QPI allows us to assign the larger (smaller) gap to the outer (inner) hybridized electron pockets. The huge value 2Δ1/kBTc = 8.7 discovered here undoubtedly proves the strong coupling mechanism. This work was supported by the Ministry of Science and Technology of China, National Natural Science Foundation of China.

  9. InAs wetting layer and quantum dots on GaAs(001) surface studied by in situ STM placed inside MBE growth chamber and kMC simulations based on first-principles calculations

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

    Tsukamoto, S.; Arakawa, Y.; Bell, G. R.

    2007-04-10

    Dynamic images of InAs quantum dots (QDs) formation are obtained using a unique scanning tunneling microscope (STM) placed within the growth chamber. These images are interpreted with the aid of kinetic Monte Carlo (kMC) simulations of the QD nucleation process. Alloy fluctuations in the InGaAs wetting layer prior to QD formation assist in the nucleation of stable InAs islands containing tens of atoms which grow extremely rapidly to form QDs. Furthermore, not all deposited In is initially incorporated into the lattice, providing a large supply of material to rapidly form QDs at the critical thickness.

  10. Coulomb blockade and charge ordering in a few layers of TTF-TCNQ investigated by low-temperature STM/STS

    NASA Astrophysics Data System (ADS)

    Jeon, Seokmin; Maksymovych, Petro

    In contrast to the vast effort on bulk crystal phases of the prototypical organic charge-transfer complex, TTF-TCNQ, study of low-dimensional phases has been limited to monolayer phases on substrates. In this state, however, none of the physics of the bulk phase is observed owing to the overwhelming effect of the substrate. We investigate the molecular structure and electronic properties of a few layers of TTF-TCNQ grown on Au(111) and Ag(111) using STM/STS at 4.3 K. By decoupling the molecular electronic state from the metal surface, we have made the first observation of the effect of confinement on the electronic properties of TTF-TCNQ. STS reveals a plethora of sharp features due to molecular orbitals, each influenced by charge-transfer between the molecules. We hypothesize the existence of a Mott-insulator state in 3-layer islands, with a Coulomb gap of ~1 eV. In contrast, the corresponding bulk phase is a Peierls insulator with a gap of ~20 meV. The root cause of the nanoscale phase is traced to simultaneous electron confinement and structural frustration, which dramatically modify the energy balance of self-ionization allowing for integer charge transfer. These studies open broad opportunities to explore correlated electron physics in molecular systems. This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

  11. A combined STM and SPA-LEED study of the “explosive” nucleation and collective diffusion in Pb/Si(111)

    DOE PAGES

    Hattab, H.; Hupalo, M.; Hershberger, M. T.; ...

    2015-08-20

    A novel type of very fast nucleation was recently found in Pb/Si(111) with 4- to 7-layer high islands becoming crystalline in an “explosive” way, when the Pb deposited amount in the wetting layer is compressed to θ c ~ 1.22 ML, well above the metallic Pb(111) density. This “explosive” nucleation is very different from classical nucleation when island growth is more gradual and islands grow in size by single adatom aggregation [8]. In order to identify the key parameters that control the nucleation we used scanning tunneling microscopy (STM) and spot profile analysis low energy electron diffraction (SPA-LEED). It wasmore » found that the number and duration of steps in iterative deposition used to approach θc and the flux rate have dramatic effects on the crystallization process. Larger depositions over shorter times induce greater spatial coverage fluctuations, so local areas can reach the critical coverage θ c easier. This can trigger the collective motion of the wetting layer from far away to build the Pb islands “explosively”. Here, the SPA-LEED experiments show that even low flux experiments in iterative deposition experiments can trigger transfer of material to the superstable 7-layer islands, as seen from the stronger satellite rings close to the (00) spot.« less

  12. The heterogeneity of verbal short-term memory impairment in aphasia.

    PubMed

    Majerus, Steve; Attout, Lucie; Artielle, Marie-Amélie; Van der Kaa, Marie-Anne

    2015-10-01

    Verbal short-term memory (STM) impairment represents a frequent and long-lasting deficit in aphasia, and it will prevent patients from recovering fully functional language abilities. The aim of this study was to obtain a more precise understanding of the nature of verbal STM impairment in aphasia, by determining whether verbal STM impairment is merely a consequence of underlying language impairment, as suggested by linguistic accounts of verbal STM, or whether verbal STM impairment reflects an additional, specific deficit. We investigated this question by contrasting item-based STM measures, supposed to depend strongly upon language activation, and order-based STM measures, supposed to reflect the operation of specific, serial order maintenance mechanisms, in a sample of patients with single-word processing deficits at the phonological and/or lexical level. A group-level analysis showed robust impairment for both item and serial order STM aspects in the aphasic group relative to an age-matched control group. An analysis of individual profiles revealed an important heterogeneity of verbal STM profiles, with patients presenting either selective item STM deficits, selective order STM deficits, generalized item and serial order STM deficits or no significant STM impairment. Item but not serial order STM impairment correlated with the severity of phonological impairment. These results disconfirm a strong version of the linguistic account of verbal STM impairment in aphasia, by showing variable impairment to both item and serial order processing aspects of verbal STM. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Structural and electronic properties of ultrathin FeSe films grown on Bi2Se3(0 0 0 1) studied by STM/STS

    NASA Astrophysics Data System (ADS)

    Singh, Udai Raj; Warmuth, Jonas; Markmann, Verena; Wiebe, Jens; Wiesendanger, Roland

    2017-01-01

    We report scanning tunnelling microscopy and spectroscopy (STM/STS) studies on one and two unit cell (UC) high FeSe thin films grown on Bi2Se3(0 0 0 1). In our thin films, we find the tetragonal phase of FeSe and dumb-bell shaped defects oriented along Se-Se bond directions. In addition, we observe striped moiré patterns with a periodicity of (7.3  ±  0.1) nm generated by the mismatch between the FeSe lattice and the Bi2Se3 lattice. We could not find any signature of a superconducting gap in the tunneling spectra measured on the surface of one and two UC thick islands of FeSe down to 6.5 K. The spectra rather show an asymmetric behavior across and a finite density of states at the Fermi level (E F) resembling those taken in the normal state of bulk FeSe.

  14. Calcium ion binding properties and the effect of phosphorylation on the intrinsically disordered Starmaker protein.

    PubMed

    Wojtas, Magdalena; Hołubowicz, Rafał; Poznar, Monika; Maciejewska, Marta; Ożyhar, Andrzej; Dobryszycki, Piotr

    2015-10-27

    Starmaker (Stm) is an intrinsically disordered protein (IDP) involved in otolith biomineralization in Danio rerio. Stm controls calcium carbonate crystal formation in vivo and in vitro. Phosphorylation of Stm affects its biomineralization properties. This study examined the effects of calcium ions and phosphorylation on the structure of Stm. We have shown that CK2 kinase phosphorylates 25 or 26 residues in Stm. Furthermore, we have demonstrated that Stm's affinity for calcium binding is dependent on its phosphorylation state. Phosphorylated Stm (StmP) has an estimated 30 ± 1 calcium binding sites per protein molecule with a dissociation constant (KD) of 61 ± 4 μM, while the unphosphorylated protein has 28 ± 3 sites and a KD of 210 ± 22 μM. Calcium ion binding induces a compaction of the Stm molecule, causing a significant decrease in its hydrodynamic radius and the formation of a secondary structure. The screening effect of Na(+) ions on calcium binding was also observed. Analysis of the hydrodynamic properties of Stm and StmP showed that Stm and StmP molecules adopt the structure of native coil-like proteins.

  15. Intrinsically disordered and pliable Starmaker-like protein from medaka (Oryzias latipes) controls the formation of calcium carbonate crystals.

    PubMed

    Różycka, Mirosława; Wojtas, Magdalena; Jakób, Michał; Stigloher, Christian; Grzeszkowiak, Mikołaj; Mazur, Maciej; Ożyhar, Andrzej

    2014-01-01

    Fish otoliths, biominerals composed of calcium carbonate with a small amount of organic matrix, are involved in the functioning of the inner ear. Starmaker (Stm) from zebrafish (Danio rerio) was the first protein found to be capable of controlling the formation of otoliths. Recently, a gene was identified encoding the Starmaker-like (Stm-l) protein from medaka (Oryzias latipes), a putative homologue of Stm and human dentine sialophosphoprotein. Although there is no sequence similarity between Stm-l and Stm, Stm-l was suggested to be involved in the biomineralization of otoliths, as had been observed for Stm even before. The molecular properties and functioning of Stm-l as a putative regulatory protein in otolith formation have not been characterized yet. A comprehensive biochemical and biophysical analysis of recombinant Stm-l, along with in silico examinations, indicated that Stm-l exhibits properties of a coil-like intrinsically disordered protein. Stm-l possesses an elongated and pliable structure that is able to adopt a more ordered and rigid conformation under the influence of different factors. An in vitro assay of the biomineralization activity of Stm-l indicated that Stm-l affected the size, shape and number of calcium carbonate crystals. The functional significance of intrinsically disordered properties of Stm-l and the possible role of this protein in controlling the formation of calcium carbonate crystals is discussed.

  16. Intrinsically Disordered and Pliable Starmaker-Like Protein from Medaka (Oryzias latipes) Controls the Formation of Calcium Carbonate Crystals

    PubMed Central

    Różycka, Mirosława; Wojtas, Magdalena; Jakób, Michał; Stigloher, Christian; Grzeszkowiak, Mikołaj; Mazur, Maciej; Ożyhar, Andrzej

    2014-01-01

    Fish otoliths, biominerals composed of calcium carbonate with a small amount of organic matrix, are involved in the functioning of the inner ear. Starmaker (Stm) from zebrafish (Danio rerio) was the first protein found to be capable of controlling the formation of otoliths. Recently, a gene was identified encoding the Starmaker-like (Stm-l) protein from medaka (Oryzias latipes), a putative homologue of Stm and human dentine sialophosphoprotein. Although there is no sequence similarity between Stm-l and Stm, Stm-l was suggested to be involved in the biomineralization of otoliths, as had been observed for Stm even before. The molecular properties and functioning of Stm-l as a putative regulatory protein in otolith formation have not been characterized yet. A comprehensive biochemical and biophysical analysis of recombinant Stm-l, along with in silico examinations, indicated that Stm-l exhibits properties of a coil-like intrinsically disordered protein. Stm-l possesses an elongated and pliable structure that is able to adopt a more ordered and rigid conformation under the influence of different factors. An in vitro assay of the biomineralization activity of Stm-l indicated that Stm-l affected the size, shape and number of calcium carbonate crystals. The functional significance of intrinsically disordered properties of Stm-l and the possible role of this protein in controlling the formation of calcium carbonate crystals is discussed. PMID:25490041

  17. Attention supports verbal short-term memory via competition between dorsal and ventral attention networks.

    PubMed

    Majerus, Steve; Attout, Lucie; D'Argembeau, Arnaud; Degueldre, Christian; Fias, Wim; Maquet, Pierre; Martinez Perez, Trecy; Stawarczyk, David; Salmon, Eric; Van der Linden, Martial; Phillips, Christophe; Balteau, Evelyne

    2012-05-01

    Interactions between the neural correlates of short-term memory (STM) and attention have been actively studied in the visual STM domain but much less in the verbal STM domain. Here we show that the same attention mechanisms that have been shown to shape the neural networks of visual STM also shape those of verbal STM. Based on previous research in visual STM, we contrasted the involvement of a dorsal attention network centered on the intraparietal sulcus supporting task-related attention and a ventral attention network centered on the temporoparietal junction supporting stimulus-related attention. We observed that, with increasing STM load, the dorsal attention network was activated while the ventral attention network was deactivated, especially during early maintenance. Importantly, activation in the ventral attention network increased in response to task-irrelevant stimuli briefly presented during the maintenance phase of the STM trials but only during low-load STM conditions, which were associated with the lowest levels of activity in the dorsal attention network during encoding and early maintenance. By demonstrating a trade-off between task-related and stimulus-related attention networks during verbal STM, this study highlights the dynamics of attentional processes involved in verbal STM.

  18. Temperature-induced structural evolution of Sm nanoparticles on Al2O3 thin film: An in-situ investigation using SRPES, XPS and STM

    NASA Astrophysics Data System (ADS)

    Xu, Qian; Hu, Shanwei; Wang, Weijia; Wang, Yan; Ju, Huanxin; Zhu, Junfa

    2018-02-01

    The structural evolution of Sm nanoclusters on ultrathin film of Al2O3 epitaxially grown on Ni3Al(111) substrate at elevated temperatures was investigated in-situ using synchrotron radiation photoemission spectroscopy (SRPES), X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). The vapor-deposited metallic Sm onto the Al2O3 thin film at 300 K is partially oxidized, leading to the appearance of both Sm2+ and Sm3+ states at low coverages, due to the charge transfer from Sm to oxide film. The complete oxidation of the Sm, i.e., all Sm2+ converted to Sm3+, occurs when the sample is annealed to 500 K. Further annealing results in the diffusion of Sm into the Al2O3 lattice. At ∼900 K, the formation of a SmAlO3 complex is observed. However, this complex starts to decompose and desorb from the surface at temperature higher than 1200 K. Interestingly, it is found that Sm can promote the oxidation of Ni3Al substrate and thicken the alumina film when Sm is deposited at room temperature onto the Al2O3/Ni3Al(111) substrate followed by annealing in oxygen environment at ∼800 K.

  19. Investigation of local modification and luminescence of a carbon nanotube by scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Katano, Satoshi; Fujita, Hiroto; Uehara, Yoichi

    2018-01-01

    We have studied the nanoscale luminescence from a multiwalled carbon nanotube (CNT) adsorbed on Au(111) using a scanning tunneling microscope (STM). STM images revealed that a number of isolated chains of CNTs can be deposited by dry contact transfer while keeping the surface clean. By injecting tunneling electrons from the STM tip to the CNT, we observed STM light emission (STM-LE) from the CNT in the visible-light range, showing electronic transitions between the bands associated with the van Hove singularity in the density of states of the CNT. The STM-LE spectrum was obviously changed after introducing the local defect created by the STM tip, indicating the controllability of the nanoscale luminescence within a single chain of a CNT.

  20. Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.

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

    Biedermann, Laura Butler

    2009-09-01

    MWNTs, their vibration spectra was more extensively studied. The thermal vibration spectra of Ag{sub 2}Ga nanoneedles was measured under both ambient and low-vacuum conditions. The operational deflection shapes of the vibrating Ag{sub 2}Ga nanoneedles was also measured, allowing confirmation of the eigenmodes of vibration. The modulus of the crystalline nanoneedles was 84.3 {+-} 1.0 GPa. Gas damping is the dominate mechanism of energy loss for nanowires oscillating under ambient conditions. The measured quality factors, Q, of oscillation are in line with theoretical predictions of air damping in the free molecular gas damping regime. In the free molecular regime, Q{sub gas} is linearly proportional to the density and diameter of the nanowire and inversely proportional to the air pressure. Since the density of the Ag{sub 2}Ga nanoneedles is three times that of the MWNTs, the Ag{sub 2}Ga nanoneedles have greater Q at atmospheric pressures. Our initial measurements of Q for Ag{sub 2}Ga nanoneedles in low-vacuum (10 Torr) suggest that the intrinsic Q of these nanoneedles may be on the order of 1000. The epitaxial carbon that grows after heating (000{bar 1}) silicon carbide (SiC) to high temperatures (1450-1600) in vacuum was also studied. At these high temperatures, the surface Si atoms sublime and the remaining C atoms reconstruct to form graphene. X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) were used to characterize the quality of the few-layer graphene (FLG) surface. The XPS studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples. STM studies revealed a wide variety of nanometer-scale features that include sharp carbon-rich ridges, moire superlattices, one-dimensional line defects, and grain boundaries. By imaging these features with atomic scale resolution, considerable insight into the growth mechanisms of FLG on the carbon-face of SiC is obtained.« less

  1. Theoretical Study of tip apex electronic structure in Scanning Tunneling Microscope

    NASA Astrophysics Data System (ADS)

    Choi, Heesung; Huang, Min; Randall, John; Cho, Kyeongjae

    2011-03-01

    Scanning Tunneling Microscope (STM) has been widely used to explore diverse surface properties with an atomic resolution, and STM tip has played a critical role in controlling surface structures. However, detailed information of atomic and electronic structure of STM tip and the fundamental understanding of STM images are still incomplete. Therefore, it is important to develop a comprehensive understanding of the electronic structure of STM tip. We have studied the atomic and electronic structures of STM tip with various transition metals (TMs) by DFT method. The d-electrons of TM tip apex atoms show different orbital states near the Fermi level. We will present comprehensive data of STM tips from our DFT calculation. Verified quantification of the tip electronic structures will lead to fundamental understanding of STM tip structure-property relationship. This work is supported by the DARPA TBN Program and the Texas ETF. DARPA Tip Based Nanofabrication Program and the Emerging Technology Fund of the State of Texas.

  2. The KNOXI Transcription Factor SHOOT MERISTEMLESS Regulates Floral Fate in Arabidopsis.

    PubMed

    Roth, Ohad; Alvarez, John; Levy, Matan; Bowman, John L; Ori, Naomi; Shani, Eilon

    2018-05-09

    Plants have evolved a unique and conserved developmental program that enables the conversion of leaves into floral organs. Elegant genetic and molecular work has identified key regulators of flower meristem identity. However, further understanding of flower meristem specification has been hampered by redundancy and by pleiotropic effects. The KNOXI transcription factor SHOOT MERISTEMLESS (STM) is a well-characterized regulator of shoot apical meristem maintenance. Arabidopsis thaliana stm loss-of-function mutants arrest shortly after germination, and therefore the knowledge on later roles of STM in later processes, including flower development, is limited. Here, we uncover a role for STM in the specification of flower meristem identity. Silencing STM in the APETALA1 (AP1) expression domain in the ap1-4 mutant background resulted in a leafy-flower phenotype, and an intermediate stm-2 allele enhanced the flower meristem identity phenotype of ap1-4. Transcriptional profiling of STM perturbation suggested that STM activity affects multiple floral fate genes, among them the F-Box protein-encoding gene UNUSUAL FLORAL ORGANS (UFO). In agreement with this notion, stm-2 enhanced the ufo-2 floral fate phenotype, and ectopic UFO expression rescued the leafy flowers in genetic backgrounds with compromised AP1 and STM activities. This work suggests a genetic mechanism that underlies the activity of STM in the specification of flower meristem identity. © 2018 American Society of Plant Biologists. All rights reserved.

  3. Explaining semantic short-term memory deficits: Evidence for the critical role of semantic control

    PubMed Central

    Hoffman, Paul; Jefferies, Elizabeth; Lambon Ralph, Matthew A.

    2011-01-01

    Patients with apparently selective short-term memory (STM) deficits for semantic information have played an important role in developing multi-store theories of STM and challenge the idea that verbal STM is supported by maintaining activation in the language system. We propose that semantic STM deficits are not as selective as previously thought and can occur as a result of mild disruption to semantic control processes, i.e., mechanisms that bias semantic processing towards task-relevant aspects of knowledge and away from irrelevant information. We tested three semantic STM patients with tasks that tapped four aspects of semantic control: (i) resolving ambiguity between word meanings, (ii) sensitivity to cues, (iii) ignoring irrelevant information and (iv) detecting weak semantic associations. All were impaired in conditions requiring more semantic control, irrespective of the STM demands of the task, suggesting a mild, but task-general, deficit in regulating semantic knowledge. This mild deficit has a disproportionate effect on STM tasks because they have high intrinsic control demands: in STM tasks, control is required to keep information active when it is no longer available in the environment and to manage competition between items held in memory simultaneously. By re-interpreting the core deficit in semantic STM patients in this way, we are able to explain their apparently selective impairment without the need for a specialised STM store. Instead, we argue that semantic STM patients occupy the mildest end of spectrum of semantic control disorders. PMID:21195105

  4. The case against specialized visual-spatial short-term memory.

    PubMed

    Morey, Candice C

    2018-05-24

    The dominant paradigm for understanding working memory, or the combination of the perceptual, attentional, and mnemonic processes needed for thinking, subdivides short-term memory (STM) according to whether memoranda are encoded in aural-verbal or visual formats. This traditional dissociation has been supported by examples of neuropsychological patients who seem to selectively lack STM for either aural-verbal, visual, or spatial memoranda, and by experimental research using dual-task methods. Though this evidence is the foundation of assumptions of modular STM systems, the case it makes for a specialized visual STM system is surprisingly weak. I identify the key evidence supporting a distinct verbal STM system-patients with apparent selective damage to verbal STM and the resilience of verbal short-term memories to general dual-task interference-and apply these benchmarks to neuropsychological and experimental investigations of visual-spatial STM. Contrary to the evidence on verbal STM, patients with apparent visual or spatial STM deficits tend to experience a wide range of additional deficits, making it difficult to conclude that a distinct short-term store was damaged. Consistently with this, a meta-analysis of dual-task visual-spatial STM research shows that robust dual-task costs are consistently observed regardless of the domain or sensory code of the secondary task. Together, this evidence suggests that positing a specialized visual STM system is not necessary. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

  5. The Nature of Verbal Short-Term Impairment in Dyslexia: The Importance of Serial Order

    PubMed Central

    Majerus, Steve; Cowan, Nelson

    2016-01-01

    Verbal short-term memory (STM) impairment is one of the most consistent associated deficits observed in developmental reading disorders such as dyslexia. Few studies have addressed the nature of this STM impairment, especially as regards the ability to temporarily store serial order information. This question is important as studies in typically developing children have shown that serial order STM abilities are predictors of oral and written language development. Associated serial order STM deficits in dyslexia may therefore further increase the learning difficulties in these populations. In this mini review, we show that specific serial order STM impairment is frequently reported in both dyslexic children and adults with a history of dyslexia. Serial order STM impairment appears to occur for the retention of both verbal and visuo-spatial sequence information. Serial order STM impairment is, however, not a characteristic of every individual dyslexic subject and is not specific to dyslexia. Future studies need to determine whether serial order STM impairment is a risk factor which, in association with phonological processing deficits, can lead to dyslexia or whether serial order STM impairment reflects associated deficits causally unrelated to dyslexia. PMID:27752247

  6. Preparation of Chemically Etched Tips for Ambient Instructional Scanning Tunneling Microscopy

    ERIC Educational Resources Information Center

    Zaccardi, Margot J.; Winkelmann, Kurt; Olson, Joel A.

    2010-01-01

    A first-year laboratory experiment that utilizes concepts of electrochemical tip etching for scanning tunneling microscopy (STM) is described. This experiment can be used in conjunction with any STM experiment. Students electrochemically etch gold STM tips using a time-efficient method, which can then be used in an instructional grade STM that…

  7. Explaining Semantic Short-Term Memory Deficits: Evidence for the Critical Role of Semantic Control

    ERIC Educational Resources Information Center

    Hoffman, Paul; Jefferies, Elizabeth; Lambon Ralph, Matthew A.

    2011-01-01

    Patients with apparently selective short-term memory (STM) deficits for semantic information have played an important role in developing multi-store theories of STM and challenge the idea that verbal STM is supported by maintaining activation in the language system. We propose that semantic STM deficits are not as selective as previously thought…

  8. Plant growth and resistance promoted by Streptomyces spp. in tomato.

    PubMed

    Dias, Maila P; Bastos, Matheus S; Xavier, Vanessa B; Cassel, Eduardo; Astarita, Leandro V; Santarém, Eliane R

    2017-09-01

    Plant Growth Promoting Rhizobacteria (PGPR) represent an alternative to improve plant growth and yield as well as to act as agents of biocontrol. This study characterized isolates of Streptomyces spp. (Stm) as PGPR, determined the antagonism of these isolates against Pectobacterium carotovorum subsp. brasiliensis (Pcb), evaluated the ability of Stm on promoting growth and modulating the defense-related metabolism of tomato plants, and the potential of Stm isolates on reducing soft rot disease in this species. The VOC profile of Stm was also verified. Promotion of plant growth was assessed indirectly through VOC emission and by direct interaction with Stm isolates in the roots. Evaluation of soft rot disease was performed in vitro on plants treated with Stm and challenged with Pcb. Enzymes related to plant defense were then analyzed in plants treated with three selected isolates of Stm, and PM1 was chosen for further Pcb-challenging experiment. Streptomyces spp. isolates displayed characteristics of PGPR. PM3 was the isolate with efficient antagonism against Pcb by dual-culture. Most of the isolates promoted growth of root and shoot of tomato plants by VOC, and PM5 was the isolate that most promoted growth by direct interaction with Stm. Soft rot disease and mortality of plants were significantly reduced when plants were treated with StmPM1. Modulation of secondary metabolism was observed with Stm treatment, and fast response of polyphenoloxidases was detected in plants pretreated with StmPM1 and challenged with Pcb. Peroxidase was significantly activated three days after infection with Pcb in plants pretreated with StmPM1. Results suggest that Streptomyces sp. PM1 and PM5 have the potential to act as PGPR. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  9. Short Term Memory, Working Memory, and Syntactic Comprehension in Aphasia

    PubMed Central

    Caplan, David; Michaud, Jennifer; Hufford, Rebecca

    2013-01-01

    Sixty one people with aphasia were tested on ten tests of short term memory (STM) and for the ability to use syntactic structure to determine the meanings of eleven types of sentences in three tasks – object manipulation, picture matching and picture matching with self-paced listening. Multilevel models showed relationships between measures of the ability to retain and manipulate item and order information in STM and accuracy and RT, and a greater relationship between these STM measures and accuracy and RT for several more complex sentence types in individual tasks. There were no effects of measures of STM that reflect the use of phonological codes or rehearsal on comprehension. There was only one effect of STM measures on self-paced listening times. There were double dissociations between performance on STM and individual comprehension tasks, indicating that normal STM is not necessary to perform normally on these tasks. The results are most easily related to the view that STM plays a facilitatory role in supporting the use of the products of the comprehension process to accomplish operations related to tasks. PMID:23865692

  10. In situ scanning tunneling microscope tip treatment device for spin polarization imaging

    DOEpatents

    Li, An-Ping [Oak Ridge, TN; Jianxing, Ma [Oak Ridge, TN; Shen, Jian [Knoxville, TN

    2008-04-22

    A tip treatment device for use in an ultrahigh vacuum in situ scanning tunneling microscope (STM). The device provides spin polarization functionality to new or existing variable temperature STM systems. The tip treatment device readily converts a conventional STM to a spin-polarized tip, and thereby converts a standard STM system into a spin-polarized STM system. The tip treatment device also has functions of tip cleaning and tip flashing a STM tip to high temperature (>2000.degree. C.) in an extremely localized fashion. Tip coating functions can also be carried out, providing the tip sharp end with monolayers of coating materials including magnetic films. The device is also fully compatible with ultrahigh vacuum sample transfer setups.

  11. Coordination of meristem and boundary functions by transcription factors in the SHOOT MERISTEMLESS regulatory network.

    PubMed

    Scofield, Simon; Murison, Alexander; Jones, Angharad; Fozard, John; Aida, Mitsuhiro; Band, Leah R; Bennett, Malcolm; Murray, James A H

    2018-04-30

    The Arabidopsis homeodomain transcription factor SHOOT MERISTEMLESS (STM) is crucial for shoot apical meristem (SAM) function, yet the components and structure of the STM gene regulatory network (GRN) are largely unknown. Here, we show that transcriptional regulators are overrepresented among STM-regulated genes and, using these as GRN components in Bayesian network analysis, we infer STM GRN associations and reveal regulatory relationships between STM and factors involved in multiple aspects of SAM function. These include hormone regulation, TCP-mediated control of cell differentiation, AIL/PLT-mediated regulation of pluripotency and phyllotaxis, and specification of meristem-organ boundary zones via CUC1. We demonstrate a direct positive transcriptional feedback loop between STM and CUC1, despite their distinct expression patterns in the meristem and organ boundary, respectively. Our further finding that STM activates expression of the CUC1-targeting microRNA miR164c combined with mathematical modelling provides a potential solution for this apparent contradiction, demonstrating that these proposed regulatory interactions coupled with STM mobility could be sufficient to provide a mechanism for CUC1 localisation at the meristem-organ boundary. Our findings highlight the central role for the STM GRN in coordinating SAM functions. © 2018. Published by The Company of Biologists Ltd.

  12. Scanning tunneling microscope assembly, reactor, and system

    DOEpatents

    Tao, Feng; Salmeron, Miquel; Somorjai, Gabor A

    2014-11-18

    An embodiment of a scanning tunneling microscope (STM) reactor includes a pressure vessel, an STM assembly, and three spring coupling objects. The pressure vessel includes a sealable port, an interior, and an exterior. An embodiment of an STM system includes a vacuum chamber, an STM reactor, and three springs. The three springs couple the STM reactor to the vacuum chamber and are operable to suspend the scanning tunneling microscope reactor within the interior of the vacuum chamber during operation of the STM reactor. An embodiment of an STM assembly includes a coarse displacement arrangement, a piezoelectric fine displacement scanning tube coupled to the coarse displacement arrangement, and a receiver. The piezoelectric fine displacement scanning tube is coupled to the coarse displacement arrangement. The receiver is coupled to the piezoelectric scanning tube and is operable to receive a tip holder, and the tip holder is operable to receive a tip.

  13. Ultra compact multitip scanning tunneling microscope with a diameter of 50 mm.

    PubMed

    Cherepanov, Vasily; Zubkov, Evgeny; Junker, Hubertus; Korte, Stefan; Blab, Marcus; Coenen, Peter; Voigtländer, Bert

    2012-03-01

    We present a multitip scanning tunneling microscope (STM) where four independent STM units are integrated on a diameter of 50 mm. The coarse positioning of the tips is done under the control of an optical microscope or scanning electron microscopy in vacuum. The heart of this STM is a new type of piezoelectric coarse approach called KoalaDrive. The compactness of the KoalaDrive allows building a four-tip STM as small as a single-tip STM with a drift of less than 0.2 nm/min at room temperature and lowest resonance frequencies of 2.5 kHz (xy) and 5.5 kHz (z). We present as examples of the performance of the multitip STM four point measurements of silicide nanowires and graphene.

  14. Unpacking Direct and Indirect Relationships of Short-Term Memory to Word Reading: Evidence From Korean-Speaking Children.

    PubMed

    Kim, Young-Suk Grace; Cho, Jeung-Ryeul; Park, Soon-Gil

    2017-08-01

    We examined the relations of short-term memory (STM), metalinguistic awareness (phonological, morphological, and orthographic awareness), and rapid automatized naming (RAN) to word reading in Korean, a language with a relatively transparent orthography. STM, metalinguistic awareness, and RAN have been shown to be important to word reading, but the nature of the relations of STM, metalinguistic awareness, and RAN to word reading has rarely been investigated. Two alternative models were fitted. In the indirect relation model, STM was hypothesized to be indirectly related to word reading via metalinguistic awareness and RAN. In the direct and indirect relations model, STM was hypothesized to be directly and indirectly related to word reading. Results from 207 beginning readers in South Korea showed that STM was directly related to word reading as well as indirectly via metalinguistic awareness and RAN. Although the direct effect of STM was relatively small (.16), the total effect incorporating the indirect effect was substantial (.42). These results suggest that STM is an important, foundational cognitive capacity that underpins metalinguistic awareness and RAN as well as word reading, and further indicate the importance of considering both direct and indirect effects of language and cognitive skills on word reading.

  15. Retrospective attention in short-term memory has a lasting effect on long-term memory across age.

    PubMed

    Strunk, Jonathan; Morgan, Lauren; Reaves, Sarah; Verhaeghen, Paul; Duarte, Audrey

    2018-04-13

    Declines in both short- and long-term memory are typical of healthy aging. Recent findings suggest that retrodictive attentional cues ("retro-cues") that indicate the location of to-be-probed items in short-term memory (STM) have a lasting impact on long-term memory (LTM) performance in young adults. Whether older adults can also use retro-cues to facilitate both STM and LTM is unknown. Young and older adults performed a visual STM task in which spatially informative retro-cues or non-informative neutral-cues were presented during STM maintenance of real-world objects. We tested participants' memory at both STM and LTM delays for objects that were previously cued with retrodictive or neutral cues during STM order to measure the lasting impact of retrospective attention on LTM. Older adults showed reduced STM and LTM capacity compared to young adults. However, they showed similar magnitude retro-cue memory benefits as young adults at both STM and LTM delays. To the best of our knowledge, this is the first study to investigate whether retro-cues in STM facilitate the encoding of objects into LTM such that they are more likely to be subsequently retrieved by older adults. Our results support the idea that retrospective attention can be an effective means by which older adults can improve their short and long-term memory performance, even in the context of reduced memory capacity.

  16. Change of short-term memory effect in acute ischemic ventricular myocardium: a computational study.

    PubMed

    Mei, Xi; Wang, Jing; Zhang, Hong; Liu, Zhi-cheng; Zhang, Zhen-xi

    2014-02-01

    The ionic mechanism of change in short-term memory (STM) during acute myocardial ischemia has not been well understood. In this paper, an advanced guinea pig ventricular model developed by Luo and Rudy was used to investigate STM property of ischemic ventricular myocardium. STM response was calculated by testing the time to reach steady-state action potential duration (APD) after an abrupt shortening of basic cycling length (BCL) in the pacing protocol. Electrical restitution curves (RCs), which can simultaneously visualize multiple aspects of APD restitution and STM, were obtained from dynamic and local S1S2 restitution portrait (RP), which consist of a longer interval stimulus (S1) and a shorter interval stimulus (S2). The angle between dynamic RC and local S1S2 RC reflects the amount of STM. Our results indicated that compared with control (normal) condition, time constant of STM response in the ischemic condition decreased significantly. Meanwhile the angle which reflects STM amount is less in ischemic model than that in control model. By tracking the effect of ischemia on intracellular ion concentration and membrane currents, we declared that changes in membrane currents caused by ischemia exert subtle influences on STM; it is only the decline of intracellular calcium concentration that give rise to the most decrement of STM. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  17. Overexpression of Salmonella enterica serovar Typhi recA gene confers fluoroquinolone resistance in Escherichia coli DH5α.

    PubMed

    Yassien, M A M; Elfaky, M A

    2015-11-01

    A spontaneous fluoroquinolone-resistant mutant (STM1) was isolated from its parent Salmonella enterica serovar Typhi (S. Typhi) clinical isolate. Unlike its parent isolate, this mutant has selective resistance to fluoroquinolones without any change in its sensitivity to various other antibiotics. DNA gyrase assays revealed that the fluoroquinolone resistance phenotype of the STM1 mutant did not result from alteration of the fluoroquinolone sensitivity of the DNA gyrase isolated from it. To study the mechanism of fluoroquinolone resistance, a genomic library from the STM1 mutant was constructed in Escherichia coli DH5α and two recombinant plasmids were obtained. Only one of these plasmids (STM1-A) conferred the selective fluoroquinolone resistance phenotype to E. coli DH5α. The chromosomal insert from STM1-A, digested with EcoRI and HindIII restriction endonucleases, produced two DNA fragments and these were cloned separately into pUC19 thereby generating two new plasmids, STM1-A1 and STM1-A2. Only STM1-A1 conferred the selective fluoroquinolone resistance phenotype to E. coli DH5α. Sequence and subcloning analyses of STM1-A1 showed the presence of an intact RecA open reading frame. Unlike that of the wild-type E. coli DH5α, protein analysis of a crude STM1-A1 extract showed overexpression of a 40 kDa protein. Western blotting confirmed the 40 kDa protein band to be RecA. When a RecA PCR product was cloned into pGEM-T and introduced into E. coli DH5α, the STM1-A11 subclone retained fluoroquinolone resistance. These results suggest that overexpression of RecA causes selective fluoroquinolone resistance in E. coli DH5α.

  18. Spectrotemporal Modulation Detection and Speech Perception by Cochlear Implant Users

    PubMed Central

    Won, Jong Ho; Moon, Il Joon; Jin, Sunhwa; Park, Heesung; Woo, Jihwan; Cho, Yang-Sun; Chung, Won-Ho; Hong, Sung Hwa

    2015-01-01

    Spectrotemporal modulation (STM) detection performance was examined for cochlear implant (CI) users. The test involved discriminating between an unmodulated steady noise and a modulated stimulus. The modulated stimulus presents frequency modulation patterns that change in frequency over time. In order to examine STM detection performance for different modulation conditions, two different temporal modulation rates (5 and 10 Hz) and three different spectral modulation densities (0.5, 1.0, and 2.0 cycles/octave) were employed, producing a total 6 different STM stimulus conditions. In order to explore how electric hearing constrains STM sensitivity for CI users differently from acoustic hearing, normal-hearing (NH) and hearing-impaired (HI) listeners were also tested on the same tasks. STM detection performance was best in NH subjects, followed by HI subjects. On average, CI subjects showed poorest performance, but some CI subjects showed high levels of STM detection performance that was comparable to acoustic hearing. Significant correlations were found between STM detection performance and speech identification performance in quiet and in noise. In order to understand the relative contribution of spectral and temporal modulation cues to speech perception abilities for CI users, spectral and temporal modulation detection was performed separately and related to STM detection and speech perception performance. The results suggest that that slow spectral modulation rather than slow temporal modulation may be important for determining speech perception capabilities for CI users. Lastly, test–retest reliability for STM detection was good with no learning. The present study demonstrates that STM detection may be a useful tool to evaluate the ability of CI sound processing strategies to deliver clinically pertinent acoustic modulation information. PMID:26485715

  19. Musical and verbal short-term memory: insights from neurodevelopmental and neurological disorders.

    PubMed

    Caclin, Anne; Tillmann, Barbara

    2018-05-09

    Auditory short-term memory (STM) is a fundamental ability to make sense of auditory information as it unfolds over time. Whether separate STM systems exist for different types of auditory information (music and speech, in particular) is a matter of debate. The present paper reviews studies that have investigated both musical and verbal STM in healthy individuals and in participants with neurodevelopmental and neurological disorders. Overall, the results are in favor of only partly shared networks for musical and verbal STM. Evidence for a distinction in STM for the two materials stems from (1) behavioral studies in healthy participants, in particular from the comparison between nonmusicians and musicians; (2) behavioral studies in congenital amusia, where a selective pitch STM deficit is observed; and (3) studies in brain-damaged patients with cases of double dissociation. In this review we highlight the need for future studies comparing STM for the same perceptual dimension (e.g., pitch) in different materials (e.g., music and speech), as well as for studies aiming at a more insightful characterization of shared and distinct mechanisms for speech and music in the different components of STM, namely encoding, retention, and retrieval. © 2018 New York Academy of Sciences.

  20. Design of a high-speed electrochemical scanning tunneling microscope.

    PubMed

    Yanson, Y I; Schenkel, F; Rost, M J

    2013-02-01

    In this paper, we present a bottom-up approach to designing and constructing a high-speed electrochemical scanning tunneling microscope (EC-STM). Using finite element analysis (FEA) calculations of the frequency response of the whole mechanical loop of the STM, we analyzed several geometries to find the most stable one that could facilitate fast scanning. To test the FEA results, we conducted measurements of the vibration amplitudes using a prototype STM setup. Based on the FEA analysis and the measurement results, we identified the potentially most disturbing vibration modes that could impair fast scanning. By modifying the design of some parts of the EC-STM, we reduced the amplitudes as well as increased the resonance frequencies of these modes. Additionally, we designed and constructed an electrochemical flow-cell that allows STM imaging in a flowing electrolyte, and built a bi-potentiostat to achieve electrochemical potential control during the measurements. Finally, we present STM images acquired during high-speed imaging in air as well as in an electrochemical environment using our newly-developed EC-STM.

  1. "I know your name, but not your number"--Patients with verbal short-term memory deficits are impaired in learning sequences of digits.

    PubMed

    Bormann, Tobias; Seyboth, Margret; Umarova, Roza; Weiller, Cornelius

    2015-06-01

    Studies on verbal learning in patients with impaired verbal short-term memory (vSTM) have revealed dissociations among types of verbal information. Patients with impaired vSTM are able to learn lists of known words but fail to acquire new word forms. This suggests that vSTM is involved in new word learning. The present study assessed both new word learning and the learning of digit sequences in two patients with impaired vSTM. In two experiments, participants were required to learn people's names, ages and professions, or their four digit 'phone numbers'. The STM patients were impaired on learning unknown family names and phone numbers, but managed to acquire other verbal information. In contrast, a patient with a severe verbal episodic memory impairment was impaired across information types. These results indicate verbal STM involvement in the learning of digit sequences. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Theory of high-resolution tunneling spin transport on a magnetic skyrmion

    NASA Astrophysics Data System (ADS)

    Palotás, Krisztián; Rózsa, Levente; Szunyogh, László

    2018-05-01

    Tunneling spin transport characteristics of a magnetic skyrmion are described theoretically in magnetic scanning tunneling microscopy (STM). The spin-polarized charge current in STM (SP-STM) and tunneling spin transport vector quantities, the longitudinal spin current and the spin transfer torque, are calculated in high spatial resolution within the same theoretical framework. A connection between the conventional charge current SP-STM image contrasts and the magnitudes of the spin transport vectors is demonstrated that enables the estimation of tunneling spin transport properties based on experimentally measured SP-STM images. A considerable tunability of the spin transport vectors by the involved spin polarizations is also highlighted. These possibilities and the combined theory of tunneling charge and vector spin transport pave the way for gaining deep insight into electric-current-induced tunneling spin transport properties in SP-STM and to the related dynamics of complex magnetic textures at surfaces.

  3. A comparison of serial order short-term memory effects across verbal and musical domains.

    PubMed

    Gorin, Simon; Mengal, Pierre; Majerus, Steve

    2018-04-01

    Recent studies suggest that the mechanisms involved in the short-term retention of serial order information may be shared across short-term memory (STM) domains such as verbal and visuospatial STM. Given the intrinsic sequential organization of musical material, the study of STM for musical information may be particularly informative about serial order retention processes and their domain-generality. The present experiment examined serial order STM for verbal and musical sequences in participants with no advanced musical expertise and experienced musicians. Serial order STM for verbal information was assessed via a serial order reconstruction task for digit sequences. In the musical domain, serial order STM was assessed using a novel melodic sequence reconstruction task maximizing the retention of tone order information. We observed that performance for the verbal and musical tasks was characterized by sequence length as well as primacy and recency effects. Serial order errors in both tasks were characterized by similar transposition gradients and ratios of fill-in:infill errors. These effects were observed for both participant groups, although the transposition gradients and ratios of fill-in:infill errors showed additional specificities for musician participants in the musical task. The data support domain-general serial order STM effects but also suggest the existence of additional domain-specific effects. Implications for models of serial order STM in verbal and musical domains are discussed.

  4. Spectroscopic scanning tunneling microscopy insights into Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Hoffman, Jennifer E.

    2011-12-01

    In the first three years since the discovery of Fe-based high Tc superconductors, scanning tunneling microscopy (STM) and spectroscopy have shed light on three important questions. First, STM has demonstrated the complexity of the pairing symmetry in Fe-based materials. Phase-sensitive quasiparticle interference (QPI) imaging and low temperature spectroscopy have shown that the pairing order parameter varies from nodal to nodeless s± within a single family, FeTe1-xSex. Second, STM has imaged C4 → C2 symmetry breaking in the electronic states of both parent and superconducting materials. As a local probe, STM is in a strong position to understand the interactions between these broken symmetry states and superconductivity. Finally, STM has been used to image the vortex state, giving insights into the technical problem of vortex pinning, and the fundamental problem of the competing states introduced when superconductivity is locally quenched by a magnetic field. Here we give a pedagogical introduction to STM and QPI imaging, discuss the specific challenges associated with extracting bulk properties from the study of surfaces, and report on progress made in understanding Fe-based superconductors using STM techniques.

  5. A cryogen-free variable temperature scanning tunneling microscope capable for inelastic electron tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Huang, Di; Wu, Shiwei

    While low temperature scanning tunneling microscope (STM) has become an indispensable research tool in surface science, its versatility is yet limited by the shortage or high cost of liquid helium. The makeshifts include the use of alternative cryogen (such as liquid nitrogen) at higher temperature or the development of helium liquefier system usually at departmental or campus wide. The ultimate solution would be the direct integration of a cryogen-free cryocooler based on GM or pulse tube closed cycle in the STM itself. However, the nasty mechanical vibration at low frequency intrinsic to cryocoolers has set the biggest obstacle because of the known challenges in vibration isolation required to high performance of STM. In this talk, we will present the design and performance of our home-built cryogen-free variable temperature STM at Fudan University. This system can obtain atomically sharp STM images and high resolution dI/dV spectra comparable to state-of-the-art low temperature STMs, but with no limitation on running hours. Moreover, we demonstrated the inelastic tunneling spectroscopy (STM-IETS) on a single CO molecule with a cryogen-free STM for the first time.

  6. Familiarity increases the number of remembered Pokémon in visual short-term memory.

    PubMed

    Xie, Weizhen; Zhang, Weiwei

    2017-05-01

    Long-term memory (LTM) can influence many aspects of short-term memory (STM), including increased STM span. However, it is unclear whether LTM enhances the quantitative or qualitative aspect of STM. That is, do we retain a larger number of representations or more precise representations in STM for familiar stimuli than unfamiliar stimuli? This study took advantage of participants' prior rich multimedia experience with Pokémon, without investing on laboratory training to examine how prior LTM influenced visual STM. In a Pokémon visual STM change detection task, participants remembered more first-generation Pokémon characters that they were more familiar with than recent-generation Pokémon characters that they were less familiar with. No significant difference in memory quality was found when quantitative and qualitative effects of LTM were isolated using receiver operating characteristic (ROC) analyses. Critically, these effects were absent in participants who were unfamiliar with first-generation Pokémon. Furthermore, several alternative interpretations were ruled out, including general video-gaming experience, subjective Pokémon preference, and verbal encoding. Together, these results demonstrated a strong link between prior stimulus familiarity in LTM and visual STM storage capacity.

  7. Verbal short-term memory shows a specific association with receptive but not productive vocabulary measures in Down syndrome.

    PubMed

    Majerus, S; Barisnikov, K

    2018-01-01

    Verbal short-term memory (STM) capacity has been considered to support vocabulary learning in typical children and adults, but evidence for this link is inconsistent for studies in individuals with Down syndrome (DS). The aim of this study was explore the role of processing demands on the association between verbal STM and vocabulary measures in DS, by comparing receptive vocabulary measures with high STM processing demands to productive vocabulary measures with low STM processing demands. Forty-seven adults with Down syndrome were administered receptive vocabulary and productive vocabulary tasks, as well as measures of verbal STM abilities and intellectual efficiency. Bayesian regression analyses showed that verbal STM abilities were strongly and specifically associated with receptive vocabulary measures but not productive lexical abilities after controlling for intellectual efficiency, and this is despite the fact that vocabulary abilities as measured by receptive and productive vocabulary tasks were closely associated. In Down syndrome, verbal STM abilities may be predictive of specific task demands associated with receptive vocabulary tasks rather than of vocabulary development per se. © 2017 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd.

  8. The Contribution of Short-Term Memory for Serial Order to Early Reading Acquisition: Evidence from a Longitudinal Study

    ERIC Educational Resources Information Center

    Perez, Trecy Martinez; Majerus, Steve; Poncelet, Martine

    2012-01-01

    Early reading acquisition skills have been linked to verbal short-term memory (STM) capacity. However, the nature of this relationship remains controversial because verbal STM, like reading acquisition, depends on the complexity of underlying phonological processing skills. This longitudinal study addressed the relation between STM and reading…

  9. The Effects of Phonological Short-Term Memory and Speech Perception on Spoken Sentence Comprehension in Children: Simulating Deficits in an Experimental Design.

    PubMed

    Higgins, Meaghan C; Penney, Sarah B; Robertson, Erin K

    2017-10-01

    The roles of phonological short-term memory (pSTM) and speech perception in spoken sentence comprehension were examined in an experimental design. Deficits in pSTM and speech perception were simulated through task demands while typically-developing children (N [Formula: see text] 71) completed a sentence-picture matching task. Children performed the control, simulated pSTM deficit, simulated speech perception deficit, or simulated double deficit condition. On long sentences, the double deficit group had lower scores than the control and speech perception deficit groups, and the pSTM deficit group had lower scores than the control group and marginally lower scores than the speech perception deficit group. The pSTM and speech perception groups performed similarly to groups with real deficits in these areas, who completed the control condition. Overall, scores were lowest on noncanonical long sentences. Results show pSTM has a greater effect than speech perception on sentence comprehension, at least in the tasks employed here.

  10. Ultra-Compact Multitip Scanning Probe Microscope with an Outer Diameter of 50 mm

    NASA Astrophysics Data System (ADS)

    Cherepanov, Vasily; Zubkov, Evgeny; Junker, Hubertus; Korte, Stefan; Blab, Marcus; Coenen, Peter; Voigtländer, Bert

    We present a multitip scanning tunneling microscope (STM) where four independent STM units are integrated on a diameter of 50 mm. The coarse positioning of the tips is done under the control of an optical microscope or an SEM in vacuum. The heart of this STM is a new type of piezoelectric coarse approach called Koala Drive which can have a diameter greater than 2.5 mm and a length smaller than 10 mm. Alternating movements of springs move a central tube which holds the STM tip or AFM sensor. This new operating principle provides a smooth travel sequence and avoids shaking which is intrinsically present for nanopositioners based on inertial motion with saw tooth driving signals. Inserting the Koala Drive in a piezo tube for xyz-scanning integrates a complete STM inside a 4 mm outer diameter piezo tube of <10 mm length. The use of the Koala Drive makes the scanning probe microscopy design ultra-compact and accordingly leads to a high mechanical stability. The drive is UHV, low temperature, and magnetic field compatible. The compactness of the Koala Drive allows building a four-tip STM as small as a single-tip STM with a drift of <0.2 nm/min and lowest resonance frequencies of 2.5 (xy) and 5.5 kHz (z). We present examples of the performance of the multitip STM designed using the Koala Drive.

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

    Nakayama, T.; Kubo, O.; Shingaya, Y.

    the research of advanced materials based on nanoscience and nanotechnology, it is often desirable to measure nanoscale local electrical conductivity at a designated position of a given sample. For this purpose, multiple-probe scanning probe microscopes (MP-SPMs), in which two, three or four scanning tunneling microscope (STM) or atomic force microscope (AFM) probes are operated independently, have been developed. Each probe in an MP-SPM is used not only for observing high-resolution STM or AFM images but also for forming an electrical contact enabling nanoscale local electrical conductivity measurement. The world's first double-probe STM (DP-STM) developed by the authors, which was subsequentlymore » modified to a triple-probe STM (TP-STM), has been used to measure the conductivities of one-dimensional metal nanowires and carbon nanotubes and also two-dimensional molecular films. A quadruple-probe STM (QP-STM) has also been developed and used to measure the conductivity of two-dimensional molecular films without the ambiguity of contact resistance between the probe and sample. Moreover, a quadruple-probe AFM (QP-AFM) with four conductive tuning-fork-type self-detection force sensing probes has been developed to measure the conductivity of a nanostructure on an insulating substrate. A general-purpose computer software to control four probes at the same time has also been developed and used in the operation of the QP-AFM. These developments and applications of MP-SPMs are reviewed in this paper.« less

  12. Relations between Short-term Memory Deficits, Semantic Processing, and Executive Function

    PubMed Central

    Allen, Corinne M.; Martin, Randi C.; Martin, Nadine

    2012-01-01

    Background Previous research has suggested separable short-term memory (STM) buffers for the maintenance of phonological and lexical-semantic information, as some patients with aphasia show better ability to retain semantic than phonological information and others show the reverse. Recently, researchers have proposed that deficits to the maintenance of semantic information in STM are related to executive control abilities. Aims The present study investigated the relationship of executive function abilities with semantic and phonological short-term memory (STM) and semantic processing in such patients, as some previous research has suggested that semantic STM deficits and semantic processing abilities are critically related to specific or general executive function deficits. Method and Procedures 20 patients with aphasia and STM deficits were tested on measures of short-term retention, semantic processing, and both complex and simple executive function tasks. Outcome and Results In correlational analyses, we found no relation between semantic STM and performance on simple or complex executive function tasks. In contrast, phonological STM was related to executive function performance in tasks that had a verbal component, suggesting that performance in some executive function tasks depends on maintaining or rehearsing phonological codes. Although semantic STM was not related to executive function ability, performance on semantic processing tasks was related to executive function, perhaps due to similar executive task requirements in both semantic processing and executive function tasks. Conclusions Implications for treatment and interpretations of executive deficits are discussed. PMID:22736889

  13. From Graphite to Graphene via Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Qi, Dejun

    The primary objective of this dissertation is to study both graphene on graphite and pristine freestanding grapheme using scanning tunneling microscopy (STM) and density functional theory (DFT) simulation technique. In the experiment part, good quality tungsten metalic tips for experiment were fabricated using our newly developed tip making setup. Then a series of measurements using a technique called electrostatic-manipulation scanning tunneling microscopy (EM-STM) of our own development were performed on a highly oriented pyrolytic graphite (HOPG) surface. The electrostatic interaction between the STM tip and the sample can be tuned to produce both reversible and irreversible large-scale movement of the graphite surface. Under this influence, atomic-resolution STM images reveal that a continuous electronic transition between two distinct patterns can be systematically controlled. DFT calculations reveal that this transition can be related to vertical displacements of the top layer of graphite relative to the bulk. Evidence for horizontal shifts in the top layer of graphite is also presented. Excellent agreement is found between experimental STM images and those simulated using DFT. In addition, the EM-STM technique was also used to controllably and reversibly pull freestanding graphene membranes up to 35 nm from their equilibrium height. Atomic-scale corrugation amplitudes 20 times larger than the STM electronic corrugation for graphene on a substrate were observed. The freestanding graphene membrane responds to a local attractive force created at the STM tip as a highly conductive yet flexible grounding plane with an elastic restoring force.

  14. Discovery and Utilization of Nanoscale and Mesoscale Enabling Materials and Processes for Optoelectronics and Electronic Interconnects

    DTIC Science & Technology

    2003-12-01

    Heating and Cooling Device 42 5.2.3 Multiple Tip STM ~ 43 5.2.3.1 Novel Nanomanipulator MM3 43 5.2.3.2 Four Tip STM Assembly 44 5.2.3.3 Vibration ...Analysis of Eddy Current Damping System of Multiple TIP STM " 44 5.2.3.4 Active Vibration Damping System 46 5.3 First Results 47 5.3.1 UHV-SEM...side: Actual device side and top view. 44 46. Setup for the vibration analysis experiment. 45 47. Relaxation of the STM unit, (a) without the eddy

  15. The use of standardised short-term and working memory tests in aphasia research: a systematic review

    PubMed Central

    Murray, Laura; Salis, Christos; Martin, Nadine; Dralle, Jenny

    2017-01-01

    Impairments of short-term and working memory (STM, WM), both verbal and non-verbal, are ubiquitous in aphasia. Increasing interest in assessing STM and WM in aphasia research and clinical practice as well as a growing evidence base of STM/WM treatments for aphasia warrant an understanding of the range of standardised STM/WM measures that have been utilised in aphasia. To date, however, no previous systematic review has focused on aphasia. Accordingly, the goals of this systematic review were: (1) to identify standardised tests of STM and WM utilised in the aphasia literature, (2) to evaluate critically the psychometric strength of these tests, and (3) to appraise critically the quality of the investigations utilising these tests. Results revealed that a very limited number of standardised tests, in the verbal and non-verbal domains, had robust psychometric properties. Standardisation samples to elicit normative data were often small, and most measures exhibited poor validity and reliability properties. Studies using these tests inconsistently documented demographic and aphasia variables essential to interpreting STM/WM test outcomes. In light of these findings, recommendations are provided to foster, in the future, consistency across aphasia studies and confidence in STM/WM tests as assessment and treatment outcome measures. PMID:27143500

  16. A cryogen-free low temperature scanning tunneling microscope capable of inelastic electron tunneling spectroscopy.

    PubMed

    Zhang, Shuai; Huang, Di; Wu, Shiwei

    2016-06-01

    The design and performance of a cryogen-free low temperature scanning tunneling microscope (STM) housed in ultrahigh vacuum (UHV) are reported. The cryogen-free design was done by directly integrating a Gifford-McMahon cycle cryocooler to a Besocke-type STM, and the vibration isolation was achieved by using a two-stage rubber bellow between the cryocooler and a UHV-STM interface with helium exchange gas cooling. A base temperature of 15 K at the STM was achieved, with a possibility to further decrease by using a cryocooler with higher cooling power and adding additional low temperature stage under the exchange gas interface. Atomically sharp STM images and high resolution dI/dV spectra on various samples were demonstrated. Furthermore, we reported the inelastic tunneling spectroscopy on a single carbon monoxide molecule adsorbed on Ag(110) surface with a cryogen-free STM for the first time. Being totally cryogen-free, the system not only saves the running cost significantly but also enables uninterrupted data acquisitions and variable temperature measurements with much ease. In addition, the system is capable of coupling light to the STM junction by a pair of lens inside the UHV chamber. We expect that these enhanced capabilities could further broaden our views to the atomic-scale world.

  17. Spatial short-term memory is impaired in dependent betel quid chewers.

    PubMed

    Chiu, Meng-Chun; Shen, Bin; Li, Shuo-Heng; Ho, Ming-Chou

    2016-08-01

    Betel quid is regarded as a human carcinogen by the World Health Organization. It remains unknown whether chewing betel quid has a chronic effect on healthy betel quid chewers' memory. The present study aims to investigate whether chewing betel quid can affect short-term memory (STM). Three groups of participants (24 dependent chewers, 24 non-dependent chewers, and 24 non-chewers) were invited to carry out the matrix span task, the object span task, and the digit span task. All span tasks' results were adopted to assess spatial STM, visual STM, and verbal STM, respectively. Besides, there are three set sizes (small, medium, and large) in each span task. For the matrix span task, results showed that the dependent chewers had worse performances than the non-dependent chewers and the non-chewers at medium and large set sizes. For the object span task and digit span task, there were no differences in between groups. In each group, recognition performances were worse with the increasing set size and showing successful manipulation of memory load. The current study provided the first evidence that dependent betel quid chewing can selectively impair spatial STM rather than visual STM and verbal STM. Theoretical and practical implications of this result are discussed.

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

    Van Dyke, Natalya; Chanchorn, Ekkawit; Van Dyke, Michael W., E-mail: mvandyke@email.wcu.edu

    Highlights: Black-Right-Pointing-Pointer Stm1p confers increased resistance to the macrolide starvation-mimic rapamycin. Black-Right-Pointing-Pointer Stm1p maintains 80S ribosome integrity during stationary phase-induced quiescence. Black-Right-Pointing-Pointer Stm1p facilitates polysome formation following quiescence exit. Black-Right-Pointing-Pointer Stm1p facilitates protein synthesis following quiescence exit. Black-Right-Pointing-Pointer Stm1p is a ribosome preservation factor under conditions of nutrient deprivation. -- Abstract: Once cells exhaust nutrients from their environment, they enter an alternative resting state known as quiescence, whereby proliferation ceases and essential nutrients are obtained through internal stores and through the catabolism of existing macromolecules and organelles. One example of this is ribophagy, the degradation of ribosomes through the processmore » of autophagy. However, some ribosomes need to be preserved for an anticipated recovery from nutrient deprivation. We found that the ribosome-associated protein Stm1p greatly increases the quantity of 80S ribosomes present in quiescent yeast cells and that these ribosomes facilitate increased protein synthesis rates once nutrients are restored. These findings suggest that Stm1p can act as a ribosome preservation factor under conditions of nutrient deprivation and restoration.« less

  19. The use of standardised short-term and working memory tests in aphasia research: a systematic review.

    PubMed

    Murray, Laura; Salis, Christos; Martin, Nadine; Dralle, Jenny

    2018-04-01

    Impairments of short-term and working memory (STM, WM), both verbal and non-verbal, are ubiquitous in aphasia. Increasing interest in assessing STM and WM in aphasia research and clinical practice as well as a growing evidence base of STM/WM treatments for aphasia warrant an understanding of the range of standardised STM/WM measures that have been utilised in aphasia. To date, however, no previous systematic review has focused on aphasia. Accordingly, the goals of this systematic review were: (1) to identify standardised tests of STM and WM utilised in the aphasia literature, (2) to evaluate critically the psychometric strength of these tests, and (3) to appraise critically the quality of the investigations utilising these tests. Results revealed that a very limited number of standardised tests, in the verbal and non-verbal domains, had robust psychometric properties. Standardisation samples to elicit normative data were often small, and most measures exhibited poor validity and reliability properties. Studies using these tests inconsistently documented demographic and aphasia variables essential to interpreting STM/WM test outcomes. In light of these findings, recommendations are provided to foster, in the future, consistency across aphasia studies and confidence in STM/WM tests as assessment and treatment outcome measures.

  20. The impact of aging and hearing status on verbal short-term memory.

    PubMed

    Verhaegen, Clémence; Collette, Fabienne; Majerus, Steve

    2014-01-01

    The aim of this study is to assess the impact of hearing status on age-related decrease in verbal short-term memory (STM) performance. This was done by administering a battery of verbal STM tasks to elderly and young adult participants matched for hearing thresholds, as well as to young normal-hearing control participants. The matching procedure allowed us to assess the importance of hearing loss as an explanatory factor of age-related STM decline. We observed that elderly participants and hearing-matched young participants showed equal levels of performance in all verbal STM tasks, and performed overall lower than the normal-hearing young control participants. This study provides evidence for recent theoretical accounts considering reduced hearing level as an important explanatory factor of poor auditory-verbal STM performance in older adults.

  1. Development of a glycoconjugate vaccine to prevent invasive Salmonella Typhimurium infections in sub-Saharan Africa

    PubMed Central

    Baliban, Scott M.; Yang, Mingjun; Ramachandran, Girish; Curtis, Brittany; Shridhar, Surekha; Laufer, Rachel S.; Wang, Jin Y.; Van Druff, John; Higginson, Ellen E.; Hegerle, Nicolas; Varney, Kristen M.; Galen, James E.; Tennant, Sharon M.; Lees, Andrew; MacKerell, Alexander D.; Levine, Myron M.; Simon, Raphael

    2017-01-01

    Invasive infections associated with non-typhoidal Salmonella (NTS) serovars Enteritidis (SE), Typhimurium (STm) and monophasic variant 1,4,[5],12:i:- are a major health problem in infants and young children in sub-Saharan Africa, and currently, there are no approved human NTS vaccines. NTS O-polysaccharides and flagellin proteins are protective antigens in animal models of invasive NTS infection. Conjugates of SE core and O-polysaccharide (COPS) chemically linked to SE flagellin have enhanced the anti-COPS immune response and protected mice against fatal challenge with a Malian SE blood isolate. We report herein the development of a STm glycoconjugate vaccine comprised of STm COPS conjugated to the homologous serovar phase 1 flagellin protein (FliC) with assessment of the role of COPS O-acetyls for functional immunity. Sun-type COPS conjugates linked through the polysaccharide reducing end to FliC were more immunogenic and protective in mice challenged with a Malian STm blood isolate than multipoint lattice conjugates (>95% vaccine efficacy [VE] versus 30–43% VE). Immunization with de-O-acetylated STm-COPS conjugated to CRM197 provided significant but reduced protection against STm challenge compared to mice immunized with native STm-COPS:CRM197 (63–74% VE versus 100% VE). Although OPS O-acetyls were highly immunogenic, post-vaccination sera that contained various O-acetyl epitope-specific antibody profiles displayed similar in vitro bactericidal activity when equivalent titers of anti-COPS IgG were assayed. In-silico molecular modeling further indicated that STm OPS forms a single dominant conformation, irrespective of O-acetylation, in which O-acetyls extend outward and are highly solvent exposed. These preclinical results establish important quality attributes for an STm vaccine that could be co-formulated with an SE-COPS:FliC glycoconjugate as a bivalent NTS vaccine for use in sub-Saharan Africa. PMID:28388624

  2. Development of a glycoconjugate vaccine to prevent invasive Salmonella Typhimurium infections in sub-Saharan Africa.

    PubMed

    Baliban, Scott M; Yang, Mingjun; Ramachandran, Girish; Curtis, Brittany; Shridhar, Surekha; Laufer, Rachel S; Wang, Jin Y; Van Druff, John; Higginson, Ellen E; Hegerle, Nicolas; Varney, Kristen M; Galen, James E; Tennant, Sharon M; Lees, Andrew; MacKerell, Alexander D; Levine, Myron M; Simon, Raphael

    2017-04-01

    Invasive infections associated with non-typhoidal Salmonella (NTS) serovars Enteritidis (SE), Typhimurium (STm) and monophasic variant 1,4,[5],12:i:- are a major health problem in infants and young children in sub-Saharan Africa, and currently, there are no approved human NTS vaccines. NTS O-polysaccharides and flagellin proteins are protective antigens in animal models of invasive NTS infection. Conjugates of SE core and O-polysaccharide (COPS) chemically linked to SE flagellin have enhanced the anti-COPS immune response and protected mice against fatal challenge with a Malian SE blood isolate. We report herein the development of a STm glycoconjugate vaccine comprised of STm COPS conjugated to the homologous serovar phase 1 flagellin protein (FliC) with assessment of the role of COPS O-acetyls for functional immunity. Sun-type COPS conjugates linked through the polysaccharide reducing end to FliC were more immunogenic and protective in mice challenged with a Malian STm blood isolate than multipoint lattice conjugates (>95% vaccine efficacy [VE] versus 30-43% VE). Immunization with de-O-acetylated STm-COPS conjugated to CRM197 provided significant but reduced protection against STm challenge compared to mice immunized with native STm-COPS:CRM197 (63-74% VE versus 100% VE). Although OPS O-acetyls were highly immunogenic, post-vaccination sera that contained various O-acetyl epitope-specific antibody profiles displayed similar in vitro bactericidal activity when equivalent titers of anti-COPS IgG were assayed. In-silico molecular modeling further indicated that STm OPS forms a single dominant conformation, irrespective of O-acetylation, in which O-acetyls extend outward and are highly solvent exposed. These preclinical results establish important quality attributes for an STm vaccine that could be co-formulated with an SE-COPS:FliC glycoconjugate as a bivalent NTS vaccine for use in sub-Saharan Africa.

  3. Out with the old? The role of selective attention in retaining targets in partial report.

    PubMed

    Lindsey, Dakota R B; Bundesen, Claus; Kyllingsbæk, Søren; Petersen, Anders; Logan, Gordon D

    2017-01-01

    In the partial-report task, subjects are asked to report only a portion of the items presented. Selective attention chooses which objects to represent in short-term memory (STM) on the basis of their relevance. Because STM is limited in capacity, one must sometimes choose which objects are removed from memory in light of new relevant information. We tested the hypothesis that the choices among newly presented information and old information in STM involve the same process-that both are acts of selective attention. We tested this hypothesis using a two-display partial-report procedure. In this procedure, subjects had to select and retain relevant letters (targets) from two sequentially presented displays. If selection in perception and retention in STM are the same process, then irrelevant letters (distractors) in the second display, which demanded attention because of their similarity to the targets, should have decreased target report from the first display. This effect was not obtained in any of four experiments. Thus, choosing objects to keep in STM is not the same process as choosing new objects to bring into STM.

  4. The relationship between semantic short-term memory and immediate serial recall of known and unknown words and nonwords: data from two Chinese individuals with aphasia.

    PubMed

    Wong, Winsy; Low, Sam-Po

    2008-07-01

    The present study investigated verbal recall of semantically preserved and degraded words and nonwords by taking into consideration the status of one's semantic short-term memory (STM). Two experiments were conducted on 2 Chinese individuals with aphasia. The first experiment showed that they had largely preserved phonological processing abilities accompanied by mild but comparable semantic processing deficits; however, their performance on STM tasks revealed a double dissociation. The second experiment found that the participant with more preserved semantic STM had better recall of known words and nonwords than of their unknown counterparts, whereas such effects were absent in the patient with severe semantic STM deficit. The results are compatible with models that assume separate phonological and semantic STM components, such as that of R. C. Martin, M. Lesch, and M. Bartha (1999). In addition, the distribution of error types was different from previous studies. This is discussed in terms of the methodology of the authors' experiments and current views regarding the nature of semantic STM and representations in the Chinese mental lexicon. (c) 2008 APA

  5. Multiple neural states of representation in short-term memory? It's a matter of attention.

    PubMed

    Larocque, Joshua J; Lewis-Peacock, Jarrod A; Postle, Bradley R

    2014-01-01

    Short-term memory (STM) refers to the capacity-limited retention of information over a brief period of time, and working memory (WM) refers to the manipulation and use of that information to guide behavior. In recent years it has become apparent that STM and WM interact and overlap with other cognitive processes, including attention (the selection of a subset of information for further processing) and long-term memory (LTM-the encoding and retention of an effectively unlimited amount of information for a much longer period of time). Broadly speaking, there have been two classes of memory models: systems models, which posit distinct stores for STM and LTM (Atkinson and Shiffrin, 1968; Baddeley and Hitch, 1974); and state-based models, which posit a common store with different activation states corresponding to STM and LTM (Cowan, 1995; McElree, 1996; Oberauer, 2002). In this paper, we will focus on state-based accounts of STM. First, we will consider several theoretical models that postulate, based on considerable behavioral evidence, that information in STM can exist in multiple representational states. We will then consider how neural data from recent studies of STM can inform and constrain these theoretical models. In the process we will highlight the inferential advantage of multivariate, information-based analyses of neuroimaging data (fMRI and electroencephalography (EEG)) over conventional activation-based analysis approaches (Postle, in press). We will conclude by addressing lingering questions regarding the fractionation of STM, highlighting differences between the attention to information vs. the retention of information during brief memory delays.

  6. Task-evoked pupillometry provides a window into the development of short-term memory capacity

    PubMed Central

    Johnson, Elizabeth L.; Miller Singley, Alison T.; Peckham, Andrew D.; Johnson, Sheri L.; Bunge, Silvia A.

    2014-01-01

    The capacity to keep multiple items in short-term memory (STM) improves over childhood and provides the foundation for the development of multiple cognitive abilities. The goal of this study was to measure the extent to which age differences in STM capacity are related to differences in task engagement during encoding. Children (n = 69, mean age = 10.6 years) and adults (n = 54, mean age = 27.5 years) performed two STM tasks: the forward digit span test from the Wechsler Intelligence Scale for Children (WISC) and a novel eyetracking digit span task designed to overload STM capacity. Building on prior research showing that task-evoked pupil dilation can be used as a real-time index of task engagement, we measured changes in pupil dilation while participants encoded long sequences of digits for subsequent recall. As expected, adults outperformed children on both STM tasks. We found similar patterns of pupil dilation while children and adults listened to the first six digits on our STM overload task, after which the adults' pupils continued to dilate and the children's began to constrict, suggesting that the children had reached their cognitive limits and that they had begun to disengage from the task. Indeed, the point at which pupil dilation peaked at encoding was a significant predictor of WISC forward span, and this relationship held even after partialing out recall performance on the STM overload task. These findings indicate that sustained task engagement at encoding is an important component of the development of STM. PMID:24659980

  7. What part of working memory is not working in ADHD? Short-term memory, the central executive and effects of reinforcement.

    PubMed

    Dovis, Sebastiaan; Van der Oord, Saskia; Wiers, Reinout W; Prins, Pier J M

    2013-08-01

    Deficits in Working Memory (WM) are related to symptoms of Attention-Deficit/Hyperactivity Disorder (ADHD). In children with ADHD visuospatial WM is most impaired. WM is composed of Short-Term Memory (STM) and a Central Executive (CE). Therefore, deficits in either or both STM and the CE may account for WM impairments in children with ADHD. WM-component studies investigating this find deficits in both STM and the CE. However, recent studies show that not only cognitive deficits, but also motivational deficits give rise to the aberrant WM performance of children with ADHD. To date, the influence of these motivational deficits on the components of WM has not been investigated. This study examined the effects of a standard (feedback-only) and a high level of reinforcement (feedback + 10 euros) on the visuospatial WM-, visuospatial STM-, and the CE performance of 86 children with ADHD and 62 typically-developing controls. With standard reinforcement the STM, CE, and WM performance of children with ADHD was worse than that of controls. High reinforcement improved STM and WM performance more in children with ADHD than in controls, but was unable to normalize their performance. High reinforcement did not appear to improve the CE-related performance of children with ADHD and controls. Motivational deficits have a detrimental effect on both the visuospatial WM performance and the STM performance of children with ADHD. Aside from motivational deficits, both the visuospatial STM and the CE of children with ADHD are impaired, and give rise to their deficits in visuospatial WM.

  8. Short-segment transverse myelitis lesions in a cohort of Latin American patients with neuromyelitis optica spectrum disorders.

    PubMed

    Carnero Contentti, Edgar; Daccach Marques, Vanessa; Soto de Castillo, Ibis; Tkachuk, Verónica; Antunes Barreira, Amilton; Armas, Elizabeth; Chiganer, Edson; de Aquino Cruz, Camila; Di Pace, José Luis; Hryb, Javier Pablo; Lavigne Moreira, Carolina; Lessa, Carmen; Molina, Omaira; Perassolo, Mónica; Soto, Arnoldo; Caride, Alejandro

    2018-05-22

    Multicenter retrospective study. The aim was to determine the frequency and magnetic resonance imaging (MRI) features of short-segment transverse myelitis (STM) in patients with neuromyelitis optica spectrum disorders (NMOSD) during a myelitis attack. Latin American diagnostic centres (Neuroimmunology Unit). A multicenter study from Argentina, Brazil and Venezuela was performed. Seventy-six patients with NMOSD were included. We analyzed 346 attacks and reviewed spinal cord MRIs performed within 30 days from spinal attack onset. Sagittal and axial characteristics on cervical and thoracic MRI (1.5 tesla) were observed. Demographics, clinical, serological, and disability data were collected. Among the 76 patients with NMOSD, isolated STM was observed in 8% (n = 6), multisegmental lesions (longitudinally extensive transverse myelitis (LETM) + STM) in 28% (n = 21; 13 had at least one STM), LETM in 42% (n = 32), and normal spinal MRI in 22% (n = 17). However, isolated STM was increased by 10% in patients with NMOSD with spinal lesions (6 out of 59) with mean attacks of 2.5 (±0.83) and last follow-up expanded disability status scale (EDSS) of 3.1 (±2.63). Positive aquaporin 4 antibodies (AQP4-ab) were found in 50%. Upper-cervical lesion was most frequently observed (5 out of 6). Myelitis was preceded by ON in all isolated patients with STM. Only one had a positive gadolinium lesion and none of these had asymptomatic spinal cord lesion. Isolated STM does not exclude NMOSD diagnosis. Therefore, APQ4-ab testing could be useful during a myelitis attack with STM.

  9. Task-evoked pupillometry provides a window into the development of short-term memory capacity.

    PubMed

    Johnson, Elizabeth L; Miller Singley, Alison T; Peckham, Andrew D; Johnson, Sheri L; Bunge, Silvia A

    2014-01-01

    The capacity to keep multiple items in short-term memory (STM) improves over childhood and provides the foundation for the development of multiple cognitive abilities. The goal of this study was to measure the extent to which age differences in STM capacity are related to differences in task engagement during encoding. Children (n = 69, mean age = 10.6 years) and adults (n = 54, mean age = 27.5 years) performed two STM tasks: the forward digit span test from the Wechsler Intelligence Scale for Children (WISC) and a novel eyetracking digit span task designed to overload STM capacity. Building on prior research showing that task-evoked pupil dilation can be used as a real-time index of task engagement, we measured changes in pupil dilation while participants encoded long sequences of digits for subsequent recall. As expected, adults outperformed children on both STM tasks. We found similar patterns of pupil dilation while children and adults listened to the first six digits on our STM overload task, after which the adults' pupils continued to dilate and the children's began to constrict, suggesting that the children had reached their cognitive limits and that they had begun to disengage from the task. Indeed, the point at which pupil dilation peaked at encoding was a significant predictor of WISC forward span, and this relationship held even after partialing out recall performance on the STM overload task. These findings indicate that sustained task engagement at encoding is an important component of the development of STM.

  10. A low-temperature scanning tunneling microscope capable of microscopy and spectroscopy in a Bitter magnet at up to 34 T.

    PubMed

    Tao, W; Singh, S; Rossi, L; Gerritsen, J W; Hendriksen, B L M; Khajetoorians, A A; Christianen, P C M; Maan, J C; Zeitler, U; Bryant, B

    2017-09-01

    We present the design and performance of a cryogenic scanning tunneling microscope (STM) which operates inside a water-cooled Bitter magnet, which can attain a magnetic field of up to 38 T. Due to the high vibration environment generated by the magnet cooling water, a uniquely designed STM and a vibration damping system are required. The STM scan head is designed to be as compact and rigid as possible, to minimize the effect of vibrational noise as well as fit the size constraints of the Bitter magnet. The STM uses a differential screw mechanism for coarse tip-sample approach, and operates in helium exchange gas at cryogenic temperatures. The reliability and performance of the STM are demonstrated through topographic imaging and scanning tunneling spectroscopy on highly oriented pyrolytic graphite at T = 4.2 K and in magnetic fields up to 34 T.

  11. Auditory short-term memory capacity correlates with gray matter density in the left posterior STS in cognitively normal and dyslexic adults.

    PubMed

    Richardson, Fiona M; Ramsden, Sue; Ellis, Caroline; Burnett, Stephanie; Megnin, Odette; Catmur, Caroline; Schofield, Tom M; Leff, Alex P; Price, Cathy J

    2011-12-01

    A central feature of auditory STM is its item-limited processing capacity. We investigated whether auditory STM capacity correlated with regional gray and white matter in the structural MRI images from 74 healthy adults, 40 of whom had a prior diagnosis of developmental dyslexia whereas 34 had no history of any cognitive impairment. Using whole-brain statistics, we identified a region in the left posterior STS where gray matter density was positively correlated with forward digit span, backward digit span, and performance on a "spoonerisms" task that required both auditory STM and phoneme manipulation. Across tasks and participant groups, the correlation was highly significant even when variance related to reading and auditory nonword repetition was factored out. Although the dyslexics had poorer phonological skills, the effect of auditory STM capacity in the left STS was the same as in the cognitively normal group. We also illustrate that the anatomical location of this effect is in proximity to a lesion site recently associated with reduced auditory STM capacity in patients with stroke damage. This result, therefore, indicates that gray matter density in the posterior STS predicts auditory STM capacity in the healthy and damaged brain. In conclusion, we suggest that our present findings are consistent with the view that there is an overlap between the mechanisms that support language processing and auditory STM.

  12. A cryogen-free low temperature scanning tunneling microscope capable of inelastic electron tunneling spectroscopy

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

    Zhang, Shuai; Huang, Di; Wu, Shiwei, E-mail: swwu@fudan.edu.cn

    The design and performance of a cryogen-free low temperature scanning tunneling microscope (STM) housed in ultrahigh vacuum (UHV) are reported. The cryogen-free design was done by directly integrating a Gifford-McMahon cycle cryocooler to a Besocke-type STM, and the vibration isolation was achieved by using a two-stage rubber bellow between the cryocooler and a UHV-STM interface with helium exchange gas cooling. A base temperature of 15 K at the STM was achieved, with a possibility to further decrease by using a cryocooler with higher cooling power and adding additional low temperature stage under the exchange gas interface. Atomically sharp STM imagesmore » and high resolution dI/dV spectra on various samples were demonstrated. Furthermore, we reported the inelastic tunneling spectroscopy on a single carbon monoxide molecule adsorbed on Ag(110) surface with a cryogen-free STM for the first time. Being totally cryogen-free, the system not only saves the running cost significantly but also enables uninterrupted data acquisitions and variable temperature measurements with much ease. In addition, the system is capable of coupling light to the STM junction by a pair of lens inside the UHV chamber. We expect that these enhanced capabilities could further broaden our views to the atomic-scale world.« less

  13. Do serotonin(1-7) receptors modulate short and long-term memory?

    PubMed

    Meneses, A

    2007-05-01

    Evidence from invertebrates to human studies indicates that serotonin (5-hydroxytryptamine; 5-HT) system modulates short- (STM) and long-term memory (LTM). This work is primarily focused on analyzing the contribution of 5-HT, cholinergic and glutamatergic receptors as well as protein synthesis to STM and LTM of an autoshaping learning task. It was observed that the inhibition of hippocampal protein synthesis or new mRNA did not produce a significant effect on autoshaping STM performance but it did impair LTM. Both non-contingent protein inhibition and 5-HT depletion showed no effects. It was basically the non-selective 5-HT receptor antagonist cyproheptadine, which facilitated STM. However, the blockade of glutamatergic and cholinergic transmission impaired STM. In contrast, the selective 5-HT(1B) receptor antagonist SB-224289 facilitated both STM and LTM. Selective receptor antagonists for the 5-HT(1A) (WAY100635), 5-HT(1D) (GR127935), 5-HT(2A) (MDL100907), 5-HT(2C/2B) (SB-200646), 5-HT(3) (ondansetron) or 5-HT(4) (GR125487), 5-HT(6) (Ro 04-6790, SB-399885 and SB-35713) or 5-HT(7) (SB-269970) did not impact STM. Nevertheless, WAY100635, MDL100907, SB-200646, GR125487, Ro 04-6790, SB-399885 or SB-357134 facilitated LTM. Notably, some of these changes shown to be independent of food-intake. Concomitantly, these data indicate that '5-HT tone via 5-HT(1B) receptors' might function in a serial manner from STM to LTM, whereas working in parallel using 5-HT(1A), 5-HT(2A), 5-HT(2B/2C), 5-HT(4), or 5-HT(6) receptors.

  14. Proteomic Investigation of the Time Course Responses of RAW 264.7 Macrophages to Infection with Salmonella enterica

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

    Shi, Liang; Chowdhury, Saiful M.; Smallwood, Heather S.

    2009-08-01

    Macrophages plan important roles in controlling Salmonella-mediated systemic infection. To investigate the responses of macrophages to Salmonella infection, we infected RAW 264.7 macrophages with Salmonella enterica serovar Typhimurium (STM) and then performed a comparative liquid chromatography-tandem mass spectrometry [LC-MS(/MS)]-based proteomics analysis of the infected macrophages. A total of 1006 macrophage and 115 STM proteins were indentified from this study. Most of STM proteins were found at late stage of the time course of infection, consistent with the fact that STM proliferates inside RAW 264.7 macrophages. Majority of the identified macrophage proteins were house keeping-related, including cytoplasmic superoxide dismutase 1 (SOD1),more » whose peptide abundances were relatively constant during the time course of infection. Compared to those in no infection control, the peptide abundances of 244 macrophage proteins (or 24% of total indentified macrophage proteins) changed considerably after STM infection. The functions of these STM infection-affected macrophage proteins were diverse and ranged from production of antibacterial nitric oxide (i.e., inducible nitric oxide synthase or iNOS) or production of prostaglandin H2 (i.e., prostaglandin-endoperoxide synthase 2, also know as cyclooxygenase-2 or COX-2) to regulation of intracellular traffic (e.g., sorting nexin or SNX 5, 6 and 9), demonstrating a global impact of STM infection on macrophage proteome. Western-blot analysis not only confirmed the LC-MS(/MS) results of SOD1, COX-2 and iNOS, but also revealed that the protein abundances of mitochondrial SOD2 increased after STM infection, indicating an infection-induced oxidative stress in mitochondria.« less

  15. Dissociations of the number and precision of visual short-term memory representations in change detection.

    PubMed

    Xie, Weizhen; Zhang, Weiwei

    2017-11-01

    The present study dissociated the number (i.e., quantity) and precision (i.e., quality) of visual short-term memory (STM) representations in change detection using receiver operating characteristic (ROC) and experimental manipulations. Across three experiments, participants performed both recognition and recall tests of visual STM using the change-detection task and the continuous color-wheel recall task, respectively. Experiment 1 demonstrated that the estimates of the number and precision of visual STM representations based on the ROC model of change-detection performance were robustly correlated with the corresponding estimates based on the mixture model of continuous-recall performance. Experiments 2 and 3 showed that the experimental manipulation of mnemonic precision using white-noise masking and the experimental manipulation of the number of encoded STM representations using consolidation masking produced selective effects on the corresponding measures of mnemonic precision and the number of encoded STM representations, respectively, in both change-detection and continuous-recall tasks. Altogether, using the individual-differences (Experiment 1) and experimental dissociation (Experiment 2 and 3) approaches, the present study demonstrated the some-or-none nature of visual STM representations across recall and recognition.

  16. Short-term memory for spatial, sequential and duration information.

    PubMed

    Manohar, Sanjay G; Pertzov, Yoni; Husain, Masud

    2017-10-01

    Space and time appear to play key roles in the way that information is organized in short-term memory (STM). Some argue that they are crucial contexts within which other stored features are embedded, allowing binding of information that belongs together within STM. Here we review recent behavioral, neurophysiological and imaging studies that have sought to investigate the nature of spatial, sequential and duration representations in STM, and how these might break down in disease. Findings from these studies point to an important role of the hippocampus and other medial temporal lobe structures in aspects of STM, challenging conventional accounts of involvement of these regions in only long-term memory.

  17. Probing the atomic structure of metallic nanoclusters with the tip of a scanning tunneling microscope.

    PubMed

    Schouteden, Koen; Lauwaet, Koen; Janssens, Ewald; Barcaro, Giovanni; Fortunelli, Alessandro; Van Haesendonck, Chris; Lievens, Peter

    2014-02-21

    Preformed Co clusters with an average diameter of 2.5 nm are produced in the gas phase and are deposited under controlled ultra-high vacuum conditions onto a thin insulating NaCl film on Au(111). Relying on a combined experimental and theoretical investigation, we demonstrate visualization of the three-dimensional atomic structure of the Co clusters by high-resolution scanning tunneling microscopy (STM) using a Cl functionalized STM tip that can be obtained on the NaCl surface. More generally, use of a functionalized STM tip may allow for systematic atomic structure determination with STM of nanoparticles that are deposited on metal surfaces.

  18. Interactive Mental Imagery and Short-Term Memory Search Rates for Words and Pictures. Report from the Project on Children's Learning and Development. Technical Report No. 317.

    ERIC Educational Resources Information Center

    Kerst, Stephen Marshall

    The purposes of this study were to determine if test stimulus was a member of the memory set and if items in an interactive image held in short term memory (STM) could be scanned simultaneously. In experiment one, 50 university subjects compared a test word with a set of one to three words held in STM. The rate of STM search was obtained by…

  19. Atomic resolution images of graphite in air

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

    Grigg, D.A.; Shedd, G.M.; Griffis, D.

    One sample used for proof of operation for atomic resolution in STM is highly oriented pyrolytic graphite (HOPG). This sample has been imaged with many different STM`s obtaining similar results. Atomic resolution images of HOPG have now been obtained using an STM designed and built at the Precision Engineering Center. This paper discusses the theoretical predictions and experimental results obtained in imaging of HOPG.

  20. EEG correlates of visual short-term memory in older age vary with adult lifespan cognitive development.

    PubMed

    Wiegand, Iris; Lauritzen, Martin J; Osler, Merete; Mortensen, Erik Lykke; Rostrup, Egill; Rask, Lene; Richard, Nelly; Horwitz, Anna; Benedek, Krisztina; Vangkilde, Signe; Petersen, Anders

    2018-02-01

    Visual short-term memory (vSTM) is a cognitive resource that declines with age. This study investigated whether electroencephalography (EEG) correlates of vSTM vary with cognitive development over individuals' lifespan. We measured vSTM performance and EEG in a lateralized whole-report task in a healthy birth cohort, whose cognitive function (intelligence quotient) was assessed in youth and late-middle age. Higher vSTM capacity (K; measured by Bundesen's theory of visual attention) was associated with higher amplitudes of the contralateral delay activity (CDA) and the central positivity (CP). In addition, rightward hemifield asymmetry of vSTM (K λ ) was associated with lower CDA amplitudes. Furthermore, more severe cognitive decline from young adulthood to late-middle age predicted higher CDA amplitudes, and the relationship between K and the CDA was less reliable in individuals who show higher levels of cognitive decline compared to individuals with preserved abilities. By contrast, there was no significant effect of lifespan cognitive changes on the CP or the relationship between behavioral measures of vSTM and the CP. Neither the CDA, nor the CP, nor the relationships between K or K λ and the event-related potentials were predicted by individuals' current cognitive status. Together, our findings indicate complex age-related changes in processes underlying behavioral and EEG measures of vSTM and suggest that the K-CDA relationship might be a marker of cognitive lifespan trajectories. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Design of a new reactor-like high temperature near ambient pressure scanning tunneling microscope for catalysis studies.

    PubMed

    Tao, Franklin Feng; Nguyen, Luan; Zhang, Shiran

    2013-03-01

    Here, we present the design of a new reactor-like high-temperature near ambient pressure scanning tunneling microscope (HT-NAP-STM) for catalysis studies. This HT-NAP-STM was designed for exploration of structures of catalyst surfaces at atomic scale during catalysis or under reaction conditions. In this HT-NAP-STM, the minimized reactor with a volume of reactant gases of ∼10 ml is thermally isolated from the STM room through a shielding dome installed between the reactor and STM room. An aperture on the dome was made to allow tip to approach to or retract from a catalyst surface in the reactor. This dome minimizes thermal diffusion from hot gas of the reactor to the STM room and thus remains STM head at a constant temperature near to room temperature, allowing observation of surface structures at atomic scale under reaction conditions or during catalysis with minimized thermal drift. The integrated quadrupole mass spectrometer can simultaneously measure products during visualization of surface structure of a catalyst. This synergy allows building an intrinsic correlation between surface structure and its catalytic performance. This correlation offers important insights for understanding of catalysis. Tests were done on graphite in ambient environment, Pt(111) in CO, graphene on Ru(0001) in UHV at high temperature and gaseous environment at high temperature. Atom-resolved surface structure of graphene on Ru(0001) at 500 K in a gaseous environment of 25 Torr was identified.

  2. About the Distinction between Working Memory and Short-Term Memory.

    PubMed

    Aben, Bart; Stapert, Sven; Blokland, Arjan

    2012-01-01

    The theoretical concepts short-term memory (STM) and working memory (WM) have been used to refer to the maintenance and the maintenance plus manipulation of information, respectively. Although they are conceptually different, the use of the terms STM and WM in literature is not always strict. STM and WM are different theoretical concepts that are assumed to reflect different cognitive functions. However, correlational studies have not been able to separate both constructs consistently and there is evidence for a large or even complete overlap. The emerging view from neurobiological studies is partly different, although there are conceptual problems troubling the interpretation of findings. In this regard, there is a crucial role for the tasks that are used to measure STM or WM (simple and complex span tasks, respectively) and for the cognitive load reflected by factors like attention and processing speed that may covary between and within these tasks. These conceptual issues are discussed based on several abstract models for the relation between STM and WM.

  3. Attenuated mutant strain of Salmonella Typhimurium lacking the ZnuABC transporter contrasts tumor growth promoting anti-cancer immune response.

    PubMed

    Chirullo, Barbara; Ammendola, Serena; Leonardi, Leonardo; Falcini, Roberto; Petrucci, Paola; Pistoia, Claudia; Vendetti, Silvia; Battistoni, Andrea; Pasquali, Paolo

    2015-07-10

    Salmonella Typhimurium has been shown to be highly effective as antitumor agent. The aim of this study was to investigate the tumor targeting efficacy and the mechanism of action of a specific attenuated mutant strain of Salmonella Typhimurium (STM) devoid of the whole operon coding for the high-affinity zinc transporter ZnuABC, which is required for bacterial growth in environments poor in zinc and for conferring full virulence to different Gram-negative pathogens.We showed that STM is able to penetrate and replicate into tumor cells in in vitro and in vivo models. The subcutaneous administration of STM in mammary adenocarcinoma mouse model led to both reduction of tumor growth and increase in life expectancy of STM treated mice. Moreover, investigating the potential mechanism behind the favorable clinical outcomes, we provide evidence that STM stimulates a potent inflammatory response and a specific immune pattern, recruiting a large number of innate and adaptive immune cells capable to contrast the immunosuppressive environment generated by tumors.

  4. Short-term memory capacity in networks via the restricted isometry property.

    PubMed

    Charles, Adam S; Yap, Han Lun; Rozell, Christopher J

    2014-06-01

    Cortical networks are hypothesized to rely on transient network activity to support short-term memory (STM). In this letter, we study the capacity of randomly connected recurrent linear networks for performing STM when the input signals are approximately sparse in some basis. We leverage results from compressed sensing to provide rigorous nonasymptotic recovery guarantees, quantifying the impact of the input sparsity level, the input sparsity basis, and the network characteristics on the system capacity. Our analysis demonstrates that network memory capacities can scale superlinearly with the number of nodes and in some situations can achieve STM capacities that are much larger than the network size. We provide perfect recovery guarantees for finite sequences and recovery bounds for infinite sequences. The latter analysis predicts that network STM systems may have an optimal recovery length that balances errors due to omission and recall mistakes. Furthermore, we show that the conditions yielding optimal STM capacity can be embodied in several network topologies, including networks with sparse or dense connectivities.

  5. Impact of auditory selective attention on verbal short-term memory and vocabulary development.

    PubMed

    Majerus, Steve; Heiligenstein, Lucie; Gautherot, Nathalie; Poncelet, Martine; Van der Linden, Martial

    2009-05-01

    This study investigated the role of auditory selective attention capacities as a possible mediator of the well-established association between verbal short-term memory (STM) and vocabulary development. A total of 47 6- and 7-year-olds were administered verbal immediate serial recall and auditory attention tasks. Both task types probed processing of item and serial order information because recent studies have shown this distinction to be critical when exploring relations between STM and lexical development. Multiple regression and variance partitioning analyses highlighted two variables as determinants of vocabulary development: (a) a serial order processing variable shared by STM order recall and a selective attention task for sequence information and (b) an attentional variable shared by selective attention measures targeting item or sequence information. The current study highlights the need for integrative STM models, accounting for conjoined influences of attentional capacities and serial order processing capacities on STM performance and the establishment of the lexical language network.

  6. Mechanism of Prism-Coupled Scanning Tunneling Microscope Light Emission

    NASA Astrophysics Data System (ADS)

    Iida, Wataru; Ahamed, Jamal U.; Katano, Satoshi; Uehara, Yoichi

    2011-09-01

    We have investigated the mechanism of scanning tunneling microscope light emission (STM-LE) in a prism-coupled configuration using finite difference time domain analysis. In this configuration, the sample is a metallic thin film evaporated on the bottom surface of a hemispherical glass prism. STM light emitted into the prism (prism-side emission) through the metallic film is measured. Since both localized surface plasmons (LSP) and surface plasmon polaritons (SPP) contribute to prism-side emission, this emission is stronger than that in conventional STM-LE measured from the sample surface side, which is radiated by LSP alone. We show that the spatial resolution of prism-side emission is determined not by the propagation length of SPP, but by the lateral size of LSP, similarly to conventional (i.e., tip side) STM-LE. Thus, we conclude that, by using the prism-coupled configuration, the signal level of STM-LE improves without the loss of spatial resolution attained in tip side emission.

  7. Neural organization of linguistic short-term memory is sensory modality-dependent: evidence from signed and spoken language.

    PubMed

    Pa, Judy; Wilson, Stephen M; Pickell, Herbert; Bellugi, Ursula; Hickok, Gregory

    2008-12-01

    Despite decades of research, there is still disagreement regarding the nature of the information that is maintained in linguistic short-term memory (STM). Some authors argue for abstract phonological codes, whereas others argue for more general sensory traces. We assess these possibilities by investigating linguistic STM in two distinct sensory-motor modalities, spoken and signed language. Hearing bilingual participants (native in English and American Sign Language) performed equivalent STM tasks in both languages during functional magnetic resonance imaging. Distinct, sensory-specific activations were seen during the maintenance phase of the task for spoken versus signed language. These regions have been previously shown to respond to nonlinguistic sensory stimulation, suggesting that linguistic STM tasks recruit sensory-specific networks. However, maintenance-phase activations common to the two languages were also observed, implying some form of common process. We conclude that linguistic STM involves sensory-dependent neural networks, but suggest that sensory-independent neural networks may also exist.

  8. A Disorder of Executive Function and Its Role in Language Processing

    PubMed Central

    Martin, Randi C.; Allen, Corinne M.

    2014-01-01

    R. Martin and colleagues have proposed separate stores for the maintenance of phonological and semantic information in short-term memory. Evidence from patients with aphasia has shown that damage to these separable buffers has specific consequences for language comprehension and production, suggesting an interdependence between language and memory systems. This article discusses recent research on aphasic patients with limited-capacity short-term memories (STMs) and reviews evidence suggesting that deficits in retaining semantic information in STM may be caused by a disorder in the executive control process of inhibition, specific to verbal representations. In contrast, a phonological STM deficit may be due to overly rapid decay. In semantic STM deficits, it is hypothesized that the inhibitory deficit produces difficulty inhibiting irrelevant verbal representations, which may lead to excessive interference. In turn, the excessive interference associated with semantic STM deficits has implications for single-word and sentence processing, and it may be the source of the reduced STM capacity shown by these patients. PMID:18720317

  9. The Value of Continuous ST-Segment Monitoring in the Emergency Department.

    PubMed

    Bovino, Leonie Rose; Funk, Marjorie; Pelter, Michele M; Desai, Mayur M; Jefferson, Vanessa; Andrews, Laura Kierol; Forte, Kenneth

    2015-01-01

    Practice standards for electrocardiographic monitoring recommend continuous ST-segment monitoring (C-STM) in patients presenting to the emergency department (ED) with signs and/or symptoms of acute coronary syndrome (ACS), but few studies have evaluated its use in the ED. We compared time to diagnosis and 30-day adverse events before and after implementation of C-STM. We also evaluated the diagnostic accuracy of C-STM in detecting ischemia and infarction. We prospectively studied 163 adults (preintervention: n = 78; intervention: n = 85) in a single ED and stratified them into low (n = 51), intermediate (n = 100), or high (n = 12) risk using History, ECG, Age, Risk factors, and Troponin (HEART) scores. The principal investigator monitored participants, activating C-STM on bedside monitors in the intervention phase. We used likelihood ratios (LRs) as the measure of diagnostic accuracy. Overall, 9% of participants were diagnosed with ACS. Median time to diagnosis did not differ before and after implementation of C-STM (5.55 vs. 5.98 hr; p = 0.43). In risk-stratified analyses, no significant pre-/postdifference in time to diagnosis was found in low-, intermediate-, or high-risk participants. There was no difference in the rate of 30-day adverse events before versus after C-STM implementation (11.5% vs. 10.6%; p = 0.85). The +LR and -LR of C-STM for ischemia were 24.0 (95% confidence interval [CI]: 1.4, 412.0) and 0.3 (95% CI: 0.02, 2.9), respectively, and for infarction were 13.7 (95% CI: 1.7, 112.3) and 0.7 (95% CI: 0.3, 1.5), respectively. Use of C-STM did not provide added diagnostic benefit for patients with signs and/or symptoms of myocardial ischemia in the ED.

  10. Impaired visual short-term memory capacity is distinctively associated with structural connectivity of the posterior thalamic radiation and the splenium of the corpus callosum in preterm-born adults.

    PubMed

    Menegaux, Aurore; Meng, Chun; Neitzel, Julia; Bäuml, Josef G; Müller, Hermann J; Bartmann, Peter; Wolke, Dieter; Wohlschläger, Afra M; Finke, Kathrin; Sorg, Christian

    2017-04-15

    Preterm birth is associated with an increased risk for lasting changes in both the cortico-thalamic system and attention; however, the link between cortico-thalamic and attention changes is as yet little understood. In preterm newborns, cortico-cortical and cortico-thalamic structural connectivity are distinctively altered, with increased local clustering for cortico-cortical and decreased integrity for cortico-thalamic connectivity. In preterm-born adults, among the various attention functions, visual short-term memory (vSTM) capacity is selectively impaired. We hypothesized distinct associations between vSTM capacity and the structural integrity of cortico-thalamic and cortico-cortical connections, respectively, in preterm-born adults. A whole-report paradigm of briefly presented letter arrays based on the computationally formalized Theory of Visual Attention (TVA) was used to quantify parameter vSTM capacity in 26 preterm- and 21 full-term-born adults. Fractional anisotropy (FA) of posterior thalamic radiations and the splenium of the corpus callosum obtained by diffusion tensor imaging were analyzed by tract-based spatial statistics and used as proxies for cortico-thalamic and cortico-cortical structural connectivity. The relationship between vSTM capacity and cortico-thalamic and cortico-cortical connectivity, respectively, was significantly modified by prematurity. In full-term-born adults, the higher FA in the right posterior thalamic radiation the higher vSTM capacity; in preterm-born adults this FA-vSTM-relationship was inversed. In the splenium, higher FA was correlated with higher vSTM capacity in preterm-born adults, whereas no significant relationship was evident in full-term-born adults. These results indicate distinct associations between cortico-thalamic and cortico-cortical integrity and vSTM capacity in preterm-and full-term-born adults. Data suggest compensatory cortico-cortical fiber re-organization for attention deficits after preterm delivery

  11. How do subvocal rehearsal and general attentional resources contribute to verbal short-term memory span?

    PubMed

    Morra, Sergio

    2015-01-01

    Whether rehearsal has a causal role in verbal STM has been controversial in the literature. Recent theories of working memory emphasize a role of attentional resources, but leave unclear how they contribute to verbal STM. Two experiments (with 49 and 102 adult participants, respectively) followed up previous studies with children, aiming to clarify the contributions of attentional capacity and rehearsal to verbal STM. Word length and presentation modality were manipulated. Experiment 1 focused on order errors, Experiment 2 on predicting individual differences in span from attentional capacity and articulation rate. Structural equation modeling showed clearly a major role of attentional capacity as a predictor of verbal STM span; but was inconclusive on whether rehearsal efficiency is an additional cause or a consequence of verbal STM. The effects of word length and modality on STM were replicated; a significant interaction was also found, showing a larger modality effect for long than short words, which replicates a previous finding on children. Item errors occurred more often with long words and correlated negatively with articulation rate. This set of findings seems to point to a role of rehearsal in maintaining item information. The probability of order errors per position increased linearly with list length. A revised version of a neo-Piagetian model was fit to the data of Experiment 2. That model was based on two parameters: attentional capacity (independently measured) and a free parameter representing loss of partly-activated information. The model could partly account for the results, but underestimated STM performance of the participants with smaller attentional capacity. It is concluded that modeling of verbal STM should consider individual and developmental differences in attentional capacity, rehearsal rate, and (perhaps) order representation.

  12. How do subvocal rehearsal and general attentional resources contribute to verbal short-term memory span?

    PubMed Central

    Morra, Sergio

    2015-01-01

    Whether rehearsal has a causal role in verbal STM has been controversial in the literature. Recent theories of working memory emphasize a role of attentional resources, but leave unclear how they contribute to verbal STM. Two experiments (with 49 and 102 adult participants, respectively) followed up previous studies with children, aiming to clarify the contributions of attentional capacity and rehearsal to verbal STM. Word length and presentation modality were manipulated. Experiment 1 focused on order errors, Experiment 2 on predicting individual differences in span from attentional capacity and articulation rate. Structural equation modeling showed clearly a major role of attentional capacity as a predictor of verbal STM span; but was inconclusive on whether rehearsal efficiency is an additional cause or a consequence of verbal STM. The effects of word length and modality on STM were replicated; a significant interaction was also found, showing a larger modality effect for long than short words, which replicates a previous finding on children. Item errors occurred more often with long words and correlated negatively with articulation rate. This set of findings seems to point to a role of rehearsal in maintaining item information. The probability of order errors per position increased linearly with list length. A revised version of a neo-Piagetian model was fit to the data of Experiment 2. That model was based on two parameters: attentional capacity (independently measured) and a free parameter representing loss of partly-activated information. The model could partly account for the results, but underestimated STM performance of the participants with smaller attentional capacity. It is concluded that modeling of verbal STM should consider individual and developmental differences in attentional capacity, rehearsal rate, and (perhaps) order representation. PMID:25798114

  13. Discovery of Salmonella Virulence Factors Translocated via Outer Membrane Vesicles to Murine Macrophages.

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

    Yoon, Hyunjin; Ansong, Charles; Adkins, Joshua N.

    We have previously shown that the regulators SpvR, FruR, IHF, PhoP/PhoQ, SsrA/SsrB, SlyA, Hnr, RpoE, SmpB, CsrA, RpoS, Crp, OmpR/EnvZ, and Hfq are essential for Salmonella Typhimurium virulence in mice. Here we use quantitative LC-MS-based proteomics profiling of in-frame deletion mutants of these 14 regulators to identify proteins that are coordinately regulated by these virulence regulators and are thus presumably novel factors contributing to Salmonella pathogenesis. Putative candidate proteins from proteomics analysis were determined, which exhibited similar abundance profiles to those of Salmonella pathogenicity island (SPI)-2 type III secretion system (TTSS) proteins. A subset of 5 proteins including STM0082, STM1548,more » PdgL, STM1633, and STM3595 was selected for further analysis. All 5 proteins were expressed inside macrophage cells and STM0082 (SrfN) was secreted into host cytoplasm. Furthermore, deletion of STM0082 attenuated virulence in mice when administered intraperitoneally as determined by competitive index. srfN transcription was positively regulated by SsrAB, however, secretion was independent of SPI-2 TTSS as well as SPI-1 TTSS and flagella. Proteins including PagK and STM2585A, which are positively regulated by PhoP/PhoQ, have sec signal peptides as predicted for SrfN and were secreted into macrophage cytoplasm regardless of SPI-2 TTSS. Isolation of outer membrane vesicles (OMVs) revealed the presence of SrfN, PagK, and STM2585A inside vesicle compartments. This result is the first case showing delivery of virulence effectors via OMVs in S. Typhimurium. Moreover, Hfq regulation of SrfN translation suggests that small non-coding RNAs may be responsible for regulating effector protein expression.« less

  14. Visual processing in reading disorders and attention-deficit/hyperactivity disorder and its contribution to basic reading ability

    PubMed Central

    Kibby, Michelle Y.; Dyer, Sarah M.; Vadnais, Sarah A.; Jagger, Audreyana C.; Casher, Gabriel A.; Stacy, Maria

    2015-01-01

    Whether visual processing deficits are common in reading disorders (RD), and related to reading ability in general, has been debated for decades. The type of visual processing affected also is debated, although visual discrimination and short-term memory (STM) may be more commonly related to reading ability. Reading disorders are frequently comorbid with ADHD, and children with ADHD often have subclinical reading problems. Hence, children with ADHD were used as a comparison group in this study. ADHD and RD may be dissociated in terms of visual processing. Whereas RD may be associated with deficits in visual discrimination and STM for order, ADHD is associated with deficits in visual-spatial processing. Thus, we hypothesized that children with RD would perform worse than controls and children with ADHD only on a measure of visual discrimination and a measure of visual STM that requires memory for order. We expected all groups would perform comparably on the measure of visual STM that does not require sequential processing. We found children with RD or ADHD were commensurate to controls on measures of visual discrimination and visual STM that do not require sequential processing. In contrast, both RD groups (RD, RD/ADHD) performed worse than controls on the measure of visual STM that requires memory for order, and children with comorbid RD/ADHD performed worse than those with ADHD. In addition, of the three visual measures, only sequential visual STM predicted reading ability. Hence, our findings suggest there is a deficit in visual sequential STM that is specific to RD and is related to basic reading ability. The source of this deficit is worthy of further research, but it may include both reduced memory for order and poorer verbal mediation. PMID:26579020

  15. Visual processing in reading disorders and attention-deficit/hyperactivity disorder and its contribution to basic reading ability.

    PubMed

    Kibby, Michelle Y; Dyer, Sarah M; Vadnais, Sarah A; Jagger, Audreyana C; Casher, Gabriel A; Stacy, Maria

    2015-01-01

    Whether visual processing deficits are common in reading disorders (RD), and related to reading ability in general, has been debated for decades. The type of visual processing affected also is debated, although visual discrimination and short-term memory (STM) may be more commonly related to reading ability. Reading disorders are frequently comorbid with ADHD, and children with ADHD often have subclinical reading problems. Hence, children with ADHD were used as a comparison group in this study. ADHD and RD may be dissociated in terms of visual processing. Whereas RD may be associated with deficits in visual discrimination and STM for order, ADHD is associated with deficits in visual-spatial processing. Thus, we hypothesized that children with RD would perform worse than controls and children with ADHD only on a measure of visual discrimination and a measure of visual STM that requires memory for order. We expected all groups would perform comparably on the measure of visual STM that does not require sequential processing. We found children with RD or ADHD were commensurate to controls on measures of visual discrimination and visual STM that do not require sequential processing. In contrast, both RD groups (RD, RD/ADHD) performed worse than controls on the measure of visual STM that requires memory for order, and children with comorbid RD/ADHD performed worse than those with ADHD. In addition, of the three visual measures, only sequential visual STM predicted reading ability. Hence, our findings suggest there is a deficit in visual sequential STM that is specific to RD and is related to basic reading ability. The source of this deficit is worthy of further research, but it may include both reduced memory for order and poorer verbal mediation.

  16. Novel Two-Step Hierarchical Screening of Mutant Pools Reveals Mutants under Selection in Chicks

    PubMed Central

    Yang, Hee-Jeong; Bogomolnaya, Lydia M.; Elfenbein, Johanna R.; Endicott-Yazdani, Tiana; Reynolds, M. Megan; Porwollik, Steffen; Cheng, Pui; Xia, Xiao-Qin

    2016-01-01

    Contaminated chicken/egg products are major sources of human salmonellosis, yet the strategies used by Salmonella to colonize chickens are poorly understood. We applied a novel two-step hierarchical procedure to identify new genes important for colonization and persistence of Salmonella enterica serotype Typhimurium in chickens. A library of 182 S. Typhimurium mutants each containing a targeted deletion of a group of contiguous genes (for a total of 2,069 genes deleted) was used to identify regions under selection at 1, 3, and 9 days postinfection in chicks. Mutants in 11 regions were under selection at all assayed times (colonization mutants), and mutants in 15 regions were under selection only at day 9 (persistence mutants). We assembled a pool of 92 mutants, each deleted for a single gene, representing nearly all genes in nine regions under selection. Twelve single gene deletion mutants were under selection in this assay, and we confirmed 6 of 9 of these candidate mutants via competitive infections and complementation analysis in chicks. STM0580, STM1295, STM1297, STM3612, STM3615, and STM3734 are needed for Salmonella to colonize and persist in chicks and were not previously associated with this ability. One of these key genes, STM1297 (selD), is required for anaerobic growth and supports the ability to utilize formate under these conditions, suggesting that metabolism of formate is important during infection. We report a hierarchical screening strategy to interrogate large portions of the genome during infection of animals using pools of mutants of low complexity. Using this strategy, we identified six genes not previously known to be needed during infection in chicks, and one of these (STM1297) suggests an important role for formate metabolism during infection. PMID:26857572

  17. Memory functioning in children with reading disabilities and/or attention deficit/hyperactivity disorder: a clinical investigation of their working memory and long-term memory functioning.

    PubMed

    Kibby, Michelle Y; Cohen, Morris J

    2008-11-01

    We examined memory functioning in children with reading disabilities (RD), Attention deficit/hyperactivity disorder (ADHD), and RD/ADHD using a clinic sample with a clinical instrument: the Children's Memory Scale, enhancing its generalizability. Participants included 23 children with RD, 30 with ADHD, 30 with RD/ADHD, and 30 controls. Children with RD presented with reduced verbal short-term memory (STM) but intact visual STM, central executive (CE), and long-term memory (LTM) functioning. Their deficit in STM appeared specific to tasks requiring phonetic coding of material. Children with ADHD displayed intact CE and LTM functioning but reduced visual-spatial STM, especially when off stimulant medication. Children with RD/ADHD had deficits consistent with both disorders.

  18. Short-Term Memory Depends on Dissociable Medial Temporal Lobe Regions in Amnestic Mild Cognitive Impairment

    PubMed Central

    Das, Sandhitsu R.; Mancuso, Lauren; Olson, Ingrid R.; Arnold, Steven E.; Wolk, David A.

    2016-01-01

    Short-term memory (STM) has generally been thought to be independent of the medial temporal lobe (MTL) in contrast to long-term memory (LTM). Prodromal Alzheimer's disease (AD) is a condition in which the MTL is a major early focus of pathology and LTM is thought disproportionately affected relative to STM. However, recent studies have suggested a role for the MTL in STM, particularly hippocampus, when binding of different elements is required. Other work has suggested involvement of extrahippocampal MTL structures, particularly in STM tasks that involve item-level memory. We examined STM for individual objects, locations, and object-location conjunctions in amnestic mild cognitive impairment (MCI), often associated with prodromal AD. Relative to age-matched, cognitively normal controls, MCI patients not only displayed impairment on object-location conjunctions but were similarly impaired for non-bound objects and locations. Moreover, across all participants, these conditions displayed dissociable correlations of cortical thinning along the long axis of the MTL and associated cortical nodes of anterior and posterior MTL networks. These findings support the role of the MTL in visual STM tasks and the division of labor of MTL in support of different types of memory representations, overlapping with findings in LTM. PMID:25725042

  19. Nanoscale coupling of photons to vibrational excitation of Ag nanoparticle 2D array studied by scanning tunneling microscope light emission spectroscopy.

    PubMed

    Katano, Satoshi; Toma, Koji; Toma, Mana; Tamada, Kaoru; Uehara, Yoichi

    2010-11-28

    Scanning tunneling microscope light emission (STM-LE) spectroscopy has been utilized to elucidate the luminescence phenomena of Ag nanoparticles capped with myristate (myristate-capped AgNP) and 2-methyl-1-propanethiolate (C(4)S-capped AgNP) on the dodecanethiol-precovered Au substrate. The STM imaging revealed that myristate-capped AgNPs form an ordered hexagonal array whereas C(4)S-capped AgNPs show imperfect ordering, indicating that a shorter alkyl chain of C(4)S-capped AgNP is not sufficient to form rigid interdigitation. It should be noted that such a nanoparticle ordering affects the luminescence properties of the Ag nanoparticle. We found that the STM-LE is only detected from the Ag nanoparticles forming the two-dimensional superlattice. This indicates that the STM-LE of the Ag nanoparticle is radiated via the collective excitation of the local surface plasmon resonance (LSPR) spread over the Ag nanoparticles. Note that the STM-LE spectra of the Ag nanoparticles exhibit spike-like peaks superimposed on the broad light emission peak. Using Raman spectroscopy, we concluded that the spike-like structure appearing in the STM-LE spectra is associated with the vibrational excitation of the molecule embedded between Ag nanoparticles.

  20. Profiles of verbal working memory growth predict speech and language development in children with cochlear implants.

    PubMed

    Kronenberger, William G; Pisoni, David B; Harris, Michael S; Hoen, Helena M; Xu, Huiping; Miyamoto, Richard T

    2013-06-01

    Verbal short-term memory (STM) and working memory (WM) skills predict speech and language outcomes in children with cochlear implants (CIs) even after conventional demographic, device, and medical factors are taken into account. However, prior research has focused on single end point outcomes as opposed to the longitudinal process of development of verbal STM/WM and speech-language skills. In this study, the authors investigated relations between profiles of verbal STM/WM development and speech-language development over time. Profiles of verbal STM/WM development were identified through the use of group-based trajectory analysis of repeated digit span measures over at least a 2-year time period in a sample of 66 children (ages 6-16 years) with CIs. Subjects also completed repeated assessments of speech and language skills during the same time period. Clusters representing different patterns of development of verbal STM (digit span forward scores) were related to the growth rate of vocabulary and language comprehension skills over time. Clusters representing different patterns of development of verbal WM (digit span backward scores) were related to the growth rate of vocabulary and spoken word recognition skills over time. Different patterns of development of verbal STM/WM capacity predict the dynamic process of development of speech and language skills in this clinical population.

  1. Fractal fluctuations in spatiotemporal variables when walking on a self-paced treadmill.

    PubMed

    Choi, Jin-Seung; Kang, Dong-Won; Seo, Jeong-Woo; Tack, Gye-Rae

    2017-12-08

    This study investigated the fractal dynamic properties of stride time (ST), stride length (SL) and stride speed (SS) during walking on a self-paced treadmill (STM) in which the belt speed is automatically controlled by the walking speed. Twelve healthy young subjects participated in the study. The subjects walked at their preferred walking speed under four conditions: STM, STM with a metronome (STM+met), fixed-speed (conventional) treadmill (FTM), and FTM with a metronome (FTM+met). To compare the fractal dynamics between conditions, the mean, variability, and fractal dynamics of ST, SL, and SS were compared. Moreover, the relationship among the variables was examined under each walking condition using three types of surrogates. The mean values of all variables did not differ between the two treadmills, and the variability of all variables was generally larger for STM than for FTM. The use of a metronome resulted in a decrease in variability in ST and SS for all conditions. The fractal dynamic characteristics of SS were maintained with STM, in contrast to FTM, and only the fractal dynamic characteristics of ST disappeared when using a metronome. In addition, the fractal dynamic patterns of the cross-correlated surrogate results were identical to those of all variables for the two treadmills. In terms of the fractal dynamic properties, STM walking was generally closer to overground walking than FTM walking. Although further research is needed, the present results will be useful in research on gait fractal dynamics and rehabilitation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. High-stability cryogenic scanning tunneling microscope based on a closed-cycle cryostat.

    PubMed

    Hackley, Jason D; Kislitsyn, Dmitry A; Beaman, Daniel K; Ulrich, Stefan; Nazin, George V

    2014-10-01

    We report on the design and operation of a cryogenic ultra-high vacuum (UHV) scanning tunneling microscope (STM) coupled to a closed-cycle cryostat (CCC). The STM is thermally linked to the CCC through helium exchange gas confined inside a volume enclosed by highly flexible rubber bellows. The STM is thus mechanically decoupled from the CCC, which results in a significant reduction of the mechanical noise transferred from the CCC to the STM. Noise analysis of the tunneling current shows current fluctuations up to 4% of the total current, which translates into tip-sample distance variations of up to 1.5 picometers. This noise level is sufficiently low for atomic-resolution imaging of a wide variety of surfaces. To demonstrate this, atomic-resolution images of Au(111) and NaCl(100)/Au(111) surfaces, as well as of carbon nanotubes deposited on Au(111), were obtained. Thermal drift analysis showed that under optimized conditions, the lateral stability of the STM scanner can be as low as 0.18 Å/h. Scanning Tunneling Spectroscopy measurements based on the lock-in technique were also carried out, and showed no detectable presence of noise from the closed-cycle cryostat. Using this cooling approach, temperatures as low as 16 K at the STM scanner have been achieved, with the complete cool-down of the system typically taking up to 12 h. These results demonstrate that the constructed CCC-coupled STM is a highly stable instrument capable of highly detailed spectroscopic investigations of materials and surfaces at the atomic scale.

  3. Familiarity Speeds Up Visual Short-term Memory Consolidation: Electrophysiological Evidence from Contralateral Delay Activities.

    PubMed

    Xie, Weizhen; Zhang, Weiwei

    2018-01-01

    To test how preexisting long-term memory influences visual STM, this study takes advantage of individual differences in participants' prior familiarity with Pokémon characters and uses an ERP component, the contralateral delay activity (CDA), to assess whether observers' prior stimulus familiarity affects STM consolidation and storage capacity. In two change detection experiments, consolidation speed, as indexed by CDA fractional area latency and/or early-window (500-800 msec) amplitude, was significantly associated with individual differences in Pokémon familiarity. In contrast, the number of remembered Pokémon stimuli, as indexed by Cowan's K and late-window (1500-2000 msec) CDA amplitude, was significantly associated with individual differences in Pokémon familiarity when STM consolidation was incomplete because of a short presentation of Pokémon stimuli (500 msec, Experiment 2), but not when STM consolidation was allowed to complete given sufficient encoding time (1000 msec, Experiment 1). Similar findings were obtained in between-group analyses when participants were separated into high-familiarity and low-familiarity groups based on their Pokémon familiarity ratings. Together, these results suggest that stimulus familiarity, as a proxy for the strength of preexisting long-term memory, primarily speeds up STM consolidation, which may subsequently lead to an increase in the number of remembered stimuli if consolidation is incomplete. These findings thus highlight the importance of research assessing how effects on representations (e.g., STM capacity) are in general related to (or even caused by) effects on processes (e.g., STM consolidation) in cognition.

  4. Relational and conjunctive binding functions dissociate in short-term memory.

    PubMed

    Parra, Mario A; Fabi, Katia; Luzzi, Simona; Cubelli, Roberto; Hernandez Valdez, Maria; Della Sala, Sergio

    2015-02-01

    Remembering complex events requires binding features within unified objects (conjunctions) and holding associations between objects (relations). Recent studies suggest that the two functions dissociate in long-term memory (LTM). Less is known about their functional organization in short-term memory (STM). The present study investigated this issue in patient AE affected by a stroke which caused damage to brain regions known to be relevant for relational functions both in LTM and in STM (i.e., the hippocampus). The assessment involved a battery of standard neuropsychological tasks and STM binding tasks. One STM binding task (Experiment 1) presented common objects and common colors forming either pairs (relations) or integrated objects (conjunctions). Free recall of relations or conjunctions was assessed. A second STM binding task used random polygons and non-primary colors instead (Experiment 2). Memory was assessed by selecting the features that made up the relations or the conjunctions from a set of single polygons and a set of single colors. The neuropsychological assessment revealed impaired delayed memory in AE. AE's pronounced relational STM binding deficits contrasted with his completely preserved conjunctive binding functions in both Experiments 1 and 2. Only 2.35% and 1.14% of the population were expected to have a discrepancy more extreme than that presented by AE in Experiments 1 and 2, respectively. Processing relations and conjunctions of very elementary nonspatial features in STM led to dissociating performances in AE. These findings may inform current theories of memory decline such as those linked to cognitive aging.

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

    Hackley, Jason D.; Kislitsyn, Dmitry A.; Beaman, Daniel K.

    We report on the design and operation of a cryogenic ultra-high vacuum (UHV) scanning tunneling microscope (STM) coupled to a closed-cycle cryostat (CCC). The STM is thermally linked to the CCC through helium exchange gas confined inside a volume enclosed by highly flexible rubber bellows. The STM is thus mechanically decoupled from the CCC, which results in a significant reduction of the mechanical noise transferred from the CCC to the STM. Noise analysis of the tunneling current shows current fluctuations up to 4% of the total current, which translates into tip-sample distance variations of up to 1.5 picometers. This noisemore » level is sufficiently low for atomic-resolution imaging of a wide variety of surfaces. To demonstrate this, atomic-resolution images of Au(111) and NaCl(100)/Au(111) surfaces, as well as of carbon nanotubes deposited on Au(111), were obtained. Thermal drift analysis showed that under optimized conditions, the lateral stability of the STM scanner can be as low as 0.18 Å/h. Scanning Tunneling Spectroscopy measurements based on the lock-in technique were also carried out, and showed no detectable presence of noise from the closed-cycle cryostat. Using this cooling approach, temperatures as low as 16 K at the STM scanner have been achieved, with the complete cool-down of the system typically taking up to 12 h. These results demonstrate that the constructed CCC-coupled STM is a highly stable instrument capable of highly detailed spectroscopic investigations of materials and surfaces at the atomic scale.« less

  6. Spectrotemporal Modulation Sensitivity as a Predictor of Speech Intelligibility for Hearing-Impaired Listeners

    PubMed Central

    Bernstein, Joshua G.W.; Mehraei, Golbarg; Shamma, Shihab; Gallun, Frederick J.; Theodoroff, Sarah M.; Leek, Marjorie R.

    2014-01-01

    Background A model that can accurately predict speech intelligibility for a given hearing-impaired (HI) listener would be an important tool for hearing-aid fitting or hearing-aid algorithm development. Existing speech-intelligibility models do not incorporate variability in suprathreshold deficits that are not well predicted by classical audiometric measures. One possible approach to the incorporation of such deficits is to base intelligibility predictions on sensitivity to simultaneously spectrally and temporally modulated signals. Purpose The likelihood of success of this approach was evaluated by comparing estimates of spectrotemporal modulation (STM) sensitivity to speech intelligibility and to psychoacoustic estimates of frequency selectivity and temporal fine-structure (TFS) sensitivity across a group of HI listeners. Research Design The minimum modulation depth required to detect STM applied to an 86 dB SPL four-octave noise carrier was measured for combinations of temporal modulation rate (4, 12, or 32 Hz) and spectral modulation density (0.5, 1, 2, or 4 cycles/octave). STM sensitivity estimates for individual HI listeners were compared to estimates of frequency selectivity (measured using the notched-noise method at 500, 1000measured using the notched-noise method at 500, 2000, and 4000 Hz), TFS processing ability (2 Hz frequency-modulation detection thresholds for 500, 10002 Hz frequency-modulation detection thresholds for 500, 2000, and 4000 Hz carriers) and sentence intelligibility in noise (at a 0 dB signal-to-noise ratio) that were measured for the same listeners in a separate study. Study Sample Eight normal-hearing (NH) listeners and 12 listeners with a diagnosis of bilateral sensorineural hearing loss participated. Data Collection and Analysis STM sensitivity was compared between NH and HI listener groups using a repeated-measures analysis of variance. A stepwise regression analysis compared STM sensitivity for individual HI listeners to

  7. Structure of a zinc oxide ultra-thin film on Rh(100)

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

    Yuhara, J.; Kato, D.; Matsui, T.

    The structural parameters of ultra-thin zinc oxide films on Rh(100) are investigated using low-energy electron diffraction intensity (LEED I–V) curves, scanning tunneling microscopy (STM), and first-principles density functional theory (DFT) calculations. From the analysis of LEED I–V curves and DFT calculations, two optimized models A and B are determined. Their structures are basically similar to the planer h-BN ZnO(0001) structure, although some oxygen atoms protrude from the surface, associated with an in-plane shift of Zn atoms. From a comparison of experimental STM images and simulated STM images, majority and minority structures observed in the STM images represent the two optimizedmore » models A and B, respectively.« less

  8. Scanning Tunneling Microscopy | Materials Science | NREL

    Science.gov Websites

    of Scanning Tunneling Microscopy Capabilities Two-dimensional STM image 2D STM image of Si(111) 7×7 clusters along a fault boundary Occupied-state STM image taken on a Si(111)7×7 surface, showing two 7×7 tip at each point, an image of the sample surface is generated (topographic image). For very flat

  9. Neural dynamics underlying attentional orienting to auditory representations in short-term memory.

    PubMed

    Backer, Kristina C; Binns, Malcolm A; Alain, Claude

    2015-01-21

    Sounds are ephemeral. Thus, coherent auditory perception depends on "hearing" back in time: retrospectively attending that which was lost externally but preserved in short-term memory (STM). Current theories of auditory attention assume that sound features are integrated into a perceptual object, that multiple objects can coexist in STM, and that attention can be deployed to an object in STM. Recording electroencephalography from humans, we tested these assumptions, elucidating feature-general and feature-specific neural correlates of auditory attention to STM. Alpha/beta oscillations and frontal and posterior event-related potentials indexed feature-general top-down attentional control to one of several coexisting auditory representations in STM. Particularly, task performance during attentional orienting was correlated with alpha/low-beta desynchronization (i.e., power suppression). However, attention to one feature could occur without simultaneous processing of the second feature of the representation. Therefore, auditory attention to memory relies on both feature-specific and feature-general neural dynamics. Copyright © 2015 the authors 0270-6474/15/351307-12$15.00/0.

  10. Improved design for a low temperature scanning tunneling microscope with an in situ tip treatment stage.

    PubMed

    Kim, J-J; Joo, S H; Lee, K S; Yoo, J H; Park, M S; Kwak, J S; Lee, Jinho

    2017-04-01

    The Low Temperature Scanning Tunneling Microscope (LT-STM) is an extremely valuable tool not only in surface science but also in condensed matter physics. For years, numerous new ideas have been adopted to perfect LT-STM performances-Ultra-Low Vibration (ULV) laboratory and the rigid STM head design are among them. Here, we present three improvements for the design of the ULV laboratory and the LT-STM: tip treatment stage, sample cleaving stage, and vibration isolation system. The improved tip treatment stage enables us to perform field emission for the purpose of tip treatment in situ without exchanging samples, while our enhanced sample cleaving stage allows us to cleave samples at low temperature in a vacuum without optical access by a simple pressing motion. Our newly designed vibration isolation system provides efficient space usage while maintaining vibration isolation capability. These improvements enhance the quality of spectroscopic imaging experiments that can last for many days and provide increased data yield, which we expect can be indispensable elements in future LT-STM designs.

  11. Short-term memory for serial order supports vocabulary development: new evidence from a novel word learning paradigm.

    PubMed

    Majerus, Steve; Boukebza, Claire

    2013-12-01

    Although recent studies suggest a strong association between short-term memory (STM) for serial order and lexical development, the precise mechanisms linking the two domains remain to be determined. This study explored the nature of these mechanisms via a microanalysis of performance on serial order STM and novel word learning tasks. In the experiment, 6- and 7-year-old children were administered tasks maximizing STM for either item or serial order information as well as paired-associate learning tasks involving the learning of novel words, visual symbols, or familiar word pair associations. Learning abilities for novel words were specifically predicted by serial order STM abilities. A measure estimating the precision of serial order coding predicted the rate of correct repetitions and the rate of phoneme migration errors during the novel word learning process. In line with recent theoretical accounts, these results suggest that serial order STM supports vocabulary development via ordered and detailed reactivation of the novel phonological sequences that characterize new words. Copyright © 2013 Elsevier Inc. All rights reserved.

  12. An ultra-high vacuum scanning tunneling microscope operating at sub-Kelvin temperatures and high magnetic fields for spin-resolved measurements

    NASA Astrophysics Data System (ADS)

    Salazar, C.; Baumann, D.; Hänke, T.; Scheffler, M.; Kühne, T.; Kaiser, M.; Voigtländer, R.; Lindackers, D.; Büchner, B.; Hess, C.

    2018-06-01

    We present the construction and performance of an ultra-low-temperature scanning tunneling microscope (STM), working in ultra-high vacuum (UHV) conditions and in high magnetic fields up to 9 T. The cryogenic environment of the STM is generated by a single-shot 3He magnet cryostat in combination with a 4He dewar system. At a base temperature (300 mK), the cryostat has an operation time of approximately 80 h. The special design of the microscope allows the transfer of the STM head from the cryostat to a UHV chamber system, where samples and STM tips can be easily exchanged. The UHV chambers are equipped with specific surface science treatment tools for the functionalization of samples and tips, including high-temperature treatments and thin film deposition. This, in particular, enables spin-resolved tunneling measurements. We present test measurements using well-known samples and tips based on superconductors and metallic materials such as LiFeAs, Nb, Fe, and W. The measurements demonstrate the outstanding performance of the STM with high spatial and energy resolution as well as the spin-resolved capability.

  13. Analysis and Prediction of Ice Shedding for a Full-Scale Heated Tail Rotor

    NASA Technical Reports Server (NTRS)

    Kreeger, Richard E.; Work, Andrew; Douglass, Rebekah; Gazella, Matthew; Koster, Zakery; Turk, Jodi

    2016-01-01

    When helicopters are to fly in icing conditions, it is necessary to consider the possibility of ice shed from the rotor blades. In 2013, a series of tests were conducted on a heated tail rotor at NASA Glenn's Icing Research Tunnel (IRT). The tests produced several shed events that were captured on camera. Three of these shed events were captured at a sufficiently high frame rate to obtain multiple images of the shed ice in flight that had a sufficiently long section of shed ice for analysis. Analysis of these shed events is presented and compared to an analytical Shedding Trajectory Model (STM). The STM is developed and assumes that the ice breaks off instantly as it reaches the end of the blade, while frictional and viscous forces are used as parameters to fit the STM. The trajectory of each shed is compared to that predicted by the STM, where the STM provides information of the shed group of ice as a whole. The limitations of the model's underlying assumptions are discussed in comparison to experimental shed events.

  14. Interface morphology of a Cr(001)/Fe(001) superlattice determined by scanning tunneling microscopy and x-ray diffraction: A comparison

    NASA Astrophysics Data System (ADS)

    Schmidt, C. M.; Bürgler, D. E.; Schaller, D. M.; Meisinger, F.; Güntherodt, H.-J.; Temst, K.

    2001-01-01

    A Cr(001)/Fe(001) superlattice with ten bilayers grown by molecular beam epitaxy on a Ag(001) substrate is studied by in situ scanning tunneling microscopy (STM) and ex situ x-ray diffraction (XRD). Layer-resolved roughness parameters determined from STM images taken in various stages of the superlattice fabrication are compared with average values reported in the literature or obtained from the fits of our XRD data. Good agreement is found for the rms roughnesses describing vertical roughness and for the lateral correlation lengths characterizing correlated as well as uncorrelated interface roughness if peculiarities of STM and XRD are taken into account. We discuss in detail (i) the possible differences between the STM topography of a free surface and the morphology of a subsequently formed interface, (ii) contributions due to chemical intermixing at the interfaces, (iii) the comparison of XRD parameters averaged over all interfaces versus layer-resolved STM parameters, and (iv) the question of the coherent field of view for the determination of rms values.

  15. Thalamo-Cortical Disruption Contributes to Short-Term Memory Deficits in Patients with Medial Temporal Lobe Damage.

    PubMed

    Voets, Natalie L; Menke, Ricarda A L; Jbabdi, Saad; Husain, Masud; Stacey, Richard; Carpenter, Katherine; Adcock, Jane E

    2015-11-01

    Short-term (STM) and long-term memory (LTM) have largely been considered as separate brain systems reflecting fronto-parietal and medial temporal lobe (MTL) functions, respectively. This functional dichotomy has been called into question by evidence of deficits on aspects of working memory in patients with MTL damage, suggesting a potentially direct hippocampal contribution to STM. As the hippocampus has direct anatomical connections with the thalamus, we tested the hypothesis that damage to thalamic nuclei regulating cortico-cortical interactions may contribute to STM deficits in patients with hippocampal dysfunction. We used diffusion-weighted magnetic resonance imaging-based tractography to identify anatomical subdivisions in patients with MTL epilepsy. From these, we measured resting-state functional connectivity with detailed cortical divisions of the frontal, temporal, and parietal lobes. Whereas thalamo-temporal functional connectivity reflected LTM performance, thalamo-prefrontal functional connectivity specifically predicted STM performance. Notably, patients with hippocampal volume loss showed thalamic volume loss, most prominent in the pulvinar region, not detected in patients with normal hippocampal volumes. Aberrant thalamo-cortical connectivity in the epileptic hemisphere was mirrored in a loss of behavioral association with STM performance specifically in patients with hippocampal atrophy. These findings identify thalamo-cortical disruption as a potential mechanism contributing to STM deficits in the context of MTL damage. © The Author 2015. Published by Oxford University Press.

  16. Expression of SHOOT MERISTEMLESS, WUSCHEL, and ASYMMETRIC LEAVES1 Homologs in the Shoots of Podostemaceae: Implications for the Evolution of Novel Shoot Organogenesis[W

    PubMed Central

    Katayama, Natsu; Koi, Satoshi; Kato, Masahiro

    2010-01-01

    Podostemaceae (the river weeds) are ecologically and morphologically unusual angiosperms. The subfamily Tristichoideae has typical shoot apical meristems (SAMs) that produce leaves, but Podostemoideae is devoid of SAMs and new leaves arise below the base of older leaves. To reveal the genetic basis for the evolution of novel shoot organogenesis in Podostemaceae, we examined the expression patterns of key regulatory genes for shoot development (i.e., SHOOT MERISTEMLESS (STM), WUSCHEL (WUS), and ASYMMETRIC LEAVES1/ROUGH SHEATH2/PHANTASTICA (ARP) orthologs) in Tristichoideae and Podostemoideae. In the SAM-mediated shoots of Tristichoideae, like in model plants, STM and WUS orthologs were expressed in the SAM. In the SAM-less shoots of Podostemoideae, STM and WUS orthologs were expressed in the initiating leaf/bract primordium. In older leaf/bract primordia, WUS expression disappeared and STM expression became restricted to the basal part, whereas ARP was expressed in the distal part in a complementary pattern to STM expression. In the reproductive shoots of Podostemoideae with a normal mode of flower development, STM and WUS were expressed in the floral meristem, but not in the floral organs, similar to the pattern in model plants. These results suggest that the leaf/bract of Podostemoideae is initiated as a SAM and differentiates into a single apical leaf/bract, resulting in the evolution of novel shoot-leaf mixed organs in Podostemaceae. PMID:20647344

  17. Short-Term Memory Depends on Dissociable Medial Temporal Lobe Regions in Amnestic Mild Cognitive Impairment.

    PubMed

    Das, Sandhitsu R; Mancuso, Lauren; Olson, Ingrid R; Arnold, Steven E; Wolk, David A

    2016-05-01

    Short-term memory (STM) has generally been thought to be independent of the medial temporal lobe (MTL) in contrast to long-term memory (LTM). Prodromal Alzheimer's disease (AD) is a condition in which the MTL is a major early focus of pathology and LTM is thought disproportionately affected relative to STM. However, recent studies have suggested a role for the MTL in STM, particularly hippocampus, when binding of different elements is required. Other work has suggested involvement of extrahippocampal MTL structures, particularly in STM tasks that involve item-level memory. We examined STM for individual objects, locations, and object-location conjunctions in amnestic mild cognitive impairment (MCI), often associated with prodromal AD. Relative to age-matched, cognitively normal controls, MCI patients not only displayed impairment on object-location conjunctions but were similarly impaired for non-bound objects and locations. Moreover, across all participants, these conditions displayed dissociable correlations of cortical thinning along the long axis of the MTL and associated cortical nodes of anterior and posterior MTL networks. These findings support the role of the MTL in visual STM tasks and the division of labor of MTL in support of different types of memory representations, overlapping with findings in LTM. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  18. Medial temporal lobe contributions to short-term memory for faces

    PubMed Central

    Race, Elizabeth; LaRocque, Karen F.; Keane, Margaret M.; Verfaellie, Mieke

    2015-01-01

    The role of the medial temporal lobes (MTL) in short-term memory (STM) remains a matter of debate. While imaging studies commonly show hippocampal activation during short-delay memory tasks, evidence from amnesic patients with MTL lesions is mixed. It has been argued that apparent STM impairments in amnesia may reflect long-term memory (LTM) contributions to performance. We challenge this conclusion by demonstrating that MTL amnesic patients show impaired delayed matching-to-sample (DMS) for faces in a task that meets both a traditional delay-based and a recently proposed distractor-based criterion for classification as a STM task. In Experiment 1, we demonstrate that our face DMS task meets the proposed distractor-based criterion for STM classification, in that extensive processing of delay-period distractor stimuli disrupts performance of healthy individuals. In Experiment 2, MTL amnesic patients with lesions extending into anterior subhippocampal cortex, but not patients with lesions limited to the hippocampus, show impaired performance on this task without distraction at delays as short as 8s, within temporal range of delay-based STM classification, in the context of intact perceptual matching performance. Experiment 3 provides support for the hypothesis that STM for faces relies on configural processing by showing that the extent to which healthy participants’ performance is disrupted by interference depends on the configural demands of the distractor task. Together, these findings are consistent with the notion that the amnesic impairment in STM for faces reflects a deficit in configural processing associated with subhippocampal cortices and provide novel evidence that the MTL supports cognition beyond the LTM domain. PMID:23937185

  19. Medial temporal lobe contributions to short-term memory for faces.

    PubMed

    Race, Elizabeth; LaRocque, Karen F; Keane, Margaret M; Verfaellie, Mieke

    2013-11-01

    The role of the medial temporal lobes (MTL) in short-term memory (STM) remains a matter of debate. Whereas imaging studies commonly show hippocampal activation during short-delay memory tasks, evidence from amnesic patients with MTL lesions is mixed. It has been argued that apparent STM impairments in amnesia may reflect long-term memory (LTM) contributions to performance. We challenge this conclusion by demonstrating that MTL amnesic patients show impaired delayed matching-to-sample (DMS) for faces in a task that meets both a traditional delay-based and a recently proposed distractor-based criterion for classification as an STM task. In Experiment 1, we demonstrate that our face DMS task meets the proposed distractor-based criterion for STM classification, in that extensive processing of delay-period distractor stimuli disrupts performance of healthy individuals. In Experiment 2, MTL amnesic patients with lesions extending into anterior subhippocampal cortex, but not patients with lesions limited to the hippocampus, show impaired performance on this task without distraction at delays as short as 8 s, within temporal range of delay-based STM classification, in the context of intact perceptual matching performance. Experiment 3 provides support for the hypothesis that STM for faces relies on configural processing by showing that the extent to which healthy participants' performance is disrupted by interference depends on the configural demands of the distractor task. Together, these findings are consistent with the notion that the amnesic impairment in STM for faces reflects a deficit in configural processing associated with subhippocampal cortices and provide novel evidence that the MTL supports cognition beyond the LTM domain. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  20. Sparse-coding denoising applied to reversible conformational switching of a porphyrin self-assembled monolayer induced by scanning tunnelling microscopy.

    PubMed

    Oliveira, J; Bragança, A M; Alcácer, L; Morgado, J; Figueiredo, M; Bioucas-Dias, J; Ferreira, Q

    2018-04-14

    Scanning tunnelling microscopy (STM) was used to induce conformational molecular switching on a self-assembled monolayer of zinc-octaethylporphyrin on a graphite/tetradecane interface at room temperature. A reversible conformational change controlled by applying a tip voltage was observed. Consecutive STM images acquired at alternating tip voltages showed that at 0.4 V the porphyrin monolayer presents a molecular arrangement formed by alternate rows with two different types of structural conformations and when the potential is increased to 0.7 V the monolayer presents only one type of conformation. In this paper, we characterize these porphyrin conformational dynamics by analyzing the STM images, which were improved for better quality and interpretation by means of a denoising algorithm, adapted to process STM images from state of the art image processing and analysis methods. STM remains the best technique to 'see' and to manipulate the matter at atomic scale. A very sharp tip a few angstroms of the surface can provide images of molecules and atoms with a powerful resolution. However, these images are strongly affected by noise which is necessary to correct and eliminate. This paper is about new computational tools specifically developed to denoise the images acquired with STM. The new algorithms were tested in STM images, obtained at room temperature, of porphyrin monolayer which presents reversible conformational change in function of the tip bias voltage. Images with high resolution, acquired in real time, show that the porphyrins have different molecular arrangements whether the tip voltage is 0.4 V or 0.7 V. © 2018 The Authors Journal of Microscopy © 2018 Royal Microscopical Society.

  1. Altered seed oil and glucosinolate levels in transgenic plants overexpressing the Brassica napus SHOOTMERISTEMLESS gene.

    PubMed

    Elhiti, Mohamed; Yang, Cunchun; Chan, Ainsley; Durnin, Douglas C; Belmonte, Mark F; Ayele, Belay T; Tahir, Muhammad; Stasolla, Claudio

    2012-07-01

    SHOOTMERISTEMLESS (STM) is a homeobox gene conserved among plant species which is required for the formation and maintenance of the shoot meristem by suppressing differentiation and maintaining an undetermined cell fate within the apical pole. To assess further the role of this gene during seed storage accumulation, transgenic Brassica napus (Bn) plants overexpressing or down-regulating BnSTM under the control of the 35S promoter were generated. Overexpression of BnSTM increased seed oil content without affecting the protein and sucrose level. These changes were accompanied by the induction of genes encoding several transcription factors promoting fatty acid (FA) synthesis: LEAFY COTYLEDON1 (BnLEC1), BnLEC2, and WRINKLE1 (BnWRI1). In addition, expression of key representative enzymes involved in sucrose metabolism, glycolysis, and FA biosynthesis was up-regulated in developing seeds ectopically expressing BnSTM. These distinctive expression patterns support the view of an increased carbon flux to the FA biosynthetic pathway in developing transformed seeds. The overexpression of BnSTM also resulted in a desirable reduction of seed glucosinolate (GLS) levels ascribed to a transcriptional repression of key enzymes participating in the GLS biosynthetic pathway, and possibly to the differential utilization of common precursors for GLS and indole-3-acetic acid synthesis. No changes in oil and GLS levels were observed in lines down-regulating BnSTM. Taken together, these findings provide evidence for a novel function for BnSTM in promoting desirable changes in seed oil and GLS levels when overexpressed in B. napus plants, and demonstrate that this gene can be used as a target for genetic improvement of oilseed species.

  2. Robust procedure for creating and characterizing the atomic structure of scanning tunneling microscope tips.

    PubMed

    Tewari, Sumit; Bastiaans, Koen M; Allan, Milan P; van Ruitenbeek, Jan M

    2017-01-01

    Scanning tunneling microscopes (STM) are used extensively for studying and manipulating matter at the atomic scale. In spite of the critical role of the STM tip, procedures for controlling the atomic-scale shape of STM tips have not been rigorously justified. Here, we present a method for preparing tips in situ while ensuring the crystalline structure and a reproducibly prepared tip structure up to the second atomic layer. We demonstrate a controlled evolution of such tips starting from undefined tip shapes.

  3. Memory integration in amnesia: prior knowledge supports verbal short-term memory.

    PubMed

    Race, Elizabeth; Palombo, Daniela J; Cadden, Margaret; Burke, Keely; Verfaellie, Mieke

    2015-04-01

    Short-term memory (STM) and long-term memory (LTM) have traditionally been considered cognitively distinct. However, it is known that STM can improve when to-be-remembered information appears in contexts that make contact with prior knowledge, suggesting a more interactive relationship between STM and LTM. The current study investigated whether the ability to leverage LTM in support of STM critically depends on the integrity of the hippocampus. Specifically, we investigated whether the hippocampus differentially supports between-domain versus within-domain STM-LTM integration given prior evidence that the representational domain of the elements being integrated in memory is a critical determinant of whether memory performance depends on the hippocampus. In Experiment 1, we investigated hippocampal contributions to within-domain STM-LTM integration by testing whether immediate verbal recall of words improves in MTL amnesic patients when words are presented in familiar verbal contexts (meaningful sentences) compared to unfamiliar verbal contexts (random word lists). Patients demonstrated a robust sentence superiority effect, whereby verbal STM performance improved in familiar compared to unfamiliar verbal contexts, and the magnitude of this effect did not differ from that in controls. In Experiment 2, we investigated hippocampal contributions to between-domain STM-LTM integration by testing whether immediate verbal recall of digits improves in MTL amnesic patients when digits are presented in a familiar visuospatial context (a typical keypad layout) compared to an unfamiliar visuospatial context (a random keypad layout). Immediate verbal recall improved in both patients and controls when digits were presented in the familiar compared to the unfamiliar keypad array, indicating a preserved ability to integrate activated verbal information with stored visuospatial knowledge. Together, these results demonstrate that immediate verbal recall in amnesia can benefit from two

  4. Imaging of subunit complexes of thermophilic bacterium H(+)-ATPase with scanning tunneling microscopy.

    PubMed

    Masai, J; Shibata, T; Kagawa, Y; Kondo, S

    1992-07-01

    Using a scanning tunneling microscope (STM), we observed reconstructed subunit complexes of H(+)-ATPase of a thermophilic bacterium. The measurement was carried out in air without conductive coating on the samples deposited on a highly oriented pyrolytic graphite (HOPG). The F1 subunit complex of the H(+)-ATPase, and an H(+)-ATPase whose F0 portion was embedded into liposomes prepared from soybean lecithin were imaged. Overall structural images of the subunit complex F1 were obtained: the structural dimensions of the STM images are in agreement with those deduced from conventional methods such as an transmission electron microscopy (TEM) and small-angle X-ray scattering (SAX) experimentation. Regarding the STM imaging of these samples, we discuss the advantages and disadvantages of the STM over those of conventional methods such as a TEM and SAX.

  5. Positive affect improves working memory: implications for controlled cognitive processing.

    PubMed

    Yang, Hwajin; Yang, Sujin; Isen, Alice M

    2013-01-01

    This study examined the effects of positive affect on working memory (WM) and short-term memory (STM). Given that WM involves both storage and controlled processing and that STM primarily involves storage processing, we hypothesised that if positive affect facilitates controlled processing, it should improve WM more than STM. The results demonstrated that positive affect, compared with neutral affect, significantly enhanced WM, as measured by the operation span task. The influence of positive affect on STM, however, was weaker. These results suggest that positive affect enhances WM, a task that involves controlled processing, not just storage processing. Additional analyses of recall and processing times and accuracy further suggest that improved WM under positive affect is not attributable to motivational differences, but results instead from improved controlled cognitive processing.

  6. Self-navigation of a scanning tunneling microscope tip toward a micron-sized graphene sample.

    PubMed

    Li, Guohong; Luican, Adina; Andrei, Eva Y

    2011-07-01

    We demonstrate a simple capacitance-based method to quickly and efficiently locate micron-sized conductive samples, such as graphene flakes, on insulating substrates in a scanning tunneling microscope (STM). By using edge recognition, the method is designed to locate and to identify small features when the STM tip is far above the surface, allowing for crash-free search and navigation. The method can be implemented in any STM environment, even at low temperatures and in strong magnetic field, with minimal or no hardware modifications.

  7. Spectrotemporal Modulation Sensitivity as a Predictor of Speech-Reception Performance in Noise With Hearing Aids

    PubMed Central

    Danielsson, Henrik; Hällgren, Mathias; Stenfelt, Stefan; Rönnberg, Jerker; Lunner, Thomas

    2016-01-01

    The audiogram predicts <30% of the variance in speech-reception thresholds (SRTs) for hearing-impaired (HI) listeners fitted with individualized frequency-dependent gain. The remaining variance could reflect suprathreshold distortion in the auditory pathways or nonauditory factors such as cognitive processing. The relationship between a measure of suprathreshold auditory function—spectrotemporal modulation (STM) sensitivity—and SRTs in noise was examined for 154 HI listeners fitted with individualized frequency-specific gain. SRTs were measured for 65-dB SPL sentences presented in speech-weighted noise or four-talker babble to an individually programmed master hearing aid, with the output of an ear-simulating coupler played through insert earphones. Modulation-depth detection thresholds were measured over headphones for STM (2cycles/octave density, 4-Hz rate) applied to an 85-dB SPL, 2-kHz lowpass-filtered pink-noise carrier. SRTs were correlated with both the high-frequency (2–6 kHz) pure-tone average (HFA; R2 = .31) and STM sensitivity (R2 = .28). Combined with the HFA, STM sensitivity significantly improved the SRT prediction (ΔR2 = .13; total R2 = .44). The remaining unaccounted variance might be attributable to variability in cognitive function and other dimensions of suprathreshold distortion. STM sensitivity was most critical in predicting SRTs for listeners < 65 years old or with HFA <53 dB HL. Results are discussed in the context of previous work suggesting that STM sensitivity for low rates and low-frequency carriers is impaired by a reduced ability to use temporal fine-structure information to detect dynamic spectra. STM detection is a fast test of suprathreshold auditory function for frequencies <2 kHz that complements the HFA to predict variability in hearing-aid outcomes for speech perception in noise. PMID:27815546

  8. Verbal short-term memory span in children: long-term modality dependent effects of intrauterine growth restriction.

    PubMed

    Geva, R; Eshel, R; Leitner, Y; Fattal-Valevski, A; Harel, S

    2008-12-01

    Recent reports showed that children born with intrauterine growth restriction (IUGR) are at greater risk of experiencing verbal short-term memory span (STM) deficits that may impede their learning capacities at school. It is still unknown whether these deficits are modality dependent. This long-term, prospective design study examined modality-dependent verbal STM functions in children who were diagnosed at birth with IUGR (n = 138) and a control group (n = 64). Their STM skills were evaluated individually at 9 years of age with four conditions of the Visual-Aural Digit Span Test (VADS; Koppitz, 1981): auditory-oral, auditory-written, visuospatial-oral and visuospatial-written. Cognitive competence was evaluated with the short form of the Wechsler Intelligence Scales for Children--revised (WISC-R95; Wechsler, 1998). We found IUGR-related specific auditory-oral STM deficits (p < .036) in conjunction with two double dissociations: an auditory-visuospatial (p < .014) and an input-output processing distinction (p < .014). Cognitive competence had a significant effect on all four conditions; however, the effect of IUGR on the auditory-oral condition was not overridden by the effect of intelligence quotient (IQ). Intrauterine growth restriction affects global competence and inter-modality processing, as well as distinct auditory input processing related to verbal STM functions. The findings support a long-term relationship between prenatal aberrant head growth and auditory verbal STM deficits by the end of the first decade of life. Empirical, clinical and educational implications are presented.

  9. Impaired semantic knowledge underlies the reduced verbal short-term storage capacity in Alzheimer's disease.

    PubMed

    Peters, Frédéric; Majerus, Steve; De Baerdemaeker, Julie; Salmon, Eric; Collette, Fabienne

    2009-12-01

    A decrease in verbal short-term memory (STM) capacity is consistently observed in patients with Alzheimer's disease (AD). Although this impairment has been mainly attributed to attentional deficits during encoding and maintenance, the progressive deterioration of semantic knowledge in early stages of AD may also be an important determinant of poor STM performance. The aim of this study was to examine the influence of semantic knowledge on verbal short-term memory storage capacity in normal aging and in AD by exploring the impact of word imageability on STM performance. Sixteen patients suffering from mild AD, 16 healthy elderly subjects and 16 young subjects performed an immediate serial recall task using word lists containing high or low imageability words. All participant groups recalled more high imageability words than low imageability words, but the effect of word imageability on verbal STM was greater in AD patients than in both the young and the elderly control groups. More precisely, AD patients showed a marked decrease in STM performance when presented with lists of low imageability words, whereas recall of high imageability words was relatively well preserved. Furthermore, AD patients displayed an abnormal proportion of phonological errors in the low imageability condition. Overall, these results indicate that the support of semantic knowledge on STM performance was impaired for lists of low imageability words in AD patients. More generally, these findings suggest that the deterioration of semantic knowledge is partly responsible for the poor verbal short-term storage capacity observed in AD.

  10. Atomic-scale imaging of DNA using scanning tunnelling microscopy.

    PubMed

    Driscoll, R J; Youngquist, M G; Baldeschwieler, J D

    1990-07-19

    The scanning tunnelling microscope (STM) has been used to visualize DNA under water, under oil and in air. Images of single-stranded DNA have shown that submolecular resolution is possible. Here we describe atomic-resolution imaging of duplex DNA. Topographic STM images of uncoated duplex DNA on a graphite substrate obtained in ultra-high vacuum are presented that show double-helical structure, base pairs, and atomic-scale substructure. Experimental STM profiles show excellent correlation with atomic contours of the van der Waals surface of A-form DNA derived from X-ray crystallography. A comparison of variations in the barrier to quantum mechanical tunnelling (barrier-height) with atomic-scale topography shows correlation over the phosphate-sugar backbone but anticorrelation over the base pairs. This relationship may be due to the different chemical characteristics of parts of the molecule. Further investigation of this phenomenon should lead to a better understanding of the physics of imaging adsorbates with the STM and may prove useful in sequencing DNA. The improved resolution compared with previously published STM images of DNA may be attributable to ultra-high vacuum, high data-pixel density, slow scan rate, a fortuitously clean and sharp tip and/or a relatively dilute and extremely clean sample solution. This work demonstrates the potential of the STM for characterization of large biomolecular structures, but additional development will be required to make such high resolution imaging of DNA and other large molecules routine.

  11. Burkholderia phymatum is a highly effective nitrogen-fixing symbiont of Mimosa spp. and fixes nitrogen ex planta.

    PubMed

    Elliott, Geoffrey N; Chen, Wen-Ming; Chou, Jui-Hsing; Wang, Hui-Chun; Sheu, Shih-Yi; Perin, Liamara; Reis, Veronica M; Moulin, Lionel; Simon, Marcelo F; Bontemps, Cyril; Sutherland, Joan M; Bessi, Rosana; de Faria, Sergio M; Trinick, Michael J; Prescott, Alan R; Sprent, Janet I; James, Euan K

    2007-01-01

    * The ability of Burkholderia phymatum STM815 to effectively nodulate Mimosa spp., and to fix nitrogen ex planta, was compared with that of the known Mimosa symbiont Cupriavidus taiwanensis LMG19424. * Both strains were equally effective symbionts of M. pudica, but nodules formed by STM815 had greater nitrogenase activity. STM815 was shown to have a broader host range across the genus Mimosa than LMG19424, nodulating 30 out of 31 species, 21 of these effectively. LMG19424 effectively nodulated only nine species. GFP-marked variants were used to visualise symbiont presence within nodules. * STM815 gave significant acetylene reduction assay (ARA) activity in semisolid JMV medium ex planta, but no ARA activity was detected with LMG19424. 16S rDNA sequences of two isolates originally from Mimosa nodules in Papua New Guinea (NGR114 and NGR195A) identified them as Burkholderia phymatum also, with nodA, nodC and nifH genes of NGR195A identical to those of STM815. * B. phymatum is therefore an effective Mimosa symbiont with a broad host range, and is the first reported beta-rhizobial strain to fix nitrogen in free-living culture.

  12. Selective Transfer Machine for Personalized Facial Action Unit Detection

    PubMed Central

    Chu, Wen-Sheng; De la Torre, Fernando; Cohn, Jeffery F.

    2014-01-01

    Automatic facial action unit (AFA) detection from video is a long-standing problem in facial expression analysis. Most approaches emphasize choices of features and classifiers. They neglect individual differences in target persons. People vary markedly in facial morphology (e.g., heavy versus delicate brows, smooth versus deeply etched wrinkles) and behavior. Individual differences can dramatically influence how well generic classifiers generalize to previously unseen persons. While a possible solution would be to train person-specific classifiers, that often is neither feasible nor theoretically compelling. The alternative that we propose is to personalize a generic classifier in an unsupervised manner (no additional labels for the test subjects are required). We introduce a transductive learning method, which we refer to Selective Transfer Machine (STM), to personalize a generic classifier by attenuating person-specific biases. STM achieves this effect by simultaneously learning a classifier and re-weighting the training samples that are most relevant to the test subject. To evaluate the effectiveness of STM, we compared STM to generic classifiers and to cross-domain learning methods in three major databases: CK+ [20], GEMEP-FERA [32] and RU-FACS [2]. STM outperformed generic classifiers in all. PMID:25242877

  13. Strategies for alignment and e-beam contact to buried atomic-precision devices in Si

    NASA Astrophysics Data System (ADS)

    Wyrick, Jonathan; Namboodiri, Pradeep; Wang, Xiqiao; Murray, Roy; Hagmann, Joseph; Li, Kai; Stewart, Michael; Richter, Curt; Silver, Richard

    STM based hydrogen lithography has proven to be a viable route to fabrication of atomic-precision electronic devices. The strength of this technique is the ability to control the lateral placement of phosphorus atoms in a single atomic layer of Si with sub-nanometer resolution. However, because of limitations in the rate at which a scanning probe can pattern a device, as well as the ultimate size of contacts that can be fabricated (on the order of a micron in length), making electrical contact to STM fabricated devices encased in Si is nontrivial. One commonly implemented solution to this challenge is to choose the exact location on a Si surface where a device is to be patterned by STM and to design fiducials to aid in navigating the probe to that predetermined location. We present results from an alternate strategy for contacting buried devices based on performing the STM lithography fabrication first, and determination of the buried structure location after the fact using topographically identifiable STM fabricated fiducials. AFM, scanning capacitance, and peak force Kelvin microscopy as well as optical microscopy techniques are evaluated as a means for device relocation and to quantify the comparative accuracy of these techniques.

  14. Spin-polarized scanning tunneling microscopy with quantitative insights into magnetic probes

    NASA Astrophysics Data System (ADS)

    Phark, Soo-hyon; Sander, Dirk

    2017-04-01

    Spin-polarized scanning tunneling microscopy and spectroscopy (spin-STM/S) have been successfully applied to magnetic characterizations of individual nanostructures. Spin-STM/S is often performed in magnetic fields of up to some Tesla, which may strongly influence the tip state. In spite of the pivotal role of the tip in spin-STM/S, the contribution of the tip to the differential conductance d I/d V signal in an external field has rarely been investigated in detail. In this review, an advanced analysis of spin-STM/S data measured on magnetic nanoislands, which relies on a quantitative magnetic characterization of tips, is discussed. Taking advantage of the uniaxial out-of-plane magnetic anisotropy of Co bilayer nanoisland on Cu(111), in-field spin-STM on this system has enabled a quantitative determination, and thereby, a categorization of the magnetic states of the tips. The resulting in-depth and conclusive analysis of magnetic characterization of the tip opens new venues for a clear-cut sub-nanometer scale spin ordering and spin-dependent electronic structure of the non-collinear magnetic state in bilayer high Fe nanoislands on Cu(111).

  15. Temporal grouping effects in musical short-term memory.

    PubMed

    Gorin, Simon; Mengal, Pierre; Majerus, Steve

    2018-07-01

    Recent theoretical accounts of verbal and visuo-spatial short-term memory (STM) have proposed the existence of domain-general mechanisms for the maintenance of serial order information. These accounts are based on the observation of similar behavioural effects across several modalities, such as temporal grouping effects. Across two experiments, the present study aimed at extending these findings, by exploring a STM modality that has received little interest so far, STM for musical information. Given its inherent rhythmic, temporal and serial organisation, the musical domain is of interest for investigating serial order STM processes such as temporal grouping. In Experiment 1, the data did not allow to determine the presence or the absence of temporal grouping effects. In Experiment 2, we observed that temporal grouping of tone sequences during encoding improves short-term recognition for serially presented probe tones. Furthermore, the serial position curves included micro-primacy and micro-recency effects, which are the hallmark characteristic of temporal grouping. Our results suggest that the encoding of serial order information in musical STM may be supported by temporal positional coding mechanisms similar to those reported in the verbal domain.

  16. Marvels and Shadows: Science and Education at the University of Puerto Rico School of Tropical Medicine under the Auspices of Columbia University: An Introduction.

    PubMed

    Mayo-Santana, Raúl; Rabionet, Silvia E; Peña-Carro, Lucy; Serrano, Adelfa E

    2016-06-01

    This essay introduces a series of five historical articles on the scientific and educational contributions of the University of Puerto Rico School of Tropical Medicine (STM), under the auspices of Columbia University (1926-1949), to the fields of tropical medicine and public health. The articles will appear in several consecutive issues, and will address various themes as follows: 1) historical antecedents of the STM, particularly institutional precedents; 2) the educational legacy of the STM; 3) a history of the STM scientific journal ("The Puerto Rico Journal of Public Health and Tropical Medicine"); 4) the scientific practices and representations that prevailed at the institution; and, 5) a brief sociocultural history of malaria in Puerto Rico, mainly from the perspective of the STM's scientific and public health activities. The authors have systematically and comprehensively studied a wide variety of documents from different sources based on multiple archives in Puerto Rico, the United States and England. The authors treat the fluid meanings of the examined historical encounters from a research perspective that privilege complex reciprocal interactions, multiple adaptations and elaborate sociocultural constructs present in a collaborative exemplar of the modernity of medical science in a neocolonial tropical context.

  17. Developmental delays in phonological recoding among children and adolescents with Down syndrome and Williams syndrome.

    PubMed

    Danielsson, Henrik; Henry, Lucy; Messer, David; Carney, Daniel P J; Rönnberg, Jerker

    2016-08-01

    This study examined the development of phonological recoding in short-term memory (STM) span tasks among two clinical groups with contrasting STM and language profiles: those with Down syndrome (DS) and Williams syndrome (WS). Phonological recoding was assessed by comparing: (1) performance on phonologically similar and dissimilar items (phonological similarity effects, PSE); and (2) items with short and long names (word length effects, WLE). Participant groups included children and adolescents with DS (n=29), WS (n=25) and typical development (n=51), all with average mental ages around 6 years. The group with WS, contrary to predictions based on their relatively strong verbal STM and language abilities, showed no evidence for phonological recoding. Those in the group with DS, with weaker verbal STM and language abilities, showed positive evidence for phonological recoding (PSE), but to a lesser degree than the typical group (who showed PSE and WLE). These findings provide new information about the memory systems of these groups of children and adolescents, and suggest that STM processes involving phonological recoding do not fit with the usual expectations of the abilities of children and adolescents with WS and DS. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Scanning Tunneling Microscopy Studies of Diamond Films and Optoelectronic Materials

    NASA Technical Reports Server (NTRS)

    Perez, Jose M.

    1996-01-01

    We present a summary of the research, citations of publications resulting from the research and abstracts of such publications. We have made no inventions in the performance of the work in this project. The main goals of the project were to set up a Chemical Vapor Deposition (CVD) diamond growth system attached to an UltraHigh Vacuum (UHV) atomic resolution Scanning Tunneling Microscopy (STM) system and carry out experiments aimed at studying the properties and growth of diamond films using atomic resolution UHV STM. We successfully achieved these goals. We observed, for the first time, the atomic structure of the surface of CVD grown epitaxial diamond (100) films using UHV STM. We studied the effects of atomic hydrogen on the CVD diamond growth process. We studied the electronic properties of the diamond (100) (2x1) surface, and the effect of alkali metal adsorbates such as Cs on the work function of this surface using UHV STM spectroscopy techniques. We also studied, using STM, new electronic materials such as carbon nanotubes and gold nanostructures. This work resulted in four publications in refereed scientific journals and five publications in refereed conference proceedings.

  19. Theoretical study of carbon-based tips for scanning tunnelling microscopy.

    PubMed

    González, C; Abad, E; Dappe, Y J; Cuevas, J C

    2016-03-11

    Motivated by recent experiments, we present here a detailed theoretical analysis of the use of carbon-based conductive tips in scanning tunnelling microscopy. In particular, we employ ab initio methods based on density functional theory to explore a graphitic, an amorphous carbon and two diamond-like tips for imaging with a scanning tunnelling microscope (STM), and we compare them with standard metallic tips made of gold and tungsten. We investigate the performance of these tips in terms of the corrugation of the STM images acquired when scanning a single graphene sheet. Moreover, we analyse the impact of the tip-sample distance and show that it plays a fundamental role in the resolution and symmetry of the STM images. We also explore in depth how the adsorption of single atoms and molecules in the tip apexes modifies the STM images and demonstrate that, in general, it leads to an improved image resolution. The ensemble of our results provides strong evidence that carbon-based tips can significantly improve the resolution of STM images, as compared to more standard metallic tips, which may open a new line of research in scanning tunnelling microscopy.

  20. Atom-by-atom assembly

    NASA Astrophysics Data System (ADS)

    Hla, Saw Wai

    2014-05-01

    Atomic manipulation using a scanning tunneling microscope (STM) tip enables the construction of quantum structures on an atom-by-atom basis, as well as the investigation of the electronic and dynamical properties of individual atoms on a one-atom-at-a-time basis. An STM is not only an instrument that is used to ‘see’ individual atoms by means of imaging, but is also a tool that is used to ‘touch’ and ‘take’ the atoms, or to ‘hear’ their movements. Therefore, the STM can be considered as the ‘eyes’, ‘hands’ and ‘ears’ of the scientists, connecting our macroscopic world to the exciting atomic world. In this article, various STM atom manipulation schemes and their example applications are described. The future directions of atomic level assembly on surfaces using scanning probe tips are also discussed.

  1. Selective scanning tunneling microscope light emission from rutile phase of VO2.

    PubMed

    Sakai, Joe; Kuwahara, Masashi; Hotsuki, Masaki; Katano, Satoshi; Uehara, Yoichi

    2016-09-28

    We observed scanning tunneling microscope light emission (STM-LE) induced by a tunneling current at the gap between an Ag tip and a VO2 thin film, in parallel to scanning tunneling spectroscopy (STS) profiles. The 34 nm thick VO2 film grown on a rutile TiO2 (0 0 1) substrate consisted of both rutile (R)- and monoclinic (M)-structure phases of a few 10 nm-sized domains at room temperature. We found that STM-LE with a certain photon energy of 2.0 eV occurs selectively from R-phase domains of VO2, while no STM-LE was observed from M-phase. The mechanism of STM-LE from R-phase VO2 was determined to be an interband transition process rather than inverse photoemission or inelastic tunneling processes.

  2. Bayesian spatial transformation models with applications in neuroimaging data.

    PubMed

    Miranda, Michelle F; Zhu, Hongtu; Ibrahim, Joseph G

    2013-12-01

    The aim of this article is to develop a class of spatial transformation models (STM) to spatially model the varying association between imaging measures in a three-dimensional (3D) volume (or 2D surface) and a set of covariates. The proposed STM include a varying Box-Cox transformation model for dealing with the issue of non-Gaussian distributed imaging data and a Gaussian Markov random field model for incorporating spatial smoothness of the imaging data. Posterior computation proceeds via an efficient Markov chain Monte Carlo algorithm. Simulations and real data analysis demonstrate that the STM significantly outperforms the voxel-wise linear model with Gaussian noise in recovering meaningful geometric patterns. Our STM is able to reveal important brain regions with morphological changes in children with attention deficit hyperactivity disorder. © 2013, The International Biometric Society.

  3. Transfer of Information from Short- to Long-Term Memory

    ERIC Educational Resources Information Center

    Modigliani, Vito; Seamon, John G.

    1974-01-01

    The present study examined current hypotheses concerning information transfer from short-term memory (STM) to long-term memory (LTM) using a Peterson STM task with word triplets presented over retention intervals of 0, 3, 6, 9, and 18 sec. (Editor)

  4. Determining the phonon energy of highly oriented pyrolytic graphite by scanning tunneling microscope light emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Uehara, Yoichi; Michimata, Junichi; Watanabe, Shota; Katano, Satoshi; Inaoka, Takeshi

    2018-03-01

    We have investigated the scanning tunneling microscope (STM) light emission spectra of isolated single Ag nanoparticles lying on highly oriented pyrolytic graphite (HOPG). The STM light emission spectra exhibited two types of spectral structures (step-like and periodic). Comparisons of the observed structures and theoretical predictions indicate that the phonon energy of the ZO mode of HOPG [M. Mohr et al., Phys. Rev. B 76, 035439 (2007)] can be determined from the energy difference between the cutoff of STM light emission and the step in the former structure, and from the period of the latter structure. Since the role of the Ag nanoparticles does not depend on the substrate materials, this method will enable the phonon energies of various materials to be measured by STM light emission spectroscopy. The spatial resolution is comparable to the lateral size of the individual Ag nanoparticles (that is, a few nm).

  5. Auditory short-term memory in the primate auditory cortex

    PubMed Central

    Scott, Brian H.; Mishkin, Mortimer

    2015-01-01

    Sounds are fleeting, and assembling the sequence of inputs at the ear into a coherent percept requires auditory memory across various time scales. Auditory short-term memory comprises at least two components: an active ‘working memory’ bolstered by rehearsal, and a sensory trace that may be passively retained. Working memory relies on representations recalled from long-term memory, and their rehearsal may require phonological mechanisms unique to humans. The sensory component, passive short-term memory (pSTM), is tractable to study in nonhuman primates, whose brain architecture and behavioral repertoire are comparable to our own. This review discusses recent advances in the behavioral and neurophysiological study of auditory memory with a focus on single-unit recordings from macaque monkeys performing delayed-match-to-sample (DMS) tasks. Monkeys appear to employ pSTM to solve these tasks, as evidenced by the impact of interfering stimuli on memory performance. In several regards, pSTM in monkeys resembles pitch memory in humans, and may engage similar neural mechanisms. Neural correlates of DMS performance have been observed throughout the auditory and prefrontal cortex, defining a network of areas supporting auditory STM with parallels to that supporting visual STM. These correlates include persistent neural firing, or a suppression of firing, during the delay period of the memory task, as well as suppression or (less commonly) enhancement of sensory responses when a sound is repeated as a ‘match’ stimulus. Auditory STM is supported by a distributed temporo-frontal network in which sensitivity to stimulus history is an intrinsic feature of auditory processing. PMID:26541581

  6. Increase in short-term memory capacity induced by down-regulating individual theta frequency via transcranial alternating current stimulation.

    PubMed

    Vosskuhl, Johannes; Huster, René J; Herrmann, Christoph S

    2015-01-01

    Working memory (WM) and short-term memory (STM) supposedly rely on the phase-amplitude coupling (PAC) of neural oscillations in the theta and gamma frequency ranges. The ratio between the individually dominant gamma and theta frequencies is believed to determine an individual's memory capacity. The aim of this study was to establish a causal relationship between the gamma/theta ratio and WM/STM capacity by means of transcranial alternating current stimulation (tACS). To achieve this, tACS was delivered at a frequency below the individual theta frequency. Thereby the individual ratio of gamma to theta frequencies was changed, resulting in an increase of STM capacity. Healthy human participants (N = 33) were allocated to two groups, one receiving verum tACS, the other underwent a sham control protocol. The electroencephalogram (EEG) was measured before stimulation and analyzed with regard to the properties of PAC between theta and gamma frequencies to determine individual stimulation frequencies. After stimulation, EEG was recorded again in order to find after-effects of tACS in the oscillatory features of the EEG. Measures of STM and WM were obtained before, during and after stimulation. Frequency spectra and behavioral data were compared between groups and different measurement phases. The tACS- but not the sham stimulated group showed an increase in STM capacity during stimulation. WM was not affected in either groups. An increase in task-related theta amplitude after stimulation was observed only for the tACS group. These augmented theta amplitudes indicated that the manipulation of individual theta frequencies was successful and caused the increase in STM capacity.

  7. Soluble thrombomodulin levels in plasma of multiple sclerosis patients and their implication.

    PubMed

    Festoff, Barry W; Li, Chaoyang; Woodhams, Barry; Lynch, Sharon

    2012-12-15

    Thrombomodulin (TM) on the cell-surface of cerebrovascular endothelial cells (CECs) is released into blood upon CEC damage. TM promotes activation of protein C (APC), an anticoagulant, anti-inflammatory, neuroprotective molecule that protects CECs and impedes inflammatory cell migration across the blood-brain barrier (BBB). Multiple sclerosis (MS) is associated with CEC damage and BBB dysfunction. We evaluated soluble TM (sTM) levels as a biomarker of BBB integrity and whether glatiramer acetate (GA) influenced sTM levels in MS patients. sTM levels quantified by 2-site ELISA from sera of healthy controls and systemic lupus erythematosus (SLE) patients (CEC-damage positive control) were compared with levels from patients with relapsing-remitting (RRMS) or secondary-progressive MS (SPMS), stratified as: RRMS/GA/no relapse, RRMS/GA/in relapse, RRMS no GA/no relapse, RRMS/no GA/in relapse; and SPMS/no GA. Additionally, soluble endothelial protein C receptor (sEPCR) levels were assessed in the non-stratified MS group, SLE patients, and controls. sTM levels were highest in RRMS patients taking GA with or without relapse, followed in decreasing order by SLE, RRMS/no GA/in relapse, SPMS, RRMS/no GA/no relapse, healthy controls. sEPCR levels were highest in MS patients, then SLE, then controls. sTM may be a useful biomarker of BBB integrity in RRMS patients. Further evaluation of sEPCR is needed. The finding that the highest sTM levels were in RRMS patients taking GA is interesting and warrants further investigation. Published by Elsevier B.V.

  8. A meta-analysis of working memory impairments in survivors of moderate-to-severe traumatic brain injury.

    PubMed

    Dunning, Darren L; Westgate, Briony; Adlam, Anna-Lynne R

    2016-10-01

    To establish the magnitude of deficits in working memory (WM) and short-term memory (STM) in those with moderate-to-severe traumatic brain injury (TBI) relative to age-matched, healthy controls and to explore the moderating effects of time since injury and age at injury on these impairments. Twenty-one studies that compared the WM and/or STM abilities of individuals with at least a moderate TBI relative to healthy controls were included in a random effects meta-analysis. Measures used to examine memory performance were categorized by modality (visuospatial, verbal) and memory system (WM, STM). Individuals with TBI had significant deficits in verbal STM (Cohen's d = .41), visuospatial WM (Cohen's d = .69), and verbal WM (Cohen's d = .37) relative to controls. Greater decrements in verbal STM and verbal WM skills were associated with longer time postinjury. Larger deficits were observed in verbal WM abilities in individuals with older age at injury. Evidence for WM impairments following TBI is consistent with previous research. Larger verbal STM and verbal WM deficits were related to a longer time postinjury, suggesting that these aspects of memory do not "recover" over time and instead, individuals might show increased rates of cognitive decline. Age at injury was associated with the severity of verbal WM impairments, with larger deficits evident for injuries that occurred later in life. Further research needs to chart the long-term effects of TBI on WM and to compare the effects of injury on verbal relative to visuospatial memory. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

  9. Note: Low-temperature scanning tunneling microscope with detachable scanner and reliable transfer mechanism for tip and sample exchange

    NASA Astrophysics Data System (ADS)

    Ge, Weifeng; Wang, Jihao; Wang, Junting; Zhang, Jing; Hou, Yubin; Lu, Qingyou

    2017-12-01

    A homebuilt low-temperature scanning tunneling microscope (STM) featuring a detachable scanner based on a double slider design, along with a reliable transfer mechanism for tip and sample exchange, is present. The coarse motor is decoupled from the scanner, which prevents the motor instabilities including vibrations and drifts from entering the tip-sample loop and thus improves the performance of the STM. In addition, in situ exchange of tips and samples can be implemented easily and reliably using a winch-type transfer mechanism. Atomically resolved images on graphite are demonstrated to show the performance of the proposed STM.

  10. Manipulating, Reacting, and Constructing Single Molecules with a Scanning Tunneling Microscope Tip

    NASA Astrophysics Data System (ADS)

    Hla, S.-W.

    The fascinating advances in atom and molecule manipulation with the scanning tunneling microscope (STM) tip allow scientists to fabricate artificial atomic scale structures, to study local quantum phenomena, or to probe physical and chemical properties of single atoms and molecules on surfaces. Recent achievements in individual synthesis of single molecules with the STM tip further open up an entirely new opportunities in nanoscience and technology. The STM manipulation techniques usef ul in the molecular construction are reviewed and prospects for future opportunities of single molecule chemical engineering and their possible implications to nano-scale science and technology are discussed.

  11. Note: Low-temperature scanning tunneling microscope with detachable scanner and reliable transfer mechanism for tip and sample exchange.

    PubMed

    Ge, Weifeng; Wang, Jihao; Wang, Junting; Zhang, Jing; Hou, Yubin; Lu, Qingyou

    2017-12-01

    A homebuilt low-temperature scanning tunneling microscope (STM) featuring a detachable scanner based on a double slider design, along with a reliable transfer mechanism for tip and sample exchange, is present. The coarse motor is decoupled from the scanner, which prevents the motor instabilities including vibrations and drifts from entering the tip-sample loop and thus improves the performance of the STM. In addition, in situ exchange of tips and samples can be implemented easily and reliably using a winch-type transfer mechanism. Atomically resolved images on graphite are demonstrated to show the performance of the proposed STM.

  12. Tip induced mechanical deformation of epitaxial graphene grown on reconstructed 6H-SiC(0001) surface during scanning tunneling and atomic force microscopy studies.

    PubMed

    Meza, José Antonio Morán; Lubin, Christophe; Thoyer, François; Cousty, Jacques

    2015-01-26

    The structural and mechanical properties of an epitaxial graphene (EG) monolayer thermally grown on top of a 6H-SiC(0001) surface were studied by combined dynamic scanning tunneling microscopy (STM) and frequency modulation atomic force microscopy (FM-AFM). Experimental STM, dynamic STM and AFM images of EG on 6H-SiC(0001) show a lattice with a 1.9 nm period corresponding to the (6 × 6) quasi-cell of the SiC surface. The corrugation amplitude of this (6 × 6) quasi-cell, measured from AFM topographies, increases with the setpoint value of the frequency shift Δf (15-20 Hz, repulsive interaction). Excitation variations map obtained simultaneously with the AFM topography shows that larger dissipation values are measured in between the topographical bumps of the (6 × 6) quasi-cell. These results demonstrate that the AFM tip deforms the graphene monolayer. During recording in dynamic STM mode, a frequency shift (Δf) map is obtained in which Δf values range from 41 to 47 Hz (repulsive interaction). As a result, we deduced that the STM tip, also, provokes local mechanical distortions of the graphene monolayer. The origin of these tip-induced distortions is discussed in terms of electronic and mechanical properties of EG on 6H-SiC(0001).

  13. Encoding, rehearsal, and recall in signers and speakers: shared network but differential engagement.

    PubMed

    Bavelier, D; Newman, A J; Mukherjee, M; Hauser, P; Kemeny, S; Braun, A; Boutla, M

    2008-10-01

    Short-term memory (STM), or the ability to hold verbal information in mind for a few seconds, is known to rely on the integrity of a frontoparietal network of areas. Here, we used functional magnetic resonance imaging to ask whether a similar network is engaged when verbal information is conveyed through a visuospatial language, American Sign Language, rather than speech. Deaf native signers and hearing native English speakers performed a verbal recall task, where they had to first encode a list of letters in memory, maintain it for a few seconds, and finally recall it in the order presented. The frontoparietal network described to mediate STM in speakers was also observed in signers, with its recruitment appearing independent of the modality of the language. This finding supports the view that signed and spoken STM rely on similar mechanisms. However, deaf signers and hearing speakers differentially engaged key structures of the frontoparietal network as the stages of STM unfold. In particular, deaf signers relied to a greater extent than hearing speakers on passive memory storage areas during encoding and maintenance, but on executive process areas during recall. This work opens new avenues for understanding similarities and differences in STM performance in signers and speakers.

  14. Encoding, Rehearsal, and Recall in Signers and Speakers: Shared Network but Differential Engagement

    PubMed Central

    Newman, A. J.; Mukherjee, M.; Hauser, P.; Kemeny, S.; Braun, A.; Boutla, M.

    2008-01-01

    Short-term memory (STM), or the ability to hold verbal information in mind for a few seconds, is known to rely on the integrity of a frontoparietal network of areas. Here, we used functional magnetic resonance imaging to ask whether a similar network is engaged when verbal information is conveyed through a visuospatial language, American Sign Language, rather than speech. Deaf native signers and hearing native English speakers performed a verbal recall task, where they had to first encode a list of letters in memory, maintain it for a few seconds, and finally recall it in the order presented. The frontoparietal network described to mediate STM in speakers was also observed in signers, with its recruitment appearing independent of the modality of the language. This finding supports the view that signed and spoken STM rely on similar mechanisms. However, deaf signers and hearing speakers differentially engaged key structures of the frontoparietal network as the stages of STM unfold. In particular, deaf signers relied to a greater extent than hearing speakers on passive memory storage areas during encoding and maintenance, but on executive process areas during recall. This work opens new avenues for understanding similarities and differences in STM performance in signers and speakers. PMID:18245041

  15. Reduced Short-Term Memory Span in Aphasia and Susceptibility to Interference: Contribution of Material-Specific Maintenance Deficits

    PubMed Central

    Barde, Laura H.F.; Schwartz, Myrna F.; Chrysikou, Evangelia G.; Thompson-Schill, Sharon L.

    2010-01-01

    Semantic short-term memory (STM) deficits have been traditionally defined as an inability to maintain semantic representations over a delay (R. Martin, Shelton & Yaffee, 1994). Yet some patients with semantic STM deficits make numerous intrusions of items from previously presented lists, thus presenting an interesting paradox: Why should an inability to maintain semantic representations produce an increase in intrusions from earlier lists? In this study, we investigated the relationship between maintenance deficits and susceptibility to interference in a group of 20 aphasic patients characterized with weak semantic or weak phonological STM. Patients and matched control participants performed a modified item-recognition task designed to elicit semantic or phonological interference from list items located one, two, or three trials back (Hamilton & R. Martin, 2007). Controls demonstrated significant effects of interference in both versions of the task. Interference in patients was predicted by the type and severity of their STM deficit; that is, shorter semantic spans were associated with greater semantic interference and shorter phonological spans were associated with greater phonological interference. We interpret these results through a new perspective, the reactivation hypothesis, and we discuss their importance for accounts emphasizing the contribution of maintenance mechanisms for STM impairments in aphasia as well as susceptibility to interference. PMID:19925813

  16. Refinement of Strut-and-Tie Model for Reinforced Concrete Deep Beams

    PubMed Central

    Panjehpour, Mohammad; Chai, Hwa Kian; Voo, Yen Lei

    2015-01-01

    Deep beams are commonly used in tall buildings, offshore structures, and foundations. According to many codes and standards, strut-and-tie model (STM) is recommended as a rational approach for deep beam analyses. This research focuses on the STM recommended by ACI 318-11 and AASHTO LRFD and uses experimental results to modify the strut effectiveness factor in STM for reinforced concrete (RC) deep beams. This study aims to refine STM through the strut effectiveness factor and increase result accuracy. Six RC deep beams with different shear span to effective-depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were experimentally tested under a four-point bending set-up. The ultimate shear strength of deep beams obtained from non-linear finite element modeling and STM recommended by ACI 318-11 as well as AASHTO LRFD (2012) were compared with the experimental results. An empirical equation was proposed to modify the principal tensile strain value in the bottle-shaped strut of deep beams. The equation of the strut effectiveness factor from AASHTTO LRFD was then modified through the aforementioned empirical equation. An investigation on the failure mode and crack propagation in RC deep beams subjected to load was also conducted. PMID:26110268

  17. Variable Temperature Scanning Tunneling Microscopy

    DTIC Science & Technology

    1991-07-01

    Tomazin, both Electrical Engineering. Build a digital integrator for the STM feedback loop: Kyle Drewry, Electrical Engineering. Write an AutoLisp ...program to automate the AutoCad design of UHV-STM chambers: Alfred Pierce (minority), Mechanical Engineering. Design a 32-bit interface board for the EISA

  18. Processes in the Development of Mathematics in Kindergarten Children from Title 1 Schools

    ERIC Educational Resources Information Center

    Foster, Matthew E.; Anthony, Jason L.; Clements, Doug H.; Sarama, Julie H.

    2015-01-01

    This study examined how well nonverbal IQ (or fluid intelligence), vocabulary, phonological awareness (PA), rapid autonomized naming (RAN), and phonological short-term memory (STM) predicted mathematics outcomes. The 208 participating kindergartners were administered tests of fluid intelligence, vocabulary, PA, RAN, STM, and numeracy in the fall…

  19. "We Actually Saw Atoms with Our Own Eyes": Conceptions and Convictions in Using the Scanning Tunneling Microscope in Junior High School

    ERIC Educational Resources Information Center

    Margel, Hannah; Eylon, Bat-Sheva; Scherz, Zahava

    2004-01-01

    The feasibility and the potential contribution of the scanning tunneling microscopy (STM) in junior high school (JHS) as an instructional tool for learning the particulate nature of matter is described. The use and power of new technologies can probably be demonstrated by the scanning tunneling microscopy (STM).

  20. The generality of working memory capacity: a latent-variable approach to verbal and visuospatial memory span and reasoning.

    PubMed

    Kane, Michael J; Hambrick, David Z; Tuholski, Stephen W; Wilhelm, Oliver; Payne, Tabitha W; Engle, Randall W

    2004-06-01

    A latent-variable study examined whether verbal and visuospatial working memory (WM) capacity measures reflect a primarily domain-general construct by testing 236 participants in 3 span tests each of verbal WM. visuospatial WM, verbal short-term memory (STM), and visuospatial STM. as well as in tests of verbal and spatial reasoning and general fluid intelligence (Gf). Confirmatory' factor analyses and structural equation models indicated that the WM tasks largely reflected a domain-general factor, whereas STM tasks, based on the same stimuli as the WM tasks, were much more domain specific. The WM construct was a strong predictor of Gf and a weaker predictor of domain-specific reasoning, and the reverse was true for the STM construct. The findings support a domain-general view of WM capacity, in which executive-attention processes drive the broad predictive utility of WM span measures, and domain-specific storage and rehearsal processes relate more strongly to domain-specific aspects of complex cognition. ((c) 2004 APA, all rights reserved)

  1. Short term memory and working memory in blind versus sighted children.

    PubMed

    Withagen, Ans; Kappers, Astrid M L; Vervloed, Mathijs P J; Knoors, Harry; Verhoeven, Ludo

    2013-07-01

    There is evidence that blind people may strengthen their memory skills to compensate for absence of vision. However, which aspects of memory are involved is open to debate and a developmental perspective is generally lacking. In the present study, we compared the short term memory (STM) and working memory (WM) of 10-year-old blind children and sighted children. STM was measured using digit span forward, name learning, and word span tasks; WM was measured using listening span and digit span backward tasks. The blind children outperformed their sighted peers on both STM and WM tasks. The enhanced capacity of the blind children on digit span and other STM tasks confirms the results of earlier research; the significantly better performance of the blind children relative to their sighted peers on verbal WM tasks is a new interesting finding. Task characteristics, including the verbal nature of the WM tasks and strategies used to perform these tasks, are discussed. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Characterization of external potential for field emission resonances and its applications on nanometer-scale measurements

    NASA Astrophysics Data System (ADS)

    Lu, Shin-Ming; Chan, Wen-Yuan; Su, Wei-Bin; Pai, Woei Wu; Liu, Hsiang-Lin; Chang, Chia-Seng

    2018-04-01

    The form of the external potential (FEP) for generating field emission resonance (FER) in a scanning tunneling microscopy (STM) junction is usually assumed to be triangular. We demonstrate that this assumption can be examined using a plot that can characterize FEP. The plot is FER energies versus the corresponding distances between the tip and sample. Through this energy–distance relationship, we discover that the FEP is nearly triangular for a blunt STM tip. However, the assumption of a triangular potential form is invalid for a sharp tip. The disparity becomes more severe as the tip is sharper. We demonstrate that the energy–distance plot can be exploited to determine the barrier width in field emission and estimate the effective sharpness of an STM tip. Because FERs were observed on Pb islands grown on the Cu(111) surface in this study, determination of the tip sharpness enabled the derivation of the subtle expansion deformation of Pb islands due to electrostatic force in the STM junction.

  3. Nanoscale assembly of superconducting vortices with scanning tunnelling microscope tip

    PubMed Central

    Ge, Jun-Yi; Gladilin, Vladimir N.; Tempere, Jacques; Xue, Cun; Devreese, Jozef T.; Van de Vondel, Joris; Zhou, Youhe; Moshchalkov, Victor V.

    2016-01-01

    Vortices play a crucial role in determining the properties of superconductors as well as their applications. Therefore, characterization and manipulation of vortices, especially at the single-vortex level, is of great importance. Among many techniques to study single vortices, scanning tunnelling microscopy (STM) stands out as a powerful tool, due to its ability to detect the local electronic states and high spatial resolution. However, local control of superconductivity as well as the manipulation of individual vortices with the STM tip is still lacking. Here we report a new function of the STM, namely to control the local pinning in a superconductor through the heating effect. Such effect allows us to quench the superconducting state at nanoscale, and leads to the growth of vortex clusters whose size can be controlled by the bias voltage. We also demonstrate the use of an STM tip to assemble single-quantum vortices into desired nanoscale configurations. PMID:27934960

  4. Localized electronic structures of graphene oxide studied using scanning tunneling microscopy and spectroscopy.

    PubMed

    Katano, Satoshi; Wei, Tao; Sasajima, Takumi; Kasama, Ryuhei; Uehara, Yoichi

    2018-06-21

    We have used scanning tunneling microscopy (STM) to elucidate the nanoscale electronic structures of graphene oxide (GO). The unreduced GO layer was imaged using STM without reduction processes when deposited on a Au(111) surface covered with an octanethiolate self-assembled monolayer (C8S-SAM). The STM image of the GO sheet exhibits a grainy structure having a thickness of about 1 nm, which is in good agreement with the previous results obtained using atomic force microscopy (AFM). We found that the C8S-SAM suppresses the adsorption of water remaining on the substrate, which would be important to accomplish the nanoscale imaging of the unreduced GO by STM. Furthermore, we successfully detected the π and π* states localized in the GO sheet using scanning tunneling spectroscopy (STS). The π-π* gap energy and the gap center are not uniform within the GO sheet, indicating the existence of various sizes of the sp2 domain and evidence for the local electronic doping by the substituents.

  5. On the effect of local barrier height in scanning tunneling microscopy: Measurement methods and control implications

    NASA Astrophysics Data System (ADS)

    Tajaddodianfar, Farid; Moheimani, S. O. Reza; Owen, James; Randall, John N.

    2018-01-01

    A common cause of tip-sample crashes in a Scanning Tunneling Microscope (STM) operating in constant current mode is the poor performance of its feedback control system. We show that there is a direct link between the Local Barrier Height (LBH) and robustness of the feedback control loop. A method known as the "gap modulation method" was proposed in the early STM studies for estimating the LBH. We show that the obtained measurements are affected by controller parameters and propose an alternative method which we prove to produce LBH measurements independent of the controller dynamics. We use the obtained LBH estimation to continuously update the gains of a STM proportional-integral (PI) controller and show that while tuning the PI gains, the closed-loop system tolerates larger variations of LBH without experiencing instability. We report experimental results, conducted on two STM scanners, to establish the efficiency of the proposed PI tuning approach. Improved feedback stability is believed to help in avoiding the tip/sample crash in STMs.

  6. Similar digit-based working memory in deaf signers and hearing non-signers despite digit span differences

    PubMed Central

    Andin, Josefine; Orfanidou, Eleni; Cardin, Velia; Holmer, Emil; Capek, Cheryl M.; Woll, Bencie; Rönnberg, Jerker; Rudner, Mary

    2013-01-01

    Similar working memory (WM) for lexical items has been demonstrated for signers and non-signers while short-term memory (STM) is regularly poorer in deaf than hearing individuals. In the present study, we investigated digit-based WM and STM in Swedish and British deaf signers and hearing non-signers. To maintain good experimental control we used printed stimuli throughout and held response mode constant across groups. We showed that deaf signers have similar digit-based WM performance, despite shorter digit spans, compared to well-matched hearing non-signers. We found no difference between signers and non-signers on STM span for letters chosen to minimize phonological similarity or in the effects of recall direction. This set of findings indicates that similar WM for signers and non-signers can be generalized from lexical items to digits and suggests that poorer STM in deaf signers compared to hearing non-signers may be due to differences in phonological similarity across the language modalities of sign and speech. PMID:24379797

  7. Theoretical characterisation of point defects on a MoS2 monolayer by scanning tunnelling microscopy.

    PubMed

    González, C; Biel, B; Dappe, Y J

    2016-03-11

    Different S and Mo vacancies as well as their corresponding antisite defects in a free-standing MoS2 monolayer are analysed by means of scanning tunnelling microscopy (STM) simulations. Our theoretical methodology, based on the Keldysh nonequilibrium Green function formalism within the density functional theory (DFT) approach, is applied to simulate STM images for different voltages and tip heights. Combining the geometrical and electronic effects, all features of the different STM images can be explained, providing a valuable guide for future experiments. Our results confirm previous reports on S atom imaging, but also reveal a strong dependence on the applied bias for vacancies and antisite defects that include extra S atoms. By contrast, when additional Mo atoms cover the S vacancies, the MoS2 gap vanishes and a bias-independent bright protrusion is obtained in the STM image. Finally, we show that the inclusion of these point defects promotes the emergence of reactive dangling bonds that may act as efficient adsorption sites for external adsorbates.

  8. Association between arsenic exposure and soluble thrombomodulin: A cross sectional study in Bangladesh

    PubMed Central

    Islam, Md. Shofikul; Rahman, Atiqur; Anjum, Adiba; Hossain, Faruk; Mohanto, Nayan Chandra; Karim, Md. Rezaul; Hoque, Md. Mominul; Saud, Zahangir Alam; Miyataka, Hideki; Himeno, Seiichiro; Hossain, Khaled

    2017-01-01

    Chronic exposure to arsenic is associated with increased morbidity and mortality from cardiovascular disease (CVD); however, plausible biomarker for early prediction and the underlying mechanism of arsenic-related CVD have not yet been clearly understood. Endothelial dysfunction plays a central role in the development of CVD. We hypothesized that endothelial damage or dysfunction is an important aspect and may be an early event of arsenic-related CVD. Soluble thrombomodulin (sTM) in serum is thought to be a specific and stable marker for endothelial damage or dysfunction. This study was designed to evaluate the association between chronic exposure to arsenic and sTM among human subjects in arsenic-endemic and non-endemic rural areas in Bangladesh. A total of 321 study subjects (217 from arsenic-endemic areas and 104 from a non-endemic area) were recruited. Subjects’ arsenic exposure levels (i.e., drinking water, hair and nail arsenic concentrations) were measured by Inductively Coupled Plasma Mass Spectroscopy. The subjects’ serum sTM levels were quantified by immunoassay kit. The average sTM levels of the subjects in arsenic-endemic and non-endemic areas were 4.58 ± 2.20 and 2.84 ± 1.29 (ng mL-1) respectively, and the difference was significant (p<0.001). Arsenic exposure levels showed a significant (water arsenic: rs = 0.339, p<0.001, hair arsenic: rs = 0.352, p<0.001 and nail arsenic: rs = 0.308, p<0.001) positive associations with sTM levels. Soluble TM levels were higher in the higher exposure gradients if we stratified the subjects into tertile groups (low, medium and high) based on the arsenic concentrations of the subjects’ drinking water, hair and nails. Finally, increased levels of sTM were negatively correlated with high density lipoprotein cholesterol (HDL-C), and positively correlated with intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Results of this study show that chronic exposure to arsenic has

  9. Factors Related to under Achievement in Science, Technology and Mathematics Education (STME) in Secondary Schools in Rivers State, Nigeria

    ERIC Educational Resources Information Center

    Obomanu, B. J.; Adaramola, M. O.

    2011-01-01

    We report a research into factors related to underachievement in science, technology and mathematics (STM) education in schools in Rivers State, Nigeria. The study investigated 240 Nigerian secondary school students, 100 parents, 140 STM teachers and 20 government officials from Port Harcourt Metropolis. Five (5) research questions and one…

  10. Visuospatial and Verbal Short-Term Memory Correlates of Vocabulary Ability in Preschool Children

    ERIC Educational Resources Information Center

    Stokes, Stephanie F.; Klee, Thomas; Kornisch, Myriam; Furlong, Lisa

    2017-01-01

    Background: Recent studies indicate that school-age children's patterns of performance on measures of verbal and visuospatial short-term memory (STM) and working memory (WM) differ across types of neurodevelopmental disorders. Because these disorders are often characterized by early language delay, administering STM and WM tests to toddlers could…

  11. 20180312 - Profiling the ToxCast library with a pluripotent human (H9) embryonic stem cell assay (SOT)

    EPA Science Inventory

    The Stemina devTOX quickPredict platform (STM) is a human pluripotent H9 stem cell-based assay that predicts developmental toxicants. Using the STM model, we screened 1065 ToxCast chemicals and entered the data into the ToxCast data analysis pipeline. Model performance was 83.3% ...

  12. STM on Gate-Tunable Graphene

    NASA Astrophysics Data System (ADS)

    Zhang, Yuanbo

    2009-03-01

    We have successfully performed atomically-resolved scanning tunneling microscopy and spectroscopy (STS) on mechanically exfoliated graphene samples having tunable back-gates. We have discovered that the tunneling spectra of graphene flakes display an unexpected gap-like feature that is pinned to the Fermi level for different gate voltages, and which coexists with another depression in density-of-states that moves with gate voltage. Extensive tests and careful analysis show that the gap-feature is due to phonon-assisted inelastic tunneling, and the depression directly marks the location of the graphene Dirac point. Using tunneling spectroscopy as a new tool, we further probe the local energetic variations of the graphene charge neutral point (Dirac point) to map out spatial electron density inhomogeneities in graphene. Such measurements are two orders of magnitude higher in resolution than previous experiments, and they can be directly correlated with nanometer scale topographic features. Based on our observation of energy-dependent periodic electronic interference patterns, our measurements also reveal the nature of impurity scattering of Dirac fermions in graphene. These results are significant for understanding the sources of electron density inhomogeneity and electron scattering in graphene, and the microscopic causes of graphene electron mobility.

  13. Prevalence and diagnostic validity of motivational impairments and deficits in visuospatial short-term memory and working memory in ADHD subtypes.

    PubMed

    Dovis, Sebastiaan; Van der Oord, Saskia; Huizenga, Hilde M; Wiers, Reinout W; Prins, Pier J M

    2015-05-01

    Deficits in working memory (WM) and reinforcement sensitivity are thought to give rise to symptoms in the combined (ADHD-C) and inattentive subtype (ADHD-I) of ADHD. Children with ADHD are especially impaired on visuospatial WM, which is composed of short-term memory (STM) and a central executive. Although deficits in visuospatial WM and reinforcement sensitivity appear characteristic of children with ADHD on a group-level, the prevalence and diagnostic validity of these impairments is still largely unknown. Moreover, studies investigating this did not control for the interaction between motivational impairments and cognitive performance in children with ADHD, and did not differentiate between ADHD subtypes. Visuospatial WM and STM tasks were administered in a standard (feedback-only) and a high-reinforcement (feedback + 10 euros) condition, to 86 children with ADHD-C, 27 children with ADHD-I (restrictive subtype), and 62 typically developing controls (aged 8-12). Reinforcement sensitivity was indexed as the difference in performance between the reinforcement conditions. WM and STM impairments were most prevalent in ADHD-C. In ADHD-I, only WM impairments, not STM impairments, were more prevalent than in controls. Motivational impairments were not common (22% impaired) and equally prevalent in both subtypes. Memory and motivation were found to represent independent neuropsychological domains. Impairment on WM, STM, and/or motivation was associated with more inattention symptoms, medication-use, and lower IQ scores. Similar results were found for analyses of diagnostic validity. The majority of children with ADHD-C is impaired on visuospatial WM. In ADHD-I, STM impairments are not more common than in controls. Within both ADHD subtypes only a minority has an abnormal sensitivity to reinforcement.

  14. Longitudinal and concurrent links between memory span, anxiety symptoms, and subsequent executive functioning in young children

    PubMed Central

    Visu-Petra, Laura; Stanciu, Oana; Benga, Oana; Miclea, Mircea; Cheie, Lavinia

    2014-01-01

    It has been conjectured that basic individual differences in attentional control influence higher-level executive functioning and subsequent academic performance in children. The current study sets out to complement the limited body of research on early precursors of executive functions (EFs). It provides both a cross-sectional, as well as a longitudinal exploration of the relationship between EF and more basic attentional control mechanisms, assessed via children's performance on memory storage tasks, and influenced by individual differences in anxiety. Multiple measures of verbal and visuospatial short-term memory (STM) were administered to children between 3 and 6 years old, alongside a non-verbal measure of intelligence, and a parental report of anxiety symptoms. After 9 months, children were re-tested on the same STM measures, at which time we also administered multiple measures of executive functioning: verbal and visuospatial working memory (WM), inhibition, and shifting. A cross-sectional view of STM development indicated that between 3 and 6 years the trajectory of visuospatial STM and EF underwent a gradual linear improvement. However, between 5 and 6 years progress in verbal STM performance stagnated. Hierarchical regression models revealed that trait anxiety was negatively associated with WM and shifting, while non-verbal intelligence was positively related to WM span. When age, gender, non-verbal intelligence, and anxiety were controlled for, STM (measured at the first assessment) was a very good predictor of overall executive performance. The models were most successful in predicting WM, followed by shifting, yet poorly predicted inhibition measures. Further longitudinal research is needed to directly address the contribution of attentional control mechanisms to emerging executive functioning and to the development of problematic behavior during early development. PMID:24904462

  15. Auditory short-term memory in the primate auditory cortex.

    PubMed

    Scott, Brian H; Mishkin, Mortimer

    2016-06-01

    Sounds are fleeting, and assembling the sequence of inputs at the ear into a coherent percept requires auditory memory across various time scales. Auditory short-term memory comprises at least two components: an active ׳working memory' bolstered by rehearsal, and a sensory trace that may be passively retained. Working memory relies on representations recalled from long-term memory, and their rehearsal may require phonological mechanisms unique to humans. The sensory component, passive short-term memory (pSTM), is tractable to study in nonhuman primates, whose brain architecture and behavioral repertoire are comparable to our own. This review discusses recent advances in the behavioral and neurophysiological study of auditory memory with a focus on single-unit recordings from macaque monkeys performing delayed-match-to-sample (DMS) tasks. Monkeys appear to employ pSTM to solve these tasks, as evidenced by the impact of interfering stimuli on memory performance. In several regards, pSTM in monkeys resembles pitch memory in humans, and may engage similar neural mechanisms. Neural correlates of DMS performance have been observed throughout the auditory and prefrontal cortex, defining a network of areas supporting auditory STM with parallels to that supporting visual STM. These correlates include persistent neural firing, or a suppression of firing, during the delay period of the memory task, as well as suppression or (less commonly) enhancement of sensory responses when a sound is repeated as a ׳match' stimulus. Auditory STM is supported by a distributed temporo-frontal network in which sensitivity to stimulus history is an intrinsic feature of auditory processing. This article is part of a Special Issue entitled SI: Auditory working memory. Published by Elsevier B.V.

  16. Domain-Generality of Timing-Based Serial Order Processes in Short-Term Memory: New Insights from Musical and Verbal Domains

    PubMed Central

    Kowialiewski, Benjamin; Majerus, Steve

    2016-01-01

    Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes. PMID:27992565

  17. Domain-Generality of Timing-Based Serial Order Processes in Short-Term Memory: New Insights from Musical and Verbal Domains.

    PubMed

    Gorin, Simon; Kowialiewski, Benjamin; Majerus, Steve

    2016-01-01

    Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes.

  18. Reading Comprehension in Boys with ADHD: The Mediating Roles of Working Memory and Orthographic Conversion.

    PubMed

    Friedman, Lauren M; Rapport, Mark D; Raiker, Joseph S; Orban, Sarah A; Eckrich, Samuel J

    2017-02-01

    Reading comprehension difficulties in children with ADHD are well established; however, limited information exists concerning the cognitive mechanisms that contribute to these difficulties and the extent to which they interact with one another. The current study examines two broad cognitive processes known to be involved in children's reading comprehension abilities-(a) working memory (i.e., central executive processes [CE], phonological short-term memory [PH STM], and visuospatial short-term memory [VS STM]) and (b) orthographic conversion (i.e., conversion of visually presented text to a phonological code)-to elucidate their unique and interactive contribution to ADHD-related reading comprehension differences. Thirty-one boys with ADHD-combined type and 30 typically developing (TD) boys aged 8 to 12 years (M = 9.64, SD = 1.22) were administered multiple counterbalanced tasks assessing WM and orthographic conversion processes. Relative to TD boys, boys with ADHD exhibited significant deficits in PH STM (d = -0.70), VS STM (d = -0.92), CE (d = -1.58), and orthographic conversion (d = -0.93). Bias-corrected, bootstrapped mediation analyses revealed that CE and orthographic conversion processes modeled separately mediated ADHD-related reading comprehension differences partially, whereas PH STM and VS STM did not. CE and orthographic conversion modeled jointly mediated ADHD-related reading comprehension differences fully wherein orthographic conversion's large magnitude influence on reading comprehension occurred indirectly through CE's impact on the orthographic system. The findings suggest that adaptive cognitive interventions designed to improve reading-related outcomes in children with ADHD may benefit by including modules that train CE and orthographic conversion processes independently and interactively.

  19. Excitation of propagating surface plasmons with a scanning tunnelling microscope.

    PubMed

    Wang, T; Boer-Duchemin, E; Zhang, Y; Comtet, G; Dujardin, G

    2011-04-29

    Inelastic electron tunnelling excitation of propagating surface plasmon polaritons (SPPs) on a thin gold film is demonstrated. This is done by combining a scanning tunnelling microscope (STM) with an inverted optical microscope. Analysis of the leakage radiation in both the image and Fourier planes unambiguously shows that the majority (up to 99.5%) of the detected photons originate from propagating SPPs with propagation lengths of the order of 10  µm. The remaining photon emission is localized under the STM tip and is attributed to a tip-gold film coupled plasmon resonance as evidenced by the bimodal spectral distribution and enhanced emission intensity observed using a silver STM tip for excitation.

  20. Scanning Tunneling Microscopy analysis of space-exposed polymer films

    NASA Technical Reports Server (NTRS)

    Kalil, Carol R.; Young, Philip R.

    1993-01-01

    The characterization of the surface of selected space-exposed polymer films by Scanning Tunneling Microscopy (STM) is reported. Principles of STM, an emerging new technique for materials analysis, are reviewed. The analysis of several films which received up to 5.8 years of low Earth orbital (LEO) exposure onboard the NASA Long Duration Exposure Facility (LDEF) is discussed. Specimens included FEP Teflon thermal blanket material, Kapton film, and several experimental polymer films. Ultraviolet and atomic oxygen-induced crazing and erosion are described. The intent of this paper is to demonstrate how STM is enhancing the understanding of LEO space environmental effects on polymer films.

  1. Doping of the step-edge Si chain: Ag on a Si(557)-Au surface

    NASA Astrophysics Data System (ADS)

    Krawiec, M.; Jałochowski, M.

    2010-11-01

    Structural and electronic properties of monatomic Ag chains on the Au-induced, highly ordered Si(557) surface are investigated by scanning tunneling microscopy (STM)/spectroscopy and first-principles density functional theory (DFT) calculations. The STM topography data show that a small amount of Ag (0.25 ML) very weakly modifies the one-dimensional structure induced by Au atoms. However, the bias-dependent STM topography and spectroscopy point to the importance of the electronic effects in this system, which are further corroborated by the DFT calculations. The obtained results suggest that Ag atoms act as electron donors leaving the geometry of the surface almost unchanged.

  2. Mechanical behavior of nanocrystalline NaCl islands on Cu(111).

    PubMed

    Bombis, Ch; Ample, F; Mielke, J; Mannsberger, M; Villagómez, C J; Roth, Ch; Joachim, C; Grill, L

    2010-05-07

    The mechanical response of ultrathin NaCl crystallites of nanometer dimensions upon manipulation with the tip of a scanning tunneling microscope (STM) is investigated, expanding STM manipulation to various nanostructuring modes of inorganic materials as cutting, moving, and cracking. In the light of theoretical calculations, our results reveal that atomic-scale NaCl islands can behave elastically and follow a classical Hooke's law. When the elastic limit of the nanocrystallites is reached, the STM tip induces atomic dislocations and consequently the regime of plastic deformation is entered. Our methodology is paving the way to understand the mechanical behavior and properties of other nanoscale materials.

  3. Lexical Learning in Bilingual Adults: The Relative Importance of Short-Term Memory for Serial Order and Phonological Knowledge

    ERIC Educational Resources Information Center

    Majerus, Steve; Poncelet, Martine; Van der Linden, Martial; Weekes, Brendan S.

    2008-01-01

    Studies of monolingual speakers have shown a strong association between lexical learning and short-term memory (STM) capacity, especially STM for serial order information. At the same time, studies of bilingual speakers suggest that phonological knowledge is the main factor that drives lexical learning. This study tested these two hypotheses…

  4. Phonological and Sensory Short-Term Memory Are Correlates and Both Affected in Developmental Dyslexia

    ERIC Educational Resources Information Center

    Laasonen, Marja; Virsu, Veijo; Oinonen, Suvi; Sandbacka, Mirja; Salakari, Anita; Service, Elisabet

    2012-01-01

    We investigated whether poor short-term memory (STM) in developmental dyslexia affects the processing of sensory stimulus sequences in addition to phonological material. STM for brief binary non-verbal stimuli (light flashes, tone bursts, finger touches, and their crossmodal combinations) was studied in 20 Finnish adults with dyslexia and 24…

  5. Improving Science, Technology and Mathematics Education in Nigeria: A Case Study of Obafemi Awolowo University, Ile-Ife

    ERIC Educational Resources Information Center

    Alaba, Sofowora Olaniyi; Adekomi, Bimbo

    2012-01-01

    The study assessed the impact of a World Bank Assisted Project "STEP-B" on teaching and learning of Science, Technology and Mathematics Education (STM) in Nigeria. It also described the contribution of Obafemi Awolowo University, Ile-Ife to the improvement of STM through research development, utilization of ICT, human resources and…

  6. The Effects of Phonological Short-Term Memory and Speech Perception on Spoken Sentence Comprehension in Children: Simulating Deficits in an Experimental Design

    ERIC Educational Resources Information Center

    Higgins, Meaghan C.; Penney, Sarah B.; Robertson, Erin K.

    2017-01-01

    The roles of phonological short-term memory (pSTM) and speech perception in spoken sentence comprehension were examined in an experimental design. Deficits in pSTM and speech perception were simulated through task demands while typically-developing children (N = 71) completed a sentence-picture matching task. Children performed the control,…

  7. EDITORIAL: Three decades of scanning tunnelling microscopy that changed the course of surface science Three decades of scanning tunnelling microscopy that changed the course of surface science

    NASA Astrophysics Data System (ADS)

    Ramachandra Rao, M. S.; Margaritondo, Giorgio

    2011-11-01

    Three decades ago, with a tiny tip of platinum, the scientific world saw the real space imaging of single atoms with unprecedented spatial resolution. This signalled the birth of one of the most versatile surface probes, based on the physics of quantum mechanical tunnelling: the scanning tunnelling microscope (STM). Invented in 1981 by Gerd Binnig and Heinrich Rohrer of IBM, Zurich, it led to their award of the 1986 Nobel Prize. Atoms, once speculated to be abstract entities used by theoreticians for mere calculations, can be seen to exist for real with the nano-eye of an STM tip that also gives real-space images of molecules and adsorbed complexes on surfaces. From a very fundamental perspective, the STM changed the course of surface science and engineering. STM also emerged as a powerful tool to study various fundamental phenomena relevant to the properties of surfaces in technological applications such as tribology, medical implants, catalysis, sensors and biology—besides elucidating the importance of local bonding geometries and defects, non-periodic structures and the co-existence of nano-scale phases. Atom-level probing, once considered a dream, has seen the light with the evolution of STM. An important off-shoot of STM was the atomic force microscope (AFM) for surface mapping of insulating samples. Then followed the development of a flurry of techniques under the general name of scanning probe microscopy (SPM). These techniques (STM, AFM, MFM, PFM etc) designed for atomic-scale-resolution imaging and spectroscopy, have led to brand new developments in surface analysis. All of these novel methods enabled researchers in recent years to image and analyse complex surfaces on microscopic and nanoscopic scales. All of them utilize a small probe for sensing the surface. The invention of AFM by Gerd Binnig, Calvin Quate and Christopher Gerber opened up new opportunities for characterization of a variety of materials, and various industrial applications could be

  8. Gold nanoparticle-based enzyme-linked antibody-aptamer sandwich assay for detection of Salmonella Typhimurium.

    PubMed

    Wu, Wenhe; Li, Jun; Pan, Dun; Li, Jiang; Song, Shiping; Rong, Mingge; Li, Zixi; Gao, Jimin; Lu, Jianxin

    2014-10-08

    Enzyme-linked immunosorbent assay (ELISA) provides a convenient means for the detection of Salmonella enterica serovar Typhimurium (STM), which is important for rapid diagnosis of foodborne pathogens. However, conventional ELISA is limited by antibody-antigen immunoreactions and suffers from poor sensitivity and tedious sample pretreatment. Therefore, development of novel ELISA remains challenging. Herein, we designed a comprehensive strategy for rapid, sensitive, and quantitative detection of STM with high specificity by gold nanoparticle-based enzyme-linked antibody-aptamer sandwich (nano-ELAAS) method. STM was captured and preconcentrated from samples with aptamer-modified magnetic particles, followed by binding with detector antibodies. Then nanoprobes carrying a large amount of reporter antibodies and horseradish peroxidase molecules were used for colorimetric signal amplification. Under the optimized reaction conditions, the nano-ELAAS assay had a quantitative detection range from 1 × 10(3) to 1 × 10(8) CFU mL(-1), a limit of detection of 1 × 10(3) CFU mL(-1), and a selectivity of >10-fold for STM in samples containing other bacteria at higher concentration with an assay time less than 3 h. In addition, the developed nanoprobes were improved in terms of detection range and/or sensitivity when compared with two commercial enzyme-labeled antibody signal reporters. Finally, the nano-ELAAS method was demonstrated to work well in milk samples, a common source of STM contamination.

  9. Neck and shoulder muscle activity and thorax movement in singing and speaking tasks with variation in vocal loudness and pitch.

    PubMed

    Pettersen, Viggo; Bjørkøy, Kåre; Torp, Hans; Westgaard, Rolf Harald

    2005-12-01

    The aim of this study was to examine respiratory phasing and loading levels of sternocleidomastoideus (STM), scalenus (SC), and upper trapezius (TR) muscles in vocalization tasks with variation in vocal loudness and pitch. Eight advanced singing students, aged 22 to 28 years, participated. Surface electromyographic (EMG) activity was recorded from STM, SC, and TR. Thorax movement was detected by two strain gauge sensors placed around the upper (upper TX) and lower (lower TX) thorax. A glissando and simplified singing and speaking tasks were performed. Sustained vowels /a:-i-ae-o:/ were sung in a glissando from lowest to highest pitch (mixed voice/falsetto) back to lowest pitch and in short singing sequences at comfortable, low, and high pitches. The same vowels were spoken softly and loudly for about the same length. The subjects inhaled between the vowels. It was concluded that the inspiratory phased STM and SC muscles produced a counterforce to compression of upper TX at high pitches in glissando. STM and SC were activated to higher levels during phonation than in inhalation. As breathing demands were reduced, STM and SC activity was lowered and the respiratory phasing of peak amplitude changed to inhalation. TR contributed to exhalation in demanding singing with long breathing cycles, but it was less active in singing tasks with short breathing cycles and was essentially inactive in simplified speaking tasks.

  10. Phonological short-term memory in logopenic variant primary progressive aphasia and mild Alzheimer's disease.

    PubMed

    Meyer, Aaron M; Snider, Sarah F; Campbell, Rachael E; Friedman, Rhonda B

    2015-10-01

    It has been argued that individuals with logopenic variant primary progressive aphasia (lvPPA) have an impairment of the phonological loop, which is a component of the short-term memory (STM) system. In contrast, this type of impairment is not thought to be present in mild typical Alzheimer's disease (AD). Thus, one would predict that people with lvPPA would score significantly lower than a matched AD group on tasks that require phonological STM. In the current study, an lvPPA group was compared with a mild AD group that was matched on age, education, and general cognitive functioning. For a subset of the tasks that involved pseudowords, the AD and lvPPA groups were compared to a healthy control group that was matched on age and education. The lvPPA group was more impaired than the AD group on all of the tasks that required phonological STM, including the pseudoword tasks, but there were no significant differences between these groups on tasks that required visuospatial STM. Compared to the healthy controls, the lvPPA group performed significantly worse on the repetition and reading of pseudowords, while the AD group did not differ significantly from the controls on these tasks. These findings are consistent with the hypothesis that phonological STM is impaired in lvPPA. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Short-Term Memory Limitations in Children: Capacity or Processing Deficits?

    ERIC Educational Resources Information Center

    Chi, Michelene T. H.

    1976-01-01

    Evaluates the assertion that short-term memory (STM) capacity increases with age and concludes that the STM capacity limitation in children is due to the deficits in the processing strategies and speeds, which presumably improve with age through cumulative learning. (JM) Available from: Memory and Cognition, Psychonomic Society, 1018 West 34…

  12. Verbal Short-Term Memory Reflects the Sublexical Organization of the Phonological Language Network: Evidence from an Incidental Phonotactic Learning Paradigm

    ERIC Educational Resources Information Center

    Majerus, Steve; Van der Linden; Martial; Mulder, Ludivine; Meulemans, Thierry; Peters, Frederic

    2004-01-01

    The nonword phonotactic frequency effect in verbal short-term memory (STM) is characterized by superior recall for nonwords containing familiar as opposed to less familiar phoneme associations. This effect is supposed to reflect the intervention of phonological long-term memory (LTM) in STM. However the lexical or sublexical nature of this LTM…

  13. Sentence Processing as a Function of Syntax, Short Term Memory Capacity, the Meaningfulness of the Stimulus and Age

    ERIC Educational Resources Information Center

    Gamlin, Peter J.

    1971-01-01

    Examines the effects of short term memory (STM) capacity, meaningfulness of stimuli, and age upon listeners' structuring of sentences. Results show that the interaction between STM capacity and meaningfulness (1) approached significance when data were collapsed over both age levels, and (2) was significant for one age level. Tables and references.…

  14. Calibration of state and transition models with FVS

    Treesearch

    Melinda Moeur; Don Vandendriesche

    2010-01-01

    The Interagency Mapping and Assessment Project (IMAP), a partnership between federal and state agencies, is developing mid-scale vegetation data and state and transition models (STM) for comparing the likely outcomes of alternative management policies on forested landscapes across the Pacific Northwest Region. In an STM, acres within a forested ecosystem transition...

  15. Surgeon-tailored polypropylene mesh as a needleless single-incision sling versus TVT-O for the treatment of female stress urinary incontinence: a comparative study.

    PubMed

    ElSheemy, Mohammed S; Fathy, Hesham; Hussein, Hussein A; Hussein, Eman A; Hassan, Sarah Mohamed

    2015-06-01

    To compare safety and efficacy of surgeon-tailored polypropylene mesh through needleless single-incision technique (STM) versus tension-free vaginal tape-obturator (TVT-O) aiming to decrease cost of treatment of stress urinary incontinence (SUI). This is important in developing countries due to limited healthcare resources. A retrospective cohort study was done at Urology and Gynecology Departments (dual-center), Cairo University, from January 2011 to August 2013. STM was inserted in 72 females, while TVT-O was inserted in 48 females. Females evaluated by cough stress test, stress and urge incontinence quality of life questionnaire (SUIQQ), Q max and abdominal leak point pressure (ALPP) were included. Different factors were compared between both groups using paired t, Wilcoxon's signed rank, McNemar, Chi-square, Fisher's exact, independent t or Mann-Whitney tests. Age, parity, previous surgeries, ALPP, intrinsic sphincter deficiency (ISD), associated prolapse and associated prolapse repair were comparable in both groups. No significant difference was found between both groups in postoperative complications (except groin pain), cure, SUIQQ indices improvement and Q max decline. In total, 65 (90 %) cured, 6 (8 %) improved while failure was detected in one (1 %) patient in STM group, while 42 (87 %) cured, 4 (8 %) improved and failure was detected in two (4 %) patients in TVT-O group. Presence of ISD (p = 0.565), urgency (p = 0.496), UUI (p = 0.531), previous surgeries (p = 0.345), associated urogenital prolapse (p = 0.218) or associated prolapse repair (p = 0.592) did not lead to any significant difference in outcome between both groups. Cost of mesh decreased from US$500 (TVT-O) to US$10 (STM). Outcome of STM is comparable to TVT-O. Furthermore, STM is more economic.

  16. Surgeon-tailored polypropylene mesh as a tension-free vaginal tape-obturator versus original TVT-O for the treatment of female stress urinary incontinence: a long-term comparative study.

    PubMed

    ElSheemy, Mohammed S; Fathy, Hesham; Hussein, Hussein A; Elsergany, Ragheb; Hussein, Eman A

    2015-10-01

    The objective of the study was to compare the safety and efficacy of surgeon-tailored polypropylene mesh (STM) through tension-free vaginal tape-obturator (TVT-O) versus original TVT-O in the treatment of stress urinary incontinence (SUI) aiming to decrease the cost of treatment. This is important in developing countries due to limited health care resources. A retrospective cohort study was done at the Urology and Gynecology Departments (dual-center), Cairo University from May 2007 to June 2010. Women evaluated by cough stress test, Stress and Urge Incontinence and Quality of Life Questionnaire (SUIQQ), maximum flow rate (Qmax), and abdominal leak point pressure (ALPP) with follow-up for at least 48 months were included. Patients with post-void residual urine > 100 ml, bladder capacity < 300 ml, or impaired compliance were excluded. The effect of different factors on outcome was compared between both groups pre- and postoperatively using the paired t, Wilcoxon signed rank, McNemar, chi-square, Fisher's exact, independent t, or Mann-Whitney tests. STM and TVT-O were inserted in 79 and 66 women, respectively. Intrinsic sphincter deficiency, ALPP, previous surgeries, associated urgency, urgency urinary incontinence (UUI), and prolapse were comparable in both groups. Operative duration was longer in STM by 10 min. No significant difference was found between both groups in complications (p = 0.462), cure (p = 0.654), and different indices of SUIQQ. In STM, 74 (93 %) were cured and 3 (4 %) improved, while SUI persisted in 2 (2 %) patients. In TVT-O, 59 (89 %) were cured and 4 (6 %) improved, while failure was detected in 3 (4 %) patients. The 5-year outcome is comparable between STM and TVT-O. Furthermore, STM is more economical due to our resterilizable modified helical passers and the cheap polypropylene mesh.

  17. Scanning tunneling microscopy, orbital-mediated tunneling spectroscopy, and ultraviolet photoelectron spectroscopy of metal(II) tetraphenylporphyrins deposited from vapor.

    PubMed

    Scudiero, L; Barlow, D E; Mazur, U; Hipps, K W

    2001-05-02

    Thin films of vapor-deposited Ni(II) and Co(II) complexes of tetraphenylporphyrin (NiTPP and CoTPP) were studied supported on gold and embedded in Al-Al(2)O(3)-MTPP-Pb tunnel diodes, where M = Ni or Co. Thin films deposited onto polycrystalline gold were analyzed by ultraviolet photoelectron spectroscopy (UPS) using He I radiation. Scanning tunneling microscopy (STM) and orbital-mediated tunneling spectroscopy (STM-OMTS) were performed on submonolayer films of CoTPP and NiTPP supported on Au(111). Inelastic electron tunneling spectroscopy (IETS) and OMTS were measured in conventional tunnel diode structures. The highest occupied pi molecular orbital of the porphyrin ring was seen in both STM-OMTS and UPS at about 6.4 eV below the vacuum level. The lowest unoccupied pi molecular orbital of the porphyrin ring was observed by STM-OMTS and by IETS-OMTS to be located near 3.4 eV below the vacuum level. The OMTS spectra of CoTPP had a band near 5.2 eV (below the vacuum level) that was attributed to transient oxidation of the central Co(II) ion. That is, it is due to electron OMT via the half-filled d(z)(2) orbital present in Co(II) of CoTPP. The NiTPP OMTS spectra show no such band, consistent with the known difficulty of oxidation of the Ni(II) ion. The STM-based OMTS allowed these two porphyrin complexes to be easily distinguished. The present work is the first report of the observation of STM-OMTS, tunnel junction OMTS, and UPS of the same compounds. Scanning tunneling microscope-based orbital-mediated tunneling provides more information than UPS or tunnel junction-based OMTS and does so with molecular-scale resolution.

  18. SteamTablesGrid: An ActiveX control for thermodynamic properties of pure water

    NASA Astrophysics Data System (ADS)

    Verma, Mahendra P.

    2011-04-01

    An ActiveX control, steam tables grid ( StmTblGrd) to speed up the calculation of the thermodynamic properties of pure water is developed. First, it creates a grid (matrix) for a specified range of temperature (e.g. 400-600 K with 40 segments) and pressure (e.g. 100,000-20,000,000 Pa with 40 segments). Using the ActiveX component SteamTables, the values of selected properties of water for each element (nodal point) of the 41×41 matrix are calculated. The created grid can be saved in a file for its reuse. A linear interpolation within an individual phase, vapor or liquid is implemented to calculate the properties at a given value of temperature and pressure. A demonstration program to illustrate the functionality of StmTblGrd is written in Visual Basic 6.0. Similarly, a methodology is presented to explain the use of StmTblGrd in MS-Excel 2007. In an Excel worksheet, the enthalpy of 1000 random datasets for temperature and pressure is calculated using StmTblGrd and SteamTables. The uncertainty in the enthalpy calculated with StmTblGrd is within ±0.03%. The calculations were performed on a personal computer that has a "Pentium(R) 4 CPU 3.2 GHz, RAM 1.0 GB" processor and Windows XP. The total execution time for the calculation with StmTblGrd was 0.3 s, while it was 60.0 s for SteamTables. Thus, the ActiveX control approach is reliable, accurate and efficient for the numerical simulation of complex systems that demand the thermodynamic properties of water at several values of temperature and pressure like steam flow in a geothermal pipeline network.

  19. Working Memory Capacity and Its Relation to Stroop Interference and Facilitation Effects in Individuals with Mild Cognitive Impairment

    ERIC Educational Resources Information Center

    Sung, Jee Eun; Kim, Jin Hee; Jeong, Jee Hyang; Kang, Heejin

    2012-01-01

    Purpose: The purposes of the study were to investigate (a) the task-specific differences in short-term memory (STM) and working memory capacity (WMC) in individuals with mild cognitive impairment (MCI) and normal elderly adults (NEAs), (b) the Stroop interference and facilitation effects, and (c) the relationship of STM and WMC to the Stroop…

  20. Auditory Short-Term Memory Capacity Correlates with Gray Matter Density in the Left Posterior STS in Cognitively Normal and Dyslexic Adults

    ERIC Educational Resources Information Center

    Richardson, Fiona M.; Ramsden, Sue; Ellis, Caroline; Burnett, Stephanie; Megnin, Odette; Catmur, Caroline; Schofield, Tom M.; Leff, Alex P.; Price, Cathy J.

    2011-01-01

    A central feature of auditory STM is its item-limited processing capacity. We investigated whether auditory STM capacity correlated with regional gray and white matter in the structural MRI images from 74 healthy adults, 40 of whom had a prior diagnosis of developmental dyslexia whereas 34 had no history of any cognitive impairment. Using…

  1. Identifying Early Links between Temperament, Short-Term and Working Memory in Preschoolers

    ERIC Educational Resources Information Center

    Visu-Petra, Laura; Cheie, Lavinia; Câmpan, Maria; Scutelnicu, Ioana; Benga, Oana

    2018-01-01

    The present study aimed to investigate early interrelationships between temperament, short-term memory (STM) and working memory (WM), while also relating them to incipient anxious traits in a sample of 4-7-year-olds. Preschoolers were evaluated using verbal and visuospatial STM and WM tasks, while parental reports were used to assess children's…

  2. Verbal Short-Term Memory Reflects the Organization of Long-Term Memory: Further Evidence from Short-Term Memory for Emotional Words

    ERIC Educational Resources Information Center

    Majerus, Steve; D'Argembeau, Arnaud

    2011-01-01

    Many studies suggest that long-term lexical-semantic knowledge is an important determinant of verbal short-term memory (STM) performance. This study explored the impact of emotional valence on word immediate serial recall as a further lexico-semantic long-term memory (LTM) effect on STM. This effect is particularly interesting for the study of…

  3. Verbal Short-Term Memory Shows a Specific Association with Receptive but Not Productive Vocabulary Measures in Down Syndrome

    ERIC Educational Resources Information Center

    Majerus, S.; Barisnikov, K.

    2018-01-01

    Background: Verbal short-term memory (STM) capacity has been considered to support vocabulary learning in typical children and adults, but evidence for this link is inconsistent for studies in individuals with Down syndrome (DS). The aim of this study was explore the role of processing demands on the association between verbal STM and vocabulary…

  4. A Closer Look at Phonology as a Predictor of Spoken Sentence Processing and Word Reading

    ERIC Educational Resources Information Center

    Myers, Suzanne; Robertson, Erin K.

    2015-01-01

    The goal of this study was to tease apart the roles of phonological awareness (pA) and phonological short-term memory (pSTM) in sentence comprehension, sentence production, and word reading. Children 6- to 10-years of age (N = 377) completed standardized tests of pA ("Elision") and pSTM ("Nonword Repetition") from the…

  5. Short-Term and Working Memory Skills in Primary School-Aged Children with Specific Language Impairment and Children with Pragmatic Language Impairment: Phonological, Linguistic and Visuo-Spatial Aspects

    ERIC Educational Resources Information Center

    Freed, Jenny; Lockton, Elaine; Adams, Catherine

    2012-01-01

    Background: Children with specific language impairment (CwSLI) are consistently reported to have short-term memory (STM) and working memory (WM) difficulties. Aim: To compare STM and WM abilities in CwSLI with children with pragmatic language impairment (CwPLI). Methods & Procedures: Primary school-aged CwSLI (n = 12) and CwPLI (n = 23) were…

  6. Automatic semantic encoding in verbal short-term memory: evidence from the concreteness effect.

    PubMed

    Campoy, Guillermo; Castellà, Judit; Provencio, Violeta; Hitch, Graham J; Baddeley, Alan D

    2015-01-01

    The concreteness effect in verbal short-term memory (STM) tasks is assumed to be a consequence of semantic encoding in STM, with immediate recall of concrete words benefiting from richer semantic representations. We used the concreteness effect to test the hypothesis that semantic encoding in standard verbal STM tasks is a consequence of controlled, attention-demanding mechanisms of strategic semantic retrieval and encoding. Experiment 1 analysed the effect of presentation rate, with slow presentations being assumed to benefit strategic, time-dependent semantic encoding. Experiments 2 and 3 provided a more direct test of the strategic hypothesis by introducing three different concurrent attention-demanding tasks. Although Experiment 1 showed a larger concreteness effect with slow presentations, the following two experiments yielded strong evidence against the strategic hypothesis. Limiting available attention resources by concurrent tasks reduced global memory performance, but the concreteness effect was equivalent to that found in control conditions. We conclude that semantic effects in STM result from automatic semantic encoding and provide tentative explanations for the interaction between the concreteness effect and the presentation rate.

  7. Solution-Synthesized Chevron Graphene Nanoribbons Exfoliated onto H:Si(100).

    PubMed

    Radocea, Adrian; Sun, Tao; Vo, Timothy H; Sinitskii, Alexander; Aluru, Narayana R; Lyding, Joseph W

    2017-01-11

    There has been tremendous progress in designing and synthesizing graphene nanoribbons (GNRs). The ability to control the width, edge structure, and dopant level with atomic precision has created a large class of accessible electronic landscapes for use in logic applications. One of the major limitations preventing the realization of GNR devices is the difficulty of transferring GNRs onto nonmetallic substrates. In this work, we developed a new approach for clean deposition of solution-synthesized atomically precise chevron GNRs onto H:Si(100) under ultrahigh vacuum. A clean transfer allowed ultrahigh-vacuum scanning tunneling microscopy (STM) to provide high-resolution imaging and spectroscopy and reveal details of the electronic structure of chevron nanoribbons that have not been previously reported. We also demonstrate STM nanomanipulation of GNRs, characterization of multilayer GNR cross-junctions, and STM nanolithography for local depassivation of H:Si(100), which allowed us to probe GNR-Si interactions and revealed a semiconducting-to-metallic transition. The results of STM measurements were shown to be in good agreement with first-principles computational modeling.

  8. A shared representation of order between encoding and recognition in visual short-term memory.

    PubMed

    Kalm, Kristjan; Norris, Dennis

    2017-07-15

    Many complex tasks require people to bind individual events into a sequence that can be held in short term memory (STM). For this purpose information about the order of the individual events in the sequence needs to be maintained in an active and accessible form in STM over a period of few seconds. Here we investigated how the temporal order information is shared between the presentation and response phases of an STM task. We trained a classification algorithm on the fMRI activity patterns from the presentation phase of the STM task to predict the order of the items during the subsequent recognition phase. While voxels in a number of brain regions represented positional information during either presentation and recognition phases, only voxels in the lateral prefrontal cortex (PFC) and the anterior temporal lobe (ATL) represented position consistently across task phases. A shared positional code in the ATL might reflect verbal recoding of visual sequences to facilitate the maintenance of order information over several seconds. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  9. The (lack of) effect of dynamic visual noise on the concreteness effect in short-term memory.

    PubMed

    Castellà, Judit; Campoy, Guillermo

    2018-05-17

    It has been suggested that the concreteness effect in short-term memory (STM) is a consequence of concrete words having more distinctive and richer semantic representations. The generation and storage of visual codes in STM could also play a crucial role on the effect because concrete words are more imaginable than abstract words. If this were the case, the introduction of a visual interference task would be expected to disrupt recall of concrete words. A Dynamic Visual Noise (DVN) display, which has been proven to eliminate the concreteness effect on long-term memory (LTM), was presented along encoding of concrete and abstract words in a STM serial recall task. Results showed a main effect of word type, with more item errors in abstract words, a main effect of DVN, which impaired global performance due to more order errors, but no interaction, suggesting that DVN did not have any impact on the concreteness effect. These findings are discussed in terms of LTM participation through redintegration processes and in terms of the language-based models of verbal STM.

  10. Compact low temperature scanning tunneling microscope with in-situ sample preparation capability.

    PubMed

    Kim, Jungdae; Nam, Hyoungdo; Qin, Shengyong; Kim, Sang-ui; Schroeder, Allan; Eom, Daejin; Shih, Chih-Kang

    2015-09-01

    We report on the design of a compact low temperature scanning tunneling microscope (STM) having in-situ sample preparation capability. The in-situ sample preparation chamber was designed to be compact allowing quick transfer of samples to the STM stage, which is ideal for preparing temperature sensitive samples such as ultra-thin metal films on semiconductor substrates. Conventional spring suspensions on the STM head often cause mechanical issues. To address this problem, we developed a simple vibration damper consisting of welded metal bellows and rubber pads. In addition, we developed a novel technique to ensure an ultra-high-vacuum (UHV) seal between the copper and stainless steel, which provides excellent reliability for cryostats operating in UHV. The performance of the STM was tested from 2 K to 77 K by using epitaxial thin Pb films on Si. Very high mechanical stability was achieved with clear atomic resolution even when using cryostats operating at 77 K. At 2 K, a clean superconducting gap was observed, and the spectrum was easily fit using the BCS density of states with negligible broadening.

  11. Characterization of a novel sialic acid transporter of the sodium solute symporter (SSS) family and in vivo comparison with known bacterial sialic acid transporters.

    PubMed

    Severi, Emmanuele; Hosie, Arthur H F; Hawkhead, Judith A; Thomas, Gavin H

    2010-03-01

    The function of sialic acids in the biology of bacterial pathogens is reflected by the diverse range of solute transporters that can recognize these sugar acids. Here, we use an Escherichia coliDeltananT strain to characterize the function of known and proposed bacterial sialic acid transporters. We discover that the STM1128 gene from Salmonella enterica serovar Typhimurium, which encodes a member of the sodium solute symporter family, is able to restore growth on sialic acid to the DeltananT strain and is able to transport [(14)C]-sialic acid. Using the DeltananT genetic background, we performed a direct in vivo comparison of the transport properties of the STM1128 protein with those of sialic acid transporters of the major facilitator superfamily and tripartite ATP-independent periplasmic families, E. coli NanT and Haemophilus influenzae SiaPQM, respectively. This revealed that both STM1128 and SiaPQM are sodium-dependent and, unlike SiaPQM, both STM1128 and NanT are reversible secondary carriers, demonstrating qualitative functional differences in the properties of sialic acid transporters used by bacteria that colonize humans.

  12. Slave systems in verbal short-term memory

    PubMed Central

    Caplan, David; Waters, Gloria; Howard, David

    2013-01-01

    Background The model of performance in short-term memory (STM) tasks that has been most influential in cognitive neuropsychological work on deficits of STM is the “working memory” model mainly associated with the work of Alan Baddeley and his colleagues. Aim This paper reviews the model. We examine the development of this theory in studies that account for STM performances in normal (non-brain-damaged) individuals, and then review the application of this theory to neuropsychological cases and specifications, modifications, and extensions of the theory that have been suggested on the basis of these cases. Our approach is to identify the major phenomena that have been discussed and to examine selected papers dealing with those phenomena in some detail. Main Contribution The main contribution is a review of the WM model that includes both normative and neuropsychological data. Conclusions We conclude that the WM model has many inconsistencies and empirical inadequacies, and that cognitive neuropsychologists might benefit from considering other models when they attempt to describe and explain patients’ performances on STM tasks. PMID:24347786

  13. Processes in the development of mathematics in kindergarten children from Title 1 schools.

    PubMed

    Foster, Matthew E; Anthony, Jason L; Clements, Doug H; Sarama, Julie H

    2015-12-01

    This study examined how well nonverbal IQ (or fluid intelligence), vocabulary, phonological awareness (PA), rapid autonomized naming (RAN), and phonological short-term memory (STM) predicted mathematics outcomes. The 208 participating kindergartners were administered tests of fluid intelligence, vocabulary, PA, RAN, STM, and numeracy in the fall of kindergarten, whereas tests of numeracy and applied problems were administered in the spring of kindergarten. Fall numeracy scores accounted for substantial variation in spring outcomes (R(2) values = .49 and .32 for numeracy and applied problems, respectively), which underscores the importance of preschool math instruction and screening for mathematics learning difficulties on entry into kindergarten. Fluid intelligence and PA significantly predicted unique variation in spring numeracy scores (ΔR(2) = .05) after controlling for autoregressive effects and classroom nesting. Fluid intelligence, PA, and STM significantly predicted unique variation in spring applied problems scores (ΔR(2) = .14) after controlling for autoregressive effects and classroom nesting. Although the contributions of fluid intelligence, PA, and STM toward math outcomes were reliable and arguably important, they were small. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Breathing mechanics during exercise with added dead space reflect mechanisms of ventilatory control.

    PubMed

    Wood, Helen E; Mitchell, Gordon S; Babb, Tony G

    2009-09-30

    Small increases in external dead space (V(D)) augment the exercise ventilatory response via a neural mechanism known as short-term modulation (STM). We hypothesized that breathing mechanics would differ during exercise, increased V(D) and STM. Men were studied at rest and during cycle exercise (10-50W) without (Control) and with added V(D) (200-600ml). With added V(D), V(T) increased via increased end-inspiratory lung volume (EILV), with no change in end-expiratory lung volume (EELV), indicating recruitment of inspiratory muscles only. With exercise, V(T) increased via both decreased EELV and increased EILV, indicating recruitment of both expiratory and inspiratory muscles. A significant interaction between the effects of exercise and V(D) on mean inspiratory flow indicated that the augmented exercise ventilatory response with added V(D) (i.e. STM) resulted from increased drive to the inspiratory muscles. These results reveal different patterns of respiratory muscle recruitment among experimental conditions. Hence, we conclude that fundamental differences exist in the neural control of ventilatory responses during exercise, increased V(D) and STM.

  15. Feature-based and object-based attention orientation during short-term memory maintenance.

    PubMed

    Ku, Yixuan

    2015-12-01

    Top-down attention biases the short-term memory (STM) processing at multiple stages. Orienting attention during the maintenance period of STM by a retrospective cue (retro-cue) strengthens the representation of the cued item and improves the subsequent STM performance. In a recent article, Backer et al. (Backer KC, Binns MA, Alain C. J Neurosci 35: 1307-1318, 2015) extended these findings from the visual to the auditory domain and combined electroencephalography to dissociate neural mechanisms underlying feature-based and object-based attention orientation. Both event-related potentials and neural oscillations explained the behavioral benefits of retro-cues and favored the theory that feature-based and object-based attention orientation were independent. Copyright © 2015 the American Physiological Society.

  16. Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement.

    PubMed

    Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua; Jia, Jin-Feng

    2015-05-01

    Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO3 surface.

  17. Fabrication of silver tips for scanning tunneling microscope induced luminescence.

    PubMed

    Zhang, C; Gao, B; Chen, L G; Meng, Q S; Yang, H; Zhang, R; Tao, X; Gao, H Y; Liao, Y; Dong, Z C

    2011-08-01

    We describe a reliable fabrication procedure of silver tips for scanning tunneling microscope (STM) induced luminescence experiments. The tip was first etched electrochemically to yield a sharp cone shape using selected electrolyte solutions and then sputter cleaned in ultrahigh vacuum to remove surface oxidation. The tip status, in particular the tip induced plasmon mode and its emission intensity, can be further tuned through field emission and voltage pulse. The quality of silver tips thus fabricated not only offers atomically resolved STM imaging, but more importantly, also allows us to perform challenging "color" photon mapping with emission spectra taken at each pixel simultaneously during the STM scan under relatively small tunnel currents and relatively short exposure time.

  18. Real-space visualization of conformation-independent oligothiophene electronic structure

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

    Taber, Benjamen N.; Kislitsyn, Dmitry A.; Gervasi, Christian F.

    2016-05-21

    We present scanning tunneling microscopy and spectroscopy (STM/STS) investigations of the electronic structures of different alkyl-substituted oligothiophenes on the Au(111) surface. STM imaging showed that on Au(111), oligothiophenes adopted distinct straight and bent conformations. By combining STS maps with STM images, we visualize, in real space, particle-in-a-box-like oligothiophene molecular orbitals. We demonstrate that different planar conformers with significant geometrical distortions of oligothiophene backbones surprisingly exhibit very similar electronic structures, indicating a low degree of conformation-induced electronic disorder. The agreement of these results with gas-phase density functional theory calculations implies that the oligothiophene interaction with the Au(111) surface is generally insensitivemore » to molecular conformation.« less

  19. Scanning tunneling microscope with two-dimensional translator.

    PubMed

    Nichols, J; Ng, K-W

    2011-01-01

    Since the invention of the scanning tunneling microscope (STM), it has been a powerful tool for probing the electronic properties of materials. Typically STM designs capable of obtaining resolution on the atomic scale are limited to a small area which can be probed. We have built an STM capable of coarse motion in two dimensions, the z- and x-directions which are, respectively, parallel and perpendicular to the tip. This allows us to image samples with very high resolution at sites separated by macroscopic distances. This device is a single unit with a compact design making it very stable. It can operate in either a horizontal or vertical configuration and at cryogenic temperatures.

  20. The Development of Automaticity in Short-Term Memory Search: Item-Response Learning and Category Learning

    ERIC Educational Resources Information Center

    Cao, Rui; Nosofsky, Robert M.; Shiffrin, Richard M.

    2017-01-01

    In short-term-memory (STM)-search tasks, observers judge whether a test probe was present in a short list of study items. Here we investigated the long-term learning mechanisms that lead to the highly efficient STM-search performance observed under conditions of consistent-mapping (CM) training, in which targets and foils never switch roles across…

  1. Turning Simple Span into Complex Span: Time for Decay or Interference from Distractors?

    ERIC Educational Resources Information Center

    Lewandowsky, Stephan; Geiger, Sonja M.; Morrell, Daniel B.; Oberauer, Klaus

    2010-01-01

    We investigated the effects of the duration and type of to-be-articulated distractors during encoding of a verbal list into short-term memory (STM). Distractors and to-be-remembered items alternated during list presentation, as in the complex-span task that underlies much of working-memory research. According to an interference model of STM, known…

  2. A Single Brief Burst Induces GluR1-Dependent Associative Short-Term Potentiation: A Potential Mechanism for Short-Term Memory

    ERIC Educational Resources Information Center

    Erickson, Martha A.; Maramara, Lauren A.; Lisman, John

    2010-01-01

    Recent work showed that short-term memory (STM) is selectively reduced in GluR1 knockout mice. This raises the possibility that a form of synaptic modification dependent on GluR1 might underlie STM. Studies of synaptic plasticity have shown that stimuli too weak to induce long-term potentiation induce short-term potentiation (STP), a phenomenon…

  3. Augmentation Award for Surface Science Research Training.

    DTIC Science & Technology

    1996-11-01

    atomic force microscopy facility. In particular, he designed an anechoic chamber for minimizing acoustical noise in our air and electrochemistry imaging...well as our new air/electochemical STM/AFM. In addition to the UHV-STM, the 11/20/96 10:43 e773 702 5863 J.F.I. I•On7 new air- levitated vactium rhnrher

  4. How Grammar Can Cope with Limited Short-Term Memory: Simultaneity and Seriality in Sign Languages

    ERIC Educational Resources Information Center

    Geraci, Carlo; Gozzi, Marta; Papagno, Costanza; Cecchetto, Carlo

    2008-01-01

    It is known that in American Sign Language (ASL) span is shorter than in English, but this discrepancy has never been systematically investigated using other pairs of signed and spoken languages. This finding is at odds with results showing that short-term memory (STM) for signs has an internal organization similar to STM for words. Moreover, some…

  5. Escaping the recent past: which stimulus dimensions influence proactive interference?

    PubMed

    Craig, Kimberly S; Berman, Marc G; Jonides, John; Lustig, Cindy

    2013-07-01

    Proactive interference occurs when information from the past disrupts current processing and is a major source of confusion and errors in short-term memory (STM; Wickens, Born, & Allen, Journal of Verbal Learning and Verbal Behavior, 2:440-445, 1963). The present investigation examines potential boundary conditions for interference, testing the hypothesis that potential competitors must be similar along task-relevant dimensions to influence proactive interference effects. We manipulated both the type of task being completed (Experiments 1, 2, and 3) and dimensions of similarity irrelevant to the current task (Experiments 4 and 5) to determine how the recent presentation of a probe item would affect the speed with which participants could reject that item. Experiments 1, 2, and 3 contrasted STM judgments, which require temporal information, with semantic and perceptual judgments, for which temporal information is irrelevant. In Experiments 4 and 5, task-irrelevant information (perceptual similarity) was manipulated within the recent probes task. We found that interference from past items affected STM task performance but did not affect performance in semantic or perceptual judgment tasks. Conversely, similarity along a nominally irrelevant perceptual dimension did not affect the magnitude of interference in STM tasks. Results are consistent with the view that items in STM are represented by noisy codes consisting of multiple dimensions and that interference occurs when items are similar to each other and, thus, compete along the dimensions relevant to target selection.

  6. Neuropeptide S overcomes short term memory deficit induced by sleep restriction by increasing prefrontal cortex activity.

    PubMed

    Thomasson, Julien; Canini, Frédéric; Poly-Thomasson, Betty; Trousselard, Marion; Granon, Sylvie; Chauveau, Frédéric

    2017-12-01

    Sleep restriction (SR) impairs short term memory (STM) that might be related to different processes. Neuropeptide S (NPS), an endogenous neuropeptide that improves short term memory, activates arousal and decreases anxiety is likely to counteract the SR-induced impairment of STM. The objective of the present study was to find common cerebral pathways in sleep restriction and NPS action in order to ultimately antagonize SR effect on memory. The STM was assessed using a spontaneous spatial alternation task in a T-maze. C57-Bl/6J male mice were distributed in 4 groups according to treatment (0.1nmol of NPS or vehicle intracerebroventricular injection) and to 20h-SR. Immediately after behavioural testing, regional c-fos immunohistochemistry was performed and used as a neural activation marker for spatial short term memory (prefrontal cortex, dorsal hippocampus) and emotional reactivity (basolateral amygdala and ventral hippocampus). Anxiety-like behaviour was assessed using elevated-plus maze task. Results showed that SR impaired short term memory performance and decreased neuronal activation in cingular cortex.NPS injection overcame SR-induced STM deficits and increased neuronal activation in infralimbic cortex. SR spared anxiety-like behavior in the elevated-plus maze. Neural activation in basolateral nucleus of amygdala and ventral hippocampus were not changed after SR.In conclusion, the present study shows that NPS overcomes SR-induced STM deficits by increasing prefrontal cortex activation independently of anxiety-like behaviour. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  7. Complex regulatory network encompassing the Csr, c-di-GMP and motility systems of Salmonella Typhimurium.

    PubMed

    Jonas, Kristina; Edwards, Adrianne N; Ahmad, Irfan; Romeo, Tony; Römling, Ute; Melefors, Ojar

    2010-02-01

    Bacterial survival depends on the ability to switch between sessile and motile lifestyles in response to changing environmental conditions. In many species, this switch is governed by (3'-5')-cyclic-diguanosine monophosphate (c-di-GMP), a signalling molecule, which is metabolized by proteins containing GGDEF and/or EAL domains. Salmonella Typhimurium contains 20 such proteins. Here, we show that the RNA-binding protein CsrA regulates the expression of eight genes encoding GGDEF, GGDEF-EAL and EAL domain proteins. CsrA bound directly to the mRNA leaders of five of these genes, suggesting that it may regulate these genes post-transcriptionally. The c-di-GMP-specific phosphodiesterase STM3611, which reciprocally controls flagella function and production of biofilm matrix components, was regulated by CsrA binding to the mRNA, but was also indirectly regulated by CsrA through the FlhDC/FliA flagella cascade and STM1344. STM1344 is an unconventional (c-di-GMP-inactive) EAL domain protein, recently identified as a negative regulator of flagella gene expression. Here, we demonstrate that CsrA directly downregulates expression of STM1344, which in turn regulates STM3611 through fliA and thus reciprocally controls motility and biofilm factors. Altogether, our data reveal that the concerted and complex regulation of several genes encoding GGDEF/EAL domain proteins allows CsrA to control the motility-sessility switch in S. Typhimurium at multiple levels.

  8. Tablet-Based Intervention for Reducing Children's Preoperative Anxiety: A Pilot Study.

    PubMed

    Chow, Cheryl H T; Van Lieshout, Ryan J; Schmidt, Louis A; Buckley, Norman

    To examine the feasibility, acceptability, and effects of a novel tablet-based application, Story-Telling Medicine (STM), in reducing children's preoperative anxiety. Children (N = 100) aged 7 to 13 years who were undergoing outpatient surgery were recruited from a local children's hospital. This study comprised 3 waves: Waves 1 (n = 30) and 2 (n = 30) examined feasibility, and Wave 3 (n = 40) examined the acceptability of STM and compared its effect on preoperative anxiety to Usual Care (UC). In Wave 3, children were randomly allocated to receive STM+UC or UC. A change in preoperative anxiety was measured using the Children's Perioperative Multidimensional Anxiety Scale (CPMAS) 7 to 14 days before surgery (T1), on the day of surgery (T2), and 1 month postoperatively (T3). Wave 1 demonstrated the feasibility of participant recruitment and data collection procedures but identified challenges with attrition at T2 and T3. Wave 2 piloted a modified protocol that addressed attrition and increased the feasibility of follow-up. In Wave 3, children in the STM+UC demonstrated greater reductions in CPMAS compared with the UC group (ΔM = 119.90, SE = 46.36, t(27) = 2.59, p = .015; 95% confidence interval = 24.78-215.02). This pilot study provides preliminary evidence that STM is a feasible and acceptable intervention for reducing children's preoperative anxiety in a busy pediatric operative setting and supports the investigation of a full-scale randomized controlled trial.

  9. Surgical outcomes in patients with primary mediastinal non-seminomatous germ cell tumours and elevated post-chemotherapy serum tumour markers.

    PubMed

    De Latour, Bertrand; Fadel, Elie; Mercier, Olaf; Mussot, Sacha; Fabre, Dominique; Fizazi, Karim; Dartevelle, Philippe

    2012-07-01

    Platinum-based chemotherapy followed by surgical resection of residual masses has become the standard treatment of patients with primary mediastinal non-seminomatous germ cell tumours (NSGCTs). Persistent serum tumour marker (STM) elevation after chemotherapy usually indicates a poor prognosis. We retrospectively assessed surgical outcomes in patients with high STM levels after chemotherapy for primary mediastinal NSGCT. Between 1983 and 2010, residual tumour excision was performed in 21 patients, 20 men and one woman with a median age of 30 years (range: 19-49 years), with primary mediastinal NSGCTs and high STM levels after platinum-based chemotherapy, followed by second-line chemotherapy in 11 patients. Alpha-fetoprotein was elevated in all 21 patients and β-human chorionic gonadotropin in three patients. Permanent histology demonstrated viable germ cell tumour (n=13), teratoma (n=3) or necrosis (n=5). After surgery, the STM levels returned to normal in 11 patients. Eight patients are alive with a median follow-up of 98 months. The 5-year survival rate was 36% and was not significantly affected by the use of preoperative second-line chemotherapy. At univariate analysis, only postoperative STM elevation and residual viable tumour, indicating incomplete resection, were significantly associated with lower survival (P=0.018 and P=0.04, respectively). In patients with primary mediastinal NSGCTs and elevated post-chemotherapy STMs, surgery is warranted when complete resection is deemed feasible. In specialized oncology centres, this aggressive approach can provide a cure in some patients.

  10. Role of 5-HT1-7 receptors in short- and long-term memory for an autoshaping task: intrahippocampal manipulations.

    PubMed

    Liy-Salmeron, Gustavo; Meneses, Alfredo

    2007-05-25

    It was previously reported that brain areas containing serotonin (5-hydroxytryptamine, 5-HT) receptors mediate memory consolidation as well as short (STM)- and long-term memory (LTM). Here the effects of systemic and intrahippocampal administration of 5-HT agonists and antagonists on an autoshaping learning task were explored, which requires hippocampal translation and transduction as well as 5-HT receptors expression. As previously reported ketamine (glutamatergic antagonist) and two well-known amnesic drugs, scopolamine (cholinergic antagonist) and dizocilpine (NMDA antagonist) impaired STM but not LTM; dizocilpine even improved the latter. Since ketamine produces hallucinations and impairs memory in humans, we address the question if well-known antipsychotic haloperidol and clozapine might affect STM deficit. Indeed, systemic administration of clozapineSTM deficit. Considering that clozapine and haloperidol are antagonists for dopaminergic D2 and 5-HT(1A/2A/6/7) receptors, systemic and intrahippocampal administration of 5-HT drugs were further explored. The ketamine STM-induced deficit was blocked by 8-OHDPAT (5-HT(1A/7) agonist) and SB-399885 (a 5-HT(6) antagonist) but not by 5-HT(1B), 5-HT(2) and 5-HT(7) antagonists, thus implicating 5-HT(1A/7) and 5-HT(6) receptors. These data also suggest that ketamine (at 10 mg/kg) represents a reliable pharmacological tool to explore memory deficits related to hippocampus and schizophrenia.

  11. Design and Analysis of Complex D-Regions in Reinforced Concrete Structures

    ERIC Educational Resources Information Center

    Yindeesuk, Sukit

    2009-01-01

    STM design provisions, such as those in Appendix A of ACI318-08, consist of rules for evaluating the capacity of the load-resisting truss that is idealized to carry the forces through the D-Region. These code rules were primarily derived from test data on simple D-Regions such as deep beams and corbels. However, these STM provisions are taken as…

  12. Water-Mediated Proton Hopping on an Iron Oxide Surface

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

    Merte, L. R.; Peng, Guowen; Bechstein, Ralf

    2012-05-18

    The diffusion of hydrogen atoms across solid oxide surfaces is often assumed to be accelerated by the presence of water molecules. Here we present a high-resolution, high-speed scanning tunneling microscopy (STM) study of the diffusion of H atoms on an FeO thin film. STM movies directly reveal a water-mediated hydrogen diffusion mechanism on the oxide surface at temperatures between 100 and 300 kelvin. Density functional theory calculations and isotope-exchange experiments confirm the STM observations, and a proton-transfer mechanism that proceeds via an H3O+-like transition state is revealed. This mechanism differs from that observed previously for rutile TiO2(110), where water dissociationmore » is a key step in proton diffusion.« less

  13. In and Si adatoms on Si(111)5×2-Au : Scanning tunneling microscopy and first-principles density functional calculations

    NASA Astrophysics Data System (ADS)

    Stępniak, A.; Nita, P.; Krawiec, M.; Jałochowski, M.

    2009-09-01

    Structural properties of monatomic indium chains on Si(111)5×2-Au surface are investigated by scanning tunneling microscopy (STM) and first-principles density functional calculations (DFT). The STM topography data show that submonolayer coverage of indium leads to a well-ordered chain structure with the same periodicity as the Si adatoms form on Si(111)5×2-Au surface. Bias-dependent STM topography and spectroscopy reveal two different mechanisms of In-atoms adsorption on the surface: bonding to Si adatoms and substitution for Si atoms in the adatom positions. Those mechanisms are further corroborated by DFT calculations. The obtained structural model of In-modified Si(111)5×2-Au surface remains in good agreement with the experimental data.

  14. Adlayer structure of octa-alkoxy-substituted copper(II) phthalocyanine on Au(111) by electrochemical scanning tunneling microscopy.

    PubMed

    Wang, Li; Ou-Yang, Liangyue; Yau, Shueh-Lin

    2008-01-01

    Electrochemical scanning tunneling microscopy (ECSTM) has been used to examine the adlayer of octa-alkoxy-substituted copper(II) phthalocyanines (CuPc(OC(8)H(17))(8)) on Au(111) in 0.1 M HClO(4), where the molecular adlayer was prepared by spontaneous adsorption from a benzene solution containing this molecule. Topography STM scans revealed long-range ordered, interweaved arrays of CuPc(OC(8)H(17))(8) with coexistent rectangular and hexagonal symmetries. High-quality STM molecular resolution yielded the internal molecular structure and the orientation of CuPc(OC(8)H(17))(8) admolecules. These STM results could shed insight into the method of generating ordered molecular assemblies of phthalocyanine molecules with long-chained substitutes on metal surface. 2007 Wiley-Liss, Inc

  15. Scanning tunneling microscope with a rotary piezoelectric stepping motor

    NASA Astrophysics Data System (ADS)

    Yakimov, V. N.

    1996-02-01

    A compact scanning tunneling microscope (STM) with a novel rotary piezoelectric stepping motor for coarse positioning has been developed. An inertial method for rotating of the rotor by the pair of piezoplates has been used in the piezomotor. Minimal angular step size was about several arcsec with the spindle working torque up to 1 N×cm. Design of the STM was noticeably simplified by utilization of the piezomotor with such small step size. A shaft eccentrically attached to the piezomotor spindle made it possible to push and pull back the cylindrical bush with the tubular piezoscanner. A linear step of coarse positioning was about 50 nm. STM resolution in vertical direction was better than 0.1 nm without an external vibration isolation.

  16. Variation in Parasympathetic Dysregulation Moderates Short-term Memory Problems in Childhood Attention-Deficit/Hyperactivity Disorder.

    PubMed

    Ward, Anthony R; Alarcón, Gabriela; Nigg, Joel T; Musser, Erica D

    2015-11-01

    Although attention deficit/hyperactivity disorder (ADHD) is associated with impairment in working memory and short-term memory, up to half of individual children with ADHD perform within a normative range. Heterogeneity in other ADHD-related mechanisms, which may compensate for or combine with cognitive weaknesses, is a likely explanation. One candidate is the robustness of parasympathetic regulation (as indexed by respiratory sinus arrhythmia; RSA). Theory and data suggest that a common neural network is likely tied to both heart-rate regulation and certain cognitive functions (including aspects of working and short-term memory). Cardiac-derived indices of parasympathetic reactivity were collected during short-term memory (STM) storage and rehearsal tasks from 243 children (116 ADHD, 127 controls). ADHD was associated with lower STM performance, replicating previous work. In addition, RSA reactivity moderated the association between STM and ADHD - both as a category and a dimension - independent of comorbidity. Specifically, conditional effects revealed that high levels of withdrawal interacted with weakened STM but high levels of augmentation moderated a positive association predicting ADHD. Thus, variations in parasympathetic reactivity may help explain neuropsychological heterogeneity in ADHD.

  17. A 30 mK, 13.5 T scanning tunneling microscope with two independent tips

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

    Roychowdhury, Anita; Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20740; Gubrud, M. A.

    We describe the design, construction, and performance of an ultra-low temperature, high-field scanning tunneling microscope (STM) with two independent tips. The STM is mounted on a dilution refrigerator and operates at a base temperature of 30 mK with magnetic fields of up to 13.5 T. We focus on the design of the two-tip STM head, as well as the sample transfer mechanism, which allows in situ transfer from an ultra high vacuum preparation chamber while the STM is at 1.5 K. Other design details such as the vibration isolation and rf-filtered wiring are also described. Their effectiveness is demonstrated viamore » spectral current noise characteristics and the root mean square roughness of atomic resolution images. The high-field capability is shown by the magnetic field dependence of the superconducting gap of Cu{sub x}Bi{sub 2}Se{sub 3}. Finally, we present images and spectroscopy taken with superconducting Nb tips with the refrigerator at 35 mK that indicate that the effective temperature of our tips/sample is approximately 184 mK, corresponding to an energy resolution of 16 μeV.« less

  18. Determination of the electrical resistivity of vertically aligned carbon nanotubes by scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Ageev, O. A.; Il'in, O. I.; Rubashkina, M. V.; Smirnov, V. A.; Fedotov, A. A.; Tsukanova, O. G.

    2015-07-01

    Techniques are developed to determine the resistance per unit length and the electrical resistivity of vertically aligned carbon nanotubes (VA CNTs) using atomic force microscopy (AFM) and scanning tunneling microscopy (STM). These techniques are used to study the resistance of VA CNTs. The resistance of an individual VA CNT calculated with the AFM-based technique is shown to be higher than the resistance of VA CNTs determined by the STM-based technique by a factor of 200, which is related to the influence of the resistance of the contact of an AFM probe to VA CNTs. The resistance per unit length and the electrical resistivity of an individual VA CNT 118 ± 39 nm in diameter and 2.23 ± 0.37 μm in height that are determined by the STM-based technique are 19.28 ± 3.08 kΩ/μm and 8.32 ± 3.18 × 10-4 Ω m, respectively. The STM-based technique developed to determine the resistance per unit length and the electrical resistivity of VA CNTs can be used to diagnose the electrical parameters of VA CNTs and to create VA CNT-based nanoelectronic elements.

  19. Whole genome sequencing of Salmonella Typhimurium illuminates distinct outbreaks caused by an endemic multi-locus variable number tandem repeat analysis type in Australia, 2014.

    PubMed

    Phillips, Anastasia; Sotomayor, Cristina; Wang, Qinning; Holmes, Nadine; Furlong, Catriona; Ward, Kate; Howard, Peter; Octavia, Sophie; Lan, Ruiting; Sintchenko, Vitali

    2016-09-15

    Salmonella Typhimurium (STM) is an important cause of foodborne outbreaks worldwide. Subtyping of STM remains critical to outbreak investigation, yet current techniques (e.g. multilocus variable number tandem repeat analysis, MLVA) may provide insufficient discrimination. Whole genome sequencing (WGS) offers potentially greater discriminatory power to support infectious disease surveillance. We performed WGS on 62 STM isolates of a single, endemic MLVA type associated with two epidemiologically independent, food-borne outbreaks along with sporadic cases in New South Wales, Australia, during 2014. Genomes of case and environmental isolates were sequenced using HiSeq (Illumina) and the genetic distance between them was assessed by single nucleotide polymorphism (SNP) analysis. SNP analysis was compared to the epidemiological context. The WGS analysis supported epidemiological evidence and genomes of within-outbreak isolates were nearly identical. Sporadic cases differed from outbreak cases by a small number of SNPs, although their close relationship to outbreak cases may represent an unidentified common food source that may warrant further public health follow up. Previously unrecognised mini-clusters were detected. WGS of STM can discriminate foodborne community outbreaks within a single endemic MLVA clone. Our findings support the translation of WGS into public health laboratory surveillance of salmonellosis.

  20. Short-term memory and long-term memory are still different.

    PubMed

    Norris, Dennis

    2017-09-01

    A commonly expressed view is that short-term memory (STM) is nothing more than activated long-term memory. If true, this would overturn a central tenet of cognitive psychology-the idea that there are functionally and neurobiologically distinct short- and long-term stores. Here I present an updated case for a separation between short- and long-term stores, focusing on the computational demands placed on any STM system. STM must support memory for previously unencountered information, the storage of multiple tokens of the same type, and variable binding. None of these can be achieved simply by activating long-term memory. For example, even a simple sequence of digits such as "1, 3, 1" where there are 2 tokens of the digit "1" cannot be stored in the correct order simply by activating the representations of the digits "1" and "3" in LTM. I also review recent neuroimaging data that has been presented as evidence that STM is activated LTM and show that these data are exactly what one would expect to see based on a conventional 2-store view. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  1. Short-Term Memory and Long-Term Memory are Still Different

    PubMed Central

    2017-01-01

    A commonly expressed view is that short-term memory (STM) is nothing more than activated long-term memory. If true, this would overturn a central tenet of cognitive psychology—the idea that there are functionally and neurobiologically distinct short- and long-term stores. Here I present an updated case for a separation between short- and long-term stores, focusing on the computational demands placed on any STM system. STM must support memory for previously unencountered information, the storage of multiple tokens of the same type, and variable binding. None of these can be achieved simply by activating long-term memory. For example, even a simple sequence of digits such as “1, 3, 1” where there are 2 tokens of the digit “1” cannot be stored in the correct order simply by activating the representations of the digits “1” and “3” in LTM. I also review recent neuroimaging data that has been presented as evidence that STM is activated LTM and show that these data are exactly what one would expect to see based on a conventional 2-store view. PMID:28530428

  2. A 30 mK, 13.5 T scanning tunneling microscope with two independent tips.

    PubMed

    Roychowdhury, Anita; Gubrud, M A; Dana, R; Anderson, J R; Lobb, C J; Wellstood, F C; Dreyer, M

    2014-04-01

    We describe the design, construction, and performance of an ultra-low temperature, high-field scanning tunneling microscope (STM) with two independent tips. The STM is mounted on a dilution refrigerator and operates at a base temperature of 30 mK with magnetic fields of up to 13.5 T. We focus on the design of the two-tip STM head, as well as the sample transfer mechanism, which allows in situ transfer from an ultra high vacuum preparation chamber while the STM is at 1.5 K. Other design details such as the vibration isolation and rf-filtered wiring are also described. Their effectiveness is demonstrated via spectral current noise characteristics and the root mean square roughness of atomic resolution images. The high-field capability is shown by the magnetic field dependence of the superconducting gap of CuxBi2Se3. Finally, we present images and spectroscopy taken with superconducting Nb tips with the refrigerator at 35 mK that indicate that the effective temperature of our tips/sample is approximately 184 mK, corresponding to an energy resolution of 16 μeV.

  3. Compact low temperature scanning tunneling microscope with in-situ sample preparation capability

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

    Kim, Jungdae; Department of Physics and EHSRC, University of Ulsan, Ulsan 680-749; Nam, Hyoungdo

    2015-09-15

    We report on the design of a compact low temperature scanning tunneling microscope (STM) having in-situ sample preparation capability. The in-situ sample preparation chamber was designed to be compact allowing quick transfer of samples to the STM stage, which is ideal for preparing temperature sensitive samples such as ultra-thin metal films on semiconductor substrates. Conventional spring suspensions on the STM head often cause mechanical issues. To address this problem, we developed a simple vibration damper consisting of welded metal bellows and rubber pads. In addition, we developed a novel technique to ensure an ultra-high-vacuum (UHV) seal between the copper andmore » stainless steel, which provides excellent reliability for cryostats operating in UHV. The performance of the STM was tested from 2 K to 77 K by using epitaxial thin Pb films on Si. Very high mechanical stability was achieved with clear atomic resolution even when using cryostats operating at 77 K. At 2 K, a clean superconducting gap was observed, and the spectrum was easily fit using the BCS density of states with negligible broadening.« less

  4. Scanning tunneling microscopy image simulation of the rutile (110) TiO2 surface with hybrid functionals and the localized basis set approach

    NASA Astrophysics Data System (ADS)

    Di Valentin, Cristiana

    2007-10-01

    In this work we present a simplified procedure to use hybrid functionals and localized atomic basis sets to simulate scanning tunneling microscopy (STM) images of stoichiometric, reduced and hydroxylated rutile (110) TiO2 surface. For the two defective systems it is necessary to introduce some exact Hartree-Fock exchange in the exchange functional in order to correctly describe the details of the electronic structure. Results are compared to the standard density functional theory and planewave basis set approach. Both methods have advantages and drawbacks that are analyzed in detail. In particular, for the localized basis set approach, it is necessary to introduce a number of Gaussian function in the vacuum region above the surface in order to correctly describe the exponential decay of the integrated local density of states from the surface. In the planewave periodic approach, a thick vacuum region is required to achieve correct results. Simulated STM images are obtained for both the reduced and hydroxylated surface which nicely compare with experimental findings. A direct comparison of the two defects as displayed in the simulated STM images indicates that the OH groups should appear brighter than oxygen vacancies in perfect agreement with the experimental STM data.

  5. Sample mounting and transfer for coupling an ultrahigh vacuum variable temperature beetle scanning tunneling microscope with conventional surface probes

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

    Nafisi, Kourosh; Ranau, Werner; Hemminger, John C.

    2001-01-01

    We present a new ultrahigh vacuum (UHV) chamber for surface analysis and microscopy at controlled, variable temperatures. The new instrument allows surface analysis with Auger electron spectroscopy, low energy electron diffraction, quadrupole mass spectrometer, argon ion sputtering gun, and a variable temperature scanning tunneling microscope (VT-STM). In this system, we introduce a novel procedure for transferring a sample off a conventional UHV manipulator and onto a scanning tunneling microscope in the conventional ''beetle'' geometry, without disconnecting the heating or thermocouple wires. The microscope, a modified version of the Besocke beetle microscope, is mounted on a 2.75 in. outer diameter UHVmore » flange and is directly attached to the base of the chamber. The sample is attached to a tripod sample holder that is held by the main manipulator. Under UHV conditions the tripod sample holder can be removed from the main manipulator and placed onto the STM. The VT-STM has the capability of acquiring images between the temperature range of 180--500 K. The performance of the chamber is demonstrated here by producing an ordered array of island vacancy defects on a Pt(111) surface and obtaining STM images of these defects.« less

  6. No recovery of memory when cognitive load is decreased.

    PubMed

    Ricker, Timothy J; Vergauwe, Evie; Hinrichs, Garrett A; Blume, Christopher L; Cowan, Nelson

    2015-05-01

    There is substantial debate in the field of short-term memory (STM) as to whether the process of active maintenance occurs through memory-trace reactivation or repair. A key difference between these 2 potential mechanisms is that a repair mechanism should lead to recovery of forgotten information. The ability to recover forgotten memories would be a panacea for STM and if possible, would warrant much future research. We examine the topic of STM recovery by varying the cognitive load of a secondary task and duration of retention of word pairs. In our key manipulation, we lighten the cognitive load partway through the retention interval, resulting in an easier task during the later portion of retention and more time for active maintenance processes to take place. Although the natural prediction arising from a repair mechanism is that memory accuracy should increase after transitioning to an easier load, we find that accuracy decreases or levels off at this point. We see this pattern across 3 experiments and can only conclude that the panacea of STM recovery does not exist. Implications for the debate over memory maintenance mechanisms are discussed. (c) 2015 APA, all rights reserved).

  7. Impaired Mitochondrial Transcription Termination Disrupts the Stromal Redox Poise in Chlamydomonas1[OPEN

    PubMed Central

    Uhmeyer, Andreas

    2017-01-01

    In photosynthetic eukaryotes, the metabolite exchange between chloroplast and mitochondria ensures efficient photosynthesis under saturating light conditions. The Chlamydomonas reinhardtii mutant stm6 is devoid of the mitochondrial transcription termination factor MOC1 and aberrantly expresses the mitochondrial genome, resulting in enhanced photosynthetic hydrogen production and diminished light tolerance. We analyzed the modulation of mitochondrial and chlororespiration during the acclimation of stm6 and the MOC1-complemented strain to excess light. Although light stress stimulated mitochondrial respiration via the energy-conserving cytochrome c pathway in both strains, the mutant was unable to fine-tune the expression and activity of oxidative phosphorylation complex I in excess light, which was accompanied by an increased mitochondrial respiration via the alternative oxidase pathway. Furthermore, stm6 failed to fully activate chlororespiration and cyclic electron flow due to a more oxidized state of the chloroplast stroma, which is caused by an increased mitochondrial electron sink capacity. Increased susceptibility to photoinhibition of PSII in stm6 demonstrates that the MOC1-dependent modulation of mitochondrial respiration helps control the stromal redox poise as a crucial part of high-light acclimation in C. reinhardtii. PMID:28500267

  8. Working memory, short-term memory, and reading disabilities: a selective meta-analysis of the literature.

    PubMed

    Swanson, H Lee; Xinhua Zheng; Jerman, Olga

    2009-01-01

    The purpose of the present study was to synthesize research that compares children with and without reading disabilities (RD) on measures of short-term memory (STM) and working memory (WM). Across a broad age, reading, and IQ range, 578 effect sizes (ESs) were computed, yielding a mean ES across studies of -.89 (SD = 1.03). A total of 257 ESs were in the moderate range for STM measures (M = -.61, 95% confidence range of -.65 to -.58), and 320 ESs were in the moderate range for WM measures (M = -.67, 95% confidence range of -.68 to -.64). The results indicated that children with RD were distinctively disadvantaged compared with average readers on (a) STM measures requiring the recall of phonemes and digit sequences and (b) WM measures requiring the simultaneous processing and storage of digits within sentence sequences and final words from unrelated sentences. No significant moderating effects emerged for age, IQ, or reading level on memory ESs. The findings indicated that domain-specific STM and WM differences between ability groups persisted across age, suggesting that a verbal deficit model that fails to efficiently draw resources from both a phonological and executive system underlies RD.

  9. Atomic-scale characterization of hydrogenated amorphous-silicon films and devices. Annual subcontract report, 14 February 1994--14 April 1995

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

    Gallagher, A.; Tanenbaum, D.; Laracuente, A.

    1995-08-01

    Properties of the hydrogenated amorphous silicon (a-Si:H) films used in photovoltaic (PV) panels are reported. The atomic-scale topology of the surface of intrinsic a-Si:H films, measured by scanning tunneling microscopy (STM) as a function of film thickness, are reported and diagnosed. For 1-500-nm-thick films deposited under normal device-quality conditions from silane discharges, most portions of these surfaces are uniformly hilly without indications of void regions. However, the STM images indicate that 2-6-nm silicon particulates are continuously deposited into the growing film from the discharge and fill approximately 0.01% of the film volume. Although the STM data are not sensitive tomore » the local electronic properties near these particulates, it is very likely that the void regions grow around them and have a deleterious effect on a-Si:H photovoltaics. Preliminary observations of particulates in the discharge, based on light scattering, confirm that particulates are present in the discharge and that many collect and agglomerate immediately downstream of the electrodes. Progress toward STM measurements of the electronic properties of cross-sectioned a-Si:H PV cells is also reported.« less

  10. An experimental study of furan adsorption and decomposition on vicinal palladium surfaces using scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Loui, A.; Chiang, S.

    2018-04-01

    The intact adsorption and decomposition of furan (C4H4O) on vicinal palladium surfaces with (111)-oriented terraces has been studied by scanning tunneling microscopy (STM) over a range of temperatures. STM images at 225 K show that furan molecules lie flat and prefer to adsorb at upper step edges. At 225 K, furan molecules adsorbed on "narrow" terraces of 20 to 45 Å in width appear to diffuse more readily than those adsorbed on "wide" terraces of 160 to 220 Å. A distinct population of smaller features appears in STM images on "narrow" terraces at 288 K and on "wide" terraces at 415 K and is identified with the C3H3 decomposition product, agreeing with prior studies which demonstrated that furan dissociates on Pd(111) to yield carbon monoxide (CO) and a C3H3 moiety in the 280 to 320 K range. Based on our direct visualization of this reaction using STM, we propose a spatial mechanism in which adsorption of furan at upper step edges allows catalysis of the dissociation, followed by diffusion of the product to lower step edges.

  11. Chronic sleep deprivation differentially affects short and long-term operant memory in Aplysia.

    PubMed

    Krishnan, Harini C; Noakes, Eric J; Lyons, Lisa C

    2016-10-01

    The induction, formation and maintenance of memory represent dynamic processes modulated by multiple factors including the circadian clock and sleep. Chronic sleep restriction has become common in modern society due to occupational and social demands. Given the impact of cognitive impairments associated with sleep deprivation, there is a vital need for a simple animal model in which to study the interactions between chronic sleep deprivation and memory. We used the marine mollusk Aplysia californica, with its simple nervous system, nocturnal sleep pattern and well-characterized learning paradigms, to assess the effects of two chronic sleep restriction paradigms on short-term (STM) and long-term (LTM) associative memory. The effects of sleep deprivation on memory were evaluated using the operant learning paradigm, learning that food is inedible, in which the animal associates a specific netted seaweed with failed swallowing attempts. We found that two nights of 6h sleep deprivation occurring during the first or last half of the night inhibited both STM and LTM. Moreover, the impairment in STM persisted for more than 24h. A milder, prolonged sleep deprivation paradigm consisting of 3 consecutive nights of 4h sleep deprivation also blocked STM, but had no effect on LTM. These experiments highlight differences in the sensitivity of STM and LTM to chronic sleep deprivation. Moreover, these results establish Aplysia as a valid model for studying the interactions between chronic sleep deprivation and associative memory paving the way for future studies delineating the mechanisms through which sleep restriction affects memory formation. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Scanning tunneling microscopy studies of pulse deposition of dinuclear organometallic molecules on Au(111)

    NASA Astrophysics Data System (ADS)

    Guo, Song; Alex Kandel, S.

    2008-01-01

    Ultrahigh-vacuum scanning tunneling microscopy (STM) was used to study trans-[Cl(dppe)2Ru(CC)6Ru(dppe)2Cl] [abbreviated as Ru2, diphenylphosphinoethane (dppe)] on Au(111). This large organometallic molecule was pulse deposited onto the Au(111) surface under ultrahigh-vacuum (UHV) conditions. UHV STM studies on the prepared sample were carried out at room temperature and 77K in order to probe molecular adsorption and to characterize the surface produced by the pulse deposition process. Isolated Ru2 molecules were successfully imaged by STM at room temperature; however, STM images were degraded by mobile toluene solvent molecules that remain on the surface after the deposition. Cooling the sample to 77K allows the solvent molecules to be observed directly using STM, and under these conditions, toluene forms organized striped domains with regular domain boundaries and a lattice characterized by 5.3 and 2.7Å intermolecular distances. When methylene chloride is used as the solvent, it forms analogous domains on the surface at 77K. Mild annealing under vacuum causes most toluene molecules to desorb from the surface; however, this annealing process may lead to thermal degradation of Ru2 molecules. Although pulse deposition is an effective way to deposit molecules on surfaces, the presence of solvent on the surface after pulse deposition is unavoidable without thermal annealing, and this annealing may cause undesired chemical changes in the adsorbates under study. Preparation of samples using pulse deposition must take into account the characteristics of sample molecules, solvent, and surfaces.

  13. Orientation-dependent imaging of electronically excited quantum dots

    NASA Astrophysics Data System (ADS)

    Nguyen, Duc; Goings, Joshua J.; Nguyen, Huy A.; Lyding, Joseph; Li, Xiaosong; Gruebele, Martin

    2018-02-01

    We previously demonstrated that we can image electronic excitations of quantum dots by single-molecule absorption scanning tunneling microscopy (SMA-STM). With this technique, a modulated laser beam periodically saturates an electronic transition of a single nanoparticle, and the resulting tunneling current modulation ΔI(x0, y0) maps out the SMA-STM image. In this paper, we first derive the basic theory to calculate ΔI(x0, y0) in the one-electron approximation. For near-resonant tunneling through an empty orbital "i" of the nanostructure, the SMA-STM signal is approximately proportional to the electron density |φi) (x0,y0)|STM signal is approximated by an orbital density map (ODM) of the resonantly excited orbital at energy Ei. The situation is more complex for correlated electron motion, but either way a slice through the excited electronic state structure in the tunneling region is imaged. We then show experimentally that we can nudge quantum dots on the surface and roll them, thus imaging excited state electronic structure of a single quantum dot at different orientations. We use density functional theory to model ODMs at various orientations, for qualitative comparison with the SMA-STM experiment. The model demonstrates that our experimentally observed signal monitors excited states, localized by defects near the surface of an individual quantum dot. The sub-nanometer super-resolution imaging technique demonstrated here could become useful for mapping out the three-dimensional structure of excited states localized by defects within nanomaterials.

  14. Orientation-dependent imaging of electronically excited quantum dots.

    PubMed

    Nguyen, Duc; Goings, Joshua J; Nguyen, Huy A; Lyding, Joseph; Li, Xiaosong; Gruebele, Martin

    2018-02-14

    We previously demonstrated that we can image electronic excitations of quantum dots by single-molecule absorption scanning tunneling microscopy (SMA-STM). With this technique, a modulated laser beam periodically saturates an electronic transition of a single nanoparticle, and the resulting tunneling current modulation ΔI(x 0 , y 0 ) maps out the SMA-STM image. In this paper, we first derive the basic theory to calculate ΔI(x 0 , y 0 ) in the one-electron approximation. For near-resonant tunneling through an empty orbital "i" of the nanostructure, the SMA-STM signal is approximately proportional to the electron density φ i x 0 ,y 0 2 of the excited orbital in the tunneling region. Thus, the SMA-STM signal is approximated by an orbital density map (ODM) of the resonantly excited orbital at energy E i . The situation is more complex for correlated electron motion, but either way a slice through the excited electronic state structure in the tunneling region is imaged. We then show experimentally that we can nudge quantum dots on the surface and roll them, thus imaging excited state electronic structure of a single quantum dot at different orientations. We use density functional theory to model ODMs at various orientations, for qualitative comparison with the SMA-STM experiment. The model demonstrates that our experimentally observed signal monitors excited states, localized by defects near the surface of an individual quantum dot. The sub-nanometer super-resolution imaging technique demonstrated here could become useful for mapping out the three-dimensional structure of excited states localized by defects within nanomaterials.

  15. Chronic Sleep Deprivation Differentially Affects Short and Long-term Operant Memory in Aplysia

    PubMed Central

    Krishnan, Harini C.; Noakes, Eric J.; Lyons, Lisa C.

    2016-01-01

    The induction, formation and maintenance of memory represent dynamic processes modulated by multiple factors including the circadian clock and sleep. Chronic sleep restriction has become common in modern society due to occupational and social demands. Given the impact of cognitive impairments associated with sleep deprivation, there is a vital need for a simple animal model in which to study the interactions between chronic sleep deprivation and memory. We used the marine mollusk Aplysia californica, with its simple nervous system, nocturnal sleep pattern and well-characterized learning paradigms, to assess the effects of two chronic sleep restriction paradigms on short-term (STM) and long-term (LTM) associative memory. The effects of sleep deprivation on memory were evaluated using the operant learning paradigm, learning that food is inedible, in which the animal associates a specific netted seaweed with failed swallowing attempts. We found that two nights of 6 h sleep deprivation occurring during the first or last half of the night inhibited both STM and LTM. Moreover, the impairment in STM persisted for more than 24 hours. A milder, prolonged sleep deprivation paradigm consisting of 3 consecutive nights of 4 h sleep deprivation also blocked STM, but had no effect on LTM. These experiments highlight differences in the sensitivity of STM and LTM to chronic sleep deprivation. Moreover, these results establish Aplysia as a valid model for studying the interactions between chronic sleep deprivation and associative memory paving the way for future studies delineating the mechanisms through which sleep restriction affects memory formation. PMID:27555235

  16. All-optical lithography process for contacting nanometer precision donor devices

    NASA Astrophysics Data System (ADS)

    Ward, D. R.; Marshall, M. T.; Campbell, D. M.; Lu, T. M.; Koepke, J. C.; Scrymgeour, D. A.; Bussmann, E.; Misra, S.

    2017-11-01

    We describe an all-optical lithography process that can make electrical contact to nanometer-precision donor devices fabricated in silicon using scanning tunneling microscopy (STM). This is accomplished by implementing a cleaning procedure in the STM that allows the integration of metal alignment marks and ion-implanted contacts at the wafer level. Low-temperature transport measurements of a patterned device establish the viability of the process.

  17. Direct control and characterization of a Schottky barrier by scanning tunneling microscopy

    NASA Technical Reports Server (NTRS)

    Bell, L. D.; Kaiser, W. J.; Hecht, M. H.; Grunthaner, F. J.

    1988-01-01

    Scanning tunneling microscopy (STM) methods are used to directly control the barrier height of a metal tunnel tip-semiconductor tunnel junction. Barrier behavior is measured by tunnel current-voltage spectroscopy and compared to theory. A unique surface preparation method is used to prepare a low surface state density Si surface. Control of band bending with this method enables STM investigation of semiconductor subsurface properties.

  18. Nanoscale Structural Changes Upon Electrooxidation of Au(111) as Probed by Potentiodynamic Scanning Tunneling Microscopy

    DTIC Science & Technology

    1994-02-01

    electrochemical formation and removal of oxide films is of broadbased practical as well as fundamental importance. Studies of noble metals, such as gold and...atomic level. At the current state of development of STM, monocrystalline gold electrodes provide efficacious choices of systems, partly in view of...several in-situ STM studies have focussed on the surface morphological changes attending oxidation and rereduction of single-crystal gold electrodes

  19. An outbreak of Salmonella Typhimurium phage type 42 associated with the consumption of raw flour.

    PubMed

    McCallum, Lisa; Paine, Shevaun; Sexton, Kerry; Dufour, Muriel; Dyet, Kristin; Wilson, Maurice; Campbell, Donald; Bandaranayake, Don; Hope, Virginia

    2013-02-01

    A cluster of salmonellosis cases caused by Salmonella Typhimurium phage type 42 (STM42) emerged in New Zealand in October 2008. STM42 isolates from a wheat-based poultry feed raw material (broll; i.e., product containing wheat flour and particles of grain) had been identified in the 2 months prior to this cluster. Initial investigations indicated that eating uncooked baking mixture was associated with illness. A case-control study was conducted to test the hypothesis that there was an association between STM42 cases and consumption of raw flour or other baking ingredients. Salmonella isolates from human and non-human sources were compared using pulsed-field gel electrophoresis (PFGE) and multiple-locus variable number tandem repeat analysis (MLVA). Environmental investigations included testing flour and other baking ingredients from case homes, unopened bags of flour purchased from retail stores, and inspection of an implicated flour mill. A case-control study of 39 cases and 66 controls found cases had 4.5 times the odds of consuming uncooked baking mixture as controls (95% confidence interval [CI] 1.6-12.5, p-value 0.001). Examination of individual baking ingredients found that, after adjusting for eggs, flour had an odds ratio (OR) of 5.7 (95% CI 1.1-29.1, p-value 0.035). After adjusting for flour, eggs had an OR of 0.8 (95% CI 0.2-3.4, p-value 0.762). PFGE patterns were identical for all STM42 isolates tested; however, MLVA distinguished isolates that were epidemiologically linked to the cluster. STM42 was recovered from flour taken from four cases' homes, two unopened packs purchased from retail stores and packs from three batches of retrieved (recalled) product. This outbreak was associated with the consumption of uncooked baking mixture containing flour contaminated with STM42. The implicated flour mill initiated a voluntary withdrawal from sale of all batches of flour thought to be contaminated. Media releases informed the public about implicated flour

  20. The approximate number system and domain-general abilities as predictors of math ability in children with normal hearing and hearing loss.

    PubMed

    Bull, Rebecca; Marschark, Marc; Nordmann, Emily; Sapere, Patricia; Skene, Wendy A

    2018-06-01

    Many children with hearing loss (CHL) show a delay in mathematical achievement compared to children with normal hearing (CNH). This study examined whether there are differences in acuity of the approximate number system (ANS) between CHL and CNH, and whether ANS acuity is related to math achievement. Working memory (WM), short-term memory (STM), and inhibition were considered as mediators of any relationship between ANS acuity and math achievement. Seventy-five CHL were compared with 75 age- and gender-matched CNH. ANS acuity, mathematical reasoning, WM, and STM of CHL were significantly poorer compared to CNH. Group differences in math ability were no longer significant when ANS acuity, WM, or STM was controlled. For CNH, WM and STM fully mediated the relationship of ANS acuity to math ability; for CHL, WM and STM only partially mediated this relationship. ANS acuity, WM, and STM are significant contributors to hearing status differences in math achievement, and to individual differences within the group of CHL. Statement of contribution What is already known on this subject? Children with hearing loss often perform poorly on measures of math achievement, although there have been few studies focusing on basic numerical cognition in these children. In typically developing children, the approximate number system predicts math skills concurrently and longitudinally, although there have been some contradictory findings. Recent studies suggest that domain-general skills, such as inhibition, may account for the relationship found between the approximate number system and math achievement. What does this study adds? This is the first robust examination of the approximate number system in children with hearing loss, and the findings suggest poorer acuity of the approximate number system in these children compared to hearing children. The study addresses recent issues regarding the contradictory findings of the relationship of the approximate number system to math ability

  1. Scanning Tunneling Optical Resonance Microscopy

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila; Wilt, Dave; Raffaelle, Ryne; Gennett, Tom; Tin, Padetha; Lau, Janice; Castro, Stephanie; Jenkins, Philip; Scheiman, Dave

    2003-01-01

    Scanning tunneling optical resonance microscopy (STORM) is a method, now undergoing development, for measuring optoelectronic properties of materials and devices on the nanoscale by means of a combination of (1) traditional scanning tunneling microscopy (STM) with (2) tunable laser spectroscopy. In STORM, an STM tip probing a semiconductor is illuminated with modulated light at a wavelength in the visible-to-near-infrared range and the resulting photoenhancement of the tunneling current is measured as a function of the illuminating wavelength. The photoenhancement of tunneling current occurs when the laser photon energy is sufficient to excite charge carriers into the conduction band of the semiconductor. Figure 1 schematically depicts a proposed STORM apparatus. The light for illuminating the semiconductor specimen at the STM would be generated by a ring laser that would be tunable across the wavelength range of interest. The laser beam would be chopped by an achromatic liquid-crystal modulator. A polarization-maintaining optical fiber would couple the light to the tip/sample junction of a commercial STM. An STM can be operated in one of two modes: constant height or constant current. A STORM apparatus would be operated in the constant-current mode, in which the height of the tip relative to the specimen would be varied in order to keep the tunneling current constant. In this mode, a feedback control circuit adjusts the voltage applied to a piezoelectric actuator in the STM that adjusts the height of the STM tip to keep the tunneling current constant. The exponential relationship between the tunneling current and tip-to-sample distance makes it relatively easy to implement this mode of operation. The choice of method by which the photoenhanced portion of the tunneling current would be measured depends on choice of the frequency at which the input illumination would be modulated (chopped). If the frequency of modulation were low enough (typically < 10 Hz) that the

  2. Imaging sequential dehydrogenation of methanol on Cu(110) with a scanning tunneling microscope.

    PubMed

    Kitaguchi, Y; Shiotari, A; Okuyama, H; Hatta, S; Aruga, T

    2011-05-07

    Adsorption of methanol and its dehydrogenation on Cu(110) were studied by using a scanning tunneling microscope (STM). Upon adsorption at 12 K, methanol preferentially forms clusters on the surface. The STM could induce dehydrogenation of methanol sequentially to methoxy and formaldehyde. This enabled us to study the binding structures of these products in a single-molecule limit. Methoxy was imaged as a pair of protrusion and depression along the [001] direction. This feature is fully consistent with the previous result that it adsorbs on the short-bridge site with the C-O axis tilted along the [001] direction. The axis was induced to flip back and forth by vibrational excitations with the STM. Two configurations were observed for formaldehyde, whose structures were proposed based on their characteristic images and motions.

  3. An easy-to-implement filter for separating photo-excited signals from topography in scanning tunneling microscopy.

    PubMed

    Wang, Kangkang; Rosenmann, Daniel; Holt, Martin; Winarski, Robert; Hla, Saw-Wai; Rose, Volker

    2013-06-01

    In order to achieve elemental and chemical sensitivity in scanning tunneling microscopy (STM), synchrotron x-rays have been applied to excite core-level electrons during tunneling. The x-ray photo-excitations result in tip currents that are superimposed onto conventional tunneling currents. While carrying important physical information, the varying x-ray induced currents can destabilize the feedback loop causing it to be unable to maintain a constant tunneling current, sometimes even causing the tip to retract fully or crash. In this paper, we report on an easy-to-implement filter circuit that can separate the x-ray induced currents from conventional tunneling currents, thereby allowing simultaneous measurements of topography and chemical contrasts. The filter and the schematic presented here can also be applied to other variants of light-assisted STM such as laser STM.

  4. Bayesian spatial transformation models with applications in neuroimaging data

    PubMed Central

    Miranda, Michelle F.; Zhu, Hongtu; Ibrahim, Joseph G.

    2013-01-01

    Summary The aim of this paper is to develop a class of spatial transformation models (STM) to spatially model the varying association between imaging measures in a three-dimensional (3D) volume (or 2D surface) and a set of covariates. Our STMs include a varying Box-Cox transformation model for dealing with the issue of non-Gaussian distributed imaging data and a Gaussian Markov Random Field model for incorporating spatial smoothness of the imaging data. Posterior computation proceeds via an efficient Markov chain Monte Carlo algorithm. Simulations and real data analysis demonstrate that the STM significantly outperforms the voxel-wise linear model with Gaussian noise in recovering meaningful geometric patterns. Our STM is able to reveal important brain regions with morphological changes in children with attention deficit hyperactivity disorder. PMID:24128143

  5. Adsorbed states of chlorophenol on Cu(110) and controlled switching of single-molecule junctions

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

    Okuyama, H., E-mail: hokuyama@kuchem.kyoto-u.ac.jp; Kitaguchi, Y.; Hattori, T.

    A molecular junction of substituted benzene (chlorophenol) is fabricated and controlled by using a scanning tunneling microscope (STM). Prior to the junction formation, the bonding geometry of the molecule on the surface is characterized by STM and electron energy loss spectroscopy (EELS). EELS shows that the OH group of chlorophenol is dissociated on Cu(110) and that the molecule is bonded nearly flat to the surface via an O atom, with the Cl group intact. We demonstrate controlled contact of an STM tip to the “available” Cl group and lift-up of the molecule while it is anchored to the surface viamore » an O atom. The asymmetric bonding motifs of the molecule to the electrodes allow for reversible control of the junction.« less

  6. All-optical lithography process for contacting nanometer precision donor devices

    DOE PAGES

    Ward, Daniel Robert; Marshall, Michael Thomas; Campbell, DeAnna Marie; ...

    2017-11-06

    In this article, we describe an all-optical lithography process that can make electrical contact to nanometer-precision donor devices fabricated in silicon using scanning tunneling microscopy (STM). This is accomplished by implementing a cleaning procedure in the STM that allows the integration of metal alignment marks and ion-implanted contacts at the wafer level. Low-temperature transport measurements of a patterned device establish the viability of the process.

  7. All-optical lithography process for contacting nanometer precision donor devices

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

    Ward, Daniel Robert; Marshall, Michael Thomas; Campbell, DeAnna Marie

    In this article, we describe an all-optical lithography process that can make electrical contact to nanometer-precision donor devices fabricated in silicon using scanning tunneling microscopy (STM). This is accomplished by implementing a cleaning procedure in the STM that allows the integration of metal alignment marks and ion-implanted contacts at the wafer level. Low-temperature transport measurements of a patterned device establish the viability of the process.

  8. Postscript: Through TCM, STM Shines Bright

    ERIC Educational Resources Information Center

    Davelaar, Eddy J.; Usher, Marius; Haarmann, Henk J.; Goshen-Gottstein, Yonatan

    2008-01-01

    We find the reply by Kahana, Sederberg, and Howard helpful in clarifying the temporal-context model (TCM) function, in particular with regard to the elimination of the recency effect by a difficult distractor under parameters that still enable long-term contiguity effects to emerge. We agree with Kahana et al. that what matters most to the…

  9. A one-day education in soft tissue massage: experiences and opinions as evaluated by nursing staff in palliative care.

    PubMed

    Cronfalk, Berit Seiger; Friedrichsen, Maria; Milberg, Anna; Strang, Peter

    2008-06-01

    Increasing awareness of well-being aspects of physical touch has spurred the appreciation for soft tissue massage (STM) as part of palliative care. Educational programs are available but with no specific focus on utilization for this kind of care. The aim was to study the feasibility of a 1-day course in STM in clarifying nursing staff's experiences and opinions, but also to shed light on their motivation and ability to employ STM in the care of dying cancer patients. In all, 135 nursing staff participated. The course consisted of theory and hands-on training (hand-foot-, back massage). Focus-groups with 30/135 randomly chosen participants were conducted 4 weeks after the intervention. This study engaged a qualitative approach using content analysis. The overall opinion of the 1-day course was positive. The majority experienced the contents of the course to be adequate and sufficient for clinical care. They emphasized the pedagogical expertise as valuable for the learning process. The majority of nurses shared the opinion that their extended knowledge clarified their attitudes on STM as a complement in palliative care. Still, a few found it to be too basic and/or intimate. Three categories emerged during the analysis: experiences of and attitudes toward the education, experiences of implementing the skills in every-day care situations, and attitudes to the physical body in nursing care. The approach to learning and the pedagogical skills of the teacher proved to be of importance for how new knowledge was perceived among nurses. The findings may encourage hospital organizations to introduce short courses in STM as an alternative to more extensive education.

  10. Selective Transfer Machine for Personalized Facial Expression Analysis

    PubMed Central

    Chu, Wen-Sheng; De la Torre, Fernando; Cohn, Jeffrey F.

    2017-01-01

    Automatic facial action unit (AU) and expression detection from videos is a long-standing problem. The problem is challenging in part because classifiers must generalize to previously unknown subjects that differ markedly in behavior and facial morphology (e.g., heavy versus delicate brows, smooth versus deeply etched wrinkles) from those on which the classifiers are trained. While some progress has been achieved through improvements in choices of features and classifiers, the challenge occasioned by individual differences among people remains. Person-specific classifiers would be a possible solution but for a paucity of training data. Sufficient training data for person-specific classifiers typically is unavailable. This paper addresses the problem of how to personalize a generic classifier without additional labels from the test subject. We propose a transductive learning method, which we refer as a Selective Transfer Machine (STM), to personalize a generic classifier by attenuating person-specific mismatches. STM achieves this effect by simultaneously learning a classifier and re-weighting the training samples that are most relevant to the test subject. We compared STM to both generic classifiers and cross-domain learning methods on four benchmarks: CK+ [44], GEMEP-FERA [67], RU-FACS [4] and GFT [57]. STM outperformed generic classifiers in all. PMID:28113267

  11. Is the word-length effect linked to subvocal rehearsal?

    PubMed

    Jacquemot, Charlotte; Dupoux, Emmanuel; Bachoud-Lévi, Anne-Catherine

    2011-04-01

    Models of phonological short-term memory (pSTM) generally distinguish between two components: a phonological buffer and a subvocal rehearsal. Evidence for these two components comes, respectively, from the phonological similarity effect and the word-length effect which disappears under articulatory suppression. But alternative theories posit that subvocal rehearsal is only an optional component of the pSTM. According to them, the depletion of the length effect under articulatory suppression results from the interference of the self-produced speech rather than the disruption of subvocal rehearsal. In order to disentangle these two theories, we tested two patients with a short-term memory deficit. FA, who presents a pseudoword repetition deficit, and FL, who does not. FA's deficit allowed for the observance of an ecological case of subvocal rehearsal disruption without any articulatory suppression task. FA's performance in pSTM tasks reveals as controls a phonological similarity effect, and contrary to controls no word-length effect. In contrast, the second patient, FL, exhibits the same effects as control subjects. This result is in accordance with models of pSTM in which the word-length effect emerges from subvocal rehearsal and disappears when this latter is disrupted. Copyright © 2010 Elsevier Srl. All rights reserved.

  12. A System for True and False Memory Prediction Based on 2D and 3D Educational Contents and EEG Brain Signals.

    PubMed

    Bamatraf, Saeed; Hussain, Muhammad; Aboalsamh, Hatim; Qazi, Emad-Ul-Haq; Malik, Amir Saeed; Amin, Hafeez Ullah; Mathkour, Hassan; Muhammad, Ghulam; Imran, Hafiz Muhammad

    2016-01-01

    We studied the impact of 2D and 3D educational contents on learning and memory recall using electroencephalography (EEG) brain signals. For this purpose, we adopted a classification approach that predicts true and false memories in case of both short term memory (STM) and long term memory (LTM) and helps to decide whether there is a difference between the impact of 2D and 3D educational contents. In this approach, EEG brain signals are converted into topomaps and then discriminative features are extracted from them and finally support vector machine (SVM) which is employed to predict brain states. For data collection, half of sixty-eight healthy individuals watched the learning material in 2D format whereas the rest watched the same material in 3D format. After learning task, memory recall tasks were performed after 30 minutes (STM) and two months (LTM), and EEG signals were recorded. In case of STM, 97.5% prediction accuracy was achieved for 3D and 96.6% for 2D and, in case of LTM, it was 100% for both 2D and 3D. The statistical analysis of the results suggested that for learning and memory recall both 2D and 3D materials do not have much difference in case of STM and LTM.

  13. Mirror buckling of freestanding graphene membranes induced by local heating due to a scanning tunneling microscope tip

    NASA Astrophysics Data System (ADS)

    Schoelz, J. K.; Neek Amal, M.; Xu, P.; Barber, S. D.; Ackerman, M. L.; Thibado, P. M.; Sadeghi, A.; Peeters, F. M.

    2014-03-01

    Scanning tunneling microscopy has been an invaluable tool in the study of graphene at the atomic scale. Several STM groups have managed to obtain atomic scale images of freestanding graphene membranes providing insight into the behavior of the stabilized ripple geometry. However, we found that the interaction between the STM tip and the freestanding graphene sample may induce additional effects. By varying the tunneling parameters, we can tune the position of the sample, in either a smooth or step like fashion. These phenomena were investigated by STM experiments, continuum elasticity theory and large scale molecular dynamics simulations. These results confirm that by increasing the tip bias, the electrostatic attraction between the tip and sample increases. When applied on a concave surface, this can result in mirror buckling which leads to a large scale movement of the sample. Interestingly, due in part to the negative coefficient of thermal expansion of graphene, buckling transitions can also be induced through local heating of the surface using the STM tip. Financial support by O.N.R. grant N00014-10-1-0181, N.S.F grant DMR-0855358, EU-Marie Curie IIF postdoc Fellowship/299855 (for M. N. A.), ESF-EuroGRAPHENE project CONGRAN, F.S.F (FWO-Vl), and Methusalem Foundation of the Flemish Government.

  14. Visual Short-Term Memory Compared in Rhesus Monkeys and Humans

    PubMed Central

    Elmore, L. Caitlin; Ma, Wei Ji; Magnotti, John F.; Leising, Kenneth J.; Passaro, Antony D.; Katz, Jeffrey S.; Wright, Anthony A.

    2011-01-01

    Summary Change detection is a popular task to study visual short-term memory (STM) in humans [1–4]. Much of this work suggests that STM has a fixed capacity of 4 ± 1 items [1–6]. Here we report the first comparison of change detection memory between humans and a species closely related to humans, the rhesus monkey. Monkeys and humans were tested in nearly identical procedures with overlapping display sizes. Although the monkeys’ STM was well fit by a 1-item fixed-capacity memory model, other monkey memory tests with 4-item lists have shown performance impossible to obtain with a 1-item capacity [7]. We suggest that this contradiction can be resolved using a continuous-resource approach more closely tied to the neural basis of memory [8,9]. In this view, items have a noisy memory representation whose noise level depends on display size due to distributed allocation of a continuous resource. In accord with this theory, we show that performance depends on the perceptual distance between items before and after the change, and d′ depends on display size in an approximately power law fashion. Our results open the door to combining the power of psychophysics, computation, and physiology to better understand the neural basis of STM. PMID:21596568

  15. Investigating ultraflexible freestanding graphene by scanning tunneling microscopy and spectroscopy

    NASA Astrophysics Data System (ADS)

    Breitwieser, R.; Hu, Yu-Cheng; Chao, Yen Cheng; Tzeng, Yi Ren; Liou, Sz-Chian; Lin, Keng Ching; Chen, Chih Wei; Pai, Woei Wu

    2017-08-01

    A strictly two-dimensional (2D) material such as freestanding graphene (FSG) is rarely investigated at the atomic scale by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). A basic difficulty in probing FSG by STM and STS is the mechanical instability when a highly compliant 2D atomic layer interacts with a proximal tip. Here we report a detailed method to conduct reliable STM and STS on FSG with atomic precision. We found that FSG is intrinsically rippled and exhibits a nonlinear strain-stress relation under applied normal forces; it shows a very soft region of bending strain and stiffer regions of in-plane tensile strain once the nanoscale ripples of FSG are eliminated. The elimination of the nanoripples can be controlled by tip-induced pulling or pushing force through the so-called closed-loop Z-V STS mode which can monitor the FSG deformation. A key factor for controllable STM and STS measurements is to select tunneling set points to place FSG in metastable configurations, as determined from stress-strain (i.e., Z-V) response. Atomic imaging and electronic states thus measured must be interpreted by considering the dynamical deformation of FSG as tunneling parameters, and therefore tip-FSG forces, are varied.

  16. Gazetteer of El Salvador,

    DTIC Science & Technology

    1982-06-01

    Cerro HLL 13 22’N 88 02’W ES07 CK87 ND16-10 H r ’t Cerru Mee El Garrobal. Loma MT 1338’N 88󈧗’W ES09 CL50 ND16-10(;,rzas., A’i- see Taisihuat, Rio STM...t’fias. RHi see Las Pifias, Rio STM 13 38’N 87 52"W ES07 DLOO ND16 IC I’iia.. Riode: see Las Pifias, Rio STM 13 38’N 87 52W ES07 DLOC ND6-1 Pineda PPL...ND16-10 San JoaqUljn, Cerro MT 13 50’N 88 39’W ES02 CL22 ND16-09 ’ n11m l𔃺 .IL-hotes. ,uebrada.- Mee La l)escabezada. Quebrada STMI 13 45’N 89 40W

  17. Real-space and real-time observation of a plasmon-induced chemical reaction of a single molecule.

    PubMed

    Kazuma, Emiko; Jung, Jaehoon; Ueba, Hiromu; Trenary, Michael; Kim, Yousoo

    2018-05-04

    Plasmon-induced chemical reactions of molecules adsorbed on metal nanostructures are attracting increased attention for photocatalytic reactions. However, the mechanism remains controversial because of the difficulty of direct observation of the chemical reactions in the plasmonic field, which is strongly localized near the metal surface. We used a scanning tunneling microscope (STM) to achieve real-space and real-time observation of a plasmon-induced chemical reaction at the single-molecule level. A single dimethyl disulfide molecule on silver and copper surfaces was dissociated by the optically excited plasmon at the STM junction. The STM study combined with theoretical calculations shows that this plasmon-induced chemical reaction occurred by a direct intramolecular excitation mechanism. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  18. Vibration compensation for high speed scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Croft, D.; Devasia, S.

    1999-12-01

    Low scanning speed is a fundamental limitation of scanning tunneling microscopes (STMs), making real time imaging of surface processes and nanofabrication impractical. The effective scanning bandwidth is currently limited by the smallest resonant vibrational frequency of the piezobased positioning system (i.e., scanner) used in the STM. Due to this limitation, the acquired images are distorted during high speed operations. In practice, the achievable scan rates are much less than 1/10th of the resonant vibrational frequency of the STM scanner. To alleviate the scanning speed limitation, this article describes an inversion-based approach that compensates for the structural vibrations in the scanner and thus, allows STM imaging at high scanning speeds (relative to the smallest resonant vibrational frequency). Experimental results are presented to show the increase in scanning speeds achievable by applying the vibration compensation methods.

  19. A high-stability scanning tunneling microscope achieved by an isolated tiny scanner with low voltage imaging capability.

    PubMed

    Wang, Qi; Hou, Yubin; Wang, Junting; Lu, Qingyou

    2013-11-01

    We present a novel homebuilt scanning tunneling microscope (STM) with high quality atomic resolution. It is equipped with a small but powerful GeckoDrive piezoelectric motor which drives a miniature and detachable scanning part to implement coarse approach. The scanning part is a tiny piezoelectric tube scanner (industry type: PZT-8, whose d31 coefficient is one of the lowest) housed in a slightly bigger polished sapphire tube, which is riding on and spring clamped against the knife edges of a tungsten slot. The STM so constructed shows low back-lashing and drifting and high repeatability and immunity to external vibrations. These are confirmed by its low imaging voltages, low distortions in the spiral scanned images, and high atomic resolution quality even when the STM is placed on the ground of the fifth floor without any external or internal vibration isolation devices.

  20. A combined scanning tunneling microscope-atomic layer deposition tool.

    PubMed

    Mack, James F; Van Stockum, Philip B; Iwadate, Hitoshi; Prinz, Fritz B

    2011-12-01

    We have built a combined scanning tunneling microscope-atomic layer deposition (STM-ALD) tool that performs in situ imaging of deposition. It operates from room temperature up to 200 °C, and at pressures from 1 × 10(-6) Torr to 1 × 10(-2) Torr. The STM-ALD system has a complete passive vibration isolation system that counteracts both seismic and acoustic excitations. The instrument can be used as an observation tool to monitor the initial growth phases of ALD in situ, as well as a nanofabrication tool by applying an electric field with the tip to laterally pattern deposition. In this paper, we describe the design of the tool and demonstrate its capability for atomic resolution STM imaging, atomic layer deposition, and the combination of the two techniques for in situ characterization of deposition.

  1. Imaging single spin probes embedded in a conductive diamagnetic layer.

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

    Messina, P.; Fradin, F.

    2009-01-01

    The detection of spin noise by means of scanning tunneling microscopy (STM) has recently been substantially improved by the work presented by Komeda and Manassen (Komeda, T.; Manassen, Y. Appl. Phys. Lett. 2008, 92, 212506). The application of this technique to molecular paramagnets requires the positioning and anchoring of paramagnetic molecules at surfaces. It also requires the possibility of tunneling high current densities into the STM-molecule-substrate tunneling junction. In this letter, we exploit the self-assembly of 1,10-phenantroline on the Au(111) surface to form a diamagnetic matrix that hosts individual molecules and dimers of diphenyl-2-picryl-hydrazyl (DPPH). STM measurements are used tomore » characterize the molecular layer. Electron spin resonance (ESR) measurements elucidate the role of thermal annealing in the preservation of the paramagnetic nature of the DPPH molecules.« less

  2. Visualizing electron pockets in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Das, Tanmoy; Markiewicz, R. S.; Bansil, A.; Balatsky, A. V.

    2012-06-01

    Fingerprints of the electron pocket in cuprates have been obtained only in numerous magnetotransport measurements, but its absence in spectroscopic observations poses a long-standing mystery. We develop a theoretical tool to provide ways to detect electron pockets via spectroscopies including scanning tunneling microscopy (STM) spectra, inelastic neutron scattering (INS), and angle-resolved photoemission spectroscopy (ARPES). We show that the quasiparticle-interference (QPI) pattern, measured by STM, shows an additional seven q vectors associated with the scattering on the electron pocket than that on the hole pocket. Furthermore, the Bogolyubov quasiparticle scatterings of the electron pocket lead to a second magnetic resonance mode in the INS spectra at a higher resonance energy. Finally, we reanalyze some STM, INS, and ARPES experimental data of several cuprates which dictates the direct fingerprints of electron pockets in these systems.

  3. An easy-to-implement filter for separating photo-excited signals from topography in scanning tunneling microscopy

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

    Wang Kangkang; Rosenmann, Daniel; Holt, Martin

    2013-06-15

    In order to achieve elemental and chemical sensitivity in scanning tunneling microscopy (STM), synchrotron x-rays have been applied to excite core-level electrons during tunneling. The x-ray photo-excitations result in tip currents that are superimposed onto conventional tunneling currents. While carrying important physical information, the varying x-ray induced currents can destabilize the feedback loop causing it to be unable to maintain a constant tunneling current, sometimes even causing the tip to retract fully or crash. In this paper, we report on an easy-to-implement filter circuit that can separate the x-ray induced currents from conventional tunneling currents, thereby allowing simultaneous measurements ofmore » topography and chemical contrasts. The filter and the schematic presented here can also be applied to other variants of light-assisted STM such as laser STM.« less

  4. Scanning tunneling microscopy study of low temperature silicon epitaxy on hydrogen/silicon(001) and phosphine adsorption on silicon(111)-7x7

    NASA Astrophysics Data System (ADS)

    Ji, Jeong-Young

    A three-chamber ultra-high-vacuum (UHV) system with preparation, scanning tunneling microscopy (STM), and chemical vapor deposition (CVD) chambers was designed and built. Here, one can perform surface preparation, STM e-beam lithography, precursor gas dosing, ion sputtering, silicon epitaxy, and various measurements such as reflection high energy electron diffraction (RHEED), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES). Processes performed in the ultra-clean preparation and gas-filled CVD chambers can be monitored by transferring the samples back to the STM chamber to take topographical images. Si deposition on H-terminated Si(001)-2x1 surfaces at temperatures 300--530 K was studied by scanning tunneling microscopy. Hydrogen apparently hinders Si adatom diffusion and enhances surface roughening. Post-growth annealing transfers the top layer atoms downward to fill in vacancies in the lower layer, restoring the crystallinity of the thin film. Hydrogen is shown to remain on the growth front up to at least 10 ML. Si deposition onto the H/Si(001)-3x1 surface at 530 K suggests that dihydride units further suppress Si adatom diffusion and increase surface roughness. PH3 adsorption on Si(111)-7x7 was studied for various exposures between 0.3--60 L at room temperature by means of the scanning-tunneling-microscopy (STM). PH3-, PH2-, H-reacted, and unreacted adatoms can be identified by analyzing STM images at different sample biases. Most of PH3 adsorbs dissociatively on the surface at initial exposure, generating H and PH2 adsorption sites, followed by molecular adsorption of PH3. Rest atoms are more reactive than the adatoms and PH 2-reacted rest atom sites are also observed in STM images. Statistical analysis shows that center adatoms are more reactive than corner adatoms and the saturation P coverage is ˜0.22 ML. Finally, 900 K annealing of a PH 3 dosed surface results in a disordered, partially P-covered surface and PH3 dosing at 900 K

  5. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P [Los Alamos, NM; Chernobrod, Boris M [Los Alamos, NM

    2010-06-29

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  6. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P.; Chernobrod, Boris M.

    2009-11-10

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of impaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  7. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P.; Chernobrod, Boris M.

    2007-12-11

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  8. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P [Los Alamos, NM; Chernobrod, Boris M [Los Alamos, NM

    2010-07-13

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  9. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P [Los Alamos, NM; Chernobrod, Boris M [Los Alamos, NM

    2009-10-27

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  10. Vertically aligned nanowires from boron-doped diamond.

    PubMed

    Yang, Nianjun; Uetsuka, Hiroshi; Osawa, Eiji; Nebel, Christoph E

    2008-11-01

    Vertically aligned diamond nanowires with controlled geometrical properties like length and distance between wires were fabricated by use of nanodiamond particles as a hard mask and by use of reactive ion etching. The surface structure, electronic properties, and electrochemical functionalization of diamond nanowires were characterized by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) as well as electrochemical techniques. AFM and STM experiments show that diamond nanowire etched for 10 s have wire-typed structures with 3-10 nm in length and with typically 11 nm spacing in between. The electrode active area of diamond nanowires is enhanced by a factor of 2. The functionalization of nanowire tips with nitrophenyl molecules is characterized by STM on clean and on nitrophenyl molecule-modified diamond nanowires. Tip-modified diamond nanowires are promising with respect to biosensor applications where controlled biomolecule bonding is required to improve chemical stability and sensing significantly.

  11. Evidence against a charge density wave on Bi(111)

    DOE PAGES

    Kim, T. K.; Wells, J.; Kirkegaard, C.; ...

    2005-08-18

    The Bi(111) surface was studied by scanning tunneling microscopy (STM), transmission electron microscopy (TEM) and angle-resolved photoemission (ARPES) in order to verify the existence of a recently proposed surface charge density wave (CDW). The STM and TEM results to not support a CDW scenario at low temperatures. Thus the quasiparticle interference pattern observed in STM confirms the spin-orbit split character of the surface states which prevents the formation of a CDW, even in the case of good nesting. The dispersion of the electronic states observed with ARPES agrees well with earlier findings. In particular, the Fermi contour of the electronmore » pocket at the centre of the surface Brillouin zone is found to have a hexagonal shape. However, no gap opening or other signatures of a CDW phase transition can be found in the temperature-dependent data.« less

  12. High temperature growth of Pt on the Rh(111) surface

    NASA Astrophysics Data System (ADS)

    Duisberg, M.; Dräger, M.; Wandelt, K.; Gruber, E. L. D.; Schmid, M.; Varga, P.

    1999-08-01

    The epitaxial growth of Pt on the Rh(111) surface at 700 K was studied with AES, UPS, ISS and STM. From AES and ISS measurements a 2D growth mode is concluded at this substrate temperature. The morphology of the surface is studied by photoemission spectra of adsorbed Xe (PAX) and STM. A disperse distribution of the Pt atoms is suggested by PAX and is consistent with an incorporation of these atoms into the first substrate layer. Atomically and chemically resolved STM measurements confirm these conclusions. The interaction of CO with the surface alloy is investigated by UPS. The CO-induced features in UP spectra show significant differences in the peak positions and shape between the clean substrate and the surface precovered with different amounts of Pt. The CO induced emissions are, thus, used for a quantitative titration of Pt on the Rh surface.

  13. Controllable dissociations of PH3 molecules on Si(001)

    NASA Astrophysics Data System (ADS)

    Liu, Qin; Lei, Yanhua; Shao, Xiji; Ming, Fangfei; Xu, Hu; Wang, Kedong; Xiao, Xudong

    2016-04-01

    We demonstrate for the first time to our knowledge that controllable dissociation of PH3 adsorption products PH x (x = 2, 1) can be realized by STM (scanning tunneling microscope) manipulation techniques at room temperature. Five dissociative products and their geometric structures are identified via combining STM experiments and first-principle calculations and simulations. In total we realize nine kinds of controllable dissociations by applying a voltage pulse among the PH3-related structures on Si(001). The dissociation rates of the five most common reactions are measured by the I-t spectrum method as a function of voltage. The suddenly increased dissociation rate at 3.3 V indicates a transition from multivibrational excitation to single-step excitation induced by inelastic tunneling electrons. Our studies prove that selectively breaking the chemical bonds of a single molecule on semiconductor surface by STM manipulation technique is feasible.

  14. Candidate gene identification of ovulation-inducing genes by RNA sequencing with an in vivo assay in zebrafish.

    PubMed

    Klangnurak, Wanlada; Fukuyo, Taketo; Rezanujjaman, M D; Seki, Masahide; Sugano, Sumio; Suzuki, Yutaka; Tokumoto, Toshinobu

    2018-01-01

    We previously reported the microarray-based selection of three ovulation-related genes in zebrafish. We used a different selection method in this study, RNA sequencing analysis. An additional eight up-regulated candidates were found as specifically up-regulated genes in ovulation-induced samples. Changes in gene expression were confirmed by qPCR analysis. Furthermore, up-regulation prior to ovulation during natural spawning was verified in samples from natural pairing. Gene knock-out zebrafish strains of one of the candidates, the starmaker gene (stm), were established by CRISPR genome editing techniques. Unexpectedly, homozygous mutants were fertile and could spawn eggs. However, a high percentage of unfertilized eggs and abnormal embryos were produced from these homozygous females. The results suggest that the stm gene is necessary for fertilization. In this study, we selected additional ovulation-inducing candidate genes, and a novel function of the stm gene was investigated.

  15. Structure of high-index GaAs surfaces - the discovery of the stable GaAs(2511) surface

    NASA Astrophysics Data System (ADS)

    Jacobi, K.; Geelhaar, L.; Márquez, J.

    We present a brief overview of surface structures of high-index GaAs surfaces, putting emphasis on recent progress in our own laboratory. By adapting a commercial scanning tunneling microscope (STM) to our molecular beam epitaxy and ultra high vacuum analysis chamber system, we have been able to atomically resolve the GaAs( {1} {1} {3})B(8 ×1), (114)Aα2(2×1), (137), (3715), and (2511) surface structures. In cooperation with P. Kratzer and M. Scheffler from the Theory Department of the Fritz-Haber Institute we determined the structure of some of these surfaces by comparing total-energy calculations and STM image simulations with the atomically resolved STM images. We present the results for the {112}, {113}, and {114} surfaces. Then we describe what led us to proceed into the inner parts of the stereographic triangle and to discover the hitherto unknown stable GaAs(2511) surface.

  16. Direct observation for atomically flat and ordered vertical {111} side-surfaces on three-dimensionally figured Si(110) substrate using scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Yang, Haoyu; Hattori, Azusa N.; Ohata, Akinori; Takemoto, Shohei; Hattori, Ken; Daimon, Hiroshi; Tanaka, Hidekazu

    2017-11-01

    A three-dimensional Si{111} vertical side-surface structure on a Si(110) wafer was fabricated by reactive ion etching (RIE) followed by wet-etching and flash-annealing treatments. The side-surface was studied with scanning tunneling microscopy (STM) in atomic scale for the first time, in addition to atomic force microscopy (AFM), scanning electron microscopy (SEM), and low-energy electron diffraction (LEED). AFM and SEM showed flat and smooth vertical side-surfaces without scallops, and STM proved the realization of an atomically-flat 7 × 7-reconstructed structure, under optimized RIE and wet-etching conditions. STM also showed that a step-bunching occurred on the produced {111} side-surface corresponding to a reversely taped side-surface with a tilt angle of a few degrees, but did not show disordered structures. Characteristic LEED patterns from both side- and top-reconstructed surfaces were also demonstrated.

  17. Study of p-diaminobenzene Adsorption on Au(111) by Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Hui; Hu, Zonghai; Eom, Daejin; Rim, Kwang; Liu, Li; Flynn, George; Venkataraman, Latha; Morgante, Alberto; Heinz, Tony

    2008-03-01

    From the well-defined conductivity obtained for various individual diamino-substituted molecules spanning two gold contacts, as well as from theoretical analysis [1], researchers have suggested that amines adsorb preferentially to coordinatively unsaturated surface Au atoms through the N lone pair. To understand the nature of the amine binding, we have applied ultrahigh vacuum scanning tunneling microscope (STM) to investigate the adsorption of p-diaminobenzene molecules on the reconstructed Au(111) surface. The STM topography images (taken at 4 K) show that the molecules adsorb preferentially to step edges, corresponding to sites of reduced Au atom coordination. The adsorbed molecules are found to display a distinctive orientation along the step edges. The two-lobe topographic structure of each molecule seen by STM is compatible with the previously calculated charge density of the HOMO level. [1] L. Venkataraman at el., Nano Lett. 7, 502 (2007).

  18. Ecstasy (MDMA) and memory function: a meta-analytic update.

    PubMed

    Laws, Keith R; Kokkalis, Joy

    2007-08-01

    A meta-analysis was conducted to examine the impact of recreational ecstasy use on short-term memory (STM), long-term memory (LTM), verbal and visual memory. We located 26 studies containing memory data for ecstasy and non-ecstasy users from which effect sizes could be derived. The analyses provided measures of STM and LTM in 610 and 439 ecstasy users and revealed moderate-to-large effect sizes (Cohen's d) of d = -0.63 and d = -0.87, respectively. The difference between STM versus LTM was non-significant. The effect size for verbal memory was large (d = -1.00) and significantly larger than the small effect size for visual memory (d = -0.27). Indeed, our analyses indicate that visual memory may be affected more by concurrent cannabis use. Finally, we found that the total lifetime number of ecstasy tablets consumed did not significantly predict memory performance. Copyright 2007 John Wiley & Sons, Ltd.

  19. Association DENV1 and DENV2 infection with high serum levels of soluble thrombomodulin and VEGF in patients with dengue fever and dengue hemorrhagic fever.

    PubMed

    Del Moral-Hernández, Oscar; Martínez-Hernández, Norma E; Mosso-Pani, Manuel A; Hernández-Sotelo, Daniel; Illades-Aguiar, Berenice; Flores-Alfaro, Eugenia; Antonio-Vejar, Verónica; Leyva-Vázquez, Marco Antonio

    2014-01-01

    INFECTION BY DENGUE VIRUS (DENV) CAN BE ASYMPTOMATIC OR MANIFEST IN TWO CLINICALLY DIFFERENTIATED FORMS: dengue fever (DF) and denguehemorrhagic fever (DHF). The principal pathophysiological characteristic of DHF is the increase in vascular permeability and the loss of plasma caused by the malfunction of the vascular endothelium that induces the release of chemical mediators. However, so far there is nothing that allows for the identification the patients that are at risk of developing the more severe form of the illness. The objective of this study was to investigate the relationship between the serum levels of soluble thrombomodulin (sTM) and VEGF with the severity of dengue and the viral serotype. 231 serum samples were analyzed, 70 DF, 80 DHF and 81 control group, all were residents of Guerrero state in Mexico. The infection by dengue virus as well and the levels of sTM and VEGF were determined using the ELISA sandwich, while the serotype was determined by real time RT-PCR. Our results show that the concentrations of sTM correlate with the degree of severity of the disease given that they are significantly higher (p<0.001) in the DHF group (median = 10.2 ng/mL) than in the DF group (median = 7.2 ng/mL), and these in turn higher than those of the control group (median = 3.3 ng/mL). The concentration of sTM was significantly higher (p=0.0002) in the patients infected with DENV2. For the VEGF, the highest levels were found in DF (median = 291.3 pg/mL) and did not correlate with the severity of the disease. In conclusion, our results indicate that sTM is a good marker for the severity of the infection by DENV, better than VEGF, and with higher sensibility and specificity.

  20. Muscular patterns and activation levels of auxiliary breathing muscles and thorax movement in classical singing.

    PubMed

    Pettersen, Viggo

    2005-01-01

    The aim of this paper is to present an overview of the findings in seven studies exploring muscular patterns and muscle activation levels in selected muscles by classical singers. In addition, the relationship of these muscles to thorax (TX) movement was investigated. Loading levels and respiratory phasing of upper trapezius (TR), sternocleidomastoideus (STM) and the scalenes (SC) were investigated in vocalization tasks with variation in vocal loudness and pitch. Further, muscle activity in the posterior neck (PN) was investigated in inhalation and phonation and, finally, TR, intercostal (INT), lateral abdominal (OBL) and anterior abdominal (RC) muscle loading in student and professional singers was examined. Muscle activity was recorded by use of an ambulatory four-channel monitoring system (Physiometer PHY 400, Premed, Norway). TX movement was traced with two strain gauge sensors (RES-117) placed around the upper TX and lower TX. A phasing of upper TR activity to INT and OBL activity was discovered, all muscles supporting the expiration phase. During phonation, TR contributes in the compression of the upper TX, thus serving as an accessory muscle of expiration. TR activity is reduced with short breathing cycles and is mostly inactive in simplified speaking tasks. During phonation, professional opera singers activate the expiratory-phased TR, INT, OBL and RC muscles to higher levels than student singers do. STM and SC show correlated activity patterns during inhalation and phonation by classical singers. During demanding singing, expiratory-phased STM and SC activity peaks produce a counterforce to the compression of upper TX at high pitches. As breathing demands are lowered, STM and SC activity are reduced and attain inspiratory phasing. Substantial muscle activity is observed in PN during inhalation and phonation. EMG biofeedback performed on TR and STM have a secondary effect of lowering EMG activity in PN. (c) 2005 S. Karger AG, Basel

  1. Atomic-Scale Characterization and Manipulation of Freestanding Graphene Using Adapted Capabilities of a Scanning Tunneling Microscope

    NASA Astrophysics Data System (ADS)

    Barber, Steven

    Graphene was the first two-dimensional material ever discovered, and it exhibits many unusual phenomena important to both pure and applied physics. To ensure the purest electronic structure, or to study graphene's elastic properties, it is often suspended over holes or trenches in a substrate. The aim of the research presented in this dissertation was to develop methods for characterizing and manipulating freestanding graphene on the atomic scale using a scanning tunneling microscope (STM). Conventional microscopy and spectroscopy techniques must be carefully reconsidered to account for movement of the extremely flexible sample. First, the acquisition of atomic-scale images of freestanding graphene using the STM and the ability to pull the graphene perpendicular to its plane by applying an electrostatic force with the STM tip are demonstrated. The atomic-scale images contained surprisingly large corrugations due to the electrostatic attractive force varying in registry with the local density of states. Meanwhile, a large range of control over the graphene height at a point was obtained by varying the tip bias voltage, and the application to strain engineering of graphene's so-called pseudomagnetic field is examined. Next, the effect of the tunneling current was investigated. With increasing current, the graphene sample moves away from the tip rather than toward it. It was determined that this must be due to local heating by the electric current, causing the graphene to contract because it has a negative coefficient of thermal expansion. Finally, by imaging a very small area, the STM can monitor the height of one location over long time intervals. Results sometimes exhibit periodic behavior, with a frequency and amplitude that depend on the tunneling current. These fluctuations are interpreted as low-frequency flexural phonon modes within elasticity theory. All of these findings set the foundation for employing a STM in the study of freestanding graphene.

  2. Memory integration in amnesia: Prior knowledge supports verbal short-term memory

    PubMed Central

    Race, Elizabeth; Palombo, Daniela J.; Cadden, Margaret; Burke, Keely; Verfaellie, Mieke

    2015-01-01

    Short-term memory (STM) and long-term memory (LTM) have traditionally been considered cognitively distinct. However, it is known that STM can improve when to-be-remembered information appears in contexts that make contact with prior knowledge, suggesting a more interactive relationship between STM and LTM. The current study investigated whether the ability to leverage LTM in support of STM critically depends on the integrity of the hippocampus. Specifically, we investigated whether the hippocampus differentially supports between-domain versus within-domain STM–LTM integration given prior evidence that the representational domain of the elements being integrated in memory is a critical determinant of whether memory performance depends on the hippocampus. In Experiment 1, we investigated hippocampal contributions to within-domain STM–LTM integration by testing whether immediate verbal recall of words improves in MTL amnesic patients when words are presented in familiar verbal contexts (meaningful sentences) compared to unfamiliar verbal contexts (random word lists). Patients demonstrated a robust sentence superiority effect, whereby verbal STM performance improved in familiar compared to unfamiliar verbal contexts, and the magnitude of this effect did not differ from that in controls. In Experiment 2, we investigated hippocampal contributions to between-domain STM–LTM integration by testing whether immediate verbal recall of digits improves in MTL amnesic patients when digits are presented in a familiar visuospatial context (a typical keypad layout) compared to an unfamiliar visuospatial context (a random keypad layout). Immediate verbal recall improved in both patients and controls when digits were presented in the familiar compared to the unfamiliar keypad array, indicating a preserved ability to integrate activated verbal information with stored visuospatial knowledge. Together, these results demonstrate that immediate verbal recall in amnesia can benefit

  3. Effect of continuous positive airway pressure treatment on short-term memory performance over 24 h of sustained wakefulness in patients with obstructive sleep apnea-hypopnea syndrome.

    PubMed

    Grenèche, Jérôme; Krieger, Jean; Bertrand, Frédéric; Erhardt, Christine; Maumy, Myriam; Tassi, Patricia

    2013-10-01

    Few studies have examined the impact of continuous positive airway pressure (CPAP) therapy on short-term memory (STM) over sustained wakefulness in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). We have investigated if impaired STM can be reversed by CPAP treatment in a 24-h sustained wakefulness paradigm. Our follow-up study was conducted with repeated-memory tasks within 12 OSAHS patients and 10 healthy controls who underwent three 32-h sessions, one before CPAP (T0) and the second (T3) and the third (T6), after 3 and 6 months of treatment, respectively, for OSAHS patients. Each session included one night of sleep followed by 24h of sustained wakefulness, during which both groups performed STM tasks including both digit span (DS) and Sternberg tasks. Untreated OSAHS patients had no deficit in the forward DS task measuring immediate memory but were impaired in STM, especially working memory assessed by the complex Sternberg task and the backward DS. However, only performance in the latter was improved after 6 months of CPAP treatment. Because the high level of memory scanning required high speed in information processing, persistent impairment on the complex Sternberg task may be attributable to working memory slowing, possibly enhanced by sustained wakefulness. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

  4. A System for True and False Memory Prediction Based on 2D and 3D Educational Contents and EEG Brain Signals

    PubMed Central

    2016-01-01

    We studied the impact of 2D and 3D educational contents on learning and memory recall using electroencephalography (EEG) brain signals. For this purpose, we adopted a classification approach that predicts true and false memories in case of both short term memory (STM) and long term memory (LTM) and helps to decide whether there is a difference between the impact of 2D and 3D educational contents. In this approach, EEG brain signals are converted into topomaps and then discriminative features are extracted from them and finally support vector machine (SVM) which is employed to predict brain states. For data collection, half of sixty-eight healthy individuals watched the learning material in 2D format whereas the rest watched the same material in 3D format. After learning task, memory recall tasks were performed after 30 minutes (STM) and two months (LTM), and EEG signals were recorded. In case of STM, 97.5% prediction accuracy was achieved for 3D and 96.6% for 2D and, in case of LTM, it was 100% for both 2D and 3D. The statistical analysis of the results suggested that for learning and memory recall both 2D and 3D materials do not have much difference in case of STM and LTM. PMID:26819593

  5. Direct Visualization of Catalytically Active Sites at the FeO–Pt(111) Interface

    DOE PAGES

    Kudernatsch, Wilhelmine; Peng, Guowen; Zeuthen, Helene; ...

    2015-05-31

    Within the area of surface science, one of the “holy grails” is to directly visualize a chemical reaction at the atomic scale. Whereas this goal has been reached by high-resolution scanning tunneling microscopy (STM) in a number of cases for reactions occurring at flat surfaces, such a direct view is often inhibited for reaction occurring at steps and interfaces. Here we have studied the CO oxidation reaction at the interface between ultrathin FeO islands and a Pt(111) support by in situ STM and density functional theory (DFT) calculations. Time-lapsed STM imaging on this inverse model catalyst in O 2 andmore » CO environments revealed catalytic activity occurring at the FeO–Pt(111) interface and directly showed that the Fe-edges host the catalytically most active sites for the CO oxidation reaction. This is an important result since previous evidence for the catalytic activity of the FeO–Pt(111) interface is essentially based on averaging techniques in conjunction with DFT calculations. As a result, the presented STM results are in accord with DFT+U calculations, in which we compare possible CO oxidation pathways on oxidized Fe-edges and O-edges. We found that the CO oxidation reaction is more favorable on the oxidized Fe-edges, both thermodynamically and kinetically.« less

  6. Interact to Survive: Phyllobacterium brassicacearum Improves Arabidopsis Tolerance to Severe Water Deficit and Growth Recovery

    PubMed Central

    Bresson, Justine; Vasseur, François; Dauzat, Myriam; Labadie, Marc; Varoquaux, Fabrice; Touraine, Bruno; Vile, Denis

    2014-01-01

    Mutualistic bacteria can alter plant phenotypes and confer new abilities to plants. Some plant growth-promoting rhizobacteria (PGPR) are known to improve both plant growth and tolerance to multiple stresses, including drought, but reports on their effects on plant survival under severe water deficits are scarce. We investigated the effect of Phyllobacterium brassicacearum STM196 strain, a PGPR isolated from the rhizosphere of oilseed rape, on survival, growth and physiological responses of Arabidopsis thaliana to severe water deficits combining destructive and non-destructive high-throughput phenotyping. Soil inoculation with STM196 greatly increased the survival rate of A. thaliana under several scenarios of severe water deficit. Photosystem II efficiency, assessed at the whole-plant level by high-throughput fluorescence imaging (F v/F m), was related to the probability of survival and revealed that STM196 delayed plant mortality. Inoculated surviving plants tolerated more damages to the photosynthetic tissues through a delayed dehydration and a better tolerance to low water status. Importantly, STM196 allowed a better recovery of plant growth after rewatering and stressed plants reached a similar biomass at flowering than non-stressed plants. Our results highlight the importance of plant-bacteria interactions in plant responses to severe drought and provide a new avenue of investigations to improve drought tolerance in agriculture. PMID:25226036

  7. Ab initio simulations of scanning-tunneling-microscope images with embedding techniques and application to C58-dimers on Au(111).

    PubMed

    Wilhelm, Jan; Walz, Michael; Stendel, Melanie; Bagrets, Alexei; Evers, Ferdinand

    2013-05-14

    We present a modification of the standard electron transport methodology based on the (non-equilibrium) Green's function formalism to efficiently simulate STM-images. The novel feature of this method is that it employs an effective embedding technique that allows us to extrapolate properties of metal substrates with adsorbed molecules from quantum-chemical cluster calculations. To illustrate the potential of this approach, we present an application to STM-images of C58-dimers immobilized on Au(111)-surfaces that is motivated by recent experiments.

  8. Characterization of Used MIL-L-7808 Lubricants.

    DTIC Science & Technology

    1985-05-01

    Gravimetric Finish 20 2.3.3 Separation of Mineral Oil by means of Sulphuric Acid 21 2.3.4 Rolls-Royce Method 1032 26 2.3.5 Conclusion 26 3 Minimum...and STM No. 1 i Application of Sulphuric Acid Method for MOC to:- IV Standards based upon ATL.9100 23 V Standards based upon ATL.9101 24 VI Standards...total acid numbers of the standards before, and after application of each technique. Considering firstly the volatile contaminant contents obtained by STM

  9. A Tandem Microscopic-Electrochemical Examination of A Charge-Induced Surface Phase Sequence: Ordered Au(110) in Aqueous Iodide Electrolytes as Probed by Potentiodynamic Scanning Tunneling Microscopy

    DTIC Science & Technology

    1994-02-01

    and Rh(lll)9-12 by STM, and halides on Au(lll) by SXRS. 1 3 ’ 1 4 For several of these systems, especially anion adsorption on gold , the adsorbate...index faces of gold in aqueous solution by means of in- situ STM combined with conventional electrochemical methods. The value of the electrochemical...structure and conversion dynamics. A related description of the Au(lO0)-I- system, along with a comparison with the behavior of the other two low-index gold

  10. On the structural and electronic properties of Ir-silicide nanowires on Si(001) surface

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

    Fatima,; Hossain, Sehtab; Mohottige, Rasika

    Iridium (Ir) modified Silicon (Si) (001) surface is studied with Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and Density Functional Theory (DFT). A model for Ir-silicide nanowires based on STM images and ab-initio calculations is proposed. According to our model, the Ir adatom is on the top of the substrate dimer row and directly binds to the dimer atoms. I-V curves measured at 77 K shows that the nanowires are metallic. DFT calculations confirm strong metallic nature of the nanowires.

  11. Growth and Electronic Structure of Heusler Compounds for Use in Electron Spin Based Devices

    DTIC Science & Technology

    2015-06-01

    either Co– or MnSi– initiated films on c(4x4) GaAs. Studies using x - ray photoemission spectroscopy (XPS), STM/STS, and transmission electron microscopy...Co– or MnSi– initiated films on c(4x4) GaAs. Studies using x - ray photoemission spectroscopy (XPS), STM/STS, and transmission electron microscopy (TEM...diagram of the Palmstrøm lab in-situ growth and char- acterization setup, with 6 MBE growth chambers, 3 scanning probe microscopes, an x - ray

  12. Neural correlates of auditory short-term memory in rostral superior temporal cortex

    PubMed Central

    Scott, Brian H.; Mishkin, Mortimer; Yin, Pingbo

    2014-01-01

    Summary Background Auditory short-term memory (STM) in the monkey is less robust than visual STM and may depend on a retained sensory trace, which is likely to reside in the higher-order cortical areas of the auditory ventral stream. Results We recorded from the rostral superior temporal cortex as monkeys performed serial auditory delayed-match-to-sample (DMS). A subset of neurons exhibited modulations of their firing rate during the delay between sounds, during the sensory response, or both. This distributed subpopulation carried a predominantly sensory signal modulated by the mnemonic context of the stimulus. Excitatory and suppressive effects on match responses were dissociable in their timing, and in their resistance to sounds intervening between the sample and match. Conclusions Like the monkeys’ behavioral performance, these neuronal effects differ from those reported in the same species during visual DMS, suggesting different neural mechanisms for retaining dynamic sounds and static images in STM. PMID:25456448

  13. Improving working memory in children with low language abilities

    PubMed Central

    Holmes, Joni; Butterfield, Sally; Cormack, Francesca; van Loenhoud, Anita; Ruggero, Leanne; Kashikar, Linda; Gathercole, Susan

    2015-01-01

    This study investigated whether working memory training is effective in enhancing verbal memory in children with low language abilities (LLA). Cogmed Working Memory Training was completed by a community sample of children aged 8–11 years with LLA and a comparison group with matched non-verbal abilities and age-typical language performance. Short-term memory (STM), working memory, language, and IQ were assessed before and after training. Significant and equivalent post-training gains were found in visuo-spatial short-term memory in both groups. Exploratory analyses across the sample established that low verbal IQ scores were strongly and highly specifically associated with greater gains in verbal STM, and that children with higher verbal IQs made greater gains in visuo-spatial short-term memory following training. This provides preliminary evidence that intensive working memory training may be effective for enhancing the weakest aspects of STM in children with low verbal abilities, and may also be of value in developing compensatory strategies. PMID:25983703

  14. Laser-combined scanning tunnelling microscopy for probing ultrafast transient dynamics.

    PubMed

    Terada, Yasuhiko; Yoshida, Shoji; Takeuchi, Osamu; Shigekawa, Hidemi

    2010-07-07

    The development of time-resolved scanning tunnelling microscopy (STM), in particular, attempts to combine STM with ultrafast laser technology, is reviewed with emphasis on observed physical quantities and spatiotemporal resolution. Ultrashort optical pulse technology has allowed us to observe transient phenomena in the femtosecond range, which, however, has the drawback of a relatively low spatial resolution due to the electromagnetic wavelength used. In contrast, STM and its related techniques, although the time resolution is limited by the circuit bandwidth (∼100 kHz), enable us to observe structures at the atomic level in real space. Our purpose has been to combine these two techniques to achieve a new technology that satisfies the requirements for exploring the ultrafast transient dynamics of the local quantum functions in organized small structures, which will advance the pursuit of future nanoscale scientific research in terms of the ultimate temporal and spatial resolutions. © 2010 IOP Publishing Ltd

  15. Intermediate Nucleation State of GaN Growth

    NASA Astrophysics Data System (ADS)

    Zheng, L. X.; Xie, M. H.; Tong, S. Y.

    2001-03-01

    Homoexpitaxial nucleation of GaN during molecular-beam epitaxy is followed by scanning tunneling microcopy (STM). We observe a metastable nucleation state, which manifests as “ghost” islands in STM images. These “ghost” islands can be irreversibly driven into normal islands by continuous STM imaging. It is further established that the “ghost” island formation is related to the presence of excess Ga atoms on the surface: Normal islands are only seen under the N-rich or stoichiometric flux condition, whereas “ghost” islands are observed under Ga-rich conditions. For intermediate excess-Ga coverages, both normal and “ghost” islands are present, however, they show distinctly different sizes, suggesting different nucleation states for the two. A growth model is proposed to account for the formation of metastable, “ghost” islands. Kinetic Monte Carlo simulation is carried out and main features of the surface are reproduced. We acknowledge financial support from HK RGC under grant Nos. 7396/00P, 7142/99P, and 7121/00P.

  16. Atomic species identification at the (101) anatase surface by simultaneous scanning tunnelling and atomic force microscopy

    PubMed Central

    Stetsovych, Oleksandr; Todorović, Milica; Shimizu, Tomoko K.; Moreno, César; Ryan, James William; León, Carmen Pérez; Sagisaka, Keisuke; Palomares, Emilio; Matolín, Vladimír; Fujita, Daisuke; Perez, Ruben; Custance, Oscar

    2015-01-01

    Anatase is a pivotal material in devices for energy-harvesting applications and catalysis. Methods for the accurate characterization of this reducible oxide at the atomic scale are critical in the exploration of outstanding properties for technological developments. Here we combine atomic force microscopy (AFM) and scanning tunnelling microscopy (STM), supported by first-principles calculations, for the simultaneous imaging and unambiguous identification of atomic species at the (101) anatase surface. We demonstrate that dynamic AFM-STM operation allows atomic resolution imaging within the material's band gap. Based on key distinguishing features extracted from calculations and experiments, we identify candidates for the most common surface defects. Our results pave the way for the understanding of surface processes, like adsorption of metal dopants and photoactive molecules, that are fundamental for the catalytic and photovoltaic applications of anatase, and demonstrate the potential of dynamic AFM-STM for the characterization of wide band gap materials. PMID:26118408

  17. Method and apparatus for differential spectroscopic atomic-imaging using scanning tunneling microscopy

    DOEpatents

    Kazmerski, Lawrence L.

    1990-01-01

    A Method and apparatus for differential spectroscopic atomic-imaging is disclosed for spatial resolution and imaging for display not only individual atoms on a sample surface, but also bonding and the specific atomic species in such bond. The apparatus includes a scanning tunneling microscope (STM) that is modified to include photon biasing, preferably a tuneable laser, modulating electronic surface biasing for the sample, and temperature biasing, preferably a vibration-free refrigerated sample mounting stage. Computer control and data processing and visual display components are also included. The method includes modulating the electronic bias voltage with and without selected photon wavelengths and frequency biasing under a stabilizing (usually cold) bias temperature to detect bonding and specific atomic species in the bonds as the STM rasters the sample. This data is processed along with atomic spatial topography data obtained from the STM raster scan to create a real-time visual image of the atoms on the sample surface.

  18. Newly developed low-temperature scanning tunneling microscope and its application to the study of superconducting materials

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

    Gao, F.; Dai, C.; Chen, Z.

    1994-05-01

    A newly developed scanning tunneling microscope (STM) capable of operating at room temperature, 77 K, and 4.2 K is presented. This compact STM has a highly symmetric and rigid tunneling unit designed as an integral frame except the coarse and fine adjustment parts. The tunneling unit is incorporated into a small vacuum chamber that is usually pumped down to 2[times]10[sup [minus]4] Pa to avoid water contamination. The fine mechanic adjustment makes the tip approach the sample in 5 nm steps. The coarse adjustment not only changes the distance between the tip and the sample, but also adjusts the tip tomore » be normal to the surface of the sample. With this low-temperature STM atomic resolution images of Bi-2212 single-crystal and large-scale topographies of a YBa[sub 2]Cu[sub 3]O[sub 7] thin film are observed at 77 K.« less

  19. Generalized effective-mass theory of subsurface scanning tunneling microscopy: Application to cleaved quantum dots

    NASA Astrophysics Data System (ADS)

    Roy, M.; Maksym, P. A.; Bruls, D.; Offermans, P.; Koenraad, P. M.

    2010-11-01

    An effective-mass theory of subsurface scanning tunneling microscopy (STM) is developed. Subsurface structures such as quantum dots embedded into a semiconductor slab are considered. States localized around subsurface structures match on to a tail that decays into the vacuum above the surface. It is shown that the lateral variation in this tail may be found from a surface envelope function provided that the effects of the slab surfaces and the subsurface structure decouple approximately. The surface envelope function is given by a weighted integral of a bulk envelope function that satisfies boundary conditions appropriate to the slab. The weight function decays into the slab inversely with distance and this slow decay explains the subsurface sensitivity of STM. These results enable STM images to be computed simply and economically from the bulk envelope function. The method is used to compute wave-function images of cleaved quantum dots and the computed images agree very well with experiment.

  20. Binding Modes of Thioflavin T Molecules to Prion Peptide Assemblies Identified by Using Scanning Tunneling Microscopy

    PubMed Central

    2011-01-01

    The widely used method to monitor the aggregation process of amyloid peptide is thioflavin T (ThT) assay, while the detailed molecular mechanism is still not clear. In this work, we report here the direct identification of the binding modes of ThT molecules with the prion peptide GNNQQNY by using scanning tunneling microscopy (STM). The assembly structures of GNNQQNY were first observed by STM on a graphite surface, and the introduction of ThT molecules to the surface facilitated the STM observations of the adsorption conformations of ThT with peptide strands. ThT molecules are apt to adsorb on the peptide assembly with β-sheet structure and oriented parallel with the peptide strands adopting four different binding modes. This effort could benefit the understanding of the mechanisms of the interactions between labeling species or inhibitory ligands and amyloid peptides, which is keenly needed for developing diagnostic and therapeutic approaches. PMID:22778872

  1. Compression-Induced Conformation and Orientation Changes in an n-Alkane Monolayer on a Au(111) Surface.

    PubMed

    Endo, Osamu; Nakamura, Masashi; Amemiya, Kenta; Ozaki, Hiroyuki

    2017-04-25

    The influence of the preparation method and adsorbed amount of n-tetratetracontane (n-C 44 H 90 ) on its orientation in a monolayer on the Au(111) surface is studied by near carbon K-edge X-ray absorption fine structure spectroscopy (C K-NEXAFS), scanning tunneling microscopy (STM) under ultrahigh vacuum, and infrared reflection-absorption spectroscopy (IRAS) at the electrochemical interface in sulfuric acid solution. The n-C 44 H 90 molecules form self-assembled lamellar structures with the chain axis parallel to the surface, as observed by STM. For small amounts adsorbed, the carbon plane is parallel to the surface (flat-on orientation). An increase in the adsorbed amount by ∼10-20% induces compression of the lamellar structure either along the lamellar axis or alkyl chain axis. The compressed molecular arrangement is observed by STM, and induced conformation and orientation changes are confirmed by in situ IRAS and C K-NEXAFS.

  2. Scanning Probe Microscopies and Their Applications Towards the Study of Superconductors

    NASA Astrophysics Data System (ADS)

    Helfrich, Jennifer Ann

    1995-11-01

    The invention of the scanning tunneling microscope (STM) in 1982 made it possible to study surfaces and structures at resolutions previously believed unattainable. Adapting the STM for low temperatures makes it possible to study superconductors with new methods and to obtain valuable information. This thesis describes a novel low temperature STM (LTSTM) that was designed and built at Northwestern University for the purpose of studying superconductors in the mixed state. At low temperatures, this LTSTM has a scan range an order of magnitude larger than other LTSTM's designed elsewhere. It is capable of low temperature imaging and obtaining dI/dV vs. V curves. A detailed study of magnetic force microscopy (MFM) probes is also presented. The fields and forces between probe and surface were computer modeled. These results are compared with results from electron holographs of MFM probes. The final section of the thesis describes an a.c. susceptibility measurement on a UPt_3 sphere. Results are presented and discussed.

  3. Acetone-Assisted Oxygen Vacancy Diffusion on TiO2(110)

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

    Xia, Yaobiao; Zhang, Bo; Ye, Jingyun

    2012-10-18

    We have studied the dynamic relationship between acetone and bridge-bonded oxygen (Ob) vacancy (VO) defect sites on the TiO2(110)-1 × 1 surface using scanning tunneling microscopy (STM) and density function theory (DFT) calculations. We report an adsorbate-assisted VO diffusion mechanism. The STM images taken at 300 K show that acetone preferably adsorbs on the VO site and is mobile. The sequential isothermal STM images directly show that the mobile acetone effectively migrates the position of VO by a combination of two acetone diffusion channels: one is the diffusion along the Ob row and moving as an alkyl group, which healsmore » the initial VO; another is the diffusion from the Ob row to the fivecoordinated Ti4+ row and then moving along the Ti4+ row as an acetone, which leaves a VO behind. The calculated acetone diffusion barriers for the two channels are comparable and agree with experimental results.« less

  4. Mn doped InSb studied at the atomic scale by cross-sectional scanning tunneling microscopy

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

    Mauger, S. J. C.; Bocquel, J.; Koenraad, P. M., E-mail: p.m.koenraad@tue.nl

    2015-11-30

    We present an atomically resolved study of metal-organic vapor epitaxy grown Mn doped InSb. Both topographic and spectroscopic measurements have been performed by cross-sectional scanning tunneling microscopy (STM). The measurements on the Mn doped InSb samples show a perfect crystal structure without any precipitates and reveal that Mn acts as a shallow acceptor. The Mn concentration of the order of ∼10{sup 20 }cm{sup −3} obtained from the cross-sectional STM data compare well with the intended doping concentration. While the pair correlation function of the Mn atoms showed that their local distribution is uncorrelated beyond the STM resolution for observing individual dopants,more » disorder in the Mn ion location giving rise to percolation pathways is clearly noted. The amount of clustering that we see is thus as expected for a fully randomly disordered distribution of the Mn atoms and no enhanced clustering or second phase material was observed.« less

  5. Measurement of a linear free energy relationship one molecule at a time

    PubMed Central

    Rao, B. V.; Kwon, K.-Y.; Liu, A.; Bartels, L.

    2004-01-01

    A systematic study of the dehydrogenation of substituted thiophenols by controlled charge injection from the tip of a scanning tunneling microscope (STM) reveals a pronounced dependence of the reaction yield on the position and the chemical nature of the substituent. We evaluate the dehydrogenation rate of para-halo-substituted species within a linear free energy relationship, namely the Hammett equation. The resultant ρ value of 1.4 can faithfully predict the reaction rates of molecules that are meta-halo-substituted or para-methyl-substituted. The positive sign of ρ suggests a negatively charged transition state at the core of the STM-induced process, and the magnitude of the ρ value indicates that the presence of the substrate does not preclude substantial substituent effects. The applicability of the Hammett equation to single-molecule chemistry offers facile prediction of the rate of STM-based single-molecule chemistry in a field, which so far has been addressed by focusing on involved quantum-mechanical modeling of its underlying processes. PMID:15601774

  6. Measurement of a linear free energy relationship one molecule at a time.

    PubMed

    Rao, B V; Kwon, K-Y; Liu, A; Bartels, L

    2004-12-28

    A systematic study of the dehydrogenation of substituted thiophenols by controlled charge injection from the tip of a scanning tunneling microscope (STM) reveals a pronounced dependence of the reaction yield on the position and the chemical nature of the substituent. We evaluate the dehydrogenation rate of para-halo-substituted species within a linear free energy relationship, namely the Hammett equation. The resultant rho value of 1.4 can faithfully predict the reaction rates of molecules that are meta-halo-substituted or para-methyl-substituted. The positive sign of rho suggests a negatively charged transition state at the core of the STM-induced process, and the magnitude of the rho value indicates that the presence of the substrate does not preclude substantial substituent effects. The applicability of the Hammett equation to single-molecule chemistry offers facile prediction of the rate of STM-based single-molecule chemistry in a field, which so far has been addressed by focusing on involved quantum-mechanical modeling of its underlying processes.

  7. Neural correlates of auditory short-term memory in rostral superior temporal cortex.

    PubMed

    Scott, Brian H; Mishkin, Mortimer; Yin, Pingbo

    2014-12-01

    Auditory short-term memory (STM) in the monkey is less robust than visual STM and may depend on a retained sensory trace, which is likely to reside in the higher-order cortical areas of the auditory ventral stream. We recorded from the rostral superior temporal cortex as monkeys performed serial auditory delayed match-to-sample (DMS). A subset of neurons exhibited modulations of their firing rate during the delay between sounds, during the sensory response, or during both. This distributed subpopulation carried a predominantly sensory signal modulated by the mnemonic context of the stimulus. Excitatory and suppressive effects on match responses were dissociable in their timing and in their resistance to sounds intervening between the sample and match. Like the monkeys' behavioral performance, these neuronal effects differ from those reported in the same species during visual DMS, suggesting different neural mechanisms for retaining dynamic sounds and static images in STM. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Recurring outbreaks of Salmonella typhimurium phage type 135 associated with the consumption of products containing raw egg in Tasmania.

    PubMed

    Stephens, Nicola; Coleman, David; Shaw, Kathleen

    2008-12-01

    Large egg-associated outbreaks of Salmonella Typhimurium 135 (STm135) that were associated with inadequate food safety practices but also linked to a common poultry farm occurred in Tasmania in 2005. A series of public health interventions were implemented to prevent further occurrences but 2 more egg-associated outbreaks in Tasmania in March 2007 and January 2008 led to a further 66 cases of STm135. This report describes these outbreaks and their links to the common source associated with the outbreaks in 2005.

  9. Note: long-range scanning tunneling microscope for the study of nanostructures on insulating substrates.

    PubMed

    Molina-Mendoza, Aday J; Rodrigo, José G; Island, Joshua; Burzuri, Enrique; Rubio-Bollinger, Gabino; van der Zant, Herre S J; Agraït, Nicolás

    2014-02-01

    The scanning tunneling microscope (STM) is a powerful tool for studying the electronic properties at the atomic level, however, it is of relatively small scanning range and the fact that it can only operate on conducting samples prevents its application to study heterogeneous samples consisting of conducting and insulating regions. Here we present a long-range scanning tunneling microscope capable of detecting conducting micro and nanostructures on insulating substrates using a technique based on the capacitance between the tip and the sample and performing STM studies.

  10. Interplay between Switching Driven by the Tunneling Current and Atomic Force of a Bistable Four-Atom Si Quantum Dot.

    PubMed

    Yamazaki, Shiro; Maeda, Keisuke; Sugimoto, Yoshiaki; Abe, Masayuki; Zobač, Vladimír; Pou, Pablo; Rodrigo, Lucia; Mutombo, Pingo; Pérez, Ruben; Jelínek, Pavel; Morita, Seizo

    2015-07-08

    We assemble bistable silicon quantum dots consisting of four buckled atoms (Si4-QD) using atom manipulation. We demonstrate two competing atom switching mechanisms, downward switching induced by tunneling current of scanning tunneling microscopy (STM) and opposite upward switching induced by atomic force of atomic force microscopy (AFM). Simultaneous application of competing current and force allows us to tune switching direction continuously. Assembly of the few-atom Si-QDs and controlling their states using versatile combined AFM/STM will contribute to further miniaturization of nanodevices.

  11. Superconducting phonon spectroscopy using a low-temperature scanning tunneling microscope

    NASA Technical Reports Server (NTRS)

    Leduc, H. G.; Kaiser, W. J.; Hunt, B. D.; Bell, L. D.; Jaklevic, R. C.

    1989-01-01

    The low-temperature scanning tunneling microscope (STM) system described by LeDuc et al. (1987) was used to observe the phonon density of states effects in a superconductor. Using techniques based on those employed in macroscopic tunneling spectroscopy, electron tunneling current-voltage (I-V) spectra were measured for NbN and Pb, and dI/dV vs V spectra were measured using standard analog derivative techniques. I-V measurements on NbN and Pb samples under typical STM conditions showed no evidence for multiparticle tunneling effects.

  12. Vacuum phonon tunneling.

    PubMed

    Altfeder, Igor; Voevodin, Andrey A; Roy, Ajit K

    2010-10-15

    Field-induced phonon tunneling, a previously unknown mechanism of interfacial thermal transport, has been revealed by ultrahigh vacuum inelastic scanning tunneling microscopy (STM). Using thermally broadened Fermi-Dirac distribution in the STM tip as in situ atomic-scale thermometer we found that thermal vibrations of the last tip atom are effectively transmitted to sample surface despite few angstroms wide vacuum gap. We show that phonon tunneling is driven by interfacial electric field and thermally vibrating image charges, and its rate is enhanced by surface electron-phonon interaction.

  13. Titan Science Return Quantification

    NASA Technical Reports Server (NTRS)

    Weisbin, Charles R.; Lincoln, William

    2014-01-01

    Each proposal for a NASA mission concept includes a Science Traceability Matrix (STM), intended to show that what is being proposed would contribute to satisfying one or more of the agency's top-level science goals. But the information traditionally provided cannot be used directly to quantitatively compare anticipated science return. We added numerical elements to NASA's STM and developed a software tool to process the data. We then applied this methodology to evaluate a group of competing concepts for a proposed mission to Saturn's moon, Titan.

  14. Scanning Tunneling Microscopic Characterization of an Engineered Organic Molecule

    DTIC Science & Technology

    2011-08-01

    attachment and wide-band MCT detector , was used. Figure 3 shows the spectra obtained for SAM of PMNBT (top), which was compared to raw crystal PMNBT...averaged in order to reduce random noise , especially in the high bias region. Figure 4d shows the average second-order STM I-V curves of each molecule...done to avoid the low signal-to- noise ratio regime of the STM (18). Our estimated value of go for dDT is about two orders of magnitude smaller than

  15. The relationship between phonological short-term memory, receptive vocabulary, and fast mapping in children with specific language impairment.

    PubMed

    Jackson, Emily; Leitao, Suze; Claessen, Mary

    2016-01-01

    Children with specific language impairment (SLI) often experience word-learning difficulties, which are suggested to originate in the early stage of word learning: fast mapping. Some previous research indicates significantly poorer fast mapping capabilities in children with SLI compared with typically developing (TD) counterparts, with a range of methodological factors impacting on the consistency of this finding. Research has explored key issues that might underlie fast mapping difficulties in children with SLI, with strong theoretical support but little empirical evidence for the role of phonological short-term memory (STM). Additionally, further research is required to explore the influence of receptive vocabulary on fast mapping capabilities. Understanding the factors associated with fast mapping difficulties that are experienced by children with SLI may lead to greater theoretically driven word-learning intervention. To investigate whether children with SLI demonstrate significant difficulties with fast mapping, and to explore the related factors. It was hypothesized that children with SLI would score significantly lower on a fast mapping production task compared with TD children, and that phonological STM and receptive vocabulary would significantly predict fast mapping production scores in both groups of children. Twenty-three children with SLI (mean = 64.39 months, SD = 4.10 months) and 26 TD children (mean = 65.92 months, SD = 2.98) were recruited from specialist language and mainstream schools. All participants took part in a unique, interactive fast-mapping task whereby nine novel objects with non-word labels were presented and production accuracy was assessed. A non-word repetition test and the Peabody Picture Vocabulary Test-Fourth Edition (PPVT-IV) were also administered as measures of phonological STM capacity and receptive vocabulary, respectively. Results of the fast-mapping task indicated that children with SLI had significantly poorer fast

  16. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy.

    PubMed

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R

    2014-04-01

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  17. Development of verbal short-term memory and working memory in children with epilepsy: Developmental delay and impact of time-related variables. A cross-sectional study.

    PubMed

    van Iterson, Loretta; de Jong, Peter F

    2018-01-01

    While short-term memory (STM) and working memory (WM) are understood as being crucial for learning, and children with epilepsy often experience learning difficulties, little is known about the age-related development of memory span tasks in children with epilepsy. Short-term memory and WM, operationalized as digit span forwards (DSF) or digit span backwards (DSB), respectively, were studied. Participants were 314 children with epilepsy and 327 typically developing children in ages between 5 and 15years and full scale intelligence quotient (FS-IQ)≥75. Cross-sectional analyses of the data were done with analyses of variance and analyses of covariance ((M)ANCOVAs) and generalized linear analyses. The analyses revealed that STM problems in epilepsy were mediated by age-related gains in WM as well as by differences in IQ. Working memory developed at a quick pace in the younger children, the pace slowed down to some extent in the later primary school years and resumed again later on. Working memory problems prevailed in epilepsy, independent of IQ and development of STM. Timing of the epilepsy in terms of age at onset and duration determined memory development. The youngest children with epilepsy showed age-appropriate development in STM but were the most vulnerable in terms of WM development. Later in the course of the epilepsy, the WM problems of the young children attenuated. In later onset epilepsy, WM problems were smaller but persisted over time. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Acute effects of single and multiple level thoracic manipulations on chronic mechanical neck pain: a randomized controlled trial

    PubMed Central

    Puntumetakul, Rungthip; Suvarnnato, Thavatchai; Werasirirat, Phurichaya; Uthaikhup, Sureeporn; Yamauchi, Junichiro; Boucaut, Rose

    2015-01-01

    Background Thoracic spine manipulation has become a popular alternative to local cervical manipulative therapy for mechanical neck pain. This study investigated the acute effects of single-level and multiple-level thoracic manipulations on chronic mechanical neck pain (CMNP). Methods Forty-eight patients with CMNP were randomly allocated to single-level thoracic manipulation (STM) at T6–T7 or multiple-level thoracic manipulation (MTM), or to a control group (prone lying). Cervical range of motion (CROM), visual analog scale (VAS), and the Thai version of the Neck Disability Index (NDI-TH) scores were measured at baseline, and at 24-hour and at 1-week follow-up. Results At 24-hour and 1-week follow-up, neck disability and pain levels were significantly (P<0.05) improved in the STM and MTM groups compared with the control group. CROM in flexion and left lateral flexion were increased significantly (P<0.05) in the STM group when compared with the control group at 1-week follow-up. The CROM in right rotation was increased significantly after MTM compared to the control group (P<0.05) at 24-hour follow-up. There were no statistically significant differences in neck disability, pain level at rest, and CROM between the STM and MTM groups. Conclusion These results suggest that both single-level and multiple-level thoracic manipulation improve neck disability, pain levels, and CROM at 24-hour and 1-week follow-up in patients with CMNP. PMID:25624764

  19. Spectrotemporal modulation sensitivity for hearing-impaired listeners: dependence on carrier center frequency and the relationship to speech intelligibility.

    PubMed

    Mehraei, Golbarg; Gallun, Frederick J; Leek, Marjorie R; Bernstein, Joshua G W

    2014-07-01

    Poor speech understanding in noise by hearing-impaired (HI) listeners is only partly explained by elevated audiometric thresholds. Suprathreshold-processing impairments such as reduced temporal or spectral resolution or temporal fine-structure (TFS) processing ability might also contribute. Although speech contains dynamic combinations of temporal and spectral modulation and TFS content, these capabilities are often treated separately. Modulation-depth detection thresholds for spectrotemporal modulation (STM) applied to octave-band noise were measured for normal-hearing and HI listeners as a function of temporal modulation rate (4-32 Hz), spectral ripple density [0.5-4 cycles/octave (c/o)] and carrier center frequency (500-4000 Hz). STM sensitivity was worse than normal for HI listeners only for a low-frequency carrier (1000 Hz) at low temporal modulation rates (4-12 Hz) and a spectral ripple density of 2 c/o, and for a high-frequency carrier (4000 Hz) at a high spectral ripple density (4 c/o). STM sensitivity for the 4-Hz, 4-c/o condition for a 4000-Hz carrier and for the 4-Hz, 2-c/o condition for a 1000-Hz carrier were correlated with speech-recognition performance in noise after partialling out the audiogram-based speech-intelligibility index. Poor speech-reception and STM-detection performance for HI listeners may be related to a combination of reduced frequency selectivity and a TFS-processing deficit limiting the ability to track spectral-peak movements.

  20. JOVE NASA-FIT program: Microgravity and aeronomy projects

    NASA Technical Reports Server (NTRS)

    Patterson, James D.; Mantovani, James G.; Rassoul, Hamid K.

    1994-01-01

    This semi-annual status report is divided into two sections: Scanning Tunneling Microscopy Lab and Aeronomy Lab. The Scanning Tunneling Microscopy (STM) research involves studying solar cell materials using the STM built at Florida Tech using a portion of our initial Jove equipment funding. One result of the participation in the FSEC project will be to design and build an STM system which is portable. This could serve as a prototype STM system which might be used on the Space Shuttle during a Spacelab mission, or onboard the proposed Space Station. The scanning tunneling microscope is only able to image the surface structure of electrically conductive crystals; by building an atomic force microscope (AFM) the surface structure of any sample, regardless of its conductivity, will be able to be imaged. With regards to the Aeronomy Lab, a total of four different mesospheric oxygen emission codes were created to calculate the intensity along the line of sight of the shuttle observations for 2972A, Herzberg I, Herzberg II, and Chamberlain bands. The thermosphere-ionosphere coupling project was completed with two major accomplishments: collection of 500 data points on modulation of neutral wind with geophysical variables, and establishment of constraints on behavior of the height of the ionosphere as a result of interaction between geophysical and geometrical factors. The magnetotail plasma project has been centered around familiarization with the subject in the form of a literature search and preprocessing of IMP-8 data.