Nanopore arrays in a silicon membrane for parallel single-molecule detection: fabrication.

PubMed

Schmidt, Torsten; Zhang, Miao; Sychugov, Ilya; Roxhed, Niclas; Linnros, Jan

2015-08-07

Solid state nanopores enable translocation and detection of single bio-molecules such as DNA in buffer solutions. Here, sub-10 nm nanopore arrays in silicon membranes were fabricated by using electron-beam lithography to define etch pits and by using a subsequent electrochemical etching step. This approach effectively decouples positioning of the pores and the control of their size, where the pore size essentially results from the anodizing current and time in the etching cell. Nanopores with diameters as small as 7 nm, fully penetrating 300 nm thick membranes, were obtained. The presented fabrication scheme to form large arrays of nanopores is attractive for parallel bio-molecule sensing and DNA sequencing using optical techniques. In particular the signal-to-noise ratio is improved compared to other alternatives such as nitride membranes suffering from a high-luminescence background.

Skew Projection of Echo-Detected EPR Spectra for Increased Sensitivity and Resolution

PubMed Central

Bowman, Michael K.; Krzyaniak, Matthew D.; Cruce, Alex A.; Weber, Ralph T.

2013-01-01

The measurement of EPR spectra during pulsed EPR experiments is commonly accomplished by recording the integral of the electron spin echo as the applied magnetic field is stepped through the spectrum. This approach to echo-detected EPR spectral measurement (ED-EPR) limits sensitivity and spectral resolution and can cause gross distortions in the resulting spectra because some of the information present in the electron spin echo is discarded in such measurements. However, Fourier Transformation of echo shapes measured at a series of magnetic field values followed by skew projection onto either a magnetic field or resonance frequency axis can increase both spectral resolution and sensitivity without the need to trade one against the other. Examples of skew-projected spectra with single crystals, glasses and powders show resolution improvements as large as a factor of seven with sensitivity increases of as much as a factor of five. PMID:23644351

Skew projection of echo-detected EPR spectra for increased sensitivity and resolution

NASA Astrophysics Data System (ADS)

Bowman, Michael K.; Krzyaniak, Matthew D.; Cruce, Alex A.; Weber, Ralph T.

2013-06-01

The measurement of EPR spectra during pulsed EPR experiments is commonly accomplished by recording the integral of the electron spin echo as the applied magnetic field is stepped through the spectrum. This approach to echo-detected EPR spectral measurement (ED-EPR) limits sensitivity and spectral resolution and can cause gross distortions in the resulting spectra because some of the information present in the electron spin echo is discarded in such measurements. However, Fourier transformation of echo shapes measured at a series of magnetic field values followed by skew projection onto either a magnetic field or resonance frequency axis can increase both spectral resolution and sensitivity without the need to trade one against the other. Examples of skew-projected spectra with single crystals, glasses and powders show resolution improvements as large as a factor of seven with sensitivity increases of as much as a factor of five.

A manual and an automatic TERS based virus discrimination

NASA Astrophysics Data System (ADS)

Olschewski, Konstanze; Kämmer, Evelyn; Stöckel, Stephan; Bocklitz, Thomas; Deckert-Gaudig, Tanja; Zell, Roland; Cialla-May, Dana; Weber, Karina; Deckert, Volker; Popp, Jürgen

2015-02-01

Rapid techniques for virus identification are more relevant today than ever. Conventional virus detection and identification strategies generally rest upon various microbiological methods and genomic approaches, which are not suited for the analysis of single virus particles. In contrast, the highly sensitive spectroscopic technique tip-enhanced Raman spectroscopy (TERS) allows the characterisation of biological nano-structures like virions on a single-particle level. In this study, the feasibility of TERS in combination with chemometrics to discriminate two pathogenic viruses, Varicella-zoster virus (VZV) and Porcine teschovirus (PTV), was investigated. In a first step, chemometric methods transformed the spectral data in such a way that a rapid visual discrimination of the two examined viruses was enabled. In a further step, these methods were utilised to perform an automatic quality rating of the measured spectra. Spectra that passed this test were eventually used to calculate a classification model, through which a successful discrimination of the two viral species based on TERS spectra of single virus particles was also realised with a classification accuracy of 91%.Rapid techniques for virus identification are more relevant today than ever. Conventional virus detection and identification strategies generally rest upon various microbiological methods and genomic approaches, which are not suited for the analysis of single virus particles. In contrast, the highly sensitive spectroscopic technique tip-enhanced Raman spectroscopy (TERS) allows the characterisation of biological nano-structures like virions on a single-particle level. In this study, the feasibility of TERS in combination with chemometrics to discriminate two pathogenic viruses, Varicella-zoster virus (VZV) and Porcine teschovirus (PTV), was investigated. In a first step, chemometric methods transformed the spectral data in such a way that a rapid visual discrimination of the two examined viruses was enabled. In a further step, these methods were utilised to perform an automatic quality rating of the measured spectra. Spectra that passed this test were eventually used to calculate a classification model, through which a successful discrimination of the two viral species based on TERS spectra of single virus particles was also realised with a classification accuracy of 91%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07033j

A split-step method to include electron–electron collisions via Monte Carlo in multiple rate equation simulations

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

Huthmacher, Klaus; Molberg, Andreas K.; Rethfeld, Bärbel

2016-10-01

A split-step numerical method for calculating ultrafast free-electron dynamics in dielectrics is introduced. The two split steps, independently programmed in C++11 and FORTRAN 2003, are interfaced via the presented open source wrapper. The first step solves a deterministic extended multi-rate equation for the ionization, electron–phonon collisions, and single photon absorption by free-carriers. The second step is stochastic and models electron–electron collisions using Monte-Carlo techniques. This combination of deterministic and stochastic approaches is a unique and efficient method of calculating the nonlinear dynamics of 3D materials exposed to high intensity ultrashort pulses. Results from simulations solving the proposed model demonstrate howmore » electron–electron scattering relaxes the non-equilibrium electron distribution on the femtosecond time scale.« less

Ultra low signals in ballistic electron emission microscopy

NASA Astrophysics Data System (ADS)

Heller, Eric

The extension of Scanning Tunneling Microscopy known as Ballistic Electron Emission Microscopy (BEEM) was expanded to allow useful data collection at lower signal levels than previously possible, and a critical BEEM shortcoming was discovered and quantified. As a separate effort, a new method for measuring SB-type step energies on Si(001) SA-type steps that under some circumstances is more accurate than previous methods was used and will be presented. Finally, extensive modifications to a Scanning Tunneling Microscope used for most of this research will be presented. First, it will be shown theoretically and experimentally that by amplifying the hot BEEM electrons that make up the useful BEEM signal before they are thermalized, internal gain can be applied specifically to these electrons without amplifying standard BEEM noise sources. It will be shown that BEEM with single hot electron sensitivity (approximately a factor of 1000 improvement in the minimum detectable BEEM signal) is attainable with modified commercially existing avalanche photodiodes. With this new low-signal capability, it was obvious that a new BEEM-like signal was being detected. We have discovered that photons generated by STM tunneling will create a false signal in most BEEM samples. Furthermore, we have characterized this effect which we call "STM-PC" and it will be demonstrated with Pd/SiO2/Si and Au/SiO2/Si samples that this false signal closely mimics BEEM and is easily confused for BEEM. We will discuss ways to separate real BEEM from this new effect. Separately, thermally generated kinks on A-type steps on the Si(001) surface were counted and analyzed to find the SB-type step energy. Previous work by others was extended by counting a new type of feature, the "switch" kink, to allow a more accurate determination of the energy of SB-steps in the presence of defects that can bow steps and cause non-thermal kinks. Considerable data collection along with this new extension allowed a more accurate determination of the SB-type kink energy than before and the first experimental evidence that it increases with tensile strain on the Si(001) surface. Modifications to an Omicron Variable Temperature Scanning Tunneling Microscope (VT-STM) will be presented. The VT-STM will be moved to the Electrical Engineering Department cleanroom of The Ohio State University and will allow in-situ studies of Molecular Beam Epitaxy (MBE) grown samples. Modifications, repairs, and operating procedures will be discussed for the VT-STM and supporting hardware. Last, work on Low Temperature Grown Gallium Arsenide (LTG-GaAs) will be presented. The ultimate goal of detecting mm-scale arsenic precipitates that form with annealing using BEEM was not successful. Precipitates were imaged with atomic force microscopy, but these same precipitates are not seen with BEEM under some conditions.

A phase contrast imaging–interferometer system for detection of multiscale electron density fluctuations on DIII-D

DOE PAGES

Davis, E. M.; Rost, J. C.; Porkolab, M.; ...

2016-08-15

Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. Here, we describe the first-ever implementation of a combined PCI-interferometer. The combined system uses a single 10:6 μm probe beam, two interference schemes, and two detectors to measure electron density uctuations at large spatiotemporal bandwidth (10 kHz < f < 5MHz and 0 cm -1 ≤ k ≤ 20 cm -1), allowing simultaneous measurement of ion- and electron-scale instabilities. Further, correlating our interferometer's measurements with those from DIII-D's pre-existing, toroidally separated interferometer allows core-localized, low-n MHD studies that may otherwisemore » be inaccessible via external magnetic measurements. In the combined diagnostic's small port requirements and minimal access restrictions make it well-suited to the harsh neutron environments and limited port space expected in next-step devices.« less

A phase contrast imaging-interferometer system for detection of multiscale electron density fluctuations on DIII-D

NASA Astrophysics Data System (ADS)

Davis, E. M.; Rost, J. C.; Porkolab, M.; Marinoni, A.; Van Zeeland, M. A.

2016-11-01

Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. This work describes the first-ever implementation of a combined PCI-interferometer. The combined system uses a single 10.6 μm probe beam, two interference schemes, and two detectors to measure electron density fluctuations at large spatiotemporal bandwidth (10 kHz

High-resolution Single Particle Analysis from Electron Cryo-microscopy Images Using SPHIRE

PubMed Central

Moriya, Toshio; Saur, Michael; Stabrin, Markus; Merino, Felipe; Voicu, Horatiu; Huang, Zhong; Penczek, Pawel A.; Raunser, Stefan; Gatsogiannis, Christos

2017-01-01

SPHIRE (SPARX for High-Resolution Electron Microscopy) is a novel open-source, user-friendly software suite for the semi-automated processing of single particle electron cryo-microscopy (cryo-EM) data. The protocol presented here describes in detail how to obtain a near-atomic resolution structure starting from cryo-EM micrograph movies by guiding users through all steps of the single particle structure determination pipeline. These steps are controlled from the new SPHIRE graphical user interface and require minimum user intervention. Using this protocol, a 3.5 Å structure of TcdA1, a Tc toxin complex from Photorhabdus luminescens, was derived from only 9500 single particles. This streamlined approach will help novice users without extensive processing experience and a priori structural information, to obtain noise-free and unbiased atomic models of their purified macromolecular complexes in their native state. PMID:28570515

Single molecule thermodynamics in biological motors.

PubMed

Taniguchi, Yuichi; Karagiannis, Peter; Nishiyama, Masayoshi; Ishii, Yoshiharu; Yanagida, Toshio

2007-04-01

Biological molecular machines use thermal activation energy to carry out various functions. The process of thermal activation has the stochastic nature of output events that can be described according to the laws of thermodynamics. Recently developed single molecule detection techniques have allowed each distinct enzymatic event of single biological machines to be characterized providing clues to the underlying thermodynamics. In this study, the thermodynamic properties in the stepping movement of a biological molecular motor have been examined. A single molecule detection technique was used to measure the stepping movements at various loads and temperatures and a range of thermodynamic parameters associated with the production of each forward and backward step including free energy, enthalpy, entropy and characteristic distance were obtained. The results show that an asymmetry in entropy is a primary factor that controls the direction in which the motor will step. The investigation on single molecule thermodynamics has the potential to reveal dynamic properties underlying the mechanisms of how biological molecular machines work.

Effect of chemical compounds on electronic tongue response to citrus juices

USDA-ARS?s Scientific Manuscript database

The electronic tongue system mimics the process of taste detection by human taste buds and recognition by the brain, hence helping in prediction of taste. With this unique capability, the electronic tongue has been used for taste detection of a wide range of food products. As a preliminary step in p...

A single dopant atom in silicon sees the light

NASA Astrophysics Data System (ADS)

Rogge, Sven

2014-03-01

Optical access to a single qubit is very attractive since it allows for readout with unprecedented high spectral resolution and long distance coupling. Substantial progress has been demonstrated for nitrogen-vacancy centers in diamond (Bernien, Nature, 2013). Optical access to qubits in silicon been an important goal but has to date only been achieved in the ensemble limit (Steger, Science, 2012). Here, we present the photoionization of an individual erbium dopant in silicon (Yin, Nature, 2013). A single-electron transistor is used as a single-shot charge detector to observe the resonant ionization of a single atom as a function of photon energy. This allows for optical addressing and electrical detection of individual erbium dopants with exceptionally narrow line width. The hyperfine coupling is clearly resolved which paves the way to single shot readout of the nuclear spin. This hybrid approach is a first step towards an optical interface to dopants in silicon. in collaboration with Chunming Yin, Milos Rancic, Gabriele G. de Boo, Nikolas Stavrias, Jeffrey C. McCallum, Matthew J. Sellars.

A Newly Developed Nested PCR Assay for the Detection of Helicobacter pylori in the Oral Cavity.

PubMed

Ismail, Hawazen; Morgan, Claire; Griffiths, Paul; Williams, John; Jenkins, Gareth

2016-01-01

To develop a new nested polymerase chain reaction (PCR) assay for identifying Helicobacter pylori DNA from dental plaque. H. pylori is one of the most common chronic bacterial pathogens in humans. The accurate detection of this organism is essential for proper patient management and for the eradication of the bacteria following treatment. Forty-nine patients (24 males and 25 females; mean age: 51; range, 19 to 94 y) were investigated for the presence of H. pylori in dental plaque by single-step PCR and nested PCR and in the stomach by single-step PCR, nested PCR, and histologic examination. The newly developed nested PCR assay identified H. pylori DNA in gastric biopsies of 18 patients who were histologically classified as H. pylori-positive and 2 additional biopsies of patients who were H. pylori-negative by histologic examination (20/49; 40.8%). Dental plaque samples collected before and after endoscopy from the 49 patients revealed that single-step PCR did not detect H. pylori but nested PCR was able to detect H. pylori DNA in 40.8% (20/49) patients. Nested PCR gave a higher detection rate (40.8%, 20/49) than that of histology (36.7%, 18/49) and single-step PCR. When nested PCR results were compared with histology results there was no significant difference between the 2 methods. Our newly developed nested PCR assay is at least as sensitive as histology and may be useful for H. pylori detection in patients unfit for endoscopic examination.

Single-Electron Detection and Spectroscopy via Relativistic Cyclotron Radiation.

PubMed

Asner, D M; Bradley, R F; de Viveiros, L; Doe, P J; Fernandes, J L; Fertl, M; Finn, E C; Formaggio, J A; Furse, D; Jones, A M; Kofron, J N; LaRoque, B H; Leber, M; McBride, E L; Miller, M L; Mohanmurthy, P; Monreal, B; Oblath, N S; Robertson, R G H; Rosenberg, L J; Rybka, G; Rysewyk, D; Sternberg, M G; Tedeschi, J R; Thümmler, T; VanDevender, B A; Woods, N L

2015-04-24

It has been understood since 1897 that accelerating charges must emit electromagnetic radiation. Although first derived in 1904, cyclotron radiation from a single electron orbiting in a magnetic field has never been observed directly. We demonstrate single-electron detection in a novel radio-frequency spectrometer. The relativistic shift in the cyclotron frequency permits a precise electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay end point, and this work demonstrates a fundamentally new approach to precision beta spectroscopy for future neutrino mass experiments.

Object detection in cinematographic video sequences for automatic indexing

NASA Astrophysics Data System (ADS)

Stauder, Jurgen; Chupeau, Bertrand; Oisel, Lionel

2003-06-01

This paper presents an object detection framework applied to cinematographic post-processing of video sequences. Post-processing is done after production and before editing. At the beginning of each shot of a video, a slate (also called clapperboard) is shown. The slate contains notably an electronic audio timecode that is necessary for audio-visual synchronization. This paper presents an object detection framework to detect slates in video sequences for automatic indexing and post-processing. It is based on five steps. The first two steps aim to reduce drastically the video data to be analyzed. They ensure high recall rate but have low precision. The first step detects images at the beginning of a shot possibly showing up a slate while the second step searches in these images for candidates regions with color distribution similar to slates. The objective is to not miss any slate while eliminating long parts of video without slate appearance. The third and fourth steps are statistical classification and pattern matching to detected and precisely locate slates in candidate regions. These steps ensure high recall rate and high precision. The objective is to detect slates with very little false alarms to minimize interactive corrections. In a last step, electronic timecodes are read from slates to automize audio-visual synchronization. The presented slate detector has a recall rate of 89% and a precision of 97,5%. By temporal integration, much more than 89% of shots in dailies are detected. By timecode coherence analysis, the precision can be raised too. Issues for future work are to accelerate the system to be faster than real-time and to extend the framework for several slate types.

Antibody-Mediated Small Molecule Detection Using Programmable DNA-Switches.

PubMed

Rossetti, Marianna; Ippodrino, Rudy; Marini, Bruna; Palleschi, Giuseppe; Porchetta, Alessandro

2018-06-13

The development of rapid, cost-effective, and single-step methods for the detection of small molecules is crucial for improving the quality and efficiency of many applications ranging from life science to environmental analysis. Unfortunately, current methodologies still require multiple complex, time-consuming washing and incubation steps, which limit their applicability. In this work we present a competitive DNA-based platform that makes use of both programmable DNA-switches and antibodies to detect small target molecules. The strategy exploits both the advantages of proximity-based methods and structure-switching DNA-probes. The platform is modular and versatile and it can potentially be applied for the detection of any small target molecule that can be conjugated to a nucleic acid sequence. Here the rational design of programmable DNA-switches is discussed, and the sensitive, rapid, and single-step detection of different environmentally relevant small target molecules is demonstrated.

Treating electron transport in MCNP{sup trademark}

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

Hughes, H.G.

1996-12-31

The transport of electrons and other charged particles is fundamentally different from that of neutrons and photons. A neutron, in aluminum slowing down from 0.5 MeV to 0.0625 MeV will have about 30 collisions; a photon will have fewer than ten. An electron with the same energy loss will undergo 10{sup 5} individual interactions. This great increase in computational complexity makes a single- collision Monte Carlo approach to electron transport unfeasible for many situations of practical interest. Considerable theoretical work has been done to develop a variety of analytic and semi-analytic multiple-scattering theories for the transport of charged particles. Themore » theories used in the algorithms in MCNP are the Goudsmit-Saunderson theory for angular deflections, the Landau an theory of energy-loss fluctuations, and the Blunck-Leisegang enhancements of the Landau theory. In order to follow an electron through a significant energy loss, it is necessary to break the electron`s path into many steps. These steps are chosen to be long enough to encompass many collisions (so that multiple-scattering theories are valid) but short enough that the mean energy loss in any one step is small (for the approximations in the multiple-scattering theories). The energy loss and angular deflection of the electron during each step can then be sampled from probability distributions based on the appropriate multiple- scattering theories. This subsumption of the effects of many individual collisions into single steps that are sampled probabilistically constitutes the ``condensed history`` Monte Carlo method. This method is exemplified in the ETRAN series of electron/photon transport codes. The ETRAN codes are also the basis for the Integrated TIGER Series, a system of general-purpose, application-oriented electron/photon transport codes. The electron physics in MCNP is similar to that of the Integrated TIGER Series.« less

Photon Counting Imaging with an Electron-Bombarded Pixel Image Sensor

PubMed Central

Hirvonen, Liisa M.; Suhling, Klaus

2016-01-01

Electron-bombarded pixel image sensors, where a single photoelectron is accelerated directly into a CCD or CMOS sensor, allow wide-field imaging at extremely low light levels as they are sensitive enough to detect single photons. This technology allows the detection of up to hundreds or thousands of photon events per frame, depending on the sensor size, and photon event centroiding can be employed to recover resolution lost in the detection process. Unlike photon events from electron-multiplying sensors, the photon events from electron-bombarded sensors have a narrow, acceleration-voltage-dependent pulse height distribution. Thus a gain voltage sweep during exposure in an electron-bombarded sensor could allow photon arrival time determination from the pulse height with sub-frame exposure time resolution. We give a brief overview of our work with electron-bombarded pixel image sensor technology and recent developments in this field for single photon counting imaging, and examples of some applications. PMID:27136556

One-step model of photoemission from single-crystal surfaces

DOE PAGES

Karkare, Siddharth; Wan, Weishi; Feng, Jun; ...

2017-02-28

In our paper, we present a three-dimensional one-step photoemission model that can be used to calculate the quantum efficiency and momentum distributions of electrons photoemitted from ordered single-crystal surfaces close to the photoemission threshold. Using Ag(111) as an example, we also show that the model can not only calculate the quantum efficiency from the surface state accurately without using any ad hoc parameters, but also provides a theoretical quantitative explanation of the vectorial photoelectric effect. This model in conjunction with other band structure and wave function calculation techniques can be effectively used to screen single-crystal photoemitters for use as electronmore » sources for particle accelerator and ultrafast electron diffraction applications.« less

Controlled chain polymerisation and chemical soldering for single-molecule electronics.

PubMed

Okawa, Yuji; Akai-Kasaya, Megumi; Kuwahara, Yuji; Mandal, Swapan K; Aono, Masakazu

2012-05-21

Single functional molecules offer great potential for the development of novel nanoelectronic devices with capabilities beyond today's silicon-based devices. To realise single-molecule electronics, the development of a viable method for connecting functional molecules to each other using single conductive polymer chains is required. The method of initiating chain polymerisation using the tip of a scanning tunnelling microscope (STM) is very useful for fabricating single conductive polymer chains at designated positions and thereby wiring single molecules. In this feature article, developments in the controlled chain polymerisation of diacetylene compounds and the properties of polydiacetylene chains are summarised. Recent studies of "chemical soldering", a technique enabling the covalent connection of single polydiacetylene chains to single functional molecules, are also introduced. This represents a key step in advancing the development of single-molecule electronics.

On the single-photon-counting (SPC) modes of imaging using an XFEL source

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

Wang, Zhehui

In this study, the requirements to achieve high detection efficiency (above 50%) and gigahertz (GHz) frame rate for the proposed 42-keV X-ray free-electron laser (XFEL) at Los Alamos are summarized. Direct detection scenarios using C (diamond), Si, Ge and GaAs semiconductor sensors are analyzed. Single-photon counting (SPC) mode and weak SPC mode using Si can potentially meet the efficiency and frame rate requirements and be useful to both photoelectric absorption and Compton physics as the photon energy increases. Multilayer three-dimensional (3D) detector architecture, as a possible means to realize SPC modes, is compared with the widely used two-dimensional (2D) hybridmore » planar electrode structure and 3D deeply entrenched electrode architecture. Demonstration of thin film cameras less than 100-μm thick with onboard thin ASICs could be an initial step to realize multilayer 3D detectors and SPC modes for XFELs.« less

On the single-photon-counting (SPC) modes of imaging using an XFEL source

DOE PAGES

Wang, Zhehui

2015-12-14

In this study, the requirements to achieve high detection efficiency (above 50%) and gigahertz (GHz) frame rate for the proposed 42-keV X-ray free-electron laser (XFEL) at Los Alamos are summarized. Direct detection scenarios using C (diamond), Si, Ge and GaAs semiconductor sensors are analyzed. Single-photon counting (SPC) mode and weak SPC mode using Si can potentially meet the efficiency and frame rate requirements and be useful to both photoelectric absorption and Compton physics as the photon energy increases. Multilayer three-dimensional (3D) detector architecture, as a possible means to realize SPC modes, is compared with the widely used two-dimensional (2D) hybridmore » planar electrode structure and 3D deeply entrenched electrode architecture. Demonstration of thin film cameras less than 100-μm thick with onboard thin ASICs could be an initial step to realize multilayer 3D detectors and SPC modes for XFELs.« less

Tandem array of nanoelectronic readers embedded coplanar to a fluidic nanochannel for correlated single biopolymer analysis

PubMed Central

Lesser-Rojas, Leonardo; Sriram, K. K.; Liao, Kuo-Tang; Lai, Shui-Chin; Kuo, Pai-Chia; Chu, Ming-Lee; Chou, Chia-Fu

2014-01-01

We have developed a two-step electron-beam lithography process to fabricate a tandem array of three pairs of tip-like gold nanoelectronic detectors with electrode gap size as small as 9 nm, embedded in a coplanar fashion to 60 nm deep, 100 nm wide, and up to 150 μm long nanochannels coupled to a world-micro-nanofluidic interface for easy sample introduction. Experimental tests with a sealed device using DNA-protein complexes demonstrate the coplanarity of the nanoelectrodes to the nanochannel surface. Further, this device could improve transverse current detection by correlated time-of-flight measurements of translocating samples, and serve as an autocalibrated velocimeter and nanoscale tandem Coulter counters for single molecule analysis of heterogeneous samples. PMID:24753731

On the Presentation of Wave Phenomena of Electrons with the Young-Feynman Experiment

ERIC Educational Resources Information Center

Matteucci, Giorgio

2011-01-01

The Young-Feynman two-hole interferometer is widely used to present electron wave-particle duality and, in particular, the buildup of interference fringes with single electrons. The teaching approach consists of two steps: (i) electrons come through only one hole but diffraction effects are disregarded and (ii) electrons come through both holes…

Interference experiment with asymmetric double slit by using 1.2-MV field emission transmission electron microscope.

PubMed

Harada, Ken; Akashi, Tetsuya; Niitsu, Kodai; Shimada, Keiko; Ono, Yoshimasa A; Shindo, Daisuke; Shinada, Hiroyuki; Mori, Shigeo

2018-01-17

Advanced electron microscopy technologies have made it possible to perform precise double-slit interference experiments. We used a 1.2-MV field emission electron microscope providing coherent electron waves and a direct detection camera system enabling single-electron detections at a sub-second exposure time. We developed a method to perform the interference experiment by using an asymmetric double-slit fabricated by a focused ion beam instrument and by operating the microscope under a "pre-Fraunhofer" condition, different from the Fraunhofer condition of conventional double-slit experiments. Here, pre-Fraunhofer condition means that each single-slit observation was performed under the Fraunhofer condition, while the double-slit observations were performed under the Fresnel condition. The interference experiments with each single slit and with the asymmetric double slit were carried out under two different electron dose conditions: high-dose for calculation of electron probability distribution and low-dose for each single electron distribution. Finally, we exemplified the distribution of single electrons by color-coding according to the above three types of experiments as a composite image.

GAGG:ce single crystalline films: New perspective scintillators for electron detection in SEM.

PubMed

Bok, Jan; Lalinský, Ondřej; Hanuš, Martin; Onderišinová, Zuzana; Kelar, Jakub; Kučera, Miroslav

2016-04-01

Single crystal scintillators are frequently used for electron detection in scanning electron microscopy (SEM). We report gadolinium aluminum gallium garnet (GAGG:Ce) single crystalline films as a new perspective scintillators for the SEM. For the first time, the epitaxial garnet films were used in a practical application: the GAGG:Ce scintillator was incorporated into a SEM scintillation electron detector and it showed improved image quality. In order to prove the GAGG:Ce quality accurately, the scintillation properties were examined using electron beam excitation and compared with frequently used scintillators in the SEM. The results demonstrate excellent emission efficiency of the GAGG:Ce single crystalline films together with their very fast scintillation decay useful for demanding SEM applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Real-Time, Single-Step Bioassay Using Nanoplasmonic Resonator With Ultra-High Sensitivity

NASA Technical Reports Server (NTRS)

Zhang, Xiang (Inventor); Chen, Fanqing Frank (Inventor); Su, Kai-Hang (Inventor); Wei, Qi-Huo (Inventor); Ellman, Jonathan A. (Inventor); Sun, Cheng (Inventor)

2014-01-01

A nanoplasmonic resonator (NPR) comprising a metallic nanodisk with alternating shielding layer(s), having a tagged biomolecule conjugated or tethered to the surface of the nanoplasmonic resonator for highly sensitive measurement of enzymatic activity. NPRs enhance Raman signals in a highly reproducible manner, enabling fast detection of protease and enzyme activity, such as Prostate Specific Antigen (paPSA), in real-time, at picomolar sensitivity levels. Experiments on extracellular fluid (ECF) from paPSA-positive cells demonstrate specific detection in a complex bio-fluid background in real-time single-step detection in very small sample volumes.

Real-time, single-step bioassay using nanoplasmonic resonator with ultra-high sensitivity

DOEpatents

Zhang, Xiang; Ellman, Jonathan A; Chen, Fanqing Frank; Su, Kai-Hang; Wei, Qi-Huo; Sun, Cheng

2014-04-01

A nanoplasmonic resonator (NPR) comprising a metallic nanodisk with alternating shielding layer(s), having a tagged biomolecule conjugated or tethered to the surface of the nanoplasmonic resonator for highly sensitive measurement of enzymatic activity. NPRs enhance Raman signals in a highly reproducible manner, enabling fast detection of protease and enzyme activity, such as Prostate Specific Antigen (paPSA), in real-time, at picomolar sensitivity levels. Experiments on extracellular fluid (ECF) from paPSA-positive cells demonstrate specific detection in a complex bio-fluid background in real-time single-step detection in very small sample volumes.

Electron Density Distribution Changes of Magnesiowüstite With Pressure

NASA Astrophysics Data System (ADS)

Diamond, M. R.; Popov, D.; Shen, G.; Jeanloz, R.

2017-12-01

Magnesiowüstite is one of the dominant minerals in the earth's lower mantle; its density and elasticity, substantially altered by its spin crossover, have direct consequence to interpreting deep-earth geophysical data. High-resolution single-crystal x-ray diffraction data can portray the 3-dimensional distribution of electron density through the Fourier transform of measured form factors. Here we present experimentally measured changes in electron density distribution of single-crystal (Mg.85,Fe.15)O as it goes through its iron(II) high-spin to low-spin electronic transition between about 40 and 60 GPa [Lin and Tsuchiya, 2008], in a diamond-anvil cell. As (Mg,Fe)O undergoes a pressure induced spin crossover (from high spin at low pressure to low spin at high pressure) due to overlap of its eg orbitals, the t2g orbitals become more pronounced to due a higher population of electrons, while the eg orbitals diminish. The spin splitting energy becomes increasingly unfavorable compared to the spin orbital pairing energy. By looking at the population of electrons at different directions in real space, we directly observe these changes in orbital occupation leading up to and during the spin crossover. Since high-Mg magnesiowüstite has a high symmetry structure at these pressure conditions, detecting relative changes in electron density distribution (comparing subsequent pressure steps) is feasible by collecting high resolution data offered by high-energy X rays and wide opening-angle diamond-anvil cells.

Microelectronic DNA assay for the detection of BRCA1 gene mutations

NASA Technical Reports Server (NTRS)

Chen, Hua; Han, Jie; Li, Jun; Meyyappan, Meyya

2004-01-01

Mutations in BRCA1 are characterized by predisposition to breast cancer, ovarian cancer and prostate cancer as well as colon cancer. Prognosis for this cancer survival depends upon the stage at which cancer is diagnosed. Reliable and rapid mutation detection is crucial for the early diagnosis and treatment. We developed an electronic assay for the detection of a representative single nucleotide polymorphism (SNP), deletion and insertion in BRCA1 gene by the microelectronics microarray instrumentation. The assay is rapid, and it takes 30 minutes for the immobilization of target DNA samples, hybridization, washing and readout. The assay is multiplexing since it is carried out at the same temperature and buffer conditions for each step. The assay is also highly specific, as the signal-to-noise ratio is much larger than recommended value (72.86 to 321.05 vs. 5) for homozygotes genotyping, and signal ratio close to the perfect value 1 for heterozygotes genotyping (1.04).

Defect Detection in Superconducting Radiofrequency Cavity Surface Using C + + and OpenCV

NASA Astrophysics Data System (ADS)

Oswald, Samantha; Thomas Jefferson National Accelerator Facility Collaboration

2014-03-01

Thomas Jefferson National Accelerator Facility (TJNAF) uses superconducting radiofrequency (SRF) cavities to accelerate an electron beam. If theses cavities have a small particle or defect, it can degrade the performance of the cavity. The problem at hand is inspecting the cavity for defects, little bubbles of niobium on the surface of the cavity. Thousands of pictures have to be taken of a single cavity and then looked through to see how many defects were found. A C + + program with Open Source Computer Vision (OpenCV) was constructed to reduce the number of hours searching through the images and finds all the defects. Using this code, the SRF group is now able to use the code to identify defects in on-going tests of SRF cavities. Real time detection is the next step so that instead of taking pictures when looking at the cavity, the camera will detect all the defects.

Model of multistep electron transfer in a single-mode polar medium

NASA Astrophysics Data System (ADS)

Feskov, S. V.; Yudanov, V. V.

2017-09-01

A mathematical model of multistep photoinduced electron transfer (PET) in a polar medium with a single relaxation time (Debye solvent) is developed. The model includes the polarization nonequilibrity formed in the vicinity of the donor-acceptor molecular system at the initial steps of photoreaction and its influence on the subsequent steps of PET. It is established that the results from numerical simulation of transient luminescence spectra of photoexcited donor-acceptor complexes (DAC) conform to calculated data obtained on the basis of the familiar experimental technique used to measure the relaxation function of solvent polarization in the vicinity of DAC in the picosecond and subpicosecond ranges.

Two-color single-photon emission from InAs quantum dots: toward logic information management using quantum light.

PubMed

Rivas, David; Muñoz-Matutano, Guillermo; Canet-Ferrer, Josep; García-Calzada, Raúl; Trevisi, Giovanna; Seravalli, Luca; Frigeri, Paola; Martínez-Pastor, Juan P

2014-02-12

In this work, we propose the use of the Hanbury-Brown and Twiss interferometric technique and a switchable two-color excitation method for evaluating the exciton and noncorrelated electron-hole dynamics associated with single photon emission from indium arsenide (InAs) self-assembled quantum dots (QDs). Using a microstate master equation model we demonstrate that our single QDs are described by nonlinear exciton dynamics. The simultaneous detection of two-color, single photon emission from InAs QDs using these nonlinear dynamics was used to design a NOT AND logic transference function. This computational functionality combines the advantages of working with light/photons as input/output device parameters (all-optical system) and that of a nanodevice (QD size of ∼ 20 nm) while also providing high optical sensitivity (ultralow optical power operational requirements). These system features represent an important and interesting step toward the development of new prototypes for the incoming quantum information technologies.

Final state interactions and the extraction of neutron single spin asymmetries from semi-inclusive deep-inelastic scattering by a transversely polarized 3He target

NASA Astrophysics Data System (ADS)

Del Dotto, A.; Kaptari, L. P.; Pace, E.; Salmè, G.; Scopetta, S.

2017-12-01

The semi-inclusive deep-inelastic electron scattering off transversely polarized 3He, i.e., the process e +3He ⃗→e'+h +X , with h being a detected fast hadron, is studied beyond the plane-wave impulse approximation. To this end, a distorted spin-dependent spectral function of a nucleon inside an A =3 nucleus is actually evaluated through a generalized eikonal approximation, in order to take into account the final state interactions between the hadronizing system and the (A -1 ) nucleon spectator one. Our realistic description of both nuclear target and final state is a substantial step forward for achieving a reliable extraction of the Sivers and Collins single spin asymmetries of the free neutron. To illustrate how and to what extent the model dependence due to the treatment of the nuclear effects is under control, we apply our approach to the extraction procedure of the neutron single spin asymmetries from those measured for 3He for values of the kinematical variables relevant both for forthcoming experiments at Jefferson Laboratory and, with an exploratory purpose, for the future Electron Ion Collider.

Cleaning and activation of beryllium-copper electron multiplier dynodes.

NASA Technical Reports Server (NTRS)

Pongratz, M. B.

1972-01-01

Description of a cleaning and activation procedure followed in preparing beryllium-copper dynodes for electron multipliers used in sounding-rocket experiments to detect auroral electrons. The initial degreasing step involved a 5-min bath in trichloroethylene in an ultrasonic cleaner. This was followed by an ultrasonic rinse in methanol and by a two-step acid pickling treatment to remove the oxides. Additional rinsing in water and methanol was followed by activation in a stainless-steel RF induction oven.

Detection of the Odor Signature of Ovarian Cancer using DNA-Decorated Carbon Nanotube Field Effect Transistor Arrays

NASA Astrophysics Data System (ADS)

Kehayias, Christopher; Kybert, Nicholas; Yodh, Jeremy; Johnson, A. T. Charlie

Carbon nanotubes are low-dimensional materials that exhibit remarkable chemical and bio-sensing properties and have excellent compatibility with electronic systems. Here, we present a study that uses an electronic olfaction system based on a large array of DNA-carbon nanotube field effect transistors vapor sensors to analyze the VOCs of blood plasma samples collected from patients with malignant ovarian cancer, patients with benign ovarian lesions, and age-matched healthy subjects. Initial investigations involved coating each CNT sensor with single-stranded DNA of a particular base sequence. 10 distinct DNA oligomers were used to functionalize the carbon nanotube field effect transistors, providing a 10-dimensional sensor array output response. Upon performing a statistical analysis of the 10-dimensional sensor array responses, we showed that blood samples from patients with malignant cancer can be reliably differentiated from those of healthy control subjects with a p-value of 3 x 10-5. The results provide preliminary evidence that the blood of ovarian cancer patients contains a discernable volatile chemical signature that can be detected using DNA-CNT nanoelectronic vapor sensors, a first step towards a minimally invasive electronic diagnostic technology for ovarian cancer.

Talbot-Lau x-ray deflectometry phase-retrieval methods for electron density diagnostics in high-energy density experiments.

PubMed

Valdivia, Maria Pia; Stutman, Dan; Stoeckl, Christian; Mileham, Chad; Begishev, Ildar A; Bromage, Jake; Regan, Sean P

2018-01-10

Talbot-Lau x-ray interferometry uses incoherent x-ray sources to measure refraction index changes in matter. These measurements can provide accurate electron density mapping through phase retrieval. An adaptation of the interferometer has been developed in order to meet the specific requirements of high-energy density experiments. This adaptation is known as a moiré deflectometer, which allows for single-shot capabilities in the form of interferometric fringe patterns. The moiré x-ray deflectometry technique requires a set of object and reference images in order to provide electron density maps, which can be costly in the high-energy density environment. In particular, synthetic reference phase images obtained ex situ through a phase-scan procedure, can provide a feasible solution. To test this procedure, an object phase map was retrieved from a single-shot moiré image obtained from a plasma-produced x-ray source. A reference phase map was then obtained from phase-stepping measurements using a continuous x-ray tube source in a small laboratory setting. The two phase maps were used to retrieve an electron density map. A comparison of the moiré and phase-stepping phase-retrieval methods was performed to evaluate single-exposure plasma electron density mapping for high-energy density and other transient plasma experiments. It was found that a combination of phase-retrieval methods can deliver accurate refraction angle mapping. Once x-ray backlighter quality is optimized, the ex situ method is expected to deliver electron density mapping with improved resolution. The steps necessary for improved diagnostic performance are discussed.

A stretchable strain sensor based on a metal nanoparticle thin film for human motion detection

NASA Astrophysics Data System (ADS)

Lee, Jaehwan; Kim, Sanghyeok; Lee, Jinjae; Yang, Daejong; Park, Byong Chon; Ryu, Seunghwa; Park, Inkyu

2014-09-01

Wearable strain sensors for human motion detection are being highlighted in various fields such as medical, entertainment and sports industry. In this paper, we propose a new type of stretchable strain sensor that can detect both tensile and compressive strains and can be fabricated by a very simple process. A silver nanoparticle (Ag NP) thin film patterned on the polydimethylsiloxane (PDMS) stamp by a single-step direct transfer process is used as the strain sensing material. The working principle is the change in the electrical resistance caused by the opening/closure of micro-cracks under mechanical deformation. The fabricated stretchable strain sensor shows highly sensitive and durable sensing performances in various tensile/compressive strains, long-term cyclic loading and relaxation tests. We demonstrate the applications of our stretchable strain sensors such as flexible pressure sensors and wearable human motion detection devices with high sensitivity, response speed and mechanical robustness.Wearable strain sensors for human motion detection are being highlighted in various fields such as medical, entertainment and sports industry. In this paper, we propose a new type of stretchable strain sensor that can detect both tensile and compressive strains and can be fabricated by a very simple process. A silver nanoparticle (Ag NP) thin film patterned on the polydimethylsiloxane (PDMS) stamp by a single-step direct transfer process is used as the strain sensing material. The working principle is the change in the electrical resistance caused by the opening/closure of micro-cracks under mechanical deformation. The fabricated stretchable strain sensor shows highly sensitive and durable sensing performances in various tensile/compressive strains, long-term cyclic loading and relaxation tests. We demonstrate the applications of our stretchable strain sensors such as flexible pressure sensors and wearable human motion detection devices with high sensitivity, response speed and mechanical robustness. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03295k

Single-electron detection and spectroscopy via relativistic cyclotron radiation

DOE PAGES

Asner, D. M.; Bradley, R. F.; de Viveiros, L.; ...

2015-04-20

Since 1897, we've understood that accelerating charges must emit electromagnetic radiation. Cyclotron radiation, the particular form of radiation emitted by an electron orbiting in a magnetic field, was first derived in 1904. Despite the simplicity of this concept, and the enormous utility of electron spectroscopy in nuclear and particle physics, single-electron cyclotron radiation has never been observed directly. We demonstrate single-electron detection in a novel radiofrequency spec- trometer. Here, we observe the cyclotron radiation emitted by individual magnetically-trapped electrons that are produced with mildly-relativistic energies by a gaseous radioactive source. The relativistic shift in the cyclotron frequency permits a precisemore » electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay endpoint, and this work demonstrates a fundamentally new approach to precision beta spectroscopy for future neutrino mass experiments.« less

Single molecule targeted sequencing for cancer gene mutation detection.

PubMed

Gao, Yan; Deng, Liwei; Yan, Qin; Gao, Yongqian; Wu, Zengding; Cai, Jinsen; Ji, Daorui; Li, Gailing; Wu, Ping; Jin, Huan; Zhao, Luyang; Liu, Song; Ge, Liangjin; Deem, Michael W; He, Jiankui

2016-05-19

With the rapid decline in cost of sequencing, it is now affordable to examine multiple genes in a single disease-targeted clinical test using next generation sequencing. Current targeted sequencing methods require a separate step of targeted capture enrichment during sample preparation before sequencing. Although there are fast sample preparation methods available in market, the library preparation process is still relatively complicated for physicians to use routinely. Here, we introduced an amplification-free Single Molecule Targeted Sequencing (SMTS) technology, which combined targeted capture and sequencing in one step. We demonstrated that this technology can detect low-frequency mutations using artificially synthesized DNA sample. SMTS has several potential advantages, including simple sample preparation thus no biases and errors are introduced by PCR reaction. SMTS has the potential to be an easy and quick sequencing technology for clinical diagnosis such as cancer gene mutation detection, infectious disease detection, inherited condition screening and noninvasive prenatal diagnosis.

Retrocausation acting in the single-electron double-slit interference experiment

NASA Astrophysics Data System (ADS)

Hokkyo, Noboru

The single electron double-slit interference experiment is given a time-symmetric interpretation and visualization in terms of the intermediate amplitude of transition between the particle source and the detection point. It is seen that the retarded (causal) amplitude of the electron wave expanding from the source shows an advanced (retrocausal) bifurcation and merging in passing through the double-slit and converges towards the detection point as if guided by the advanced (retrocausal) wave from the detected electron. An experiment is proposed to confirm the causation-retrocausation symmetry of the electron behavior by observing the insensitivity of the interference pattern to non-magnetic obstacles placed in the shadows of the retarded and advanced waves appearing on the rear and front sides of the double-slit.

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

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

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin

We use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated and therebymore » the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

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

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin

Here, we use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated andmore » thereby the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

DOE PAGES

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin; ...

2017-09-05

Here, we use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated andmore » thereby the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Production of the Q2 doubly excited states of the hydrogen molecule by electron impact in a single step

NASA Astrophysics Data System (ADS)

Santos, Leonardo O.; Rocha, Alexandre B.; Faria, Nelson Velho de Castro; Jalbert, Ginette

2017-03-01

We calculate the single step cross sections for excitation of Q 2 states of H2 and its subsequent dissociation. The cross section calculations were performed within the first Born approximation and the electronic wave functions were obtained via State-Averaged Multiconfigurational Self-Consistent Field followed by Configuration Interaction. We have assumed autoionization is the only important process competing with dissociation into neutral atoms. We have estimated its probability through a semi classical approach and compared with results of literature. Special attention was given to the Q 2 1Σg +(1) state which, as has been shown in a previous work, may dissociate into H(2 sσ) + H(2 sσ) fragments (some figures in this article are in colour only in the electronic version).

Charge transfer to ground-state ions produces free electrons

PubMed Central

You, D.; Fukuzawa, H.; Sakakibara, Y.; Takanashi, T.; Ito, Y.; Maliyar, G. G.; Motomura, K.; Nagaya, K.; Nishiyama, T.; Asa, K.; Sato, Y.; Saito, N.; Oura, M.; Schöffler, M.; Kastirke, G.; Hergenhahn, U.; Stumpf, V.; Gokhberg, K.; Kuleff, A. I.; Cederbaum, L. S.; Ueda, K

2017-01-01

Inner-shell ionization of an isolated atom typically leads to Auger decay. In an environment, for example, a liquid or a van der Waals bonded system, this process will be modified, and becomes part of a complex cascade of relaxation steps. Understanding these steps is important, as they determine the production of slow electrons and singly charged radicals, the most abundant products in radiation chemistry. In this communication, we present experimental evidence for a so-far unobserved, but potentially very important step in such relaxation cascades: Multiply charged ionic states after Auger decay may partially be neutralized by electron transfer, simultaneously evoking the creation of a low-energy free electron (electron transfer-mediated decay). This process is effective even after Auger decay into the dicationic ground state. In our experiment, we observe the decay of Ne2+ produced after Ne 1s photoionization in Ne–Kr mixed clusters. PMID:28134238

Detection of single-nucleotide polymorphisms using gold nanoparticles and single-strand-specific nucleases.

PubMed

Chen, Yen-Ting; Hsu, Chiao-Ling; Hou, Shao-Yi

2008-04-15

The current study reports an assay approach that can detect single-nucleotide polymorphisms (SNPs) and identify the position of the point mutation through a single-strand-specific nuclease reaction and a gold nanoparticle assembly. The assay can be implemented via three steps: a single-strand-specific nuclease reaction that allows the enzyme to truncate the mutant DNA; a purification step that uses capture probe-gold nanoparticles and centrifugation; and a hybridization reaction that induces detector probe-gold nanoparticles, capture probe-gold nanoparticles, and the target DNA to form large DNA-linked three-dimensional aggregates of gold nanoparticles. At high temperature (63 degrees C in the current case), the purple color of the perfect match solution would not change to red, whereas a mismatched solution becomes red as the assembled gold nanoparticles separate. Using melting analysis, the position of the point mutation could be identified. This assay provides a convenient colorimetric detection that enables point mutation identification without the need for expensive mass spectrometry. To our knowledge, this is the first report concerning SNP detection based on a single-strand-specific nuclease reaction and a gold nanoparticle assembly.

Single step signal group-imidazole labeling of organic phosphate groups under aqueous conditions

DOEpatents

Giese, Roger W.; Wang, Poguang

1996-01-01

Compounds and methods for single step, covalent labeling of the phosphate group of an organic substance under aqueous conditions are described. The labeling compound includes any kind of detectable signal group covalently bound to an imidazole moiety, which can be imidazole or a substituted imidazole. A preferred labeling compound has the formula ##STR1##

Subdecoherence time generation and detection of orbital entanglement in quantum dots.

PubMed

Brange, F; Malkoc, O; Samuelsson, P

2015-05-01

Recent experiments have demonstrated subdecoherence time control of individual single-electron orbital qubits. Here we propose a quantum-dot-based scheme for generation and detection of pairs of orbitally entangled electrons on a time scale much shorter than the decoherence time. The electrons are entangled, via two-particle interference, and transferred to the detectors during a single cotunneling event, making the scheme insensitive to charge noise. For sufficiently long detector dot lifetimes, cross-correlation detection of the dot charges can be performed with real-time counting techniques, providing for an unambiguous short-time Bell inequality test of orbital entanglement.

Powder-in-tube and thick-film methods of fabricating high temperature superconductors having enhanced biaxial texture

DOEpatents

Goyal, Amit; Kroeger, Donald M.

2003-11-11

A method for forming an electronically active biaxially textured article includes the steps of providing a substrate having a single crystal metal or metal alloy surface, deforming the substrate to form an elongated substrate surface having biaxial texture and depositing an epitaxial electronically active layer on the biaxially textured surface. The method can include at least one annealing step after the deforming step to produce the biaxially textured substrate surface. The invention can be used to form improved biaxially textured articles, such as superconducting wire and tape articles having improved J.sub.c values.

Preparation and Loading Process of Single Crystalline Samples into a Gas Environmental Cell Holder for In Situ Atomic Resolution Scanning Transmission Electron Microscopic Observation.

PubMed

Straubinger, Rainer; Beyer, Andreas; Volz, Kerstin

2016-06-01

A reproducible way to transfer a single crystalline sample into a gas environmental cell holder for in situ transmission electron microscopic (TEM) analysis is shown in this study. As in situ holders have only single-tilt capability, it is necessary to prepare the sample precisely along a specific zone axis. This can be achieved by a very accurate focused ion beam lift-out preparation. We show a step-by-step procedure to prepare the sample and transfer it into the gas environmental cell. The sample material is a GaP/Ga(NAsP)/GaP multi-quantum well structure on Si. Scanning TEM observations prove that it is possible to achieve atomic resolution at very high temperatures in a nitrogen environment of 100,000 Pa.

Growth of single-layer boron nitride dome-shaped nanostructures catalysed by iron clusters.

PubMed

Torre, A La; Åhlgren, E H; Fay, M W; Ben Romdhane, F; Skowron, S T; Parmenter, C; Davies, A J; Jouhannaud, J; Pourroy, G; Khlobystov, A N; Brown, P D; Besley, E; Banhart, F

2016-08-11

We report on the growth and formation of single-layer boron nitride dome-shaped nanostructures mediated by small iron clusters located on flakes of hexagonal boron nitride. The nanostructures were synthesized in situ at high temperature inside a transmission electron microscope while the e-beam was blanked. The formation process, typically originating at defective step-edges on the boron nitride support, was investigated using a combination of transmission electron microscopy, electron energy loss spectroscopy and computational modelling. Computational modelling showed that the domes exhibit a nanotube-like structure with flat circular caps and that their stability was comparable to that of a single boron nitride layer.

Amide Neighbouring-Group Effects in Peptides: Phenylalanine as Relay Amino Acid in Long-Distance Electron Transfer.

PubMed

Nathanael, Joses G; Gamon, Luke F; Cordes, Meike; Rablen, Paul R; Bally, Thomas; Fromm, Katharina M; Giese, Bernd; Wille, Uta

2018-05-04

In nature, proteins serve as media for long-distance electron transfer (ET) to carry out redox reactions in distant compartments. This ET occurs either by a single-step superexchange or through a multi-step charge hopping process, which uses side chains of amino acids as stepping stones. In this study we demonstrate that Phe can act as a relay amino acid for long-distance electron hole transfer through peptides. The considerably increased susceptibility of the aromatic ring to oxidation is caused by the lone pairs of neighbouring amide carbonyl groups, which stabilise the Phe radical cation. This neighbouring-amide-group effect helps improve understanding of the mechanism of extracellular electron transfer through conductive protein filaments (pili) of anaerobic bacteria during mineral respiration. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Repetitive readout of a single electronic spin via quantum logic with nuclear spin ancillae.

PubMed

Jiang, L; Hodges, J S; Maze, J R; Maurer, P; Taylor, J M; Cory, D G; Hemmer, P R; Walsworth, R L; Yacoby, A; Zibrov, A S; Lukin, M D

2009-10-09

Robust measurement of single quantum bits plays a key role in the realization of quantum computation and communication as well as in quantum metrology and sensing. We have implemented a method for the improved readout of single electronic spin qubits in solid-state systems. The method makes use of quantum logic operations on a system consisting of a single electronic spin and several proximal nuclear spin ancillae in order to repetitively readout the state of the electronic spin. Using coherent manipulation of a single nitrogen vacancy center in room-temperature diamond, full quantum control of an electronic-nuclear system consisting of up to three spins was achieved. We took advantage of a single nuclear-spin memory in order to obtain a 10-fold enhancement in the signal amplitude of the electronic spin readout. We also present a two-level, concatenated procedure to improve the readout by use of a pair of nuclear spin ancillae, an important step toward the realization of robust quantum information processors using electronic- and nuclear-spin qubits. Our technique can be used to improve the sensitivity and speed of spin-based nanoscale diamond magnetometers.

Silver-dendrimer nanocomposites as oligonucleotide labels for electrochemical stripping detection of DNA hybridization.

PubMed

Jin, Xin; Zhou, Ling; Zhu, Bo; Jiang, Xue; Zhu, Ningning

2018-06-01

Silver-dendrimer nanocomposites were synthesized and used as oligonucleotide labels for electrochemical stripping detection of DNA hybridization. The synthesized silver-dendrimer nanocomposites were characterized by UV-vis spectrophotometry, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Ratios of silver/dendrimer were optimized in order to obtain stable nanocomposites with maximal silver loading in the interior of a polymeric shell. The silver-dendrimer nanocomposites were attached to sequence-known DNA probes specific to colitoxin, and used to detect probe hybridization by dissolution of the silver nanoparticles in the interior of dendrimer in a diluted nitric acid, followed by measurement of Ag + ions by anodic stripping voltammetry (ASV). Use of differential pulse voltammetry for the stripping step, along with optimization of the ASV conditions, enabled a detection limit of 0.78 pM. The present strategy, in combination with dendrimer-encapsulated copper labeled oligonucleotides probe reported previously, could potentially be used to detect single or multiple DNA targets in one sample. Copyright © 2018 Elsevier B.V. All rights reserved.

Cp2 TiX Complexes for Sustainable Catalysis in Single-Electron Steps.

PubMed

Richrath, Ruben B; Olyschläger, Theresa; Hildebrandt, Sven; Enny, Daniel G; Fianu, Godfred D; Flowers, Robert A; Gansäuer, Andreas

2018-04-25

We present a combined electrochemical, kinetic, and synthetic study with a novel and easily accessible class of titanocene catalysts for catalysis in single-electron steps. The tailoring of the electronic properties of our Cp 2 TiX-catalysts that are prepared in situ from readily available Cp 2 TiX 2 is achieved by varying the anionic ligand X. Of the complexes investigated, Cp 2 TiOMs proved to be either equal or substantially superior to the best catalysts developed earlier. The kinetic and thermodynamic properties pertinent to catalysis have been determined. They allow a mechanistic understanding of the subtle interplay of properties required for an efficient oxidative addition and reduction. Therefore, our study highlights that efficient catalysts do not require the elaborate covalent modification of the cyclopentadienyl ligands. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Integrating Sub-3 nm Plasmonic Gaps into Solid-State Nanopores.

PubMed

Shi, Xin; Verschueren, Daniel; Pud, Sergii; Dekker, Cees

2018-05-01

Plasmonic nanopores combine the advantages of nanopore sensing and surface plasmon resonances by introducing confined electromagnetic fields to a solid-state nanopore. Ultrasmall nanogaps between metallic nanoantennas can generate the extremely enhanced localized electromagnetic fields necessary for single-molecule optical sensing and manipulation. Challenges in fabrication, however, hamper the integration of such nanogaps into nanopores. Here, a top-down approach for integrating a plasmonic antenna with an ultrasmall nanogap into a solid-state nanopore is reported. Employing a two-step e-beam lithography process, the reproducible fabrication of nanogaps down to a sub-1 nm scale is demonstrated. Subsequently, nanopores are drilled through the 20 nm SiN membrane at the center of the nanogap using focused-electron-beam sculpting with a transmission electron microscope, at the expense of a slight gap expansion for the smallest gaps. Using this approach, sub-3 nm nanogaps can be readily fabricated on solid-state nanopores. The functionality of these plasmonic nanopores for single-molecule detection is shown by performing DNA translocations. These integrated devices can generate intense electromagnetic fields at the entrance of the nanopore and can be expected to find applications in nanopore-based single-molecule trapping and optical sensing. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Single-crystalline nanogap electrodes: enhancing the nanowire-breakdown process with a gaseous environment.

PubMed

Suga, Hiroshi; Sumiya, Touru; Furuta, Shigeo; Ueki, Ryuichi; Miyazawa, Yosuke; Nishijima, Takuya; Fujita, Jun-ichi; Tsukagoshi, Kazuhito; Shimizu, Tetsuo; Naitoh, Yasuhisa

2012-10-24

A method for fabricating single-crystalline nanogaps on Si substrates was developed. Polycrystalline Pt nanowires on Si substrates were broken down by current flow under various gaseous environments. The crystal structure of the nanogap electrode was evaluated using scanning electron microscopy and transmission electron microscopy. Nanogap electrodes sandwiched between Pt-large-crystal-grains were obtained by the breakdown of the wire in an O(2) or H(2) atmosphere. These nanogap electrodes show intense spots in the electron diffraction pattern. The diffraction pattern corresponds to Pt (111), indicating that single-crystal grains are grown by the electrical wire breakdown process in an O(2) or H(2) atmosphere. The Pt wires that have (111)-texture and coherent boundaries can be considered ideal as interconnectors for single molecular electronics. The simple method for fabrication of a single-crystalline nanogap is one of the first steps toward standard nanogap electrodes for single molecular instruments and opens the door to future research on physical phenomena in nanospaces.

Chemical Vapor Deposition Of Silicon Carbide

NASA Technical Reports Server (NTRS)

Powell, J. Anthony; Larkin, David J.; Matus, Lawrence G.; Petit, Jeremy B.

1993-01-01

Large single-crystal SiC boules from which wafers of large area cut now being produced commerically. Availability of wafers opens door for development of SiC semiconductor devices. Recently developed chemical vapor deposition (CVD) process produces thin single-crystal SiC films on SiC wafers. Essential step in sequence of steps used to fabricate semiconductor devices. Further development required for specific devices. Some potential high-temperature applications include sensors and control electronics for advanced turbine engines and automobile engines, power electronics for electromechanical actuators for advanced aircraft and for space power systems, and equipment used in drilling of deep wells. High-frequency applications include communication systems, high-speed computers, and microwave power transistors. High-radiation applications include sensors and controls for nuclear reactors.

Energy transducing redox steps of the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae

PubMed Central

Juárez, Oscar; Morgan, Joel E.; Nilges, Mark J.; Barquera, Blanca

2010-01-01

Na+-NQR is a unique respiratory enzyme that couples the free energy of electron transfer reactions to electrogenic pumping of sodium across the cell membrane. This enzyme is found in many marine and pathogenic bacteria where it plays an analogous role to the H+-pumping complex I. It has generally been assumed that the sodium pump of Na+-NQR operates on the basis of thermodynamic coupling between reduction of a single redox cofactor and the binding of sodium at a nearby site. In this study, we have defined the coupling to sodium translocation of individual steps in the redox reaction of Na+-NQR. Sodium uptake takes place in the reaction step in which an electron moves from the 2Fe-2S center to FMNC, while the translocation of sodium across the membrane dielectric (and probably its release into the external medium) occurs when an electron moves from FMNB to riboflavin. This argues against a single-site coupling model because the redox steps that drive these two parts of the sodium pumping process do not have any redox cofactor in common. The significance of these results for the mechanism of coupling is discussed, and we proposed that Na+-NQR operates through a novel mechanism based on kinetic coupling, mediated by conformational changes. PMID:20616050

A rapid, ratiometric, enzyme-free, and sensitive single-step miRNA detection using three-way junction based FRET probes

NASA Astrophysics Data System (ADS)

Luo, Qingying; Liu, Lin; Yang, Cai; Yuan, Jing; Feng, Hongtao; Chen, Yan; Zhao, Peng; Yu, Zhiqiang; Jin, Zongwen

2018-03-01

MicroRNAs (miRNAs) are single stranded endogenous molecules composed of only 18-24 nucleotides which are critical for gene expression regulating the translation of messenger RNAs. Conventional methods based on enzyme-assisted nucleic acid amplification techniques have many problems, such as easy contamination, high cost, susceptibility to false amplification, and tendency to have sequence mismatches. Here we report a rapid, ratiometric, enzyme-free, sensitive, and highly selective single-step miRNA detection using three-way junction assembled (or self-assembled) FRET probes. The developed strategy can be operated within the linear range from subnanomolar to hundred nanomolar concentrations of miRNAs. In comparison with the traditional approaches, our method showed high sensitivity for the miRNA detection and extreme selectivity for the efficient discrimination of single-base mismatches. The results reveal that the strategy paved a new avenue for the design of novel highly specific probes applicable in diagnostics and potentially in microscopic imaging of miRNAs in real biological environments.

Single-nucleus Hi-C of mammalian oocytes and zygotes.

PubMed

Gassler, Johanna; Flyamer, Ilya M; Tachibana, Kikuë

2018-01-01

The 3D folding of the genome is linked to essential nuclear processes including gene expression, DNA repair, and replication. Chromatin conformation capture assays such as Hi-C are providing unprecedented insights into higher-order chromatin structure. Bulk Hi-C of millions of cells enables detection of average chromatin features at high resolution but is challenging to apply to rare cell types. This chapter describes our recently developed single-nucleus Hi-C (snHi-C) approach for detection of chromatin contacts in single nuclei of murine oocytes and one-cell embryos (zygotes). The step-by-step protocol includes isolation of these cells, extraction of nuclei, fixation, restriction digestion, ligation, and whole genome amplification. Contacts obtained by snHi-C allow detection of chromatin features including loops, topologically associating domains, and compartments when averaged over the genome. The combination of snHi-C with other single-cell techniques in these and other rare cell types will likely provide a comprehensive picture of how chromatin architecture shapes cell identity. © 2018 Elsevier Inc. All rights reserved.

Two in one: making electron and ion measurements using a single MCP in future top hat instruments.

NASA Astrophysics Data System (ADS)

Bedington, Robert; Saito, Yoshifumi

To allow for the reduced use of spacecraft resources in future missions, we are developing techniques to enable both electrons and ions to be measured in a single top hat instrument. Top hat energy analyser instruments typically analyse charged particles from a few eV to a few tens keV. They consist of an electrostatic, energy-analyser section and a detector. MCPs (micro-channel plates) are the most commonly used detectors, because of their high sensitivity and strong heritage in space instrumentation. To detect the lowest energies of charged particles, a pre-accelerating bias potential is applied to the front surface of the MCP, however this voltage cannot be altered quickly without drastically affecting the detector response. Any instrument that detects both electrons and ions, will therefore typically use two detectors (with fixed voltages)—one for electrons, one for ions, and will often use two separate energy analysers. Significant resource savings are available however if just a single MCP can be used. This can be achieved by having incoming ions (and optionally incoming electrons also) impact a secondary electron emitting material, and thus release secondary electrons to be detected by a positively biased (electron-detecting) MCP. Unlike MCPs, the electrostatic, energy-analyser sections are able to have their voltages cycled extremely rapidly, so that they can be made to sample electrons and then ions in quick succession with minimal design changes required. Two secondary electron conversion methods are being investigated: ultra-thin carbon foils, and dynodes. Using carbon foils in front of the MCPs, incoming ions can be detected by the secondary electrons they release, while incoming electrons pass straight through them. Using dynodes all incoming particles can be converted to secondary electrons before detection. The challenges include finding materials with uniform electron emission responses for the desired energies and particles, managing electric fields and scattered primary electrons. Experiments pertaining to this research will be discussed. These investigations are being pursued as prototype developments for the SCOPE mission for use on the EISA (Electron & Ion Spectrum Analyzer) instrument.

Rapid comprehensive characterization of crude oils by thermogravimetry coupled to fast modulated gas chromatography-single photon ionization time-of-flight mass spectrometry.

PubMed

Wohlfahrt, S; Fischer, M; Saraji-Bozorgzad, M; Matuschek, G; Streibel, T; Post, E; Denner, T; Zimmermann, R

2013-09-01

Comprehensive multi-dimensional hyphenation of a thermogravimetry device (i.e. a thermobalance) to gas chromatography and single photon ionization-time-of-flight mass spectrometry (TG-GC×SPI-MS) has been used to investigate two crude oil samples of different geographical origin. The source of the applied vacuum ultraviolet radiation is an electron beam pumped rare gas excimer lamp (EBEL). The soft photoionization favors the formation of molecular ions. Introduction of a fast, rapidly modulated gas chromatographic separation step in comparison with solely TG-SPI-MS enables strongly enhanced detection especially with such highly complex organic matrices as crude oil. In contrast with former TG-SPI-MS measurements, separation and identification of overlying substances is possible because of different GC retention times. The specific contribution of isobaric compounds to one mass signal is determined for alkanes, naphthalenes, alkylated benzenes, and other compounds.

Effects of dual task on turning ability in stroke survivors and older adults.

PubMed

Hollands, K L; Agnihotri, D; Tyson, S F

2014-09-01

Turning is an integral component of independent mobility in which stroke survivors frequently fall. This study sought to measure the effects of competing cognitive demands on the stepping patterns of stroke survivors, compared to healthy age-match adults, during turning as a putative mechanism for falls. Walking and turning (90°) was assessed under single (walking and turning alone) and dual task (subtracting serial 3s while walking and turning) conditions using an electronic, pressure-sensitive walkway. Dependent measures were time to turn, variability in time to turn, step length, step width and single support time during three steps of the turn. Turning ability in single and dual task conditions was compared between stroke survivors (n=17, mean ± SD: 59 ± 113 months post-stroke, 64 ± 10 years of age) and age-matched healthy counterparts (n=15). Both groups took longer, were more variable, tended to widen the second step and, crucially, increased single support time on the inside leg of the turn while turning and distracted. Increased single support time during turning may represent biomechanical mechanism, within stepping patterns of turning under distraction, for increased risk of falls for both stroke survivors and older adults. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

Nano-Electromechanical Systems: Displacement Detection and the Mechanical Single Electron Shuttle

NASA Astrophysics Data System (ADS)

Blick, R. H.; Beil, F. W.; Höhberger, E.; Erbe, A.; Weiss, C.

For an introduction to nano-electromechanical systems we present measurements on nanomechanical resonators operating in the radio frequency range. We discuss in detail two different schemes of displacement detection for mechanical resonators, namely conventional reflection measurements of a probing signal and direct detection by capacitive coupling via a gate electrode. For capacitive detection we employ an on-chip preamplifier, which enables direct measurements of the resonator's disp lacement. We observe that the mechanical quality factor of the resonator depends on the detection technique applied, which is verified in model calculations and report on the detection of sub-harmonics. In the second part we extend our investigations to include transport of single electrons through an electron island on the tip of a nanomachined mechanical pendulum. The pendulum is operated by applying a modulating electromagnetic field in the range of 1 - 200 MHz, leading to mechanical oscillations between two laterally integrated source and drain contacts. Forming tunneling barriers the metallic tip shuttles single electrons from source to drain. The resulting tunneling current shows distinct features corresponding to the discrete mechanical eigenfrequencies of the pendulum. We report on measurements covering the temperature range from 300 K down to 4.2 K. The transport properties of the device are compared in detail to model calculations based on a Master-equation approach.

Single step signal group-imidazole labeling of organic phosphate groups under aqueous conditions

DOEpatents

Giese, R.W.; Wang, P.

1996-04-30

Compounds and methods for single step, covalent labeling of the phosphate group of an organic substance under aqueous conditions are described. The labeling compound includes any kind of detectable signal group covalently bound to an imidazole moiety, which can be imidazole or a substituted imidazole. A preferred labeling compound has the formula shown in the accompanying diagram. 4 figs.

Biomolecule detection based on Si single-electron transistors for practical use

NASA Astrophysics Data System (ADS)

Nakajima, Anri; Kudo, Takashi; Furuse, Sadaharu

2013-07-01

Experimental and theoretical analyses demonstrated that ultra-sensitive biomolecule detection can be achieved using a Si single-electron transistor (SET). A multi-island channel structure was used to enable room-temperature operation. Coulomb oscillation increases transconductance without increasing channel width, which increases detection sensitivity to a charged target. A biotin-modified SET biosensor was used to detect streptavidin at a dilute concentration. In addition, an antibody-functionalized SET biosensor was used for immunodetection of prostate-specific antigen, demonstrating its suitability for practical use. The feasibility of ultra-sensitive detection of biomolecules for practical use by using a SET biosensor was clearly proven through this systematic study.

High-resolution, high-throughput imaging with a multibeam scanning electron microscope.

PubMed

Eberle, A L; Mikula, S; Schalek, R; Lichtman, J; Knothe Tate, M L; Zeidler, D

2015-08-01

Electron-electron interactions and detector bandwidth limit the maximal imaging speed of single-beam scanning electron microscopes. We use multiple electron beams in a single column and detect secondary electrons in parallel to increase the imaging speed by close to two orders of magnitude and demonstrate imaging for a variety of samples ranging from biological brain tissue to semiconductor wafers. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Strong spin-photon coupling in silicon

NASA Astrophysics Data System (ADS)

Samkharadze, N.; Zheng, G.; Kalhor, N.; Brousse, D.; Sammak, A.; Mendes, U. C.; Blais, A.; Scappucci, G.; Vandersypen, L. M. K.

2018-03-01

Long coherence times of single spins in silicon quantum dots make these systems highly attractive for quantum computation, but how to scale up spin qubit systems remains an open question. As a first step to address this issue, we demonstrate the strong coupling of a single electron spin and a single microwave photon. The electron spin is trapped in a silicon double quantum dot, and the microwave photon is stored in an on-chip high-impedance superconducting resonator. The electric field component of the cavity photon couples directly to the charge dipole of the electron in the double dot, and indirectly to the electron spin, through a strong local magnetic field gradient from a nearby micromagnet. Our results provide a route to realizing large networks of quantum dot–based spin qubit registers.

Single-ion adsorption and switching in carbon nanotubes

DOE PAGES

Bushmaker, Adam W.; Oklejas, Vanessa; Walker, Don; ...

2016-01-25

Single-ion detection has, for many years, been the domain of large devices such as the Geiger counter, and studies on interactions of ionized gasses with materials have been limited to large systems. To date, there have been no reports on single gaseous ion interaction with microelectronic devices, and single neutral atom detection techniques have shown only small, barely detectable responses. Here we report the observation of single gaseous ion adsorption on individual carbon nanotubes (CNTs), which, because of the severely restricted one-dimensional current path, experience discrete, quantized resistance increases of over two orders of magnitude. Only positive ions cause changes,more » by the mechanism of ion potentialinduced carrier depletion, which is supported by density functional and Landauer transport theory. Lastly, our observations reveal a new single-ion/CNT heterostructure with novel electronic properties, and demonstrate that as electronics are ultimately scaled towards the one-dimensional limit, atomic-scale effects become increasingly important.« less

Instrumental requirements for the detection of electron beam-induced object excitations at the single atom level in high-resolution transmission electron microscopy.

PubMed

Kisielowski, C; Specht, P; Gygax, S M; Barton, B; Calderon, H A; Kang, J H; Cieslinski, R

2015-01-01

This contribution touches on essential requirements for instrument stability and resolution that allows operating advanced electron microscopes at the edge to technological capabilities. They enable the detection of single atoms and their dynamic behavior on a length scale of picometers in real time. It is understood that the observed atom dynamic is intimately linked to the relaxation and thermalization of electron beam-induced sample excitation. Resulting contrast fluctuations are beam current dependent and largely contribute to a contrast mismatch between experiments and theory if not considered. If explored, they open the possibility to study functional behavior of nanocrystals and single molecules at the atomic level in real time. Copyright © 2014 Elsevier Ltd. All rights reserved.

Detecting and locating light atoms from high-resolution STEM images: The quest for a single optimal design.

PubMed

Gonnissen, J; De Backer, A; den Dekker, A J; Sijbers, J; Van Aert, S

2016-11-01

In the present paper, the optimal detector design is investigated for both detecting and locating light atoms from high resolution scanning transmission electron microscopy (HR STEM) images. The principles of detection theory are used to quantify the probability of error for the detection of light atoms from HR STEM images. To determine the optimal experiment design for locating light atoms, use is made of the so-called Cramér-Rao Lower Bound (CRLB). It is investigated if a single optimal design can be found for both the detection and location problem of light atoms. Furthermore, the incoming electron dose is optimised for both research goals and it is shown that picometre range precision is feasible for the estimation of the atom positions when using an appropriate incoming electron dose under the optimal detector settings to detect light atoms. Copyright © 2016 Elsevier B.V. All rights reserved.

Two-step passivation for enhanced InGaN/GaN light emitting diodes with step graded electron injectors

NASA Astrophysics Data System (ADS)

Sheremet, V.; Genç, M.; Gheshlaghi, N.; Elçi, M.; Sheremet, N.; Aydınlı, A.; Altuntaş, I.; Ding, K.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

2018-01-01

Enhancement of InGaN/GaN based light emitting diode performance with step graded electron injectors through a two-step passivation is reported. Perimeter passivation of LED dies with SiO2 immediately following ICP mesa etch in addition to conventional Si3N4 dielectric surface passivation leads to decrease in the reverse bias leakage current by a factor of two as well as a decrease in the shunt current under forward bias by an order of magnitude. Mitigation of the leakage currents owing to the two-step passivation leads to significant increase in the radiant intensity of LEDs by more than a factor of two compared to the conventional single step surface passivation. Further, micro-dome patterned surface of Si3N4 passivation layer allow enhanced light extraction from LEDs.

Functionalization of monolithic and porous three-dimensional graphene by one-step chitosan electrodeposition for enzymatic biosensor.

PubMed

Liu, Jiyang; Wang, Xiaohui; Wang, Tianshu; Li, Dan; Xi, Fengna; Wang, Jin; Wang, Erkang

2014-11-26

Biological modification of monolithic and porous 3D graphene is of great significance for extending its application in fabricating highly sensitive biosensors. The present work reports on the first biofunctionalization of monolithic and freestanding 3D graphene foam for one-step preparation of reagentless enzymatic biosensors by controllable chitosan (CS) electrodeposition technology. Using a homogeneous three-component electrodeposition solution containing a ferrocene (Fc) grafted CS hybrid (Fc-CS), glucose oxidase (GOD), and single-walled carbon nanotubes (SWNTs), a homogeneous biocomposite film of Fc-CS/SWNTs/GOD was immobilized on the surface of 3D graphene foam by one-step electrodeposition. The Fc groups grafted on chitosan can be stably immobilized on the 3D graphene surface and keep their original electrochemical activity. The SWNTs doped into the Fc-CS matrix act as a nanowire to facilitate electron transfer and improve the conductivity of the biocomposite film. Combined with the extraordinary properties of 3D graphene foam including large active surface area, high conductivity, and fast mass transport dynamics, the 3D graphene based enzymatic biosensor achieved a large linear range (5.0 μM to 19.8 mM), a low detection limit (1.2 μM), and rapid response (reaching the 95% steady-state response within 8 s) for reagentless detection of glucose in the phosphate buffer solution.

Electronic components embedded in a single graphene nanoribbon.

PubMed

Jacobse, P H; Kimouche, A; Gebraad, T; Ervasti, M M; Thijssen, J M; Liljeroth, P; Swart, I

2017-07-25

The use of graphene in electronic devices requires a band gap, which can be achieved by creating nanostructures such as graphene nanoribbons. A wide variety of atomically precise graphene nanoribbons can be prepared through on-surface synthesis, bringing the concept of graphene nanoribbon electronics closer to reality. For future applications it is beneficial to integrate contacts and more functionality directly into single ribbons by using heterostructures. Here, we use the on-surface synthesis approach to fabricate a metal-semiconductor junction and a tunnel barrier in a single graphene nanoribbon consisting of 5- and 7-atom wide segments. We characterize the atomic scale geometry and electronic structure by combined atomic force microscopy, scanning tunneling microscopy, and conductance measurements complemented by density functional theory and transport calculations. These junctions are relevant for developing contacts in all-graphene nanoribbon devices and creating diodes and transistors, and act as a first step toward complete electronic devices built into a single graphene nanoribbon.Adding functional electronic components to graphene nanoribbons requires precise control over their atomic structure. Here, the authors use a bottom-up approach to build a metal-semiconductor junction and a tunnel barrier directly into a single graphene nanoribbon, an exciting development for graphene-based electronic devices.

Direct detection of a transport-blocking trap in a nanoscaled silicon single-electron transistor by radio-frequency reflectometry

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

Villis, B. J.; Sanquer, M.; Jehl, X.

2014-06-09

The continuous downscaling of transistors results in nanoscale devices which require fewer and fewer charged carriers for their operation. The ultimate charge controlled device, the single-electron transistor (SET), controls the transfer of individual electrons. It is also the most sensitive electrometer, and as a result the electron transport through it can be dramatically affected by nearby charges. Standard direct-current characterization techniques, however, are often unable to unambiguously detect and resolve the origin of the observed changes in SET behavior arising from changes in the charge state of a capacitively coupled trap. Using a radio-frequency (RF) reflectometry technique, we are ablemore » to unequivocally detect this process, in very close agreement with modeling of the trap's occupation probability.« less

Photocleavable DNA Barcoding Antibodies for Multiplexed Protein Analysis in Single Cells.

PubMed

Ullal, Adeeti V; Weissleder, Ralph

2015-01-01

We describe a DNA-barcoded antibody sensing technique for single cell protein analysis in which the barcodes are photocleaved and digitally detected without amplification steps (Ullal et al., Sci Transl Med 6:219, 2014). After photocleaving the unique ~70 mer DNA barcodes we use a fluorescent hybridization technology for detection, similar to what is commonly done for nucleic acid readouts. This protocol offers a simple method for multiplexed protein detection using 100+ antibodies and can be performed on clinical samples as well as single cells.

Enzyme-free Detection of Hydrogen Peroxide from Cerium Oxide Nanoparticles Immobilized on Poly(4-vinylpyridine) Self-Assembled Monolayers

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

Gaynor, James D.; Karakoti, Ajay S.; Inerbaev, Talgat

2013-05-02

A single layer of oxygen-deficient cerium oxide nanoparticles (CNPs) are immobilized on microscopic glass slide using poly(4-vinylpyridine) (PVP) self-assembled monolayers (SAMs). A specific colorimetric property of CNPs when reacted with hydrogen peroxide allows for the direct, single-step peroxide detection which can be used in medical diagnosis and explosives detection. Multiple PVP-CNP immobilized layers improve sensitivity of detection and the sensor can be regenerated for reuse.

Permeability of Dental Adhesives – A SEM Assessment

PubMed Central

Malacarne-Zanon, Juliana; de Andrade e Silva, Safira M.; Wang, Linda; de Goes, Mario F.; Martins, Adriano Luis; Narvaes-Romani, Eliene O.; Anido-Anido, Andrea; Carrilho, Marcela R. O.

2010-01-01

Objectives: To morphologically evaluate the permeability of different commercial dental adhesives using scanning electron microscopy. Methods: Seven adhesive systems were evaluated: one three-step system (Scotchbond Multi-Purpose - MP); one two-step self-etching primer system (Clearfil SE Bond – SE); three two-step etch-and-rinse systems (Single Bond 2 – SB; Excite – EX; One-Step – OS); and two single-step self-etching adhesives (Adper Prompt – AP; One-Up Bond F – OU). The mixture of primer and bond agents of the Clearfil SE Bond system (SE-PB) was also tested. The adhesives were poured into a brass mold (5.8 mm x 0.8 mm) and light-cured for 80 s at 650 mW/cm2. After a 24 h desiccation process, the specimens were immersed in a 50% ammoniac silver nitrate solution for tracer permeation. Afterwards, they were sectioned in ultra-fine slices, carbon-coated, and analyzed under backscattered electrons in a scanning electron microscopy. Results: MP and SE showed slight and superficial tracer permeation. In EX, SB, and OS, permeation extended beyond the inner superficies of the specimens. SE-PB did not mix well, and most of the tracer was precipitated into the primer agent. In AP and OU, “water-trees” were observed all over the specimens. Conclusions: Different materials showed distinct permeability in aqueous solution. The extent of tracer permeation varied according to the composition of each material and it was more evident in the more hydrophilic and solvated ones. PMID:20922163

Rapid Waterborne Pathogen Detection with Mobile Electronics.

PubMed

Wu, Tsung-Feng; Chen, Yu-Chen; Wang, Wei-Chung; Kucknoor, Ashwini S; Lin, Che-Jen; Lo, Yu-Hwa; Yao, Chun-Wei; Lian, Ian

2017-06-09

Pathogen detection in water samples, without complex and time consuming procedures such as fluorescent-labeling or culture-based incubation, is essential to public safety. We propose an immunoagglutination-based protocol together with the microfluidic device to quantify pathogen levels directly from water samples. Utilizing ubiquitous complementary metal-oxide-semiconductor (CMOS) imagers from mobile electronics, a low-cost and one-step reaction detection protocol is developed to enable field detection for waterborne pathogens. 10 mL of pathogen-containing water samples was processed using the developed protocol including filtration enrichment, immune-reaction detection and imaging processing. The limit of detection of 10 E. coli O157:H7 cells/10 mL has been demonstrated within 10 min of turnaround time. The protocol can readily be integrated into a mobile electronics such as smartphones for rapid and reproducible field detection of waterborne pathogens.

dc-plasma-sprayed electronic-tube device

DOEpatents

Meek, T.T.

1982-01-29

An electronic tube and associated circuitry which is produced by dc plasma arc spraying techniques is described. The process is carried out in a single step automated process whereby both active and passive devices are produced at very low cost. The circuitry is extremely reliable and is capable of functioning in both high radiation and high temperature environments. The size of the electronic tubes produced are more than an order of magnitude smaller than conventional electronic tubes.

Elucidating the Structure-Reactivity Correlations of Phenothiazine-Based Fluorescent Probes toward ClO.

PubMed

Wang, Shichao; Zhang, Boyu; Wang, Wenjing; Feng, Gang; Yuan, Daqiang; Zhang, Xuanjun

2018-06-07

In this work, with the aim of developing effective molecular probes and investigating the structure-reactivity correlation, a short series of phenothiazine-based fluorescent probes are designed for the detection of ClO - with differing electron push-pull groups. Sensing experiment results and single-crystal X-ray analysis with the aid of time-dependent DFT (TD-DFT) calculations reveal that substituting groups with increasing electron-withdrawing ability can increase the dihedral angle of the phenothiazine moiety and reduce the gap energy of the probes, leading to enhanced reactivity toward ClO - . Both PT1 and PT2 show two-color switching upon detection of ClO - . PT1, with the strong electron-donating group thiophene, shows a fluorescence color switch from salmon to blue. PT2, with a medium electron-donating/accepting group benzothiazole, shows a fluorescence color switch from red to green. However, both PT1 and PT2 show almost no response to ONOO - . Through the introduction of strong electron-withdrawing ketone combined with a cyano group, PT3 shows a cyan emission upon detection of ClO - and weak red emission upon detection of ONOO - . HRMS and 1 H NMR results confirm that PT1 and PT2 have the same sensing mode, in which the divalent sulfur of phenothiazine can be oxidized to sulfoxide by ClO - . Upon reaction with ClO - , PT3 experiences two-step reactions. It is first oxidized into the sulfone structure by ClO - , and then transformed into sulfoxide phenothiazine aldehyde. Upon encountering ONOO - , PT3 changes into an aldehyde structure and some nonfluorescent byproducts. Owing to their special selectivity and high sensitivity, PT1 and PT2 are applied to image the endogenous ClO - in macrophage cells and zebrafish larvae. This study is expected to provide useful guidelines for probe design for various applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Observation of entanglement of a single photon with a trapped atom.

PubMed

Volz, Jürgen; Weber, Markus; Schlenk, Daniel; Rosenfeld, Wenjamin; Vrana, Johannes; Saucke, Karen; Kurtsiefer, Christian; Weinfurter, Harald

2006-01-27

We report the observation of entanglement between a single trapped atom and a single photon at a wavelength suitable for low-loss communication over large distances, thereby achieving a crucial step towards long range quantum networks. To verify the entanglement, we introduce a single atom state analysis. This technique is used for full state tomography of the atom-photon qubit pair. The detection efficiency and the entanglement fidelity are high enough to allow in a next step the generation of entangled atoms at large distances, ready for a final loophole-free Bell experiment.

Critical Motor Number for Fractional Steps of Cytoskeletal Filaments in Gliding Assays

PubMed Central

Li, Xin; Lipowsky, Reinhard; Kierfeld, Jan

2012-01-01

In gliding assays, filaments are pulled by molecular motors that are immobilized on a solid surface. By varying the motor density on the surface, one can control the number of motors that pull simultaneously on a single filament. Here, such gliding assays are studied theoretically using Brownian (or Langevin) dynamics simulations and taking the local force balance between motors and filaments as well as the force-dependent velocity of the motors into account. We focus on the filament stepping dynamics and investigate how single motor properties such as stalk elasticity and step size determine the presence or absence of fractional steps of the filaments. We show that each gliding assay can be characterized by a critical motor number, . Because of thermal fluctuations, fractional filament steps are only detectable as long as . The corresponding fractional filament step size is where is the step size of a single motor. We first apply our computational approach to microtubules pulled by kinesin-1 motors. For elastic motor stalks that behave as linear springs with a zero rest length, the critical motor number is found to be , and the corresponding distributions of the filament step sizes are in good agreement with the available experimental data. In general, the critical motor number depends on the elastic stalk properties and is reduced to for linear springs with a nonzero rest length. Furthermore, is shown to depend quadratically on the motor step size . Therefore, gliding assays consisting of actin filaments and myosin-V are predicted to exhibit fractional filament steps up to motor number . Finally, we show that fractional filament steps are also detectable for a fixed average motor number as determined by the surface density (or coverage) of the motors on the substrate surface. PMID:22927953

Gold Nanorod-based Photo-PCR System for One-Step, Rapid Detection of Bacteria

PubMed Central

Kim, Jinjoo; Kim, Hansol; Park, Ji Ho; Jon, Sangyong

2017-01-01

The polymerase chain reaction (PCR) has been an essential tool for diagnosis of infectious diseases, but conventional PCR still has some limitations with respect to applications to point-of-care (POC) diagnostic systems that require rapid detection and miniaturization. Here we report a light-based PCR method, termed as photo-PCR, which enables rapid detection of bacteria in a single step. In the photo-PCR system, poly(enthylene glycol)-modified gold nanorods (PEG-GNRs), used as a heat generator, are added into the PCR mixture, which is subsequently periodically irradiated with a 808-nm laser to create thermal cycling. Photo-PCR was able to significantly reduce overall thermal cycling time by integrating bacterial cell lysis and DNA amplification into a single step. Furthermore, when combined with KAPA2G fast polymerase and cooling system, the entire process of bacterial genomic DNA extraction and amplification was further shortened, highlighting the potential of photo-PCR for use in a portable, POC diagnostic system. PMID:29071186

Detection of single electron spin resonance in a double quantum dota)

NASA Astrophysics Data System (ADS)

Koppens, F. H. L.; Buizert, C.; Vink, I. T.; Nowack, K. C.; Meunier, T.; Kouwenhoven, L. P.; Vandersypen, L. M. K.

2007-04-01

Spin-dependent transport measurements through a double quantum dot are a valuable tool for detecting both the coherent evolution of the spin state of a single electron, as well as the hybridization of two-electron spin states. In this article, we discuss a model that describes the transport cycle in this regime, including the effects of an oscillating magnetic field (causing electron spin resonance) and the effective nuclear fields on the spin states in the two dots. We numerically calculate the current flow due to the induced spin flips via electron spin resonance, and we study the detector efficiency for a range of parameters. The experimental data are compared with the model and we find a reasonable agreement.

Crystal step edges can trap electrons on the surfaces of n-type organic semiconductors.

PubMed

He, Tao; Wu, Yanfei; D'Avino, Gabriele; Schmidt, Elliot; Stolte, Matthias; Cornil, Jérôme; Beljonne, David; Ruden, P Paul; Würthner, Frank; Frisbie, C Daniel

2018-05-30

Understanding relationships between microstructure and electrical transport is an important goal for the materials science of organic semiconductors. Combining high-resolution surface potential mapping by scanning Kelvin probe microscopy (SKPM) with systematic field effect transport measurements, we show that step edges can trap electrons on the surfaces of single crystal organic semiconductors. n-type organic semiconductor crystals exhibiting positive step edge surface potentials display threshold voltages that increase and carrier mobilities that decrease with increasing step density, characteristic of trapping, whereas crystals that do not have positive step edge surface potentials do not have strongly step density dependent transport. A device model and microelectrostatics calculations suggest that trapping can be intrinsic to step edges for crystals of molecules with polar substituents. The results provide a unique example of a specific microstructure-charge trapping relationship and highlight the utility of surface potential imaging in combination with transport measurements as a productive strategy for uncovering microscopic structure-property relationships in organic semiconductors.

Extremely Efficient Multiple Electron-hole Pair Generation in Carbon Nanotube Photodiodes

NASA Astrophysics Data System (ADS)

Gabor, Nathaniel

2010-03-01

The efficient generation of multiple electron-hole (e-h) pairs from a single photon could improve the efficiency of photovoltaic solar cells beyond standard thermodynamic limits [1] and has been the focus of much recent work in semiconductor nanomaterials [2,3]. In single walled carbon nanotubes (SWNTs), the small Fermi velocity and low dielectric constant suggests that electron-electron interactions are very strong and that high-energy carriers should efficiently generate e-h pairs. Here, I will discuss observations of highly efficient generation of e-h pairs due to impact excitation in SWNT p-n junction photodiodes [4]. To investigate optoelectronic transport properties of individual SWNT photodiodes, we focus a laser beam over the device while monitoring the electronic characteristics. Optical excitation into the second electronic subband E22 ˜ 2 EGAP leads to striking photocurrent steps in the device I-VSD characteristics that occur at voltage intervals of the band gap energy EGAP/ e. Spatially and spectrally resolved photocurrent combined with temperature-dependent studies suggest that these steps result from efficient generation of multiple e-h pairs from a single hot E22 carrier. We conclude that in the SWNT photodiode, a single photon with energy greater than 2EGAP is converted into multiple e-h pairs, leading to enhanced photocurrent and increased photo-conversion efficiency. [1] W. Shockley, and H. J. Queisser, Journal of Applied Physics 32, 510 (1961). [2] R. D. Schaller, and V. I. Klimov, Physical Review Letters 92 (18), 186601 (2004). [3] R. J. Ellingson, et al, Nano Letters, 5 (5), 865-871 (2005). [4] Nathaniel M. Gabor, Zhaohui Zhong, Ken Bosnick, Jiwoong Park, and Paul McEuen, Science, 325, 1367 (2009).

Robust w-Estimators for Cryo-EM Class Means

PubMed Central

Huang, Chenxi; Tagare, Hemant D.

2016-01-01

A critical step in cryogenic electron microscopy (cryo-EM) image analysis is to calculate the average of all images aligned to a projection direction. This average, called the “class mean”, improves the signal-to-noise ratio in single particle reconstruction (SPR). The averaging step is often compromised because of outlier images of ice, contaminants, and particle fragments. Outlier detection and rejection in the majority of current cryo-EM methods is done using cross-correlation with a manually determined threshold. Empirical assessment shows that the performance of these methods is very sensitive to the threshold. This paper proposes an alternative: a “w-estimator” of the average image, which is robust to outliers and which does not use a threshold. Various properties of the estimator, such as consistency and influence function are investigated. An extension of the estimator to images with different contrast transfer functions (CTFs) is also provided. Experiments with simulated and real cryo-EM images show that the proposed estimator performs quite well in the presence of outliers. PMID:26841397

Robust w-Estimators for Cryo-EM Class Means.

PubMed

Huang, Chenxi; Tagare, Hemant D

2016-02-01

A critical step in cryogenic electron microscopy (cryo-EM) image analysis is to calculate the average of all images aligned to a projection direction. This average, called the class mean, improves the signal-to-noise ratio in single-particle reconstruction. The averaging step is often compromised because of the outlier images of ice, contaminants, and particle fragments. Outlier detection and rejection in the majority of current cryo-EM methods are done using cross-correlation with a manually determined threshold. Empirical assessment shows that the performance of these methods is very sensitive to the threshold. This paper proposes an alternative: a w-estimator of the average image, which is robust to outliers and which does not use a threshold. Various properties of the estimator, such as consistency and influence function are investigated. An extension of the estimator to images with different contrast transfer functions is also provided. Experiments with simulated and real cryo-EM images show that the proposed estimator performs quite well in the presence of outliers.

Dendrimer enriched single-use aptasensor for impedimetric detection of activated protein C.

PubMed

Erdem, Arzum; Congur, Gulsah

2014-05-01

A novel impedimetric aptasensor for detection of human activated protein C (APC) was introduced for the first time in the present study. An enhanced sensor response was obtained using poly(amidoamine) (PAMAM) dendrimer having 16 succinamic acid surface groups (generation 2, G2-PS), that was modified onto the surface of screen printed graphite electrode (G2-PS/SPE). An amino modified DNA aptamer was then immobilized onto the surface of G2-PS modified SPE. The selective interaction of APT with its cognate protein, APC was investigated using different electrochemical techniques; differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The microscopic characterization was consecutively performed before/after each modification/interaction step using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The selectivity of aptasensor was tested in the presence of numerous proteins; protein C, thrombin, bovine serum albumin, factor Va and chromogenic substrate in different buffer mediums. The APC detection in the artificial serum; fetal bovine serum (FBS) was also performed impedimetrically. This dendrimer modified aptasensor technology brings several advantages: being single-use, fast screening with low-cost per measurement and resulting in sensitive detection of APC with the detection limits of 0.74 μg/mL (0.46 pmol in 35 μL sample) in buffer medium, and 2.03 μg/mL (1.27 pmol in 35 μL sample) in serum. Copyright © 2014 Elsevier B.V. All rights reserved.

Cryo-electron microscopy and single molecule fluorescent microscopy detect CD4 receptor induced HIV size expansion prior to cell entry

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

Pham, Son; CSIRO Australian Animal Health Laboratory, Victoria 3220; Tabarin, Thibault

Viruses are often thought to have static structure, and they only remodel after the viruses have entered target cells. Here, we detected a size expansion of virus particles prior to viral entry using cryo-electron microscopy (cryo-EM) and single molecule fluorescence imaging. HIV expanded both under cell-free conditions with soluble receptor CD4 (sCD4) targeting the CD4 binding site on the HIV-1 envelope protein (Env) and when HIV binds to receptor on cellular membrane. We have shown that the HIV Env is needed to facilitate receptor induced virus size expansions, showing that the ‘lynchpin’ for size expansion is highly specific. We demonstratemore » that the size expansion required maturation of HIV and an internal capsid core with wild type stability, suggesting that different HIV compartments are linked and are involved in remodelling. Our work reveals a previously unknown event in HIV entry, and we propose that this pre-entry priming process enables HIV particles to facilitate the subsequent steps in infection. - Highlights: • Cell free viruses are able to receive external trigger that leads to apparent size expansion. • Virus envelope and CD4 receptor engagement is the lynchpin of virus size expansion. • Internal capsid organisation can influence receptor mediated virus size expansion. • Pre-existing virus-associated lipid membrane in cell free virus can accommodate the receptor mediated virus size expansion.« less

Single-electron random-number generator (RNG) for highly secure ubiquitous computing applications

NASA Astrophysics Data System (ADS)

Uchida, Ken; Tanamoto, Tetsufumi; Fujita, Shinobu

2007-11-01

Since the security of all modern cryptographic techniques relies on unpredictable and irreproducible digital keys generated by random-number generators (RNGs), the realization of high-quality RNG is essential for secure communications. In this report, a new RNG, which utilizes single-electron phenomena, is proposed. A room-temperature operating silicon single-electron transistor (SET) having nearby an electron pocket is used as a high-quality, ultra-small RNG. In the proposed RNG, stochastic single-electron capture/emission processes to/from the electron pocket are detected with high sensitivity by the SET, and result in giant random telegraphic signals (GRTS) on the SET current. It is experimentally demonstrated that the single-electron RNG generates extremely high-quality random digital sequences at room temperature, in spite of its simple configuration. Because of its small-size and low-power properties, the single-electron RNG is promising as a key nanoelectronic device for future ubiquitous computing systems with highly secure mobile communication capabilities.

Advanced metal lift-off process using electron-beam flood exposure of single-layer photoresist

NASA Astrophysics Data System (ADS)

Minter, Jason P.; Ross, Matthew F.; Livesay, William R.; Wong, Selmer S.; Narcy, Mark E.; Marlowe, Trey

1999-06-01

In the manufacture of many types of integrated circuit and thin film devices, it is desirable to use a lift-of process for the metallization step to avoid manufacturing problems encountered when creating metal interconnect structures using plasma etch. These problems include both metal adhesion and plasma etch difficulties. Key to the success of the lift-off process is the creation of a retrograde or undercut profile in the photoresists before the metal deposition step. Until now, lift-off processing has relied on costly multi-layer photoresists schemes, image reversal, and non-repeatable photoresist processes to obtain the desired lift-off profiles in patterned photoresist. This paper present a simple, repeatable process for creating robust, user-defined lift-off profiles in single layer photoresist using a non-thermal electron beam flood exposure. For this investigation, lift-off profiles created using electron beam flood exposure of many popular photoresists were evaluated. Results of lift-off profiles created in positive tone AZ7209 and ip3250 are presented here.

Ultrasensitive protein detection in blood serum using gold nanoparticle probes by single molecule spectroscopy

NASA Astrophysics Data System (ADS)

Chen, Jiji; Wang, Chungang; Irudayaraj, Joseph

2009-07-01

A one-step rapid and ultrasensitive immunoassay capable of detecting proteins in blood serum is developed using gold nanoprobes and fluorescence correlation spectroscopy (FCS). In this approach we take advantage of the inherent photoluminescence property of gold nanoparticles (GNPs) to develop a fluorophore-free assay to observe binding entities by monitoring the diffusion of bound versus unbound molecules in a limited confocal volume. 40-nm GNPs conjugated separately with rabbit anti-IgG (Fc) and goat anti-IgG (Fab) when incubated in blood serum containing IgG forms a sandwich structure constituting dimers and oligomers that can be differentiated by to detect IgG in blood serum at a limit of detection (LOD) of 5 pg/ml. The novelty of integrating GNPs with FCS to develop a sensitive blood immunoassay brings single molecule methods one step closer to the clinic.

An electrochemical sensing platform based on local repression of electrolyte diffusion for single-step, reagentless, sensitive detection of a sequence-specific DNA-binding protein.

PubMed

Zhang, Yun; Liu, Fang; Nie, Jinfang; Jiang, Fuyang; Zhou, Caibin; Yang, Jiani; Fan, Jinlong; Li, Jianping

2014-05-07

In this paper, we report for the first time an electrochemical biosensor for single-step, reagentless, and picomolar detection of a sequence-specific DNA-binding protein using a double-stranded, electrode-bound DNA probe terminally modified with a redox active label close to the electrode surface. This new methodology is based upon local repression of electrolyte diffusion associated with protein-DNA binding that leads to reduction of the electrochemical response of the label. In the proof-of-concept study, the resulting electrochemical biosensor was quantitatively sensitive to the concentrations of the TATA binding protein (TBP, a model analyte) ranging from 40 pM to 25.4 nM with an estimated detection limit of ∼10.6 pM (∼80 to 400-fold improvement on the detection limit over previous electrochemical analytical systems).

Activation Thermodynamics and H/D Kinetic Isotope Effect of the Hox to HredH+ Transition in [FeFe] Hydrogenase.

PubMed

Ratzloff, Michael W; Wilker, Molly B; Mulder, David W; Lubner, Carolyn E; Hamby, Hayden; Brown, Katherine A; Dukovic, Gordana; King, Paul W

2017-09-20

Molecular complexes between CdSe nanocrystals and Clostridium acetobutylicum [FeFe] hydrogenase I (CaI) enabled light-driven control of electron transfer for spectroscopic detection of redox intermediates during catalytic proton reduction. Here we address the route of electron transfer from CdSe→CaI and activation thermodynamics of the initial step of proton reduction in CaI. The electron paramagnetic spectroscopy of illuminated CdSe:CaI showed how the CaI accessory FeS cluster chain (F-clusters) functions in electron transfer with CdSe. The H ox →H red H + reduction step measured by Fourier-transform infrared spectroscopy showed an enthalpy of activation of 19 kJ mol -1 and a ∼2.5-fold kinetic isotope effect. Overall, these results support electron injection from CdSe into CaI involving F-clusters, and that the H ox →H red H + step of catalytic proton reduction in CaI proceeds by a proton-dependent process.

Changes in step-width during dual-task walking predicts falls.

PubMed

Nordin, E; Moe-Nilssen, R; Ramnemark, A; Lundin-Olsson, L

2010-05-01

The aim was to evaluate whether gait pattern changes between single- and dual-task conditions were associated with risk of falling in older people. Dual-task cost (DTC) of 230 community living, physically independent people, 75 years or older, was determined with an electronic walkway. Participants were followed up each month for 1 year to record falls. Mean and variability measures of gait characteristics for 5 dual-task conditions were compared to single-task walking for each participant. Almost half (48%) of the participants fell at least once during follow-up. Risk of falling increased in individuals where DTC for performing a subtraction task demonstrated change in mean step-width compared to single-task walking. Risk of falling decreased in individuals where DTC for carrying a cup and saucer demonstrated change compared to single-task walking in mean step-width, mean step-time, and step-length variability. Degree of change in gait characteristics related to a change in risk of falling differed between measures. Prognostic guidance for fall risk was found for the above DTCs in mean step-width with a negative likelihood ratio of 0.5 and a positive likelihood ratio of 2.3, respectively. Findings suggest that changes in step-width, step-time, and step-length with dual tasking may be related to future risk of falling. Depending on the nature of the second task, DTC may indicate either an increased risk of falling, or a protective strategy to avoid falling. Copyright 2010. Published by Elsevier B.V.

VO{sub 2} (A): Reinvestigation of crystal structure, phase transition and crystal growth mechanisms

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

Rao Popuri, Srinivasa; University of Bordeaux, ICMCB, UPR 9048, F-33608 Pessac; National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, Plautius Andronescu Str. No. 1, 300224 Timisoara

2014-05-01

Well crystallized VO{sub 2} (A) microrods were grown via a single step hydrothermal reaction in the presence of V{sub 2}O{sub 5} and oxalic acid. With the advantage of high crystalline samples, we propose P4/ncc as an appropriate space group at room temperature. From morphological studies, we found that the oriented attachment and layer by layer growth mechanisms are responsible for the formation of VO{sub 2} (A) micro rods. The structural and electronic transitions in VO{sub 2} (A) are strongly first order in nature, and a marked difference between the structural transition temperatures and electronic transitions temperature was evidenced. The reversiblemore » intra- (LTP-A to HTP-A) and irreversible inter- (HTP-A to VO{sub 2} (M1)) structural phase transformations were studied by in-situ powder X-ray diffraction. Attempts to increase the size of the VO{sub 2} (A) microrods are presented and the possible formation steps for the flower-like morphologies of VO{sub 2} (M1) are described. - Graphical abstract: Using a single step and template free hydrothermal synthesis, well crystallized VO{sub 2} (A) microrods were prepared and the P4/ncc space group was assigned to the room temperature crystal structure. Reversible and irreversible phase transitions among different VO{sub 2} polymorphs were identified and their progressive nature was highlighted. Attempts to increase the microrods size, involving layer by layer formation mechanisms, are presented. - Highlights: • Highly crystallized VO{sub 2} (A) microrods were grown via a single step hydrothermal process. • The P4/ncc space group was determined for VO{sub 2} (A) at room temperature. • The electronic structure and progressive nature of the structural phase transition were investigated. • A weak coupling between structural and electronic phase transitions was identified. • Different crystallite morphologies were discussed in relation with growth mechanisms.« less

Improving the Mechanical Properties of the Fusion Zone in Electron-Beam Welded Ti-5Al-5Mo-5V-3Cr Alloys

NASA Astrophysics Data System (ADS)

Marvel, Christopher J.; Sabol, Joseph C.; Pasang, Timotius; Watanabe, Masashi; Misiolek, Wojciech Z.

2017-04-01

It is well-known that ω-phase precipitates embrittle Ti-5553 alloys and that ω-phase embrittlement can be overcome with appropriate heat treatments. However, the microstructural evolution of electron-beam welded Ti-5553 is not as understood as compared to the cast or wrought material. This study compared the microstructures of as-welded and post-weld heat-treated specimens by scanning and transmission electron microscopy, and similarly compared the localized mechanical behavior of the fusion zones with microhardness testing and digital image correlation coupled tensile testing. The primary observations were that the embrittling ω-phase precipitates formed upon cooling, and could not be fully solutionized in a single-step treatment of 1077 K (804 °C) for 1 hour. It was also discovered that nanoscale α-phase precipitates nucleated after the single-step treatment, although they were small in number and sparsely distributed. However, a two-step heat treatment of 1077 K (804 °C) for 1 hour and 873 K (600 °C) for 4 hours completely solutionized the ω-phase and produced a dense network of 2- μm-wide α-phase plates, which significantly improved the mechanical properties. Overall, this study has shown that post-weld heat treatments improve the strength and ductility of electron-beam welded Ti-5553 alloys by controlling ω- and α-phase evolution.

Electrical DNA biosensor using aluminium interdigitated electrode for E.Coli O157:H7 detection

NASA Astrophysics Data System (ADS)

Natasha, N. Z.; Rajapaksha, R. D. A. A.; Uda, M. N. A.; Hashim, U.

2017-09-01

Escherichia Coli (E.Coli) O157:H7 is the one of the most dangerous foodborne pathogens based diseases that presence in our daily life that causes illness and death increase every year. Aluminum Interdigitated Electrode (Al IDE) biosensor was introduced to detect E.Coli O157:H7 in earlier stage. In this paper we investigated ssDNA of E.Coli O157:H7 bacteria detection through electrical behavior of Al IDE sensor. The physical properties of Al IDE biosensor has been characterized using Low Power Microscope (LPM), High Power Microscope (HPM), Scanning Electron Microscope (SEM) and 3D Nano Profiler. The bare Al IDE was electrical characterized by using I-V measurement. The surface modification was accomplished by salinization using APTES and immobilization using Carboxylic Probe E.Coli which was the first step in preparing Al IDE biosensor. Geared up prepared biosensor was hybridized with complementary, non-complementary and single based mismatch ssDNA to confirmed specificity detection of E Coli O157:H7 ssDNA target. The Current - Voltage was performed for each step such as bare Al IDE, surface modification, immobilization and hybridization. Sensitivity measurement was accomplished using different concentration of complementary ssDNA target from 1 fM - 10 µM. Selectivity measurements was achieved using same concentration which was 10 µM concentration for complement, non-complement and mismatch E.Coli O157:H7 ssDNA target. It's totally proved that the Al IDE able to detect specific and small current down to Femtomolar concentration.

Single Electron Tunneling

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

Ruggiero, Steven T.

Financial support for this project has led to advances in the science of single-electron phenomena. Our group reported the first observation of the so-called ''Coulomb Staircase'', which was produced by tunneling into ultra-small metal particles. This work showed well-defined tunneling voltage steps of width e/C and height e/RC, demonstrating tunneling quantized on the single-electron level. This work was published in a now well-cited Physical Review Letter. Single-electron physics is now a major sub-field of condensed-matter physics, and fundamental work in the area continues to be conducted by tunneling in ultra-small metal particles. In addition, there are now single-electron transistors thatmore » add a controlling gate to modulate the charge on ultra-small photolithographically defined capacitive elements. Single-electron transistors are now at the heart of at least one experimental quantum-computer element, and single-electron transistor pumps may soon be used to define fundamental quantities such as the farad (capacitance) and the ampere (current). Novel computer technology based on single-electron quantum dots is also being developed. In related work, our group played the leading role in the explanation of experimental results observed during the initial phases of tunneling experiments with the high-temperature superconductors. When so-called ''multiple-gap'' tunneling was reported, the phenomenon was correctly identified by our group as single-electron tunneling in small grains in the material. The main focus throughout this project has been to explore single electron phenomena both in traditional tunneling formats of the type metal/insulator/particles/insulator/metal and using scanning tunneling microscopy to probe few-particle systems. This has been done under varying conditions of temperature, applied magnetic field, and with different materials systems. These have included metals, semi-metals, and superconductors. Amongst a number of results, we have verified that clusters of down to one, two, and three metal atoms can be identified with single-electron techniques. We have also, extended the regime of single-electron phenomenology through the observation of single-electron effects in metal droplets in the high-conductance regime.« less

Automated detection and analysis of particle beams in laser-plasma accelerator simulations

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

Ushizima, Daniela Mayumi; Geddes, C.G.; Cormier-Michel, E.

Numerical simulations of laser-plasma wakefield (particle) accelerators model the acceleration of electrons trapped in plasma oscillations (wakes) left behind when an intense laser pulse propagates through the plasma. The goal of these simulations is to better understand the process involved in plasma wake generation and how electrons are trapped and accelerated by the wake. Understanding of such accelerators, and their development, offer high accelerating gradients, potentially reducing size and cost of new accelerators. One operating regime of interest is where a trapped subset of electrons loads the wake and forms an isolated group of accelerated particles with low spread inmore » momentum and position, desirable characteristics for many applications. The electrons trapped in the wake may be accelerated to high energies, the plasma gradient in the wake reaching up to a gigaelectronvolt per centimeter. High-energy electron accelerators power intense X-ray radiation to terahertz sources, and are used in many applications including medical radiotherapy and imaging. To extract information from the simulation about the quality of the beam, a typical approach is to examine plots of the entire dataset, visually determining the adequate parameters necessary to select a subset of particles, which is then further analyzed. This procedure requires laborious examination of massive data sets over many time steps using several plots, a routine that is unfeasible for large data collections. Demand for automated analysis is growing along with the volume and size of simulations. Current 2D LWFA simulation datasets are typically between 1GB and 100GB in size, but simulations in 3D are of the order of TBs. The increase in the number of datasets and dataset sizes leads to a need for automatic routines to recognize particle patterns as particle bunches (beam of electrons) for subsequent analysis. Because of the growth in dataset size, the application of machine learning techniques for scientific data mining is increasingly considered. In plasma simulations, Bagherjeiran et al. presented a comprehensive report on applying graph-based techniques for orbit classification. They used the KAM classifier to label points and components in single and multiple orbits. Love et al. conducted an image space analysis of coherent structures in plasma simulations. They used a number of segmentation and region-growing techniques to isolate regions of interest in orbit plots. Both approaches analyzed particle accelerator data, targeting the system dynamics in terms of particle orbits. However, they did not address particle dynamics as a function of time or inspected the behavior of bunches of particles. Ruebel et al. addressed the visual analysis of massive laser wakefield acceleration (LWFA) simulation data using interactive procedures to query the data. Sophisticated visualization tools were provided to inspect the data manually. Ruebel et al. have integrated these tools to the visualization and analysis system VisIt, in addition to utilizing efficient data management based on HDF5, H5Part, and the index/query tool FastBit. In Ruebel et al. proposed automatic beam path analysis using a suite of methods to classify particles in simulation data and to analyze their temporal evolution. To enable researchers to accurately define particle beams, the method computes a set of measures based on the path of particles relative to the distance of the particles to a beam. To achieve good performance, this framework uses an analysis pipeline designed to quickly reduce the amount of data that needs to be considered in the actual path distance computation. As part of this process, region-growing methods are utilized to detect particle bunches at single time steps. Efficient data reduction is essential to enable automated analysis of large data sets as described in the next section, where data reduction methods are steered to the particular requirements of our clustering analysis. Previously, we have described the application of a set of algorithms to automate the data analysis and classification of particle beams in the LWFA simulation data, identifying locations with high density of high energy particles. These algorithms detected high density locations (nodes) in each time step, i.e. maximum points on the particle distribution for only one spatial variable. Each node was correlated to a node in previous or later time steps by linking these nodes according to a pruned minimum spanning tree (PMST). We call the PMST representation 'a lifetime diagram', which is a graphical tool to show temporal information of high dense groups of particles in the longitudinal direction for the time series. Electron bunch compactness was described by another step of the processing, designed to partition each time step, using fuzzy clustering, into a fixed number of clusters.« less

Atomic-resolution single-spin magnetic resonance detection concept based on tunneling force microscopy

NASA Astrophysics Data System (ADS)

Payne, A.; Ambal, K.; Boehme, C.; Williams, C. C.

2015-05-01

A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single-electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy system noise. The results show that the approach could provide single-spin measurement of electrically isolated qubit states with atomic spatial resolution at room temperature.

Two-step entanglement concentration for arbitrary electronic cluster state

NASA Astrophysics Data System (ADS)

Zhao, Sheng-Yang; Liu, Jiong; Zhou, Lan; Sheng, Yu-Bo

2013-12-01

We present an efficient protocol for concentrating an arbitrary four-electron less-entangled cluster state into a maximally entangled cluster state. As a two-step entanglement concentration protocol (ECP), it only needs one pair of less-entangled cluster state, which makes this ECP more economical. With the help of electronic polarization beam splitter (PBS) and the charge detection, the whole concentration process is essentially the quantum nondemolition (QND) measurement. Therefore, the concentrated maximally entangled state can be remained for further application. Moreover, the discarded terms in some traditional ECPs can be reused to obtain a high success probability. It is feasible and useful in current one-way quantum computation.

A simple method for detection of gunshot residue particles from hands, hair, face, and clothing using scanning electron microscopy/wavelength dispersive X-ray (SEM/WDX).

PubMed

Kage, S; Kudo, K; Kaizoji, A; Ryumoto, J; Ikeda, H; Ikeda, N

2001-07-01

We devised a simple and rapid method for detection of gunshot residue (GSR) particles, using scanning electron microscopy/wavelength dispersive X-ray (SEM/WDX) analysis. Experiments were done on samples containing GSR particles obtained from hands, hair, face, and clothing, using double-sided adhesive coated aluminum stubs (tape-lift method). SEM/WDX analyses for GSR were carried out in three steps: the first step was map analysis for barium (Ba) to search for GSR particles from lead styphnate primed ammunition, or tin (Sn) to search for GSR particles from mercury fulminate primed ammunition. The second step was determination of the location of GSR particles by X-ray imaging of Ba or Sn at a magnification of x 1000-2000 in the SEM, using data of map analysis, and the third step was identification of GSR particles, using WDX spectrometers. Analysis of samples from each primer of a stub took about 3 h. Practical applications were shown for utility of this method.

Source Detection with Bayesian Inference on ROSAT All-Sky Survey Data Sample

NASA Astrophysics Data System (ADS)

Guglielmetti, F.; Voges, W.; Fischer, R.; Boese, G.; Dose, V.

2004-07-01

We employ Bayesian inference for the joint estimation of sources and background on ROSAT All-Sky Survey (RASS) data. The probabilistic method allows for detection improvement of faint extended celestial sources compared to the Standard Analysis Software System (SASS). Background maps were estimated in a single step together with the detection of sources without pixel censoring. Consistent uncertainties of background and sources are provided. The source probability is evaluated for single pixels as well as for pixel domains to enhance source detection of weak and extended sources.

Introduction to Density Functional Theory: Calculations by Hand on the Helium Atom

ERIC Educational Resources Information Center

Baseden, Kyle A.; Tye, Jesse W.

2014-01-01

Density functional theory (DFT) is a type of electronic structure calculation that has rapidly gained popularity. In this article, we provide a step-by-step demonstration of a DFT calculation by hand on the helium atom using Slater's X-Alpha exchange functional on a single Gaussian-type orbital to represent the atomic wave function. This DFT…

Detection and classification of virus from electron micrograms

NASA Astrophysics Data System (ADS)

Strömberg, Jan-Olov

2010-04-01

I will present a PhD project were Diffusion Geometry is used in classification of virus particles in cell kernels from electron micrograms. I will give a very short introduction to Diffusion Geometry and discuss the main classification steps. Some preliminary result from a Master Thesis will be presented.

Comparative analysis of peak-detection techniques for comprehensive two-dimensional chromatography.

PubMed

Latha, Indu; Reichenbach, Stephen E; Tao, Qingping

2011-09-23

Comprehensive two-dimensional gas chromatography (GC×GC) is a powerful technology for separating complex samples. The typical goal of GC×GC peak detection is to aggregate data points of analyte peaks based on their retention times and intensities. Two techniques commonly used for two-dimensional peak detection are the two-step algorithm and the watershed algorithm. A recent study [4] compared the performance of the two-step and watershed algorithms for GC×GC data with retention-time shifts in the second-column separations. In that analysis, the peak retention-time shifts were corrected while applying the two-step algorithm but the watershed algorithm was applied without shift correction. The results indicated that the watershed algorithm has a higher probability of erroneously splitting a single two-dimensional peak than the two-step approach. This paper reconsiders the analysis by comparing peak-detection performance for resolved peaks after correcting retention-time shifts for both the two-step and watershed algorithms. Simulations with wide-ranging conditions indicate that when shift correction is employed with both algorithms, the watershed algorithm detects resolved peaks with greater accuracy than the two-step method. Copyright © 2011 Elsevier B.V. All rights reserved.

LiCoPO4 cathode from a CoHPO4·xH2O nanoplate precursor for high voltage Li-ion batteries

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

Choi, Daiwon; Li, Xiaolin; Henderson, Wesley A.

2016-02-01

Highly crystalline LiCoPO4/C cathode has been synthesized without any impurities via single step solid-state reaction using CoHPO4xH2O nanoplates as a precursor obtained by simple precipitation route. The electrochemical test shows specific capacity as high as 125mAh/g at charge/discharge rate of C/10. Synthesis approach for obtaining CoHPO4xH2O nanoplate precursor and final LiCoPO4/C cathode using single step solid-state reaction have been characterized using X-ray diffraction, thermos gravimetric analyses (TGA) – differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The electrochemical test and cycling stability using different electrolytes, additive and separator have been investigated.

Development of a rapid and sensitive one-step reverse transcription-nested polymerase chain reaction in a single tube using the droplet-polymerase chain reaction machine.

PubMed

Yamaguchi, Akemi; Matsuda, Kazuyuki; Sueki, Akane; Taira, Chiaki; Uehara, Masayuki; Saito, Yasunori; Honda, Takayuki

2015-08-25

Reverse transcription (RT)-nested polymerase chain reaction (PCR) is a time-consuming procedure because it has several handling steps and is associated with the risk of cross-contamination during each step. Therefore, a rapid and sensitive one-step RT-nested PCR was developed that could be performed in a single tube using a droplet-PCR machine. The K562 BCR-ABL mRNA-positive cell line as well as bone marrow aspirates from 5 patients with chronic myelogenous leukemia (CML) and 5 controls without CML were used. We evaluated one-step RT-nested PCR using the droplet-PCR machine. One-step RT-nested PCR performed in a single tube using the droplet-PCR machine enabled the detection of BCR-ABL mRNA within 40min, which was 10(3)-fold superior to conventional RT nested PCR using three steps in separate tubes. The sensitivity of the one-step RT-nested PCR was 0.001%, with sample reactivity comparable to that of the conventional assay. One-step RT-nested PCR was developed using the droplet-PCR machine, which enabled all reactions to be performed in a single tube accurately and rapidly and with high sensitivity. This one-step RT-nested PCR may be applicable to a wide spectrum of genetic tests in clinical laboratories. Copyright © 2015 Elsevier B.V. All rights reserved.

Visualizing repetitive diffusion activity of double-strand RNA binding proteins by single molecule fluorescence assays.

PubMed

Koh, Hye Ran; Wang, Xinlei; Myong, Sua

2016-08-01

TRBP, one of double strand RNA binding proteins (dsRBPs), is an essential cofactor of Dicer in the RNA interference pathway. Previously we reported that TRBP exhibits repetitive diffusion activity on double strand (ds)RNA in an ATP independent manner. In the TRBP-Dicer complex, the diffusion mobility of TRBP facilitates Dicer-mediated RNA cleavage. Such repetitive diffusion of dsRBPs on a nucleic acid at the nanometer scale can be appropriately captured by several single molecule detection techniques. Here, we provide a step-by-step guide to four different single molecule fluorescence assays by which the diffusion activity of dsRBPs on dsRNA can be detected. One color assay, termed protein induced fluorescence enhancement enables detection of unlabeled protein binding and diffusion on a singly labeled RNA. Two-color Fluorescence Resonance Energy Transfer (FRET) in which labeled dsRBPs is applied to labeled RNA, allows for probing the motion of protein along the RNA axis. Three color FRET reports on the diffusion movement of dsRBPs from one to the other end of RNA. The single molecule pull down assay provides an opportunity to collect dsRBPs from mammalian cells and examine the protein-RNA interaction at single molecule platform. Copyright © 2016 Elsevier Inc. All rights reserved.

Multiplexed electronically programmable multimode ionization detector for chromatography

DOEpatents

Wise, M.B.; Buchanan, M.V.

1988-05-19

Method and apparatus for detecting and differentiating organic compounds based on their electron affinity. An electron capture detector cell (ECD) is operated in a plurality of multiplexed electronically programmable operating modes to alter the detector response during a single sampling cycle to acquire multiple simultaneous chromatograms corresponding to each of the different operating modes. The cell is held at a constant subatmospheric pressure while the electron collection bias voltage applied to the cell is modulated electronically to allow acquisition of multiple chromatograms for a single sample elution from a chromatograph representing three distinctly different response modes. A system is provided which automatically controls the programmed application of bias pulses at different intervals and/or amplitudes to switch the detector from an ionization mode to the electron capture mode and various degrees therebetween to provide an improved means of tuning an ECD for multimode detection and improved specificity. 6 figs.

Detection of magnetic circular dichroism in amorphous materials utilizing a single-crystalline overlayer

DOE PAGES

Lin, J.; Zhong, X. Y.; Song, C.; ...

2017-12-27

Physicists are fascinated with topological defects in solid-state materials, because by breaking the translational symmetry they offer emerging properties that are not present in their parental phases. For example, edge dislocations—the 2π phase-winding topological defects—in antiferromagnetic NiO crystals can exhibit ferromagnetic behaviors. Herein, we study how these defects could give rise to exotic topological orders when they interact with a high energy electron beam. To probe this interaction, we formed a coherent electron nanobeam in a scanning transmission electron microscope and recorded the far-field transmitted patterns as the beam steps through the edge dislocation core in [001] NiO. Surprisingly, wemore » found the amplitude patterns of the <020> Bragg disks evolve in a similar manner to the evolution of an annular solar eclipse. Using the ptychographic technique, we recovered the missing phase information in the diffraction plane and revealed the topological phase vortices in the diffracted beams. Through atomic topological defects, the wave function of electrons can be converted from plane wave to electron vortex. This approach provides a new perspective for boosting the collection efficiency of magnetic circular dichroism spectra with high spatial resolution and understanding the relationship between symmetry breaking and exotic property of individual topological defect at atomic level.« less

Detection of magnetic circular dichroism in amorphous materials utilizing a single-crystalline overlayer

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

Lin, J.; Zhong, X. Y.; Song, C.

Physicists are fascinated with topological defects in solid-state materials, because by breaking the translational symmetry they offer emerging properties that are not present in their parental phases. For example, edge dislocations—the 2π phase-winding topological defects—in antiferromagnetic NiO crystals can exhibit ferromagnetic behaviors. Herein, we study how these defects could give rise to exotic topological orders when they interact with a high energy electron beam. To probe this interaction, we formed a coherent electron nanobeam in a scanning transmission electron microscope and recorded the far-field transmitted patterns as the beam steps through the edge dislocation core in [001] NiO. Surprisingly, wemore » found the amplitude patterns of the <020> Bragg disks evolve in a similar manner to the evolution of an annular solar eclipse. Using the ptychographic technique, we recovered the missing phase information in the diffraction plane and revealed the topological phase vortices in the diffracted beams. Through atomic topological defects, the wave function of electrons can be converted from plane wave to electron vortex. This approach provides a new perspective for boosting the collection efficiency of magnetic circular dichroism spectra with high spatial resolution and understanding the relationship between symmetry breaking and exotic property of individual topological defect at atomic level.« less

Joint estimation of vertical total electron content (VTEC) and satellite differential code biases (SDCBs) using low-cost receivers

NASA Astrophysics Data System (ADS)

Zhang, Baocheng; Teunissen, Peter J. G.; Yuan, Yunbin; Zhang, Hongxing; Li, Min

2018-04-01

Vertical total electron content (VTEC) parameters estimated using global navigation satellite system (GNSS) data are of great interest for ionosphere sensing. Satellite differential code biases (SDCBs) account for one source of error which, if left uncorrected, can deteriorate performance of positioning, timing and other applications. The customary approach to estimate VTEC along with SDCBs from dual-frequency GNSS data, hereinafter referred to as DF approach, consists of two sequential steps. The first step seeks to retrieve ionospheric observables through the carrier-to-code leveling technique. This observable, related to the slant total electron content (STEC) along the satellite-receiver line-of-sight, is biased also by the SDCBs and the receiver differential code biases (RDCBs). By means of thin-layer ionospheric model, in the second step one is able to isolate the VTEC, the SDCBs and the RDCBs from the ionospheric observables. In this work, we present a single-frequency (SF) approach, enabling the joint estimation of VTEC and SDCBs using low-cost receivers; this approach is also based on two steps and it differs from the DF approach only in the first step, where we turn to the precise point positioning technique to retrieve from the single-frequency GNSS data the ionospheric observables, interpreted as the combination of the STEC, the SDCBs and the biased receiver clocks at the pivot epoch. Our numerical analyses clarify how SF approach performs when being applied to GPS L1 data collected by a single receiver under both calm and disturbed ionospheric conditions. The daily time series of zenith VTEC estimates has an accuracy ranging from a few tenths of a TEC unit (TECU) to approximately 2 TECU. For 73-96% of GPS satellites in view, the daily estimates of SDCBs do not deviate, in absolute value, more than 1 ns from their ground truth values published by the Centre for Orbit Determination in Europe.

Label-Free Direct Electronic Detection of Biomolecules with Amorphous Silicon Nanostructures

PubMed Central

Lund, John; Mehta, Ranjana; Parviz, Babak A.

2007-01-01

We present the fabrication and characterization of a nano-scale sensor made of amorphous silicon for the label-free, electronic detection of three classes of biologically important molecules: ions, oligonucleotides, and proteins. The sensor structure has an active element which is a 50 nm wide amorphous silicon semicircle and has a total footprint of less than 4 μm2. We demonstrate the functionalization of the sensor with receptor molecules and the electronic detection of three targets: H+ ions, short single-stranded DNAs, and streptavidin. The sensor is able to reliably distinguish single base-pair mismatches in 12 base long strands of DNA and monitor the introduction and identification of straptavidin in real-time. The versatile sensor structure can be readily functionalized with a wide range of receptor molecules and is suitable for integration with high-speed electronic circuits as a post-process on an integrated circuit chip. PMID:17292148

Detection of isolated protein-bound metal ions by single-particle cryo-STEM.

PubMed

Elad, Nadav; Bellapadrona, Giuliano; Houben, Lothar; Sagi, Irit; Elbaum, Michael

2017-10-17

Metal ions play essential roles in many aspects of biological chemistry. Detecting their presence and location in proteins and cells is important for understanding biological function. Conventional structural methods such as X-ray crystallography and cryo-transmission electron microscopy can identify metal atoms on protein only if the protein structure is solved to atomic resolution. We demonstrate here the detection of isolated atoms of Zn and Fe on ferritin, using cryogenic annular dark-field scanning transmission electron microscopy (cryo-STEM) coupled with single-particle 3D reconstructions. Zn atoms are found in a pattern that matches precisely their location at the ferroxidase sites determined earlier by X-ray crystallography. By contrast, the Fe distribution is smeared along an arc corresponding to the proposed path from the ferroxidase sites to the mineral nucleation sites along the twofold axes. In this case the single-particle reconstruction is interpreted as a probability distribution function based on the average of individual locations. These results establish conditions for detection of isolated metal atoms in the broader context of electron cryo-microscopy and tomography.

Detection of isolated protein-bound metal ions by single-particle cryo-STEM

PubMed Central

Elad, Nadav; Bellapadrona, Giuliano; Houben, Lothar; Sagi, Irit; Elbaum, Michael

2017-01-01

Metal ions play essential roles in many aspects of biological chemistry. Detecting their presence and location in proteins and cells is important for understanding biological function. Conventional structural methods such as X-ray crystallography and cryo-transmission electron microscopy can identify metal atoms on protein only if the protein structure is solved to atomic resolution. We demonstrate here the detection of isolated atoms of Zn and Fe on ferritin, using cryogenic annular dark-field scanning transmission electron microscopy (cryo-STEM) coupled with single-particle 3D reconstructions. Zn atoms are found in a pattern that matches precisely their location at the ferroxidase sites determined earlier by X-ray crystallography. By contrast, the Fe distribution is smeared along an arc corresponding to the proposed path from the ferroxidase sites to the mineral nucleation sites along the twofold axes. In this case the single-particle reconstruction is interpreted as a probability distribution function based on the average of individual locations. These results establish conditions for detection of isolated metal atoms in the broader context of electron cryo-microscopy and tomography. PMID:28973937

Variable tunneling barriers in FEBID based PtC metal-matrix nanocomposites as a transducing element for humidity sensing.

PubMed

Kolb, Florian; Schmoltner, Kerstin; Huth, Michael; Hohenau, Andreas; Krenn, Joachim; Klug, Andreas; List, Emil J W; Plank, Harald

2013-08-02

The development of simple gas sensing concepts is still of great interest for science and technology. The demands on an ideal device would be a single-step fabrication method providing a device which is sensitive, analyte-selective, quantitative, and reversible without special operating/reformation conditions such as high temperatures or special environments. In this study we demonstrate a new gas sensing concept based on a nanosized PtC metal-matrix system fabricated in a single step via focused electron beam induced deposition (FEBID). The sensors react selectively on polar H2O molecules quantitatively and reversibly without any special reformation conditions after detection events, whereas non-polar species (O2, CO2, N2) produce no response. The key elements are isolated Pt nanograins (2-3 nm) which are embedded in a dielectric carbon matrix. The electrical transport in such materials is based on tunneling effects in the correlated variable range hopping regime, where the dielectric carbon matrix screens the electric field between the particles, which governs the final conductivity. The specific change of these dielectric properties by the physisorption of polar gas molecules (H2O) can change the tunneling probability and thus the overall conductivity, allowing their application as a simple and straightforward sensing concept.

A rapid and efficient newly established method to detect COL1A1-PDGFB gene fusion in dermatofibrosarcoma protuberans

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

Yokoyama, Yoko; Shimizu, Akira; Okada, Etsuko

Highlights: Black-Right-Pointing-Pointer We developed new method to rapidly identify COL1A1-PDGFB fusion in DFSP. Black-Right-Pointing-Pointer New PCR method using a single primer pair detected COL1A1-PDGFB fusion in DFSP. Black-Right-Pointing-Pointer This is the first report of DFSP with a novel COL1A1 breakpoint in exon 5. -- Abstract: The detection of fusion transcripts of the collagen type 1{alpha}1 (COL1A1) and platelet-derived growth factor-BB (PDGFB) genes by genetic analysis has recognized as a reliable and valuable molecular tool for the diagnosis of dermatofibrosarcoma protuberans (DFSP). To detect the COL1A1-PDGFB fusion, almost previous reports performed reverse transcription polymerase chain reaction (RT-PCR) using multiplex forward primersmore » from COL1A1. However, it has possible technical difficulties with respect to the handling of multiple primers and reagents in the procedure. The objective of this study is to establish a rapid, easy, and efficient one-step method of PCR using only a single primer pair to detect the fusion transcripts of the COL1A1 and PDGFB in DFSP. To validate new method, we compared the results of RT-PCR in five patients of DFSP between the previous method using multiplex primers and our established one-step RT-PCR using a single primer pair. In all cases of DFSP, the COL1A1-PDGFB fusion was detected by both previous method and newly established one-step PCR. Importantly, we detected a novel COL1A1 breakpoint in exon 5. The newly developed method is valuable to rapidly identify COL1A1-PDGFB fusion transcripts in DFSP.« less

Circular dichroism in photo-single-ionization of unoriented atoms.

PubMed

Feagin, James M

2002-01-28

We predict circular dichroism in photo-single-ionization angular distributions from spherically symmetric atomic states if the ionized electron is detected using two-slit interferometry. We demonstrate that the resulting electron interference pattern captures phase information on quadrupole corrections to the photoionization amplitude lost in conventional angular distributions.

Toward single-chirality carbon nanotube device arrays.

PubMed

Vijayaraghavan, Aravind; Hennrich, Frank; Stürzl, Ninette; Engel, Michael; Ganzhorn, Marc; Oron-Carl, Matti; Marquardt, Christoph W; Dehm, Simone; Lebedkin, Sergei; Kappes, Manfred M; Krupke, Ralph

2010-05-25

The large-scale integration of devices consisting of individual single-walled carbon nanotubes (SWCNT), all of the same chirality, is a critical step toward their electronic, optoelectronic, and electromechanical application. Here, the authors realize two related goals, the first of which is the fabrication of high-density, single-chirality SWCNT device arrays by dielectrophoretic assembly from monodisperse SWCNT solution obtained by polymer-mediated sorting. Such arrays are ideal for correlating measurements using various techniques across multiple identical devices, which is the second goal. The arrays are characterized by voltage-contrast scanning electron microscopy, electron transport, photoluminescence (PL), and Raman spectroscopy and show identical signatures as expected for single-chirality SWCNTs. In the assembled nanotubes, a large D peak in Raman spectra, a large dark-exciton peak in PL spectra as well as lowered conductance and slow switching in electron transport are all shown to be correlated to each other. By comparison to control samples, we conclude that these are the result of scattering from electronic and not structural defects resulting from the polymer wrapping, similar to what has been predicted for DNA wrapping.

Measuring Conformational Dynamics of Single Biomolecules Using Nanoscale Electronic Devices

NASA Astrophysics Data System (ADS)

Akhterov, Maxim V.; Choi, Yongki; Sims, Patrick C.; Olsen, Tivoli J.; Gul, O. Tolga; Corso, Brad L.; Weiss, Gregory A.; Collins, Philip G.

2014-03-01

Molecular motion can be a rate-limiting step of enzyme catalysis, but motions are typically too quick to resolve with fluorescent single molecule techniques. Recently, we demonstrated a label-free technique that replaced fluorophores with nano-electronic circuits to monitor protein motions. The solid-state electronic technique used single-walled carbon nanotube (SWNT) transistors to monitor conformational motions of a single molecule of T4 lysozyme while processing its substrate, peptidoglycan. As lysozyme catalyzes the hydrolysis of glycosidic bonds, two protein domains undergo 8 Å hinge bending motion that generates an electronic signal in the SWNT transistor. We describe improvements to the system that have extended our temporal resolution to 2 μs . Electronic recordings at this level of detail directly resolve not just transitions between open and closed conformations but also the durations for those transition events. Statistical analysis of many events determines transition timescales characteristic of enzyme activity and shows a high degree of variability within nominally identical chemical events. The high resolution technique can be readily applied to other complex biomolecules to gain insights into their kinetic parameters and catalytic function.

Detecting single-electron events in TEM using low-cost electronics and a silicon strip sensor.

PubMed

Gontard, Lionel C; Moldovan, Grigore; Carmona-Galán, Ricardo; Lin, Chao; Kirkland, Angus I

2014-04-01

There is great interest in developing novel position-sensitive direct detectors for transmission electron microscopy (TEM) that do not rely in the conversion of electrons into photons. Direct imaging improves contrast and efficiency and allows the operation of the microscope at lower energies and at lower doses without loss in resolution, which is especially important for studying soft materials and biological samples. We investigate the feasibility of employing a silicon strip detector as an imaging detector for TEM. This device, routinely used in high-energy particle physics, can detect small variations in electric current associated with the impact of a single charged particle. The main advantages of using this type of sensor for direct imaging in TEM are its intrinsic radiation hardness and large detection area. Here, we detail design, simulation, fabrication and tests in a TEM of the front-end electronics developed using low-cost discrete components and discuss the limitations and applications of this technology for TEM.

Observation of entanglement between a quantum dot spin and a single photon.

PubMed

Gao, W B; Fallahi, P; Togan, E; Miguel-Sanchez, J; Imamoglu, A

2012-11-15

Entanglement has a central role in fundamental tests of quantum mechanics as well as in the burgeoning field of quantum information processing. Particularly in the context of quantum networks and communication, a main challenge is the efficient generation of entanglement between stationary (spin) and propagating (photon) quantum bits. Here we report the observation of quantum entanglement between a semiconductor quantum dot spin and the colour of a propagating optical photon. The demonstration of entanglement relies on the use of fast, single-photon detection, which allows us to project the photon into a superposition of red and blue frequency components. Our results extend the previous demonstrations of single-spin/single-photon entanglement in trapped ions, neutral atoms and nitrogen-vacancy centres to the domain of artificial atoms in semiconductor nanostructures that allow for on-chip integration of electronic and photonic elements. As a result of its fast optical transitions and favourable selection rules, the scheme we implement could in principle generate nearly deterministic entangled spin-photon pairs at a rate determined ultimately by the high spontaneous emission rate. Our observation constitutes a first step towards implementation of a quantum network with nodes consisting of semiconductor spin quantum bits.

Comparison of culture, single and multiplex real-time PCR for detection of Sabin poliovirus shedding in recently vaccinated Indian children.

PubMed

Giri, Sidhartha; Rajan, Anand K; Kumar, Nirmal; Dhanapal, Pavithra; Venkatesan, Jayalakshmi; Iturriza-Gomara, Miren; Taniuchi, Mami; John, Jacob; Abraham, Asha Mary; Kang, Gagandeep

2017-08-01

Although, culture is considered the gold standard for poliovirus detection from stool samples, real-time PCR has emerged as a faster and more sensitive alternative. Detection of poliovirus from the stool of recently vaccinated children by culture, single and multiplex real-time PCR was compared. Of the 80 samples tested, 55 (68.75%) were positive by culture compared to 61 (76.25%) and 60 (75%) samples by the single and one step multiplex real-time PCR assays respectively. Real-time PCR (singleplex and multiplex) is more sensitive than culture for poliovirus detection in stool, although the difference was not statistically significant. © 2017 Wiley Periodicals, Inc.

Thin-film transistor fabricated in single-crystalline transparent oxide semiconductor.

PubMed

Nomura, Kenji; Ohta, Hiromichi; Ueda, Kazushige; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

2003-05-23

We report the fabrication of transparent field-effect transistors using a single-crystalline thin-film transparent oxide semiconductor, InGaO3(ZnO)5, as an electron channel and amorphous hafnium oxide as a gate insulator. The device exhibits an on-to-off current ratio of approximately 106 and a field-effect mobility of approximately 80 square centimeters per volt per second at room temperature, with operation insensitive to visible light irradiation. The result provides a step toward the realization of transparent electronics for next-generation optoelectronics.

Studying the Stoichiometry of Epidermal Growth Factor Receptor in Intact Cells using Correlative Microscopy.

PubMed

Peckys, Diana B; de Jonge, Niels

2015-09-11

This protocol describes the labeling of epidermal growth factor receptor (EGFR) on COS7 fibroblast cells, and subsequent correlative fluorescence microscopy and environmental scanning electron microscopy (ESEM) of whole cells in hydrated state. Fluorescent quantum dots (QDs) were coupled to EGFR via a two-step labeling protocol, providing an efficient and specific protein labeling, while avoiding label-induced clustering of the receptor. Fluorescence microscopy provided overview images of the cellular locations of the EGFR. The scanning transmission electron microscopy (STEM) detector was used to detect the QD labels with nanoscale resolution. The resulting correlative images provide data of the cellular EGFR distribution, and the stoichiometry at the single molecular level in the natural context of the hydrated intact cell. ESEM-STEM images revealed the receptor to be present as monomer, as homodimer, and in small clusters. Labeling with two different QDs, i.e., one emitting at 655 nm and at 800 revealed similar characteristic results.

Using the time shift in single pushbroom datatakes to detect ships and their heading

NASA Astrophysics Data System (ADS)

Willburger, Katharina A. M.; Schwenk, Kurt

2017-10-01

The detection of ships from remote sensing data has become an essential task for maritime security. The variety of application scenarios includes piracy, illegal fishery, ocean dumping and ships carrying refugees. While techniques using data from SAR sensors for ship detection are widely common, there is only few literature discussing algorithms based on imagery of optical camera systems. A ship detection algorithm for optical pushbroom data has been developed. It takes advantage of the special detector assembly of most of those scanners, which allows apart from the detection of a ship also the calculation of its heading out of a single acquisition. The proposed algorithm for the detection of moving ships was developed with RapidEye imagery. It algorithm consists mainly of three steps: the creation of a land-watermask, the object extraction and the deeper examination of each single object. The latter step is built up by several spectral and geometric filters, making heavy use of the inter-channel displacement typical for pushbroom sensors with multiple CCD lines, finally yielding a set of ships and their direction of movement. The working principle of time-shifted pushbroom sensors and the developed algorithm is explained in detail. Furthermore, we present our first results and give an outlook to future improvements.

Evaluation of the new electron-transport algorithm in MCNP6.1 for the simulation of dose point kernel in water

NASA Astrophysics Data System (ADS)

Antoni, Rodolphe; Bourgois, Laurent

2017-12-01

In this work, the calculation of specific dose distribution in water is evaluated in MCNP6.1 with the regular condensed history algorithm the "detailed electron energy-loss straggling logic" and the new electrons transport algorithm proposed the "single event algorithm". Dose Point Kernel (DPK) is calculated with monoenergetic electrons of 50, 100, 500, 1000 and 3000 keV for different scoring cells dimensions. A comparison between MCNP6 results and well-validated codes for electron-dosimetry, i.e., EGSnrc or Penelope, is performed. When the detailed electron energy-loss straggling logic is used with default setting (down to the cut-off energy 1 keV), we infer that the depth of the dose peak increases with decreasing thickness of the scoring cell, largely due to combined step-size and boundary crossing artifacts. This finding is less prominent for 500 keV, 1 MeV and 3 MeV dose profile. With an appropriate number of sub-steps (ESTEP value in MCNP6), the dose-peak shift is almost complete absent to 50 keV and 100 keV electrons. However, the dose-peak is more prominent compared to EGSnrc and the absorbed dose tends to be underestimated at greater depths, meaning that boundaries crossing artifact are still occurring while step-size artifacts are greatly reduced. When the single-event mode is used for the whole transport, we observe the good agreement of reference and calculated profile for 50 and 100 keV electrons. Remaining artifacts are fully vanished, showing a possible transport treatment for energies less than a hundred of keV and accordance with reference for whatever scoring cell dimension, even if the single event method initially intended to support electron transport at energies below 1 keV. Conversely, results for 500 keV, 1 MeV and 3 MeV undergo a dramatic discrepancy with reference curves. These poor results and so the current unreliability of the method is for a part due to inappropriate elastic cross section treatment from the ENDF/B-VI.8 library in those energy ranges. Accordingly, special care has to be taken in setting choice for calculating electron dose distribution with MCNP6, in particular with regards to dosimetry or nuclear medicine applications.

Multi-Element CZT Array for Nuclear Safeguards Applications

NASA Astrophysics Data System (ADS)

Kwak, S.-W.; Lee, A.-R.; Shin, J.-K.; Park, U.-R.; Park, S.; Kim, Y.; Chung, H.

2016-12-01

Due to its electronic properties, a cadmium zinc telluride (CZT) detector has been used as a hand-held portable nuclear measurement instrument. However, a CZT detector has low detection efficiency because of a limitation of its single crystal growth. To address its low efficiency, we have constructed a portable four-CZT array based gamma-ray spectrometer consisting of a CZT array, electronics for signal processing and software. Its performance has been characterized in terms of energy resolution and detection efficiency using radioactive sources and nuclear materials. Experimental results showed that the detection efficiency of the four-CZT array based gamma-ray spectrometer was much higher than that of a single CZT detector in the array. The FWHMs of the CZT array were 9, 18, and 21 keV at 185.7, 662, and 1,332 keV, respectively. Some gamma-rays in a range of 100 keV to 200 keV were not clear in a single crystal detector while those from the CZT array system were observed to be clear. The energy resolution of the CZT array system was only slightely worse than those of the single CZT detectors. By combining several single crystals and summing signals from each single detector at a digital electronic circuit, the detection efficiency of a CZT array system increased without degradation of its energy resolution. The technique outlined in this paper shows a very promising method for designing a CZT-based gamma-ray spectroscopy that overcomes the fundamental limitations of a small volume CZT detector.

Distributed Feedback Laser Based on Single Crystal Perovskite

NASA Astrophysics Data System (ADS)

Sun, Shang; Xiao, Shumin; Song, Qinghai

2017-06-01

We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry-Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3 microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

In vivo myosin step-size from zebrafish skeletal muscle

PubMed Central

Ajtai, Katalin; Sun, Xiaojing; Takubo, Naoko; Wang, Yihua

2016-01-01

Muscle myosins transduce ATP free energy into actin displacement to power contraction. In vivo, myosin side chains are modified post-translationally under native conditions, potentially impacting function. Single myosin detection provides the ‘bottom-up’ myosin characterization probing basic mechanisms without ambiguities inherent to ensemble observation. Macroscopic muscle physiological experimentation provides the definitive ‘top-down’ phenotype characterizations that are the concerns in translational medicine. In vivo single myosin detection in muscle from zebrafish embryo models for human muscle fulfils ambitions for both bottom-up and top-down experimentation. A photoactivatable green fluorescent protein (GFP)-tagged myosin light chain expressed in transgenic zebrafish skeletal muscle specifically modifies the myosin lever-arm. Strychnine induces the simultaneous contraction of the bilateral tail muscles in a live embryo, causing them to be isometric while active. Highly inclined thin illumination excites the GFP tag of single lever-arms and its super-resolution orientation is measured from an active isometric muscle over a time sequence covering many transduction cycles. Consecutive frame lever-arm angular displacement converts to step-size by its product with the estimated lever-arm length. About 17% of the active myosin steps that fall between 2 and 7 nm are implicated as powerstrokes because they are beyond displacements detected from either relaxed or ATP-depleted (rigor) muscle. PMID:27249818

The role of nanotechnology in single-cell detection: a review.

PubMed

Wang, Changling; Zhang, Yuxiang; Xia, Mingdian; Zhu, Xingxi; Qi, Shitao; Shen, Huaqiang; Liu, Tiebing; Tang, Liming

2014-10-01

Biological processes in single cells, such as signal transduction, DNA duplication, and protein synthesis and trafficking, occur in subcellular compartments at nanoscale level. Achieving high spatial-temporal resolution, high sensitivity, and high specificity in single-cell detection poses a great challenge. Nanotechnology, which has been widely applied in the fields of medicine, electronics, biomaterials, and energy production, has the potential to provide solutions for single-cell detection. Here we present a review of the use of nanotechnology in single-cell detection over the past two decades. First, we review the main areas of scientific interest, including morphology, ion concentration, DNA, RNA, protein, intracellular temperature, elements, and mechanical properties. Second, four categories of application of nanotechnology to single-cell detection are described: nanomanipulation, nanodevices, nanomaterials as labels, and nano Secondary ion mass spectrometry. Finally, the prospects and future trends in single-cell detection and analysis are discussed.

A New Method for the Fast Analysis of Trihalomethanes in Tap and Recycled Waters Using Headspace Gas Chromatography with Micro-Electron Capture Detection.

PubMed

Alexandrou, Lydon D; Meehan, Barry J; Morrison, Paul D; Jones, Oliver A H

2017-05-15

Chemical disinfection of water supplies brings significant public health benefits by reducing microbial contamination. The process can however, result in the formation of toxic compounds through interactions between disinfectants and organic material in the source water. These new compounds are termed disinfection by-products (DBPs). The most common are the trihalomethanes (THMs) such as trichloromethane (chloroform), dichlorobromomethane, chlorodibromomethane and tribromomethane (bromoform); these are commonly reported as a single value for total trihalomethanes (TTHMs). Analysis of DBPs is commonly performed via time- and solvent-intensive sample preparation techniques such as liquid-liquid and solid phase extraction. In this study, a method using headspace gas chromatography with micro-electron capture detection was developed and applied for the analysis of THMs in drinking and recycled waters from across Melbourne (Victoria, Australia). The method allowed almost complete removal of the sample preparation step whilst maintaining trace level detection limits (>1 ppb). All drinking water samples had TTHM concentrations below the Australian regulatory limit of 250 µg/L but some were above the U.S. EPA limit of 60 µg/L. The highest TTHM concentration was 67.2 µg/L and lowest 22.9 µg/L. For recycled water, samples taken directly from treatment plants held significantly higher concentrations (153.2 µg/L TTHM) compared to samples from final use locations (4.9-9.3 µg/L).

Low-cost, high-sensitivity SERS nano-bio-chip for kinase profiling, drug monitoring and environmental detection: a translational platform technology

NASA Astrophysics Data System (ADS)

Chen, Yi; Liu, Logan

2014-03-01

The interaction of biomolecules and solid-state nanomaterials at the nano-bio interfaces is a long-lasting research topic in nanotechnology. Historically, fundamental problems, such as the electron transfer, energy transfer, and plasmonic interaction at the bio-nano interfaces, have been intensively studied, and revolutionary technologies, such as molecular electronics, peptide chips, nanoplasmonic sensors, have been created. With the combined effort of molecular dynamics simulation and surface-enhanced Raman spectroscopy, we studied the external electric field-induced conformation changes of dodecapeptide probes tethered to a nanostructured metallic surface. Through this study, we demonstrated a reversible manipulation of the biomolecule conformations as well as an in situ eletro-optical detection of the subnanometer conformational changes at the bio-nano interfaces. Based on the proof-of-concept established in this study, we further propose a novel nanophotonic peptide phosphorylation sensor for high-sensitive peptide kinase profiling. We have also demonstrated the same SERS nano-bio-chip can be used for environmental monitoring applications, such as detection of contaminants in drinking water at ultralow concentrates. The fabrication of this nanosensor is based on a single step, lithography-less nanomanufacturing process, which can produce hundreds of these chips in several minutes with nearly 100% yield and uniformity. Therefore, the demonstrated research can be readily translated into industrial mass productions.

Detection of ricin in food using electrochemiluminescence-based technology.

PubMed

Garber, Eric A E; O'Brien, Thomas W

2008-01-01

Ricin is a toxic ribosome inactivating protein (RIP-II) present in beans of the castor plant, Ricinus communis. Its potential as a biodefense threat has made the rapid, sensitive detection of ricin in food important to the U.S. Food and Drug Administration. Samples of juice, dairy products, soda, vegetables, bakery products, chocolate, and condiments were spiked with varying concentrations of ricin and analyzed using a 96-well format, electrochemiluminescence (ECL) immunoassay. Assay configurations included the use of a monoclonal capture antibody coupled with either a polyclonal or monoclonal detector antibody. The samples and detector antibodies were either added sequentially or in combination during the capture step. Using the polyclonal antibody, 0.04 ng/mL ricin was detected in analytical samples prepared from several beverages. By simultaneously incubating the sample with detector antibody, it was possible to decrease the assay time to a single 20 min incubation step with a limit of detection <10 ng/mL. Assays run according to this single incubation step exhibited a hook effect (decrease in signal at high concentrations of ricin), but because of the large signal-to-noise ratio associated with the ECL assay, the response remained above background and detectable. Thus, the ECL assay was uniquely suited for the screening of samples for ricin.

Production and characterization of a single-chain variable fragment linked alkaline phosphatase fusion protein for detection of O,O-diethyl organophosphorus pesticides in a one-step enzyme-linked immunosorbent assay

USDA-ARS?s Scientific Manuscript database

A single-chain variable fragment (scFv) and alkaline phosphatase (AP) fusion protein for detection of O, O-diethyl organophosphorus pesticides (OPs) was produced and characterized. The scFv gene was prepared by cloning VL and VH genes from a hybridoma cell secreting monoclonal antibody with broad-s...

One-by-one single-molecule detection of mutated nucleobases by monitoring tunneling current using a DNA tip.

PubMed

Bui, Phuc Tan; Nishino, Tomoaki; Shiigi, Hiroshi; Nagaoka, Tsutomu

2015-01-31

A DNA molecule was utilized as a probe tip to achieve single-molecule genetic diagnoses. Hybridization of the probe and target DNAs resulted in electron tunneling along the emergent double-stranded DNA. Simple stationary monitoring of the tunneling current leads to single-molecule DNA detection and discovery of base mismatches and methylation.

Advances in shutter drive technology to enhance man-portable infrared cameras

NASA Astrophysics Data System (ADS)

Durfee, David

2012-06-01

With an emphasis on highest reliability, infrared (IR) imagers have traditionally used simplest-possible shutters and field-proven technology. Most commonly, single-step rotary or linear magnetic actuators have been used with good success. However, several newer shutter drive technologies offer benefits in size and power reduction, enabling man-portable imagers that are more compact, lighter, and more durable. This paper will discuss improvements in shutter and shutter drive technology, which enable smaller and more power-efficient imagers. Topics will transition from single-step magnetic actuators to multi-stepping magnetic drives, latching vs. balanced systems for blade position shock-resistance, motor and geared motor drives, and associated stepper driver electronics. It will highlight performance tradeoffs pertinent to man-portable military systems.

One-Step Synthesis of Fluorescent Boron Nitride Quantum Dots via a Hydrothermal Strategy Using Melamine as Nitrogen Source for the Detection of Ferric Ions.

PubMed

Huo, Bingbing; Liu, Bingping; Chen, Tao; Cui, Liang; Xu, Gengfang; Liu, Mengli; Liu, Jingquan

2017-10-10

A facile and effective approach for the preparation of functionalized born nitride quantum dots (BNQDs) with blue fluorescence was explored by the hydrothermal treatment of the mixture of boric acid and melamine at 200 °C for 15 h. The as-prepared BNQDs were characterized by transmission electron microscopy (TEM), high-resolution TEM, atomic force microscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and fluorescence spectroscopy. The single layered BNQDs with the average size of 3 nm showed a blue light emission under the illumination of the UV light. The BNQDs could be easily dispersed in an aqueous medium and applied as fluorescent probes for selective detection of Fe 3+ with remarkable selectivity and sensitivity (the lowest detection limit was 0.3 μM). The fluorescence fiber imaging demonstrated that the as-prepared quantum dots could be used as a valuable fluorchrome. Therefore, the BNQDs could be envisioned for potential applications in many fields such as biocompatible staining, fluorescent probes, and biological labeling.

Multiplexed electronically programmable multimode ionization detector for chromatography

DOEpatents

Wise, Marcus B.; Buchanan, Michelle V.

1989-01-01

Method and apparatus for detecting and differentiating organic compounds based on their electron affinity. An electron capture detector cell (ECD) is operated in a plurality of multiplexed electroncially programmable operating modes to alter the detector response during a single sampling cycle to acquire multiple simultaneous chromatograms corresponding to each of the different operating modes. The cell is held at a constant subatmospheric pressure while the electron collection bias voltage applied to the cell is modulated electronically to allow acquisition of multiple chromatograms for a single sample elution from a chromatograph representing three distinctly different response modes. A system is provided which automatically controls the programmed application of bias pulses at different intervals and/or amplitudes to switch the detector from an ionization mode to the electron capture mode and various degrees therebetween to provide an improved means of tuning an ECD for multimode detection and improved specificity.

Luminescent Li-based metal-organic framework tailored for the selective detection of explosive nitroaromatic compounds: direct observation of interaction sites.

PubMed

Kim, Tae Kyung; Lee, Jae Hwa; Moon, Dohyun; Moon, Hoi Ri

2013-01-18

A luminescent lithium metal-organic framework (MOF) is constructed from the solvothermal reaction of Li(+) and a well-designed organic ligand, bis(4-carboxyphenyl)-N-methylamine (H(2)CPMA). A Li-based MOF can detect an explosive aromatic compound containing nitro groups as an explosophore, by showing a dramatic color change with concurrent luminescence quenching in the solid state. The detection sites are proven directly through single-crystal-to-single-crystal transformations, which show strong interactions between the aromatic rings of the electron-rich CPMA(2-) molecules and the electron-deficient nitrobenzene.

Concept for room temperature single-spin tunneling force microscopy with atomic spatial resolution

NASA Astrophysics Data System (ADS)

Payne, Adam

A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy (AFM) system noise. The results show that the approach could provide single-spin measurement of electrically isolated defect states with atomic spatial resolution at room temperature.

16 CFR 316.5 - Prohibition on charging a fee or imposing other requirements on recipients who wish to opt out.

Code of Federal Regulations, 2010 CFR

2010-01-01

... TRADE COMMISSION REGULATIONS UNDER SPECIFIC ACTS OF CONGRESS CAN-SPAM RULE § 316.5 Prohibition on... other than the recipient's electronic mail address and opt-out preferences, or take any other steps except sending a reply electronic mail message or visiting a single Internet Web page, in order to: (a...

Large scale variation in DNA copy number in chicken breeds

USDA-ARS?s Scientific Manuscript database

Background Detecting genetic variation is a critical step in elucidating the molecular mechanisms underlying phenotypic diversity. Until recently, such detection has mostly focused on single nucleotide polymorphisms (SNPs) because of the ease in screening complete genomes. Another type of variant, c...

Importance of Relativistic Effects and Electron Correlation in Structure Factors and Electron Density of Diphenyl Mercury and Triphenyl Bismuth.

PubMed

Bučinský, Lukáš; Jayatilaka, Dylan; Grabowsky, Simon

2016-08-25

This study investigates the possibility of detecting relativistic effects and electron correlation in single-crystal X-ray diffraction experiments using the examples of diphenyl mercury (HgPh2) and triphenyl bismuth (BiPh3). In detail, the importance of electron correlation (ECORR), relativistic effects (REL) [distinguishing between total, scalar and spin-orbit (SO) coupling relativistic effects] and picture change error (PCE) on the theoretical electron density, its topology and its Laplacian using infinite order two component (IOTC) wave functions is discussed. This is to develop an understanding of the order of magnitude and shape of these different effects as they manifest in the electron density. Subsequently, the same effects are considered for the theoretical structure factors. It becomes clear that SO and PCE are negligible, but ECORR and scalar REL are important in low- and medium-order reflections on absolute and relative scales-not in the high-order region. As a further step, Hirshfeld atom refinement (HAR) and subsequent X-ray constrained wavefunction (XCW) fitting have been performed for the compound HgPh2 with various relativistic and nonrelativistic wave functions against the experimental structure factors. IOTC calculations of theoretical structure factors and relativistic HAR as well as relativistic XCW fitting are presented for the first time, accounting for both scalar and spin-orbit relativistic effects.

Mechanism-Based Condition Screening for Sustainable Catalysis in Single-Electron Steps by Cyclic Voltammetry.

PubMed

Liedtke, Theresa; Spannring, Peter; Riccardi, Ludovico; Gansäuer, Andreas

2018-04-23

A cyclic-voltammetry-based screening method for Cp 2 TiX-catalyzed reactions is introduced. Our mechanism-based approach enables the study of the influence of various additives on the electrochemically generated active catalyst Cp 2 TiX, which is in equilibrium with catalytically inactive [Cp 2 TiX 2 ] - . Thioureas and ureas are most efficient in the generation of Cp 2 TiX in THF. Knowing the precise position of the equilibrium between Cp 2 TiX and [Cp 2 TiX 2 ] - allowed us to identify reaction conditions for the bulk electrolysis of Cp 2 TiX 2 complexes and for Cp 2 TiX-catayzed radical arylations without having to carry out the reactions. Our time- and resource-efficient approach is of general interest for the design of catalytic reactions that proceed in single-electron steps. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Critical motor number for fractional steps of cytoskeletal filaments in gliding assays.

PubMed

Li, Xin; Lipowsky, Reinhard; Kierfeld, Jan

2012-01-01

In gliding assays, filaments are pulled by molecular motors that are immobilized on a solid surface. By varying the motor density on the surface, one can control the number N of motors that pull simultaneously on a single filament. Here, such gliding assays are studied theoretically using brownian (or Langevin) dynamics simulations and taking the local force balance between motors and filaments as well as the force-dependent velocity of the motors into account. We focus on the filament stepping dynamics and investigate how single motor properties such as stalk elasticity and step size determine the presence or absence of fractional steps of the filaments. We show that each gliding assay can be characterized by a critical motor number, N(c). Because of thermal fluctuations, fractional filament steps are only detectable as long as N < N(c). The corresponding fractional filament step size is l/N where l is the step size of a single motor. We first apply our computational approach to microtubules pulled by kinesin-1 motors. For elastic motor stalks that behave as linear springs with a zero rest length, the critical motor number is found to be N(c) = 4, and the corresponding distributions of the filament step sizes are in good agreement with the available experimental data. In general, the critical motor number N(c) depends on the elastic stalk properties and is reduced to N(c) = 3 for linear springs with a nonzero rest length. Furthermore, N(c) is shown to depend quadratically on the motor step size l. Therefore, gliding assays consisting of actin filaments and myosin-V are predicted to exhibit fractional filament steps up to motor number N = 31. Finally, we show that fractional filament steps are also detectable for a fixed average motor number as determined by the surface density (or coverage) of the motors on the substrate surface.

Direct measurement of electron transfer distance decay constants of single redox proteins by electrochemical tunneling spectroscopy.

PubMed

Artés, Juan M; Díez-Pérez, Ismael; Sanz, Fausto; Gorostiza, Pau

2011-03-22

We present a method to measure directly and at the single-molecule level the distance decay constant that characterizes the rate of electron transfer (ET) in redox proteins. Using an electrochemical tunneling microscope under bipotentiostatic control, we obtained current−distance spectroscopic recordings of individual redox proteins confined within a nanometric tunneling gap at a well-defined molecular orientation. The tunneling current decays exponentially, and the corresponding decay constant (β) strongly supports a two-step tunneling ET mechanism. Statistical analysis of decay constant measurements reveals differences between the reduced and oxidized states that may be relevant to the control of ET rates in enzymes and biological electron transport chains.

Performance optimization of detector electronics for millimeter laser ranging

NASA Technical Reports Server (NTRS)

Cova, Sergio; Lacaita, A.; Ripamonti, Giancarlo

1993-01-01

The front-end electronic circuitry plays a fundamental role in determining the performance actually obtained from ultrafast and highly sensitive photodetectors. We deal here with electronic problems met working with microchannel plate photomultipliers (MCP-PMTs) and single photon avalanche diodes (SPADs) for detecting single optical photons and measuring their arrival time with picosecond resolution. The performance of available fast circuits is critically analyzed. Criteria for selecting the most suitable electronics are derived and solutions for exploiting the detector performance are presented and discussed.

Single electron counting using a dual MCP assembly

NASA Astrophysics Data System (ADS)

Yang, Yuzhen; Liu, Shulin; Zhao, Tianchi; Yan, Baojun; Wang, Peiliang; Yu, Yang; Lei, Xiangcui; Yang, Luping; Wen, Kaile; Qi, Ming; Heng, Yuekun

2016-09-01

The gain, pulse height resolution and peak-to-valley ratio of single electrons detected by using a Chevron configured Microchannel Plate (MCP) assembly are studied. The two MCPs are separated by a 280 μm gap and are biased by four electrodes. The purpose of the study is to determine the optimum bias voltage arrangements for single electron counting. By comparing the results of various bias voltage combinations, we conclude that good performance for the electron counting can be achieved by operating the MCP assembly in saturation mode. In addition, by applying a small reverse bias voltage across the gap while adjusting the bias voltages of the MCPs, optimum performance of electron counting can be obtained.

Effects of low energy E-beam irradiation on graphene and graphene field effect transistors and raman metrology of graphene on split gate test structures

NASA Astrophysics Data System (ADS)

Rao, Gayathri S.

2011-12-01

Apart from its compelling performance in conventional nanoelectronic device geometries, graphene is an appropriate candidate to study certain interesting phenomenon (e.g. the Veselago lens effect) predicted on the basis of its linear electron dispersion relation. A key requirement for the observation of such phenomenon in graphene and for its use in conventional field-effect transistor (FET) devices is the need to minimize defects such as consisting of -- or resulting from -- adsorbates and lattice non-uniformities, and reduce deleterious substrate effects. Consequently the investigation of the origin and interaction of defects in the graphene lattice is essential to improve and tailor graphene-based device performance. In this thesis, optical spectroscopic studies on the influence of low-energy electron irradiation on adsorbate-induced defectivity and doping for substrate supported and suspended graphene were carried out along with spectroscopic and transport measurements on graphene FETs. A comparative investigation of the effects of single-step versus multi-step, low-energy electron irradiation (500 eV) on suspended, substrate supported graphene and on graphene FETs is reported. E-beam irradiation (single-step and multi-step) of substrate-supported graphene resulted in an increase in the Raman ID/IG ratio largely from hydrogenation due to radiolysis of the interfacial water layer between the graphene and the SiO2 substrate and from irradiated surface adsorbates. GFETs subjected to single and multi-step irradiation showed n-doping from CNP (charge neutrality point) shift of ˜ -8 and ˜ -16 V respectively. Correlation of this data with Raman analysis of suspended and supported graphene samples implied a strong role of the substrate and irradiation sequence in determining the level of doping. A correspondingly higher reduction in mobility per incident electron was also observed for GFETs subjected to multi-step irradiation compared to single step, in line with measured Raman ID/IG ratios. Additionally, the Raman G-band DeltaFWHM variation was strongly dependent on the nature of the e-beam irradiation and the presence of the substrate. Single-step irradiated, substrate-supported graphene exhibited substantial broadening while multi-step irradiation resulted in G-band narrowing. This behavior was not observed for suspended graphene which indicated the addition or elimination of substrate-induced phonon-relaxation mechanisms in response to each type of irradiation. The narrowing of the FWHM (G) in the multi-step case is attributed to doping consistent with the Dirac point shift of ˜ -16V and the removal of Landau phonon damping above Ef > ℏwG2 . In strong contrast, single step irradiation of substrate supported graphene yielded a broadening of the FWHM (G) accompanied by a CNP shift of ˜ -8V indicating appreciable n-doping. This reveals the presence of alternate phonon decay channels even when Landau damping above Ef > ℏwG2 is removed. It is proposed in this dissertation that this phenomenon is linked to hybridization of silicon oxide defect states (induced by single-step e-beam irradiation) and graphene electron states. This hybridization promotes a graphene phonon decay channel distinct from Landau damping, the latter being forbidden under sufficient doping. It is proposed that the alternate phonon decay channel involves two-component inelastic scattering, wherein the graphene phonons transfer energy to the carriers in the lattice which in turn couple to the polar phonons of the substrate resulting in mobility reduction. Furthermore, it is proposed that this defect-induced, graphene phonon decay channel is inhibited in multi-step e-beam irradiation due to the presence of adsorbates on the graphene introduced during ambient exposure between radiation cycles. On e-beam irradiation the adsorbates induce polar orientation of water dipoles at the graphene/SiO2 interface. This polar layer shifts the hybridized defect bands closer to the graphene Dirac bands thereby reducing the inelastic scattering and inhibiting the phonon decay medicated by SiO2 surface polar phonons (SPP). This model also explains the enhancement of n-type doping in GFETS observed for multi-step irradiation. These results highlight the impact of substrate defects and interaction of induced defectivity with the e-beam along with the role of interfacial water in impacting graphene device performance. The thesis also presents data on Raman-based characterization of graphene including layer number determination and carrier concentration measurement. Determination of layer number for graphene exfoliates focused on the splitting of the 2D Raman band. In addition, an alternate Raman-based thickness metrology was evaluated for CVD-based, polycrystalline graphene. Both were carried out on split gate test structures as a method for monolayer or bilayer confirmation in device geometries. In addition, carrier concentration measurements of exfoliates on 300nm SiO2 and split-gate test structure substrate have also been characterized with back gate biasing. These measurements made use of the stiffening of the Raman G-band with doping and the narrowing of the G-band FWHM. These results were important for validating conclusions from the e-beam irradiation experiments mentioned above regarding carrier doping.

A Novel Immunoreagent for the Specific and Sensitive Detection of the Explosive Triacetone Triperoxide (TATP).

PubMed

Walter, Maria Astrid; Panne, Ulrich; Weller, Michael G

2011-07-07

Triacetone triperoxide (TATP) is a primary explosive, which was used in various terrorist attacks in the past. For the development of biosensors, immunochemical µ-TAS, electronic noses, immunological test kits, or test strips, the availability of antibodies of high quality is crucial. Recently, we presented the successful immunization of mice, based on the design, synthesis, and conjugation of a novel TATP derivative. Here, the long-term immunization of rabbits is shown, which resulted in antibodies of extreme selectivity and more than 1,000 times better affinity in relation to the antibodies from mice. Detection limits below 10 ng L-1 (water) were achieved. The working range covers more than four decades, calculated from a precision profile. The cross-reactivity tests revealed an extraordinary selectivity of the antibodies-not a single compound could be identified as a relevant cross-reactant. The presented immunoreagent might be a major step for the development of highly sensitive and selective TATP detectors particularly for security applications.

Electronic and rovibrational quantum chemical analysis of C3P-: the next interstellar anion?

NASA Astrophysics Data System (ADS)

Fortenberry, Ryan C.; Lukemire, Joseph A.

2015-11-01

C3P- is analogous to the known interstellar anion C3N- with phosphorus replacing nitrogen in a simple step down the periodic table. In this work, it is shown that C3P- is likely to possess a dipole-bound excited state. It has been hypothesized and observationally supported that dipole-bound excited states are an avenue through which anions could be formed in the interstellar medium. Additionally, C3P- has a valence excited state that may lead to further stabilization of this molecule, and C3P- has a larger dipole moment than neutral C3P (˜6 D versus ˜4 D). As such, C3P- is probably a more detectable astromolecule than even its corresponding neutral radical. Highly accurate quantum chemical quartic force fields are also applied to C3P- and its singly 13C substituted isotopologues in order to provide structures, vibrational frequencies, and spectroscopic constants that may aid in its detection.

A Novel Immunoreagent for the Specific and Sensitive Detection of the Explosive Triacetone Triperoxide (TATP)

PubMed Central

Walter, Maria Astrid; Panne, Ulrich; Weller, Michael G.

2011-01-01

Triacetone triperoxide (TATP) is a primary explosive, which was used in various terrorist attacks in the past. For the development of biosensors, immunochemical µ-TAS, electronic noses, immunological test kits, or test strips, the availability of antibodies of high quality is crucial. Recently, we presented the successful immunization of mice, based on the design, synthesis, and conjugation of a novel TATP derivative. Here, the long-term immunization of rabbits is shown, which resulted in antibodies of extreme selectivity and more than 1,000 times better affinity in relation to the antibodies from mice. Detection limits below 10 ng L−1 (water) were achieved. The working range covers more than four decades, calculated from a precision profile. The cross-reactivity tests revealed an extraordinary selectivity of the antibodies—not a single compound could be identified as a relevant cross-reactant. The presented immunoreagent might be a major step for the development of highly sensitive and selective TATP detectors particularly for security applications. PMID:25586922

Activation Thermodynamics and H/D Kinetic Isotope Effect of the H ox to H red H + Transition in [FeFe] Hydrogenase

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

Ratzloff, Michael W.; Wilker, Molly B.; Mulder, David W.

Molecular complexes between CdSe nanocrystals and Clostridium acetobutylicum [FeFe] hydrogenase I (CaI) enabled light-driven control of electron transfer for spectroscopic detection of redox intermediates during catalytic proton reduction. Here in this paper we address the route of electron transfer from CdSe→CaI and activation thermodynamics of the initial step of proton reduction in CaI. The electron paramagnetic spectroscopy of illuminated CdSe:CaI showed how the CaI accessory FeS cluster chain (F-clusters) functions in electron transfer with CdSe. The H ox→H redH + reduction step measured by Fourier-transform infrared spectroscopy showed an enthalpy of activation of 19 kJ mol -1 and a ~2.5-foldmore » kinetic isotope effect. Overall these results support electron injection from CdSe into CaI involving F-clusters, and that the H ox→H redH + step of catalytic proton reduction in CaI proceeds by a proton-dependent process.« less

Activation Thermodynamics and H/D Kinetic Isotope Effect of the H ox to H red H + Transition in [FeFe] Hydrogenase

DOE PAGES

Ratzloff, Michael W.; Wilker, Molly B.; Mulder, David W.; ...

2017-08-29

Molecular complexes between CdSe nanocrystals and Clostridium acetobutylicum [FeFe] hydrogenase I (CaI) enabled light-driven control of electron transfer for spectroscopic detection of redox intermediates during catalytic proton reduction. Here in this paper we address the route of electron transfer from CdSe→CaI and activation thermodynamics of the initial step of proton reduction in CaI. The electron paramagnetic spectroscopy of illuminated CdSe:CaI showed how the CaI accessory FeS cluster chain (F-clusters) functions in electron transfer with CdSe. The H ox→H redH + reduction step measured by Fourier-transform infrared spectroscopy showed an enthalpy of activation of 19 kJ mol -1 and a ~2.5-foldmore » kinetic isotope effect. Overall these results support electron injection from CdSe into CaI involving F-clusters, and that the H ox→H redH + step of catalytic proton reduction in CaI proceeds by a proton-dependent process.« less

Coherent radio-frequency detection for narrowband direct comb spectroscopy.

PubMed

Anstie, James D; Perrella, Christopher; Light, Philip S; Luiten, Andre N

2016-02-22

We demonstrate a scheme for coherent narrowband direct optical frequency comb spectroscopy. An extended cavity diode laser is injection locked to a single mode of an optical frequency comb, frequency shifted, and used as a local oscillator to optically down-mix the interrogating comb on a fast photodetector. The high spectral coherence of the injection lock generates a microwave frequency comb at the output of the photodiode with very narrow features, enabling spectral information to be further down-mixed to RF frequencies, allowing optical transmittance and phase to be obtained using electronics commonly found in the lab. We demonstrate two methods for achieving this step: a serial mode-by-mode approach and a parallel dual-comb approach, with the Cs D1 transition at 894 nm as a test case.

Dual core quantum dots for highly quantitative ratiometric detection of trypsin activity in cystic fibrosis patients

NASA Astrophysics Data System (ADS)

Castelló Serrano, Iván; Stoica, Georgiana; Matas Adams, Alba; Palomares, Emilio

2014-10-01

We present herein two colour encoded silica nanospheres (2nanoSi) for the fluorescence quantitative ratiometric determination of trypsin in humans. Current detection methods for cystic fibrosis diagnosis are slow, costly and suffer from false positives. The 2nanoSi proved to be a highly sensitive, fast (minutes), and single-step approach nanosensor for the screening and diagnosis of cystic fibrosis, allowing the quantification of trypsin concentrations in a wide range relevant for clinical applications (25-350 μg L-1). Furthermore, as trypsin is directly related to the development of cystic fibrosis (CF), different human genotypes, i.e. CF homozygotic, CF heterozygotic, and unaffected, respectively, can be determined using our 2nanoSi nanospheres. We anticipate the 2nanoSi system to be a starting point for non-invasive, easy-to-use and cost effective ratiometric fluorescent biomarkers for recessive genetic diseases like human cystic fibrosis. In a screening program in which the goal is to detect disease and also the carrier status, early diagnosis could be of great help.We present herein two colour encoded silica nanospheres (2nanoSi) for the fluorescence quantitative ratiometric determination of trypsin in humans. Current detection methods for cystic fibrosis diagnosis are slow, costly and suffer from false positives. The 2nanoSi proved to be a highly sensitive, fast (minutes), and single-step approach nanosensor for the screening and diagnosis of cystic fibrosis, allowing the quantification of trypsin concentrations in a wide range relevant for clinical applications (25-350 μg L-1). Furthermore, as trypsin is directly related to the development of cystic fibrosis (CF), different human genotypes, i.e. CF homozygotic, CF heterozygotic, and unaffected, respectively, can be determined using our 2nanoSi nanospheres. We anticipate the 2nanoSi system to be a starting point for non-invasive, easy-to-use and cost effective ratiometric fluorescent biomarkers for recessive genetic diseases like human cystic fibrosis. In a screening program in which the goal is to detect disease and also the carrier status, early diagnosis could be of great help. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03952a

A simplified focusing and astigmatism correction method for a scanning electron microscope

NASA Astrophysics Data System (ADS)

Lu, Yihua; Zhang, Xianmin; Li, Hai

2018-01-01

Defocus and astigmatism can lead to blurred images and poor resolution. This paper presents a simplified method for focusing and astigmatism correction of a scanning electron microscope (SEM). The method consists of two steps. In the first step, the fast Fourier transform (FFT) of the SEM image is performed and the FFT is subsequently processed with a threshold to achieve a suitable result. In the second step, the threshold FFT is used for ellipse fitting to determine the presence of defocus and astigmatism. The proposed method clearly provides the relationships between the defocus, the astigmatism and the direction of stretching of the FFT, and it can determine the astigmatism in a single image. Experimental studies are conducted to demonstrate the validity of the proposed method.

Enhanced sensitivity of self-assembled-monolayer-based SPR immunosensor for detection of benzaldehyde using a single-step multi-sandwich immunoassay.

PubMed

Gobi, K Vengatajalabathy; Matsumoto, Kiyoshi; Toko, Kiyoshi; Ikezaki, Hidekazu; Miura, Norio

2007-04-01

This paper describes the fabrication and sensing characteristics of a self-assembled monolayer (SAM)-based surface plasmon resonance (SPR) immunosensor for detection of benzaldehyde (BZ). The functional sensing surface was fabricated by the immobilization of a benzaldehyde-ovalbumin conjugate (BZ-OVA) on Au-thiolate SAMs containing carboxyl end groups. Covalent binding of BZ-OVA on SAM was found to be dependent on the composition of the base SAM, and it is improved very much with the use of a mixed monolayer strategy. Based on SPR angle measurements, the functional sensor surface is established as a compact monolayer of BZ-OVA bound on the mixed SAM. The BZ-OVA-bound sensor surface undergoes immunoaffinity binding with anti-benzaldehyde antibody (BZ-Ab) selectively. An indirect inhibition immunoassay principle has been applied, in which analyte benzaldehyde solution was incubated with an optimal concentration of BZ-Ab for 5 min and injected over the sensor chip. Analyte benzaldehyde undergoes immunoreaction with BZ-Ab and makes it inactive for binding to BZ-OVA on the sensor chip. As a result, the SPR angle response decreases with an increase in the concentration of benzaldehyde. The fabricated immunosensor demonstrates a low detection limit (LDL) of 50 ppt (pg mL(-1)) with a response time of 5 min. Antibodies bound to the sensor chip during an immunoassay could be detached by a brief exposure to acidic pepsin. With this surface regeneration, reusability of the same sensor chip for as many as 30 determination cycles has been established. Sensitivity has been enhanced further with the application of an additional single-step multi-sandwich immunoassay step, in which the BZ-Ab bound to the sensor chip was treated with a mixture of biotin-labeled secondary antibody, streptavidin and biotin-bovine serum albumin (Bio-BSA) conjugate. With this approach, the SPR sensor signal increased by ca. 12 times and the low detection limit improved to 5 ppt with a total response time of no more than ca. 10 min. Figure A single-step multi-sandwich immunoassay step increases SPR sensor signal by ca. 12 times affording a low detection limit for benzaldehyde of 5 ppt.

Self-assembly and continuous growth of hexagonal graphene flakes on liquid Cu

NASA Astrophysics Data System (ADS)

Cho, Seong-Yong; Kim, Min-Sik; Kim, Minsu; Kim, Ki-Ju; Kim, Hyun-Mi; Lee, Do-Joong; Lee, Sang-Hoon; Kim, Ki-Bum

2015-07-01

Graphene growth on liquid Cu has received great interest, owing to the self-assembly behavior of hexagonal graphene flakes with aligned orientation and to the possibility of forming a single grain of graphene through a commensurate growth of these graphene flakes. Here, we propose and demonstrate a two-step growth process which allows the formation of self-assembled, completely continuous graphene on liquid Cu. After the formation of full coverage on the liquid Cu, grain boundaries were revealed via selective hydrogen etching and the original grain boundaries were clearly resolved. This result indicates that, while the flakes self-assembled with the same orientation, there still remain structural defects, gaps and voids that were not resolved by optical microscopy or scanning electron microscopy. To overcome this limitation, the two-step growth process was employed, consisting of a sequential process of a normal single-layer graphene growth and self-assembly process with a low carbon flux, followed by the final stage of graphene growth at a high degree of supersaturation with a high carbon flux. Continuity of the flakes was verified via hydrogen etching and a NaCl-assisted oxidation process, as well as by measuring the electrical properties of the graphene grown by the two-step process. Two-step growth can provide a continuous graphene layer, but commensurate stitching should be further studied.Graphene growth on liquid Cu has received great interest, owing to the self-assembly behavior of hexagonal graphene flakes with aligned orientation and to the possibility of forming a single grain of graphene through a commensurate growth of these graphene flakes. Here, we propose and demonstrate a two-step growth process which allows the formation of self-assembled, completely continuous graphene on liquid Cu. After the formation of full coverage on the liquid Cu, grain boundaries were revealed via selective hydrogen etching and the original grain boundaries were clearly resolved. This result indicates that, while the flakes self-assembled with the same orientation, there still remain structural defects, gaps and voids that were not resolved by optical microscopy or scanning electron microscopy. To overcome this limitation, the two-step growth process was employed, consisting of a sequential process of a normal single-layer graphene growth and self-assembly process with a low carbon flux, followed by the final stage of graphene growth at a high degree of supersaturation with a high carbon flux. Continuity of the flakes was verified via hydrogen etching and a NaCl-assisted oxidation process, as well as by measuring the electrical properties of the graphene grown by the two-step process. Two-step growth can provide a continuous graphene layer, but commensurate stitching should be further studied. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03352g

[First attempts of detecting fetal cells in the maternal circulation].

PubMed

Nagy, Gyula Richárd; Bán, Zoltán; Sipos, Ferenc; Fent, János; Oroszné Nagy, Judit; Beke, Artúr; Furész, József; Papp, Zoltán

2004-10-31

In prenatal diagnosis there is great interest for noninvasive diagnostic methods. Authors report their first results in detecting fetal cells in the maternal circulation during pregnancy. The aim of the study was to detect fetal gender from maternal peripheral blood samples during pregnancy. Authors have analysed fetal nucleated red blood cells. In 12 cases after a double density Percoll gradient separation they labelled the surface antigens of the cells with anti-glycophorin-A and anti-CD45 fluorescent antibodies, did an intracellular staining of the epsilon haemoglobin chain, and analysed the cells with flow cytometry. The CD45 negative/glycophorin-A positive/epsilon-haemoglobin chain positive cells were considered as fetal cells. Having the results, in another 13 cases magnetic activated cell sorting with CD71 antibody were used as an enrichment step. Authors made an intracellular staining of the epsilon haemoglobin chain, the positive cells were isolated by micromanipulation, and analysed by single cell fluorescent polymerase chain reaction. Primers for the amelogenin gene were used to detect fetal gender. Only the Percoll enrichment step itself is not enough for using the samples for diagnostic molecular-biologic examinations, a following enrichment step is needed. For this the authors used magnetic activated cell sorting with CD71 antibody. With the help of this enrichment step, after the intracellular staining of the epsilon haemoglobin chain the direct micromanipulator isolation of the epsilon haemoglobin chain positive cells could be done. After analysing single cells by fluorescent polymerase chain reaction, in 8 out of the 11 comparable cases the results were similar to those, what was found during the genetic amniocentesis. In 2 cases from this 8, genetic amniocentesis proved Klinefelter syndrome, which they could also confirm with the examination of fetal cells in the maternal circulation. The results of the study suggest that the method described above can be useful in prenatal genetic diagnosis, and improving it could be useful to detect other genetic abnormalities (chromosomal abnormalities, single gene disorders) as well.

User's manual: Computer-aided design programs for inductor-energy-storage dc-to-dc electronic power converters

NASA Technical Reports Server (NTRS)

Huffman, S.

1977-01-01

Detailed instructions on the use of two computer-aided-design programs for designing the energy storage inductor for single winding and two winding dc to dc converters are provided. Step by step procedures are given to illustrate the formatting of user input data. The procedures are illustrated by eight sample design problems which include the user input and the computer program output.

Processing of fullerene-single wall carbon nanotube complex for bulk heterojunction photovoltaic cells

NASA Astrophysics Data System (ADS)

Li, Cheng; Mitra, Somenath

2007-12-01

A fullerene-single wall carbon nanotube (C60-SWCNT) complex is used as a component of the photoactive layer in bulk heterojunction photovoltaic cells. This complex synthesized by microwave-assisted reaction takes advantage of the electron accepting feature of C60 and the high electron transport capability of SWCNTs. In this paper, quantum efficiency enhancement by increasing light absorption and by bringing about appropriate morphological rearrangements via solvent vapor treatment and thermal annealing is presented. The optimum combination of these steps led to an increase in efficiency by as much as 87.5%.

Fabrication of Highly Sensitive Nonenzymatic Electrochemical H₂O₂ Sensor Based on Pt Nanoparticles Anchored Reduced Graphene Oxide.

PubMed

Dhara, Keerthy; Ramachandran, T; Nair, Bipin G; Babu, T G Satheesh

2018-06-01

A highly sensitive nonenzymatic hydrogen peroxide (H2O2) sensor was fabricated using platinum nanoparticles decorated reduced graphene oxide (Pt/rGO) nanocomposite. The Pt/rGO nanocomposite was prepared by single-step chemical reduction method. Nanocomposite was characterized by various analytical techniques including Raman spectroscopy, X-ray diffraction, field emission scanning electron microscope and high-resolution transmission electron microscopy. Screen printed electrodes (SPEs) were fabricated and the nanocomposite was cast on the working area of the SPE. Cyclic voltammetry and amperometry demonstrated that the Pt/rGO/SPE displayed much higher electrocatalytic activity towards the reduction of H2O2 than the other modified electrodes. The sensor exhibited wide linear detection range (from 10 μM to 8 mM), very high sensitivity of 1848 μA mM-1 cm-2 and a lower limit of detection of 0.06 μM. The excellent performance of Pt/rGO/SPE sensor were attributed to the reduced graphene oxide being used as an effective matrix to load a number of Pt nanoparticles and the synergistic amplification effect of the two kinds of nanomaterials. Moreover, the sensor showed remarkable features such as good reproducibility, repeatability, long-term stability, and selectivity.

Work function and temperature dependence of electron tunneling through an N-type perylene diimide molecular junction with isocyanide surface linkers.

PubMed

Smith, Christopher E; Xie, Zuoti; Bâldea, Ioan; Frisbie, C Daniel

2018-01-18

Conducting probe atomic force microscopy (CP-AFM) was employed to examine electron tunneling in self-assembled monolayer (SAM) junctions. A 2.3 nm long perylene tetracarboxylic acid diimide (PDI) acceptor molecule equipped with isocyanide linker groups was synthesized, adsorbed onto Ag, Au and Pt substrates, and the current-voltage (I-V) properties were measured by CP-AFM. The dependence of the low-bias resistance (R) on contact work function indicates that transport is LUMO-assisted ('n-type behavior'). A single-level tunneling model combined with transition voltage spectroscopy (TVS) was employed to analyze the experimental I-V curves and to extract the effective LUMO position ε l = E LUMO - E F and the effective electronic coupling (Γ) between the PDI redox core and the contacts. This analysis revealed a strong Fermi level (E F ) pinning effect in all the junctions, likely due to interface dipoles that significantly increased with increasing contact work function, as revealed by scanning Kelvin probe microscopy (SKPM). Furthermore, the temperature (T) dependence of R was found to be substantial. For Pt/Pt junctions, R varied more than two orders of magnitude in the range 248 K < T < 338 K. Importantly, the R(T) data are consistent with a single step electron tunneling mechanism and allow independent determination of ε l , giving values compatible with estimates of ε l based on analysis of the full I-V data. Theoretical analysis revealed a general criterion to unambiguously rule out a two-step transport mechanism: namely, if measured resistance data exhibit a pronounced Arrhenius-type temperature dependence, a two-step electron transfer scenario should be excluded in cases where the activation energy depends on contact metallurgy. Overall, our results indicate (1) the generality of the Fermi level pinning phenomenon in molecular junctions, (2) the utility of employing the single level tunneling model for determining essential electronic structure parameters (ε l and Γ), and (3) the importance of changing the nature of the contacts to verify transport mechanisms.

Anti-dynamic-crosstalk method for single photon LIDAR detection

NASA Astrophysics Data System (ADS)

Zhang, Fan; Liu, Qiang; Gong, Mali; Fu, Xing

2017-11-01

With increasing number of vehicles equipped with light detection and ranging (LIDAR), crosstalk is identified as a critical and urgent issue in the range detection for active collision avoidance. Chaotic pulse position modulation (CPPM) applied in the transmitting pulse train has been shown to prevent crosstalk as well as range ambiguity. However, static and unified strategy on discrimination threshold and the number of accumulated pulse is not valid against crosstalk with varying number of sources and varying intensity of each source. This paper presents an adaptive algorithm to distinguish the target echo from crosstalk with dynamic and unknown level of intensity in the context of intelligent vehicles. New strategy is given based on receiver operating characteristics (ROC) curves that consider the detection requirements of the probability of detection and false alarm for the scenario with varying crosstalk. In the adaptive algorithm, the detected results are compared by the new strategy with both the number of accumulated pulses and the threshold being raised step by step, so that the target echo can be exactly identified from crosstalk with the dynamic and unknown level of intensity. The validity of the algorithm has been verified through the experiments with a single photon detector and the time correlated single photo counting (TCSPC) technique, demonstrating a marked drop in required shots for identifying the target compared with static and unified strategy

Room-temperature current blockade in atomically defined single-cluster junctions

NASA Astrophysics Data System (ADS)

Lovat, Giacomo; Choi, Bonnie; Paley, Daniel W.; Steigerwald, Michael L.; Venkataraman, Latha; Roy, Xavier

2017-11-01

Fabricating nanoscopic devices capable of manipulating and processing single units of charge is an essential step towards creating functional devices where quantum effects dominate transport characteristics. The archetypal single-electron transistor comprises a small conducting or semiconducting island separated from two metallic reservoirs by insulating barriers. By enabling the transfer of a well-defined number of charge carriers between the island and the reservoirs, such a device may enable discrete single-electron operations. Here, we describe a single-molecule junction comprising a redox-active, atomically precise cobalt chalcogenide cluster wired between two nanoscopic electrodes. We observe current blockade at room temperature in thousands of single-cluster junctions. Below a threshold voltage, charge transfer across the junction is suppressed. The device is turned on when the temporary occupation of the core states by a transiting carrier is energetically enabled, resulting in a sequential tunnelling process and an increase in current by a factor of ∼600. We perform in situ and ex situ cyclic voltammetry as well as density functional theory calculations to unveil a two-step process mediated by an orbital localized on the core of the cluster in which charge carriers reside before tunnelling to the collector reservoir. As the bias window of the junction is opened wide enough to include one of the cluster frontier orbitals, the current blockade is lifted and charge carriers can tunnel sequentially across the junction.

Gigahertz single-electron pumping in silicon with an accuracy better than 9.2 parts in 10{sup 7}

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

Yamahata, Gento, E-mail: yamahata.gento@lab.ntt.co.jp; Karasawa, Takeshi; Fujiwara, Akira

2016-07-04

High-speed and high-accuracy pumping of a single electron is crucial for realizing an accurate current source, which is a promising candidate for a quantum current standard. Here, using a high-accuracy measurement system traceable to primary standards, we evaluate the accuracy of a Si tunable-barrier single-electron pump driven by a single sinusoidal signal. The pump operates at frequencies up to 6.5 GHz, producing a current of more than 1 nA. At 1 GHz, the current plateau with a level of about 160 pA is found to be accurate to better than 0.92 ppm (parts per million), which is a record value for 1-GHz operation. At 2 GHz,more » the current plateau offset from 1ef (∼320 pA) by 20 ppm is observed. The current quantization accuracy is improved by applying a magnetic field of 14 T, and we observe a current level of 1ef with an accuracy of a few ppm. The presented gigahertz single-electron pumping with a high accuracy is an important step towards a metrological current standard.« less

Attosecond Optics and Technology: Progress to Date and Future Prospects [Invited

DTIC Science & Technology

2016-06-01

1s electron in the hydrogen atom experiences is 5.14 × 109 V∕cm. In such a strong external field, an electron can be freed from an atom via tunneling ...been replaced by laser diodes , which leads to user-friendly products that deliver either single-longitudinal mode beams for pumping laser oscillators...steps. First, an electron is released by tunneling through the potential barrier formed by the atomic Coulomb field and the driving laser field. Then

Nanoantenna enhancement for telecom-wavelength superconducting single photon detectors.

PubMed

Heath, Robert M; Tanner, Michael G; Drysdale, Timothy D; Miki, Shigehito; Giannini, Vincenzo; Maier, Stefan A; Hadfield, Robert H

2015-02-11

Superconducting nanowire single photon detectors are rapidly emerging as a key infrared photon-counting technology. Two front-side-coupled silver dipole nanoantennas, simulated to have resonances at 1480 and 1525 nm, were fabricated in a two-step process. An enhancement of 50 to 130% in the system detection efficiency was observed when illuminating the antennas. This offers a pathway to increasing absorption into superconducting nanowires, creating larger active areas, and achieving more efficient detection at longer wavelengths.

Silicon displacement threshold energy determined by electron paramagnetic resonance and positron annihilation spectroscopy in cubic and hexagonal polytypes of silicon carbide

NASA Astrophysics Data System (ADS)

Kerbiriou, X.; Barthe, M.-F.; Esnouf, S.; Desgardin, P.; Blondiaux, G.; Petite, G.

2007-05-01

Both for electronic and nuclear applications, it is of major interest to understand the properties of point defects into silicon carbide (SiC). Low energy electron irradiations are supposed to create primary defects into materials. SiC single crystals have been irradiated with electrons at two beam energies in order to investigate the silicon displacement threshold energy into SiC. This paper presents the characterization of the electron irradiation-induced point defects into both polytypes hexagonal (6H) and cubic (3C) SiC single crystals by using both positron annihilation spectroscopy (PAS) and electron paramagnetic resonance (EPR). The nature and the concentration of the generated point defects depend on the energy of the electron beam and the polytype. After an electron irradiation at an energy of 800 keV vSi mono-vacancies and vSi-vC di-vacancies are detected in both 3C and 6H-SiC polytypes. On the contrary, the nature of point defects detected after an electron irradiation at 190 keV strongly depends on the polytype. Into 6H-SiC crystals, silicon Frenkel pairs vSi-Si are detected whereas only carbon vacancy related defects are detected into 3C-SiC crystals. The difference observed in the distribution of defects detected into the two polytypes can be explained by the different values of the silicon displacement threshold energies for 3C and 6H-SiC. By comparing the calculated theoretical numbers of displaced atoms with the defects numbers measured using EPR, the silicon displacement threshold energy has been estimated to be slightly lower than 20 eV in the 6H polytype and close to 25 eV in the 3C polytype.

High-Precision Displacement Sensing of Monolithic Piezoelectric Disk Resonators Using a Single-Electron Transistor

NASA Astrophysics Data System (ADS)

Li, J.; Santos, J. T.; Sillanpää, M. A.

2018-02-01

A single-electron transistor (SET) can be used as an extremely sensitive charge detector. Mechanical displacements can be converted into charge, and hence, SETs can become sensitive detectors of mechanical oscillations. For studying small-energy oscillations, an important approach to realize the mechanical resonators is to use piezoelectric materials. Besides coupling to traditional electric circuitry, the strain-generated piezoelectric charge allows for measuring ultrasmall oscillations via SET detection. Here, we explore the usage of SETs to detect the shear-mode oscillations of a 6-mm-diameter quartz disk resonator with a resonance frequency around 9 MHz. We measure the mechanical oscillations using either a conventional DC SET, or use the SET as a homodyne or heterodyne mixer, or finally, as a radio-frequency single-electron transistor (RF-SET). The RF-SET readout is shown to be the most sensitive method, allowing us to measure mechanical displacement amplitudes below 10^{-13} m. We conclude that a detection based on a SET offers a potential to reach the sensitivity at the quantum limit of the mechanical vibrations.

High-Precision Displacement Sensing of Monolithic Piezoelectric Disk Resonators Using a Single-Electron Transistor

NASA Astrophysics Data System (ADS)

Li, J.; Santos, J. T.; Sillanpää, M. A.

2018-06-01

A single-electron transistor (SET) can be used as an extremely sensitive charge detector. Mechanical displacements can be converted into charge, and hence, SETs can become sensitive detectors of mechanical oscillations. For studying small-energy oscillations, an important approach to realize the mechanical resonators is to use piezoelectric materials. Besides coupling to traditional electric circuitry, the strain-generated piezoelectric charge allows for measuring ultrasmall oscillations via SET detection. Here, we explore the usage of SETs to detect the shear-mode oscillations of a 6-mm-diameter quartz disk resonator with a resonance frequency around 9 MHz. We measure the mechanical oscillations using either a conventional DC SET, or use the SET as a homodyne or heterodyne mixer, or finally, as a radio-frequency single-electron transistor (RF-SET). The RF-SET readout is shown to be the most sensitive method, allowing us to measure mechanical displacement amplitudes below 10^{-13} m. We conclude that a detection based on a SET offers a potential to reach the sensitivity at the quantum limit of the mechanical vibrations.

Conditional Dispersive Readout of a CMOS Single-Electron Memory Cell

NASA Astrophysics Data System (ADS)

Schaal, S.; Barraud, S.; Morton, J. J. L.; Gonzalez-Zalba, M. F.

2018-05-01

Quantum computers require interfaces with classical electronics for efficient qubit control, measurement, and fast data processing. Fabricating the qubit and the classical control layer using the same technology is appealing because it will facilitate the integration process, improving feedback speeds and offering potential solutions to wiring and layout challenges. Integrating classical and quantum devices monolithically, using complementary metal-oxide-semiconductor (CMOS) processes, enables the processor to profit from the most mature industrial technology for the fabrication of large-scale circuits. We demonstrate a CMOS single-electron memory cell composed of a single quantum dot and a transistor that locks charge on the quantum-dot gate. The single-electron memory cell is conditionally read out by gate-based dispersive sensing using a lumped-element L C resonator. The control field-effect transistor (FET) and quantum dot are fabricated on the same chip using fully depleted silicon-on-insulator technology. We obtain a charge sensitivity of δ q =95 ×10-6e Hz-1 /2 when the quantum-dot readout is enabled by the control FET, comparable to results without the control FET. Additionally, we observe a single-electron retention time on the order of a second when storing a single-electron charge on the quantum dot at millikelvin temperatures. These results demonstrate first steps towards time-based multiplexing of gate-based dispersive readout in CMOS quantum devices opening the path for the development of an all-silicon quantum-classical processor.

Electron and fluorescence spectra of a water molecule irradiated by an x-ray free-electron laser pulse

NASA Astrophysics Data System (ADS)

Schäfer, Julia M.; Inhester, Ludger; Son, Sang-Kil; Fink, Reinhold F.; Santra, Robin

2018-05-01

With the highly intense x-ray light generated by x-ray free-electron lasers (XFELs), molecular samples can be ionized many times in a single pulse. Here we report on a computational study of molecular spectroscopy at the high x-ray intensity provided by XFELs. Calculated photoelectron, Auger electron, and x-ray fluorescence spectra are presented for a single water molecule that reaches many electronic hole configurations through repeated ionization steps. The rich details shown in the spectra depend on the x-ray pulse parameters in a nonintuitive way. We discuss how the observed trends can be explained by the competition of microscopic electronic transition processes. A detailed comparison between spectra calculated within the independent-atom model and within the molecular-orbital framework highlights the chemical sensitivity of the spectral lines of multiple-hole configurations. Our results demonstrate how x-ray multiphoton ionization-related effects such as charge-rearrangement-enhanced x-ray ionization of molecules and frustrated absorption manifest themselves in the electron and fluorescence spectra.

Real-time fluorescence ligase chain reaction for sensitive detection of single nucleotide polymorphism based on fluorescence resonance energy transfer.

PubMed

Sun, Yueying; Lu, Xiaohui; Su, Fengxia; Wang, Limei; Liu, Chenghui; Duan, Xinrui; Li, Zhengping

2015-12-15

Most of practical methods for detection of single nucleotide polymorphism (SNP) need at least two steps: amplification (usually by PCR) and detection of SNP by using the amplification products. Ligase chain reaction (LCR) can integrate the amplification and allele discrimination in one step. However, the detection of LCR products still remains a great challenge for highly sensitive and quantitative SNP detection. Herein, a simple but robust strategy for real-time fluorescence LCR has been developed for highly sensitive and quantitative SNP detection. A pair of LCR probes are firstly labeled with a fluorophore and a quencher, respectively. When the pair of LCR probes are ligated in LCR, the fluorophore will be brought close to the quencher, and thus, the fluorescence will be specifically quenched by fluorescence resonance energy transfer (FRET). The decrease of fluorescence intensity resulted from FRET can be real-time monitored in the LCR process. With the proposed real-time fluorescence LCR assay, 10 aM DNA targets or 100 pg genomic DNA can be accurately determined and as low as 0.1% mutant DNA can be detected in the presence of a large excess of wild-type DNA, indicating the high sensitivity and specificity. The real-time measuring does not require the detection step after LCR and gives a wide dynamic range for detection of DNA targets (from 10 aM to 1 pM). As LCR has been widely used for detection of SNP, DNA methylation, mRNA and microRNA, the real-time fluorescence LCR assay shows great potential for various genetic analysis. Copyright © 2015 Elsevier B.V. All rights reserved.

Electron source for a mini ion trap mass spectrometer

DOEpatents

Dietrich, Daniel D.; Keville, Robert F.

1995-01-01

An ion trap which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10.sup.9 and commercial mass spectrometers requiring 10.sup.4 ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products.

Automated Discovery of Elementary Chemical Reaction Steps Using Freezing String and Berny Optimization Methods.

PubMed

Suleimanov, Yury V; Green, William H

2015-09-08

We present a simple protocol which allows fully automated discovery of elementary chemical reaction steps using in cooperation double- and single-ended transition-state optimization algorithms--the freezing string and Berny optimization methods, respectively. To demonstrate the utility of the proposed approach, the reactivity of several single-molecule systems of combustion and atmospheric chemistry importance is investigated. The proposed algorithm allowed us to detect without any human intervention not only "known" reaction pathways, manually detected in the previous studies, but also new, previously "unknown", reaction pathways which involve significant atom rearrangements. We believe that applying such a systematic approach to elementary reaction path finding will greatly accelerate the discovery of new chemistry and will lead to more accurate computer simulations of various chemical processes.

Formation of a cytochrome c-nitrous oxide reductase complex is obligatory for N2O reduction by Paracoccus pantotrophus.

PubMed

Rasmussen, Tim; Brittain, Thomas; Berks, Ben C; Watmough, Nicholas J; Thomson, Andrew J

2005-11-07

Nitrous oxide reductase (N2OR) catalyses the final step of bacterial denitrification, the two-electron reduction of nitrous oxide (N2O) to dinitrogen (N2). N2OR contains two metal centers; a binuclear copper center, CuA, that serves to receive electrons from soluble donors, and a tetranuclear copper-sulfide center, CuZ, at the active site. Stopped flow experiments at low ionic strengths reveal rapid electron transfer (kobs=150 s-1) between reduced horse heart (HH) cytochrome c and the CuA center in fully oxidized N2OR. When fully reduced N2OR was mixed with oxidized cytochrome c, a similar rate of electron transfer was recorded for the reverse reaction, followed by a much slower internal electron transfer from CuZ to CuA(kobs=0.1-0.4 s-1). The internal electron transfer process is likely to represent the rate-determining step in the catalytic cycle. Remarkably, in the absence of cytochrome c, fully reduced N2OR is inert towards its substrate, even though sufficient electrons are stored to initiate a single turnover. However, in the presence of reduced cytochrome c and N2O, a single turnover occurs after a lag-phase. We propose that a conformational change in N2OR is induced by its specific interaction with cytochrome c that in turn either permits electron transfer between CuA and CuZ or controls the rate of N2O decomposition at the active site.

Electronic Procedures for Medical Operations

NASA Technical Reports Server (NTRS)

2015-01-01

Electronic procedures are replacing text-based documents for recording the steps in performing medical operations aboard the International Space Station. S&K Aerospace, LLC, has developed a content-based electronic system-based on the Extensible Markup Language (XML) standard-that separates text from formatting standards and tags items contained in procedures so they can be recognized by other electronic systems. For example, to change a standard format, electronic procedures are changed in a single batch process, and the entire body of procedures will have the new format. Procedures can be quickly searched to determine which are affected by software and hardware changes. Similarly, procedures are easily shared with other electronic systems. The system also enables real-time data capture and automatic bookmarking of current procedure steps. In Phase II of the project, S&K Aerospace developed a Procedure Representation Language (PRL) and tools to support the creation and maintenance of electronic procedures for medical operations. The goal is to develop these tools in such a way that new advances can be inserted easily, leading to an eventual medical decision support system.

Imaging nanoscale spatial modulation of a relativistic electron beam with a MeV ultrafast electron microscope

NASA Astrophysics Data System (ADS)

Lu, Chao; Jiang, Tao; Liu, Shengguang; Wang, Rui; Zhao, Lingrong; Zhu, Pengfei; Liu, Yaqi; Xu, Jun; Yu, Dapeng; Wan, Weishi; Zhu, Yimei; Xiang, Dao; Zhang, Jie

2018-03-01

An accelerator-based MeV ultrafast electron microscope (MUEM) has been proposed as a promising tool to the study structural dynamics at the nanometer spatial scale and the picosecond temporal scale. Here, we report experimental tests of a prototype MUEM where high quality images with nanoscale fine structures were recorded with a pulsed ˜3 MeV picosecond electron beam. The temporal and spatial resolutions of the MUEM operating in the single-shot mode are about 4 ps (FWHM) and 100 nm (FWHM), corresponding to a temporal-spatial resolution of 4 × 10-19 s m, about 2 orders of magnitude higher than that achieved with state-of-the-art single-shot keV UEM. Using this instrument, we offer the demonstration of visualizing the nanoscale periodic spatial modulation of an electron beam, which may be converted into longitudinal density modulation through emittance exchange to enable production of high-power coherent radiation at short wavelengths. Our results mark a great step towards single-shot nanometer-resolution MUEMs and compact intense x-ray sources that may have widespread applications in many areas of science.

Semi-conducting single-walled carbon nanotubes are detrimental when compared to metallic single-walled carbon nanotubes for electrochemical applications.

PubMed

Dong, Qi; Nasir, Muhammad Zafir Mohamad; Pumera, Martin

2017-10-18

As-synthetized single walled carbon nanotubes (SWCNTs) contain both metallic and semiconducting nanotubes. For the electronics, it is desirable to separate semiconducting SWCNTs (s-SWCNTs) from the metallic ones as s-SWCNTs provide desirable electronic properties. Here we test whether ultrapure semi-conducting single-walled carbon nanotubes (s-SWCNTs) provide advantageous electrochemical properties over the as prepared SWCNTs which contain a mixture of semiconducting and metallic CNTs. We test them as a transducer platform which enhanced the detection of target analytes (ascorbic acid, dopamine, uric acid) when compared to a bare glassy carbon (GC) electrode. Despite that, the two materials exhibit significantly different electrochemical properties and performances. A mixture of m-SWCNTs and s-SWCNTs demonstrated superior performance over ultrapure s-SWCNTs with greater peak currents and pronounced shift in peak potentials to lower values in cyclic and differential pulse voltammetry for the detection of target analytes. The mixture of m- and s-SWCNTs displayed about a 4 times improved heterogeneous electron transfer rate as compared to bare GC and a 2 times greater heterogeneous electron transfer rate than s-SWCNTs, demonstrating that ultrapure SWCNTs do not provide any major enhancement over the as prepared SWCNTs.

A Simple Method to Simultaneously Detect and Identify Spikes from Raw Extracellular Recordings.

PubMed

Petrantonakis, Panagiotis C; Poirazi, Panayiota

2015-01-01

The ability to track when and which neurons fire in the vicinity of an electrode, in an efficient and reliable manner can revolutionize the neuroscience field. The current bottleneck lies in spike sorting algorithms; existing methods for detecting and discriminating the activity of multiple neurons rely on inefficient, multi-step processing of extracellular recordings. In this work, we show that a single-step processing of raw (unfiltered) extracellular signals is sufficient for both the detection and identification of active neurons, thus greatly simplifying and optimizing the spike sorting approach. The efficiency and reliability of our method is demonstrated in both real and simulated data.

A Front-End electronics board for single photo-electron timing and charge from MaPMT

NASA Astrophysics Data System (ADS)

Giordano, F.; Breton, D.; Beigbeder, C.; De Robertis, G.; Fusco, P.; Gargano, F.; Liuzzi, R.; Loparco, F.; Mazziotta, M. N.; Rizzi, V.; Tocut, V.

2013-08-01

A Front-End (FE) design based on commercial operational amplifiers has been developed to read-out signals from a Multianode PhotoMultiplier Tube (MaPMT). The overall design has been optimised for single photo-electron signal from the Hamamatsu H8500. The signal is collected by a current sensitive preamplifier and then it is fed into both a ECL fast discriminator and a shaper for analog output readout in differential mode. The analog signal and the digital gates are then registered on VME ADC and TDC modules respectively. Performances in terms of linearity, gain and timing resolution will be discussed, presenting results obtained on a test bench with differentiated step voltage inputs and also with a prototype electronic board plugged into the H8500 PMT illuminated by a picosecond laser.

Simultaneous Detection of Four Foodborne Viruses in Food Samples Using a One-Step Multiplex Reverse Transcription PCR.

PubMed

Lee, Shin-Young; Kim, Mi-Ju; Kim, Hyun-Joong; Jeong, KwangCheol Casey; Kim, Hae-Yeong

2018-02-28

A one-step multiplex reverse transcription PCR (RT-PCR) method comprising six primer sets (for the detection of norovirus GI and GII, hepatitis A virus, rotavirus, and astrovirus) was developed to simultaneously detect four kinds of pathogenic viruses. The size of the PCR products for norovirus GI and GII, hepatitis A virus (VP3/VP1 and P2A regions), rotavirus, and astrovirus were 330, 164, 244, 198, 629, and 449 bp, respectively. The RT-PCR with the six primer sets showed specificity for the pathogenic viruses. The detection limit of the developed multiplex RT-PCR, as evaluated using serially diluted viral RNAs, was comparable to that of one-step single RT-PCR. Moreover, this multiplex RT-PCR was evaluated using food samples such as water, oysters, lettuce, and vegetable product. These food samples were artificially spiked with the four kinds of viruses in diverse combinations, and the spiked viruses in all food samples were detected successfully.

ROOM TEMPERATURE BULK AND TEMPLATE-FREE SYNTHESIS OF LEUCOEMARLDINE POLYANILINE NANOFIBERS

EPA Science Inventory

An extremely simple single-step method is described for the bulk synthesis of nanofibers of the electronic polymer polyaniline in fully reduced state (leucoemarldine form) without using any reducing agents, surfactants, and/or large amounts of insoluble templates. Chemical oxida...

Novel structure formation at the bottom surface of porous anodic alumina fabricated by single step anodization process.

PubMed

Ali, Ghafar; Ahmad, Maqsood; Akhter, Javed Iqbal; Maqbool, Muhammad; Cho, Sung Oh

2010-08-01

A simple approach for the growth of long-range highly ordered nanoporous anodic alumina film in H(2)SO(4) electrolyte through a single step anodization without any additional pre-anodizing procedure is reported. Free-standing porous anodic alumina film of 180 microm thickness with through hole morphology was obtained. A simple and single step process was used for the detachment of alumina from aluminum substrate. The effect of anodizing conditions, such as anodizing voltage and time on the pore diameter and pore ordering is discussed. The metal/oxide and oxide/electrolyte interfaces were examined by high resolution scanning transmission electron microscope. The arrangement of pores on metal/oxide interface was well ordered with smaller diameters than that of the oxide/electrolyte interface. The inter-pore distance was larger in metal/oxide interface as compared to the oxide/electrolyte interface. The size of the ordered domain was found to depend strongly upon anodizing voltage and time. (c) 2010 Elsevier Ltd. All rights reserved.

A New Method for the Fast Analysis of Trihalomethanes in Tap and Recycled Waters Using Headspace Gas Chromatography with Micro-Electron Capture Detection

PubMed Central

Alexandrou, Lydon D.; Meehan, Barry J.; Morrison, Paul D.; Jones, Oliver A. H.

2017-01-01

Chemical disinfection of water supplies brings significant public health benefits by reducing microbial contamination. The process can however, result in the formation of toxic compounds through interactions between disinfectants and organic material in the source water. These new compounds are termed disinfection by-products (DBPs). The most common are the trihalomethanes (THMs) such as trichloromethane (chloroform), dichlorobromomethane, chlorodibromomethane and tribromomethane (bromoform); these are commonly reported as a single value for total trihalomethanes (TTHMs). Analysis of DBPs is commonly performed via time- and solvent-intensive sample preparation techniques such as liquid–liquid and solid phase extraction. In this study, a method using headspace gas chromatography with micro-electron capture detection was developed and applied for the analysis of THMs in drinking and recycled waters from across Melbourne (Victoria, Australia). The method allowed almost complete removal of the sample preparation step whilst maintaining trace level detection limits (>1 ppb). All drinking water samples had TTHM concentrations below the Australian regulatory limit of 250 µg/L but some were above the U.S. EPA limit of 60 µg/L. The highest TTHM concentration was 67.2 µg/L and lowest 22.9 µg/L. For recycled water, samples taken directly from treatment plants held significantly higher concentrations (153.2 µg/L TTHM) compared to samples from final use locations (4.9–9.3 µg/L). PMID:28505068

On-Chip Magnetic Platform for Single-Particle Manipulation with Integrated Electrical Feedback.

PubMed

Monticelli, Marco; Torti, Andrea; Cantoni, Matteo; Petti, Daniela; Albisetti, Edoardo; Manzin, Alessandra; Guerriero, Erica; Sordan, Roman; Gervasoni, Giacomo; Carminati, Marco; Ferrari, Giorgio; Sampietro, Marco; Bertacco, Riccardo

2016-02-17

Methods for the manipulation of single magnetic particles have become very interesting, in particular for in vitro biological studies. Most of these studies require an external microscope to provide the operator with feedback for controlling the particle motion, thus preventing the use of magnetic particles in high-throughput experiments. In this paper, a simple and compact system with integrated electrical feedback is presented, implementing in the very same device both the manipulation and detection of the transit of single particles. The proposed platform is based on zig-zag shaped magnetic nanostructures, where transverse magnetic domain walls are pinned at the corners and attract magnetic particles in suspension. By applying suitable external magnetic fields, the domain walls move to the nearest corner, thus causing the step by step displacement of the particles along the nanostructure. The very same structure is also employed for detecting the bead transit. Indeed, the presence of the magnetic particle in suspension over the domain wall affects the depinning field required for its displacement. This characteristic field can be monitored through anisotropic magnetoresistance measurements, thus implementing an integrated electrical feedback of the bead transit. In particular, the individual manipulation and detection of single 1-μm sized beads is demonstrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electric field imaging of single atoms

PubMed Central

Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D.; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi

2017-01-01

In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures. PMID:28555629

Step-height measurement with a low coherence interferometer using continuous wavelet transform

NASA Astrophysics Data System (ADS)

Jian, Zhang; Suzuki, Takamasa; Choi, Samuel; Sasaki, Osami

2013-12-01

With the development of electronic technology in recent years, electronic components become increasingly miniaturized. At the same time a more accurate measurement method becomes indispensable. In the current measurement of nano-level, the Michelson interferometer with the laser diode is widely used, the method can measure the object accurately without touching the object. However it can't measure the step height that is larger than the half-wavelength. In this study, we improve the conventional Michelson interferometer by using a super luminescent diode and continuous wavelet transform, which can detect the time that maximizes the amplitude of the interference signal. We can accurately measure the surface-position of the object with this time. The method used in this experiment measured the step height of 20 microns.

Electronic properties of single Ge/Si quantum dot grown by ion beam sputtering deposition.

PubMed

Wang, C; Ke, S Y; Yang, J; Hu, W D; Qiu, F; Wang, R F; Yang, Y

2015-03-13

The dependence of the electronic properties of a single Ge/Si quantum dot (QD) grown by the ion-beam sputtering deposition technique on growth temperature and QD diameter is investigated by conductive atomic force microscopy (CAFM). The Si-Ge intermixing effect is demonstrated to be important for the current distribution of single QDs. The current staircase induced by the Coulomb blockade effect is observed at higher growth temperatures (>700 °C) due to the formation of an additional barrier between dislocated QDs and Si substrate for the resonant tunneling of holes. According to the proposed single-hole-tunneling model, the fact that the intermixing effect is observed to increase as the incoherent QD size decreases may explain the increase in the starting voltage of the current staircase and the decrease in the current step width.

Detecting Kondo Entanglement by Electron Conductance

NASA Astrophysics Data System (ADS)

Yoo, Gwangsu; Lee, S.-S. B.; Sim, H.-S.

2018-04-01

Quantum entanglement between an impurity spin and electrons nearby is a key property of the single-channel Kondo effects. We show that the entanglement can be detected by measuring electron conductance through a double quantum dot in an orbital Kondo regime. We derive a relation between the entanglement and the conductance, when the SU(2) spin symmetry of the regime is weakly broken. The relation reflects the universal form of many-body states near the Kondo fixed point. Using it, the spatial distribution of the entanglement—hence, the Kondo cloud—can be detected, with breaking of the symmetry spatially nonuniformly by electrical means.

Evidence for Defect-Mediated Tunneling in Hexagonal Boron Nitride-Based Junctions.

PubMed

Chandni, U; Watanabe, K; Taniguchi, T; Eisenstein, J P

2015-11-11

We investigate electron tunneling through atomically thin layers of hexagonal boron nitride (hBN). Metal (Cr/Au) and semimetal (graphite) counter-electrodes are employed. While the direct tunneling resistance increases nearly exponentially with barrier thickness as expected, the thicker junctions also exhibit clear signatures of Coulomb blockade, including strong suppression of the tunnel current around zero bias and step-like features in the current at larger biases. The voltage separation of these steps suggests that single-electron charging of nanometer-scale defects in the hBN barrier layer are responsible for these signatures. We find that annealing the metal-hBN-metal junctions removes these defects and the Coulomb blockade signatures in the tunneling current.

Oxoferryl-porphyrin radical catalytic intermediate in cytochrome bd oxidases protects cells from formation of reactive oxygen species.

PubMed

Paulus, Angela; Rossius, Sebastiaan Gijsbertus Hendrik; Dijk, Madelon; de Vries, Simon

2012-03-16

The quinol-linked cytochrome bd oxidases are terminal oxidases in respiration. These oxidases harbor a low spin heme b(558) that donates electrons to a binuclear heme b(595)/heme d center. The reaction with O(2) and subsequent catalytic steps of the Escherichia coli cytochrome bd-I oxidase were investigated by means of ultra-fast freeze-quench trapping followed by EPR and UV-visible spectroscopy. After the initial binding of O(2), the O-O bond is heterolytically cleaved to yield a kinetically competent heme d oxoferryl porphyrin π-cation radical intermediate (compound I) magnetically interacting with heme b(595). Compound I accumulates to 0.75-0.85 per enzyme in agreement with its much higher rate of formation (~20,000 s(-1)) compared with its rate of decay (~1,900 s(-1)). Compound I is next converted to a short lived heme d oxoferryl intermediate (compound II) in a phase kinetically matched to the oxidation of heme b(558) before completion of the reaction. The results indicate that cytochrome bd oxidases like the heme-copper oxidases break the O-O bond in a single four-electron transfer without a peroxide intermediate. However, in cytochrome bd oxidases, the fourth electron is donated by the porphyrin moiety rather than by a nearby amino acid. The production of reactive oxygen species by the cytochrome bd oxidase was below the detection level of 1 per 1000 turnovers. We propose that the two classes of terminal oxidases have mechanistically converged to enzymes in which the O-O bond is broken in a single four-electron transfer reaction to safeguard the cell from the formation of reactive oxygen species.

Oxoferryl-Porphyrin Radical Catalytic Intermediate in Cytochrome bd Oxidases Protects Cells from Formation of Reactive Oxygen Species*

PubMed Central

Paulus, Angela; Rossius, Sebastiaan Gijsbertus Hendrik; Dijk, Madelon; de Vries, Simon

2012-01-01

The quinol-linked cytochrome bd oxidases are terminal oxidases in respiration. These oxidases harbor a low spin heme b558 that donates electrons to a binuclear heme b595/heme d center. The reaction with O2 and subsequent catalytic steps of the Escherichia coli cytochrome bd-I oxidase were investigated by means of ultra-fast freeze-quench trapping followed by EPR and UV-visible spectroscopy. After the initial binding of O2, the O–O bond is heterolytically cleaved to yield a kinetically competent heme d oxoferryl porphyrin π-cation radical intermediate (compound I) magnetically interacting with heme b595. Compound I accumulates to 0.75–0.85 per enzyme in agreement with its much higher rate of formation (∼20,000 s−1) compared with its rate of decay (∼1,900 s−1). Compound I is next converted to a short lived heme d oxoferryl intermediate (compound II) in a phase kinetically matched to the oxidation of heme b558 before completion of the reaction. The results indicate that cytochrome bd oxidases like the heme-copper oxidases break the O–O bond in a single four-electron transfer without a peroxide intermediate. However, in cytochrome bd oxidases, the fourth electron is donated by the porphyrin moiety rather than by a nearby amino acid. The production of reactive oxygen species by the cytochrome bd oxidase was below the detection level of 1 per 1000 turnovers. We propose that the two classes of terminal oxidases have mechanistically converged to enzymes in which the O–O bond is broken in a single four-electron transfer reaction to safeguard the cell from the formation of reactive oxygen species. PMID:22287551

“Ultra-high resolution optical trap with single fluorophore sensitivity”

PubMed Central

Comstock, Matthew J; Ha, Taekjip; Chemla, Yann R

2013-01-01

We present a single-molecule instrument that combines a timeshared ultra-high resolution dual optical trap interlaced with a confocal fluorescence microscope. In a demonstration experiment, individual single-fluorophore labeled DNA oligonucleotides were observed to bind and unbind to complementary DNA suspended between two trapped beads. Simultaneous with the single-fluorophore detection, coincident angstrom-scale changes in tether extension could be clearly observed. Fluorescence readout allowed us to determine the duplex melting rate as a function of force. The new instrument will enable the simultaneous measurement of angstrom-scale mechanical motion of individual DNA-binding proteins (e.g., single base pair stepping of DNA translocases) along with the detection of fluorescently labeled protein properties (e.g., internal configuration). PMID:21336286

NanoCluster Beacons as reporter probes in rolling circle enhanced enzyme activity detection

NASA Astrophysics Data System (ADS)

Juul, Sissel; Obliosca, Judy M.; Liu, Cong; Liu, Yen-Liang; Chen, Yu-An; Imphean, Darren M.; Knudsen, Birgitta R.; Ho, Yi-Ping; Leong, Kam W.; Yeh, Hsin-Chih

2015-04-01

As a newly developed assay for the detection of endogenous enzyme activity at the single-catalytic-event level, Rolling Circle Enhanced Enzyme Activity Detection (REEAD) has been used to measure enzyme activity in both single human cells and malaria-causing parasites, Plasmodium sp. Current REEAD assays rely on organic dye-tagged linear DNA probes to report the rolling circle amplification products (RCPs), the cost of which may hinder the widespread use of REEAD. Here we show that a new class of activatable probes, NanoCluster Beacons (NCBs), can simplify the REEAD assays. Easily prepared without any need for purification and capable of large fluorescence enhancement upon hybridization, NCBs are cost-effective and sensitive. Compared to conventional fluorescent probes, NCBs are also more photostable. As demonstrated in reporting the human topoisomerases I (hTopI) cleavage-ligation reaction, the proposed NCBs suggest a read-out format attractive for future REEAD-based diagnostics.As a newly developed assay for the detection of endogenous enzyme activity at the single-catalytic-event level, Rolling Circle Enhanced Enzyme Activity Detection (REEAD) has been used to measure enzyme activity in both single human cells and malaria-causing parasites, Plasmodium sp. Current REEAD assays rely on organic dye-tagged linear DNA probes to report the rolling circle amplification products (RCPs), the cost of which may hinder the widespread use of REEAD. Here we show that a new class of activatable probes, NanoCluster Beacons (NCBs), can simplify the REEAD assays. Easily prepared without any need for purification and capable of large fluorescence enhancement upon hybridization, NCBs are cost-effective and sensitive. Compared to conventional fluorescent probes, NCBs are also more photostable. As demonstrated in reporting the human topoisomerases I (hTopI) cleavage-ligation reaction, the proposed NCBs suggest a read-out format attractive for future REEAD-based diagnostics. Electronic supplementary information (ESI) available: The detailed steps of NCB preparation, REEAD assay and STEM imaging. The sequences of the sNCB and the REEAD substrate. See DOI: 10.1039/c5nr01705j

Imaging MALDI MS of Dosed Brain Tissues Utilizing an Alternative Analyte Pre-extraction Approach

NASA Astrophysics Data System (ADS)

Quiason, Cristine M.; Shahidi-Latham, Sheerin K.

2015-06-01

Matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry has been adopted in the pharmaceutical industry as a useful tool to detect xenobiotic distribution within tissues. A unique sample preparation approach for MALDI imaging has been described here for the extraction and detection of cobimetinib and clozapine, which were previously undetectable in mouse and rat brain using a single matrix application step. Employing a combination of a buffer wash and a cyclohexane pre-extraction step prior to standard matrix application, the xenobiotics were successfully extracted and detected with an 8 to 20-fold gain in sensitivity. This alternative approach for sample preparation could serve as an advantageous option when encountering difficult to detect analytes.

Step-gate polysilicon nanowires field effect transistor compatible with CMOS technology for label-free DNA biosensor.

PubMed

Wenga, G; Jacques, E; Salaün, A-C; Rogel, R; Pichon, L; Geneste, F

2013-02-15

Currently, detection of DNA hybridization using fluorescence-based detection technique requires expensive optical systems and complex bioinformatics tools. Hence, the development of new low cost devices that enable direct and highly sensitive detection stimulates a lot of research efforts. Particularly, devices based on silicon nanowires are emerging as ultrasensitive electrical sensors for the direct detection of biological species thanks to their high surface to volume ratio. In this study, we propose innovative devices using step-gate polycrystalline silicon nanowire FET (poly-Si NW FETs), achieved with simple and low cost fabrication process, and used as ultrasensitive electronic sensor for DNA hybridization. The poly-SiNWs are synthesized using the sidewall spacer formation technique. The detailed fabrication procedure for a step-gate NWFET sensor is described in this paper. No-complementary and complementary DNA sequences were clearly discriminated and detection limit to 1 fM range is observed. This first result using this nano-device is promising for the development of low cost and ultrasensitive polysilicon nanowires based DNA sensors compatible with the CMOS technology. Copyright © 2012 Elsevier B.V. All rights reserved.

A Comparative Study of Chemically and Biologically Synthesized MgO Nanomaterial for Liquefied Petroleum Gas Detection

NASA Astrophysics Data System (ADS)

Thirupathi, Rampelly; Solleti, Goutham; Sreekanth, Tirumala; Sadasivuni, Kishor Kumar; Venkateswara Rao, Kalagadda

2018-03-01

The exceptional chemical and physical properties of nanostructured materials are extremely suitable for designing new and enhanced sensing devices, particularly gas sensors and biosensors. The present work describes the synthesis of magnesium oxide (MgO) nanoparticles through two methods: a green synthesis using aloe vera plant extract and a chemical method using a glycine-based solution combustion route. In a single step, the extracted organic molecules from aloe vera plants were used to reduce metal ions by the green method. MgO nanoparticles were coated onto the interdigital electrode using the drop-drying method. The dynamic gas-sensing characteristics were measured for liquefied petroleum gas (LPG) at different concentrations and various temperatures. The MgO nanoparticles were characterized by using x-ray diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy to determine the size and structure of the particles. The product's functional properties were analyzed by Fourier transform-infrared spectroscopy and UV-visible spectroscopy. We found that the LPG sensing behavior of biologically synthesized MgO registers excellent sensitivity at various operating temperatures.

A Comparative Study of Chemically and Biologically Synthesized MgO Nanomaterial for Liquefied Petroleum Gas Detection

NASA Astrophysics Data System (ADS)

Thirupathi, Rampelly; Solleti, Goutham; Sreekanth, Tirumala; Sadasivuni, Kishor Kumar; Venkateswara Rao, Kalagadda

2018-07-01

The exceptional chemical and physical properties of nanostructured materials are extremely suitable for designing new and enhanced sensing devices, particularly gas sensors and biosensors. The present work describes the synthesis of magnesium oxide (MgO) nanoparticles through two methods: a green synthesis using aloe vera plant extract and a chemical method using a glycine-based solution combustion route. In a single step, the extracted organic molecules from aloe vera plants were used to reduce metal ions by the green method. MgO nanoparticles were coated onto the interdigital electrode using the drop-drying method. The dynamic gas-sensing characteristics were measured for liquefied petroleum gas (LPG) at different concentrations and various temperatures. The MgO nanoparticles were characterized by using x-ray diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy to determine the size and structure of the particles. The product's functional properties were analyzed by Fourier transform-infrared spectroscopy and UV-visible spectroscopy. We found that the LPG sensing behavior of biologically synthesized MgO registers excellent sensitivity at various operating temperatures.

Quartz-Seq2: a high-throughput single-cell RNA-sequencing method that effectively uses limited sequence reads.

PubMed

Sasagawa, Yohei; Danno, Hiroki; Takada, Hitomi; Ebisawa, Masashi; Tanaka, Kaori; Hayashi, Tetsutaro; Kurisaki, Akira; Nikaido, Itoshi

2018-03-09

High-throughput single-cell RNA-seq methods assign limited unique molecular identifier (UMI) counts as gene expression values to single cells from shallow sequence reads and detect limited gene counts. We thus developed a high-throughput single-cell RNA-seq method, Quartz-Seq2, to overcome these issues. Our improvements in the reaction steps make it possible to effectively convert initial reads to UMI counts, at a rate of 30-50%, and detect more genes. To demonstrate the power of Quartz-Seq2, we analyzed approximately 10,000 transcriptomes from in vitro embryonic stem cells and an in vivo stromal vascular fraction with a limited number of reads.

Charge and spin control of ultrafast electron and hole dynamics in single CdSe/ZnSe quantum dots

NASA Astrophysics Data System (ADS)

Hinz, C.; Gumbsheimer, P.; Traum, C.; Holtkemper, M.; Bauer, B.; Haase, J.; Mahapatra, S.; Frey, A.; Brunner, K.; Reiter, D. E.; Kuhn, T.; Seletskiy, D. V.; Leitenstorfer, A.

2018-01-01

We study the dynamics of photoexcited electrons and holes in single negatively charged CdSe/ZnSe quantum dots with two-color femtosecond pump-probe spectroscopy. An initial characterization of the energy level structure is performed at low temperatures and magnetic fields of up to 5 T. Emission and absorption resonances are assigned to specific transitions between few-fermion states by a theoretical model based on a configuration interaction approach. To analyze the dynamics of individual charge carriers, we initialize the quantum system into excited trion states with defined energy and spin. Subsequently, the time-dependent occupation of the trion ground state is monitored by spectrally resolved differential transmission measurements. We observe subpicosecond dynamics for a hole excited to the D shell. The energy dependence of this D -to-S shell intraband transition is investigated in quantum dots of varying size. Excitation of an electron-hole pair in the respective p shells leads to the formation of singlet and triplet spin configurations. Relaxation of the p -shell singlet is observed to occur on a time scale of a few picoseconds. Pumping of p -shell triplet transitions opens up two pathways with distinctly different scattering times. These processes are shown to be governed by the mixing of singlet and triplet states due to exchange interactions enabling simultaneous electron and hole spin flips. To isolate the relaxation channels, we align the spin of the residual electron by a magnetic field and employ laser pulses of defined helicity. This step provides ultrafast preparation of a fully inverted trion ground state of the quantum dot with near unity probability, enabling deterministic addition of a single photon to the probe pulse. Therefore our experiments represent a significant step towards using single quantum emitters with well-controled inversion to manipulate the photon statistics of ultrafast light pulses.

Single-step process to improve the mechanical properties of carbon nanotube yarn.

PubMed

Evora, Maria Cecilia; Lu, Xinyi; Hiremath, Nitilaksha; Kang, Nam-Goo; Hong, Kunlun; Uribe, Roberto; Bhat, Gajanan; Mays, Jimmy

2018-01-01

Carbon nanotube (CNT) yarns exhibit low tensile strength compared to conventional high-performance carbon fibers due to the facile sliding of CNTs past one another. Electron beam (e-beam) irradiation was employed for in a single-step surface modification of CNTs to improve the mechanical properties of this material. To this end, CNT yarns were simultaneously functionalized and crosslinked using acrylic acid (AA) and acrylonitrile (AN) in an e-beam irradiation process. The chemical modification of CNT yarns was confirmed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning electron microscopy (SEM). The best improvement in mechanical properties was achieved on a sample treated with an aqueous solution of AA and subsequent irradiation. CNT yarn treatment with AA enhanced the strength (444.5 ± 68.4 MPa) by more than 75% and the modulus (21.5 ± 0.6 GPa) by more than 144% as compared to untreated CNT yarn (strength 251 ± 26.5 MPa and modulus 8.8 ± 1.2 GPa).

Single-step process to improve the mechanical properties of carbon nanotube yarn

PubMed Central

Lu, Xinyi; Hiremath, Nitilaksha; Kang, Nam-Goo; Hong, Kunlun; Uribe, Roberto; Bhat, Gajanan; Mays, Jimmy

2018-01-01

Carbon nanotube (CNT) yarns exhibit low tensile strength compared to conventional high-performance carbon fibers due to the facile sliding of CNTs past one another. Electron beam (e-beam) irradiation was employed for in a single-step surface modification of CNTs to improve the mechanical properties of this material. To this end, CNT yarns were simultaneously functionalized and crosslinked using acrylic acid (AA) and acrylonitrile (AN) in an e-beam irradiation process. The chemical modification of CNT yarns was confirmed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning electron microscopy (SEM). The best improvement in mechanical properties was achieved on a sample treated with an aqueous solution of AA and subsequent irradiation. CNT yarn treatment with AA enhanced the strength (444.5 ± 68.4 MPa) by more than 75% and the modulus (21.5 ± 0.6 GPa) by more than 144% as compared to untreated CNT yarn (strength 251 ± 26.5 MPa and modulus 8.8 ± 1.2 GPa). PMID:29527431

Detecting structural variances of Co 3O 4 catalysts by controlling beam-induced sample alterations in the vacuum of a transmission electron microscope

DOE PAGES

Kisielowski, C.; Frei, H.; Specht, P.; ...

2016-11-02

This article summarizes core aspects of beam-sample interactions in research that aims at exploiting the ability to detect single atoms at atomic resolution by mid-voltage transmission electron microscopy. Investigating the atomic structure of catalytic Co 3O 4 nanocrystals underscores how indispensable it is to rigorously control electron dose rates and total doses to understand native material properties on this scale. We apply in-line holography with variable dose rates to achieve this goal. Genuine object structures can be maintained if dose rates below ~100 e/Å 2s are used and the contrast required for detection of single atoms is generated by capturing largemore » image series. Threshold doses for the detection of single atoms are estimated. An increase of electron dose rates and total doses to common values for high resolution imaging of solids stimulates object excitations that restructure surfaces, interfaces, and defects and cause grain reorientation or growth. We observe a variety of previously unknown atom configurations in surface proximity of the Co 3O 4 spinel structure. These are hidden behind broadened diffraction patterns in reciprocal space but become visible in real space by solving the phase problem. Finallly, an exposure of the Co 3O 4 spinel structure to water vapor or other gases induces drastic structure alterations that can be captured in this manner.« less

Developments in Analytical Chemistry: Acoustically Levitated Drop Reactors for Enzyme Reaction Kinetics and Single-Walled Carbon Nanotube-Based Sensors for Detection of Toxic Organic Phosphonates

ERIC Educational Resources Information Center

Field, Christopher Ryan

2009-01-01

Developments in analytical chemistry were made using acoustically levitated small volumes of liquid to study enzyme reaction kinetics and by detecting volatile organic compounds in the gas phase using single-walled carbon nanotubes. Experience gained in engineering, electronics, automation, and software development from the design and…

Fully integrated lab-on-a-disc for nucleic acid analysis of food-borne pathogens.

PubMed

Kim, Tae-Hyeong; Park, Juhee; Kim, Chi-Ju; Cho, Yoon-Kyoung

2014-04-15

This paper describes a micro total analysis system for molecular analysis of Salmonella, a major food-borne pathogen. We developed a centrifugal microfluidic device, which integrated the three main steps of pathogen detection, DNA extraction, isothermal recombinase polymerase amplification (RPA), and detection, onto a single disc. A single laser diode was utilized for wireless control of valve actuation, cell lysis, and noncontact heating in the isothermal amplification step, thereby yielding a compact and miniaturized system. To achieve high detection sensitivity, rare cells in large volumes of phosphate-buffered saline (PBS) and milk samples were enriched before loading onto the disc by using antibody-coated magnetic beads. The entire procedure, from DNA extraction through to detection, was completed within 30 min in a fully automated fashion. The final detection was carried out using lateral flow strips by direct visual observation; detection limit was 10 cfu/mL and 10(2) cfu/mL in PBS and milk, respectively. Our device allows rapid molecular diagnostic analysis and does not require specially trained personnel or expensive equipment. Thus, we expect that it would have an array of potential applications, including in the detection of food-borne pathogens, environmental monitoring, and molecular diagnostics in resource-limited settings.

Probe-based measurement of lateral single-electron transfer between individual molecules

PubMed Central

Steurer, Wolfram; Fatayer, Shadi; Gross, Leo; Meyer, Gerhard

2015-01-01

The field of molecular electronics aims at using single molecules as functional building blocks for electronics components, such as switches, rectifiers or transistors. A key challenge is to perform measurements with atomistic control over the alignment of the molecule and its contacting electrodes. Here we use atomic force microscopy to examine charge transfer between weakly coupled pentacene molecules on insulating films with single-electron sensitivity and control over the atomistic details. We show that, in addition to the imaging capability, the probe tip can be used to control the charge state of individual molecules and to detect charge transfers to/from the tip, as well as between individual molecules. Our approach represents a novel route for molecular charge transfer studies with a host of opportunities, especially in combination with single atom/molecule manipulation and nanopatterning techniques. PMID:26387533

Microwave-assisted one-step patterning of aqueous colloidal silver.

PubMed

Yang, G; Zhou, Y W; Guo, Z R; Wan, Y; Ding, Q; Bai, T T; Wang, C L; Gu, N

2012-07-05

A new approach of utilizing microwave to pattern gradient concentric silver nanoparticle ring structures has been presented. The width and height of a single ring and the space between adjacent rings can be adjusted by changing the silver colloidal concentration and the microwave output power. By simply enhancing the ambient vapour pressure to the saturated value during microwave-assisted evaporation, sub-100 nm rings can be deposited in between adjacent micro-rings over a distance of millimetres. Combined with microwave sintering, this approach can also create conductive silver tracks in a single step, showing huge potential in fabricating micro- and nano-electronic devices in an ultra-fast and cost-effective fashion.

Detection of neuron membranes in electron microscopy images using a serial neural network architecture.

PubMed

Jurrus, Elizabeth; Paiva, Antonio R C; Watanabe, Shigeki; Anderson, James R; Jones, Bryan W; Whitaker, Ross T; Jorgensen, Erik M; Marc, Robert E; Tasdizen, Tolga

2010-12-01

Study of nervous systems via the connectome, the map of connectivities of all neurons in that system, is a challenging problem in neuroscience. Towards this goal, neurobiologists are acquiring large electron microscopy datasets. However, the shear volume of these datasets renders manual analysis infeasible. Hence, automated image analysis methods are required for reconstructing the connectome from these very large image collections. Segmentation of neurons in these images, an essential step of the reconstruction pipeline, is challenging because of noise, anisotropic shapes and brightness, and the presence of confounding structures. The method described in this paper uses a series of artificial neural networks (ANNs) in a framework combined with a feature vector that is composed of image intensities sampled over a stencil neighborhood. Several ANNs are applied in series allowing each ANN to use the classification context provided by the previous network to improve detection accuracy. We develop the method of serial ANNs and show that the learned context does improve detection over traditional ANNs. We also demonstrate advantages over previous membrane detection methods. The results are a significant step towards an automated system for the reconstruction of the connectome. Copyright 2010 Elsevier B.V. All rights reserved.

An integrated direct loop-mediated isothermal amplification microdevice incorporated with an immunochromatographic strip for bacteria detection in human whole blood and milk without a sample preparation step.

PubMed

Lee, Dohwan; Kim, Yong Tae; Lee, Jee Won; Kim, Do Hyun; Seo, Tae Seok

2016-05-15

We have developed an integrated direct loop-mediated isothermal amplification (Direct LAMP) microdevice incorporated with an immunochromatographic strip (ICS) to identify bacteria contaminated in real samples. The Direct LAMP is a novel isothermal DNA amplification technique which does not require thermal cycling steps as well as any sample preparation steps such as cell lysis and DNA extraction for amplifying specific target genes. In addition, the resultant amplicons were colorimetrically detected on the ICS, thereby enabling the entire genetic analysis process to be simplified. The two functional units (Direct LAMP and ICS) were integrated on a single device without use of the tedious and complicated microvalve and tubing systems. The utilization of a slidable plate allows us to manipulate the fluidic control in the microchannels manually and the sequential operation of the Direct LAMP and ICS detection could be performed by switching the slidable plate to each functional unit. Thus, the combination of the direct isothermal amplification without any sample preparation and thermal cycling steps, the ICS based amplicon detection by naked eyes, and the slidable plate to eliminate the microvalves in the integrated microdevice would be an ideal platform for point-of-care DNA diaganotics. On the integrated Direct LAMP-ICS microdevice, we could analyze Staphylococcus aureus (S. aureus) and Escherichia coli O157:H7 (E. coli O157:H7) contaminated in human whole blood or milk at a single-cell level within 1h. Copyright © 2015 Elsevier B.V. All rights reserved.

Electron spin resonance from NV centers in diamonds levitating in an ion trap

NASA Astrophysics Data System (ADS)

Delord, T.; Nicolas, L.; Schwab, L.; Hétet, G.

2017-03-01

We report observations of the electron spin resonance (ESR) of nitrogen vacancy centers in diamonds that are levitating in an ion trap. Using a needle Paul trap operating under ambient conditions, we demonstrate efficient microwave driving of the electronic spin and show that the spin properties of deposited diamond particles measured by the ESR are retained in the Paul trap. We also exploit the ESR signal to show angle stability of single trapped mono-crystals, a necessary step towards spin-controlled levitating macroscopic objects.

76 FR 67200 - Prospective Grant of Exclusive License: Electron Paramagnetic Resonance Devices and Systems for...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-31

... that is a unique combination of: (1) multi-gradient Single Point Imaging involving global phase...-encoding gradients. The combination approach of single point imaging with the spin-echo signal detection...

Computing in the presence of soft bit errors. [caused by single event upset on spacecraft

NASA Technical Reports Server (NTRS)

Rasmussen, R. D.

1984-01-01

It is shown that single-event-upsets (SEUs) due to cosmic rays are a significant source of single bit error in spacecraft computers. The physical mechanism of SEU, electron hole generation by means of Linear Energy Transfer (LET), it discussed with reference made to the results of a study of the environmental effects on computer systems of the Galileo spacecraft. Techniques for making software more tolerant of cosmic ray effects are considered, including: reducing the number of registers used by the software; continuity testing of variables; redundant execution of major procedures for error detection; and encoding state variables to detect single-bit changes. Attention is also given to design modifications which may reduce the cosmic ray exposure of on-board hardware. These modifications include: shielding components operating in LEO; removing low-power Schottky parts; and the use of CMOS diodes. The SEU parameters of different electronic components are listed in a table.

Realization of a four-step molecular switch in scanning tunneling microscope manipulation of single chlorophyll-a molecules

PubMed Central

Iancu, Violeta; Hla, Saw-Wai

2006-01-01

Single chlorophyll-a molecules, a vital resource for the sustenance of life on Earth, have been investigated by using scanning tunneling microscope manipulation and spectroscopy on a gold substrate at 4.6 K. Chlorophyll-a binds on Au(111) via its porphyrin unit while the phytyl-chain is elevated from the surface by the support of four CH3 groups. By injecting tunneling electrons from the scanning tunneling microscope tip, we are able to bend the phytyl-chain, which enables the switching of four molecular conformations in a controlled manner. Statistical analyses and structural calculations reveal that all reversible switching mechanisms are initiated by a single tunneling-electron energy-transfer process, which induces bond rotation within the phytyl-chain. PMID:16954201

Methods for Integrated Air Sampling and DNA Analysis for Detection of Airborne Fungal Spores

PubMed Central

Williams, Roger H.; Ward, Elaine; McCartney, H. Alastair

2001-01-01

Integrated air sampling and PCR-based methods for detecting airborne fungal spores, using Penicillium roqueforti as a model fungus, are described. P. roqueforti spores were collected directly into Eppendorf tubes using a miniature cyclone-type air sampler. They were then suspended in 0.1% Nonidet P-40, and counted using microscopy. Serial dilutions of the spores were made. Three methods were used to produce DNA for PCR tests: adding untreated spores to PCRs, disrupting spores (fracturing of spore walls to release the contents) using Ballotini beads, and disrupting spores followed by DNA purification. Three P. roqueforti-specific assays were tested: single-step PCR, nested PCR, and PCR followed by Southern blotting and probing. Disrupting the spores was found to be essential for achieving maximum sensitivity of the assay. Adding untreated spores to the PCR did allow the detection of P. roqueforti, but this was never achieved when fewer than 1,000 spores were added to the PCR. By disrupting the spores, with or without subsequent DNA purification, it was possible to detect DNA from a single spore. When known quantities of P. roqueforti spores were added to air samples consisting of high concentrations of unidentified fungal spores, pollen, and dust, detection sensitivity was reduced. P. roqueforti DNA could not be detected using untreated or disrupted spore suspensions added to the PCRs. However, using purified DNA, it was possible to detect 10 P. roqueforti spores in a background of 4,500 other spores. For all DNA extraction methods, nested PCR was more sensitive than single-step PCR or PCR followed by Southern blotting. PMID:11375150

Detection Technique and Overview of EPT-HET of Solar Orbiter

NASA Astrophysics Data System (ADS)

Kulkarni, S. R.; Tammen, J.; Boden, S.; Steinhagen, J.; Elftmann, R.; Martin-Garcia, C.; Boettcher, S. I.; Seimetz, L.; Ravanbakhsh, A.; Mahesh, Y.; Schuster, B.; Kulemzin, A.; Wimmer-Schweingruber, R. F.; Rodriguez-Pacheco, J.; Prieto, M.; Sanchez, S.

2016-12-01

The Energetic Particle Detector (EPD) suite for ESA's Solar Orbiter will provide key measurements to address particle acceleration at and near the Sun. The EPD suite consists of four sensors (STEP, SIS, EPT, and HET). The Electron Proton Telescope (EPT) is designed to cleanly separate and measure electrons in the energy range from 20 - 400 keV and protons from 20 - 7000 keV. The Solar Orbiter EPT electron measurements from 20 - 400 keV will cover the gap with some overlap between suprathermal electrons measured by STEP and high energy electrons measured by HET. The proton measurements from 20 -7000 keV will partially cover the gap between STEP and HET. The Electron and Proton Telescope relies on the magnet/foil-technique. The High-Energy Telescope (HET) will measure electrons from 300 keV up to about 30 MeV, protons from 10 -100 MeV, and heavy ions from 20 to 200 MeV/nuc by dE/dx -Total E technique. Thus, HET covers the energy range which is of specific interest for studies of the space environment and will perform the measurements needed to understand the origin of high-energy events at the Sun which occasionally accelerate particles to such high energies that they can penetrate the Earth's atmosphere and be measured at ground level. Here we present the current development status of EPT-HET and calibration results of units.

Auxotonic to isometric contraction transitioning in a beating heart causes myosin step-size to down shift

PubMed Central

Sun, Xiaojing; Wang, Yihua; Ajtai, Katalin

2017-01-01

Myosin motors in cardiac ventriculum convert ATP free energy to the work of moving blood volume under pressure. The actin bound motor cyclically rotates its lever-arm/light-chain complex linking motor generated torque to the myosin filament backbone and translating actin against resisting force. Previous research showed that the unloaded in vitro motor is described with high precision by single molecule mechanical characteristics including unitary step-sizes of approximately 3, 5, and 8 nm and their relative step-frequencies of approximately 13, 50, and 37%. The 3 and 8 nm unitary step-sizes are dependent on myosin essential light chain (ELC) N-terminus actin binding. Step-size and step-frequency quantitation specifies in vitro motor function including duty-ratio, power, and strain sensitivity metrics. In vivo, motors integrated into the muscle sarcomere form the more complex and hierarchically functioning muscle machine. The goal of the research reported here is to measure single myosin step-size and step-frequency in vivo to assess how tissue integration impacts motor function. A photoactivatable GFP tags the ventriculum myosin lever-arm/light-chain complex in the beating heart of a live zebrafish embryo. Detected single GFP emission reports time-resolved myosin lever-arm orientation interpreted as step-size and step-frequency providing single myosin mechanical characteristics over the active cycle. Following step-frequency of cardiac ventriculum myosin transitioning from low to high force in relaxed to auxotonic to isometric contraction phases indicates that the imposition of resisting force during contraction causes the motor to down-shift to the 3 nm step-size accounting for >80% of all the steps in the near-isometric phase. At peak force, the ATP initiated actomyosin dissociation is the predominant strain inhibited transition in the native myosin contraction cycle. The proposed model for motor down-shifting and strain sensing involves ELC N-terminus actin binding. Overall, the approach is a unique bottom-up single molecule mechanical characterization of a hierarchically functional native muscle myosin. PMID:28423017

Silicon Photomultiplier Performance in High ELectric Field

NASA Astrophysics Data System (ADS)

Montoya, J.; Morad, J.

2016-12-01

Roughly 27% of the universe is thought to be composed of dark matter. The Large Underground Xenon (LUX) relies on the emission of light from xenon atoms after a collision with a dark matter particle. After a particle interaction in the detector, two things can happen: the xenon will emit light and charge. The charge (electrons), in the liquid xenon needs to be pulled into the gas section so that it can interact with gas and emit light. This allows LUX to convert a single electron into many photons. This is done by applying a high voltage across the liquid and gas regions, effectively ripping electrons out of the liquid xenon and into the gas. The current device used to detect photons is the photomultiplier tube (PMT). These devices are large and costly. In recent years, a new technology that is capable of detecting single photons has emerged, the silicon photomultiplier (SiPM). These devices are cheaper and smaller than PMTs. Their performance in a high electric fields, such as those found in LUX, are unknown. It is possible that a large electric field could introduce noise on the SiPM signal, drowning the single photon detection capability. My hypothesis is that SiPMs will not observe a significant increase is noise at an electric field of roughly 10kV/cm (an electric field within the range used in detectors like LUX). I plan to test this hypothesis by first rotating the SiPMs with no applied electric field between two metal plates roughly 2 cm apart, providing a control data set. Then using the same angles test the dark counts with the constant electric field applied. Possibly the most important aspect of LUX, is the photon detector because it's what detects the signals. Dark matter is detected in the experiment by looking at the ratio of photons to electrons emitted for a given interaction in the detector. Interactions with a low electron to photon ratio are more like to be dark matter events than those with a high electron to photon ratio. The ability to distinguish these ratios relies on the high sensitivity to single photons. To achieve a similar sensitivity to dark matter interactions as LUX, the new SiPM devices need to operate in the same conditions without any loss in sensitivity to single photons. Knowing that this new type of technology operates in high electric field without issues, could save hundreds of thousands of dollars and valuable space.

Step-scan T cell-based differential Fourier transform infrared photoacoustic spectroscopy (DFTIR-PAS) for detection of ambient air contaminants

NASA Astrophysics Data System (ADS)

Liu, Lixian; Mandelis, Andreas; Huan, Huiting; Melnikov, Alexander

2016-10-01

A step-scan differential Fourier transform infrared photoacoustic spectroscopy (DFTIR-PAS) using a commercial FTIR spectrometer was developed theoretically and experimentally for air contaminant monitoring. The configuration comprises two identical, small-size and low-resonance-frequency T cells satisfying the conflicting requirements of low chopping frequency and limited space in the sample compartment. Carbon dioxide (CO2) IR absorption spectra were used to demonstrate the capability of the DFTIR-PAS method to detect ambient pollutants. A linear amplitude response to CO2 concentrations from 100 to 10,000 ppmv was observed, leading to a theoretical detection limit of 2 ppmv. The differential mode was able to suppress the coherent noise, thereby imparting the DFTIR-PAS method with a better signal-to-noise ratio and lower theoretical detection limit than the single mode. The results indicate that it is possible to use step-scan DFTIR-PAS with T cells as a quantitative method for high sensitivity analysis of ambient contaminants.

A Miniaturized Linear Wire Ion Trap with Electron Ionization and Single Photon Ionization Sources

NASA Astrophysics Data System (ADS)

Wu, Qinghao; Tian, Yuan; Li, Ailin; Andrews, Derek; Hawkins, Aaron R.; Austin, Daniel E.

2017-05-01

A linear wire ion trap (LWIT) with both electron ionization (EI) and single photon ionization (SPI) sources was built. The SPI was provided by a vacuum ultraviolet (VUV) lamp with the ability to softly ionize organic compounds. The VUV lamp was driven by a pulse amplifier, which was controlled by a pulse generator, to avoid the detection of photons during ion detection. Sample gas was introduced through a leak valve, and the pressure in the system is shown to affect the signal-to-noise ratio and resolving power. Under optimized conditions, the limit of detection (LOD) for benzene was 80 ppbv using SPI, better than the LOD using EI (137 ppbv). System performance was demonstrated by distinguishing compounds in different classes from gasoline.

Detecting uniaxial single domain grains with a modified IRM technique

NASA Astrophysics Data System (ADS)

Mitra, R.; Tauxe, L.; Gee, J. S.

2011-12-01

Mid-ocean ridge basalt (MORB) specimens have often been found to have high ratios of saturation remanence to saturation magnetization (Mrs/Ms). This has been attributed either to dominant cubic anisotropy or to insufficient saturating field leading to overestimation of Mrs/Ms of a dominantly uniaxial single domain (USD) assemblage. To resolve this debate, we develop an independent technique to detect USD assemblages. The experimental protocol involves subjecting the specimen to bidirectional impulse fields at each step. The experiment is similar to the conventional isothermal remanent magnetization (IRM) acquisition experiment but the field is applied twice, in antiparallel directions. We define a new parameter, IRAT, as the ratio of the remanences at each field step and show it to have characteristic behaviour for the two assemblages; IRAT ˜1 at all field steps for USD and <1 with a strong field dependence for multi-axial single domain (MSD) grains. We verified the theoretical predictions experimentally with representative USD and MSD specimens. Experiments with MORBs gave low IRATs for specimens having high Mrs/Ms. This argues for a dominant MSD assemblage in the MORBs, possibly cubic in nature. Although undersaturation of the samples can indeed be a contributing factor to the exceptionally high Mrs/Ms, this study shows that the nature of the assemblage cannot be dominantly USD.

Direct optical detection of protein-ligand interactions.

PubMed

Gesellchen, Frank; Zimmermann, Bastian; Herberg, Friedrich W

2005-01-01

Direct optical detection provides an excellent means to investigate interactions of molecules in biological systems. The dynamic equilibria inherent to these systems can be described in greater detail by recording the kinetics of a biomolecular interaction. Optical biosensors allow direct detection of interaction patterns without the need for labeling. An overview covering several commercially available biosensors is given, with a focus on instruments based on surface plasmon resonance (SPR) and reflectometric interference spectroscopy (RIFS). Potential assay formats and experimental design, appropriate controls, and calibration procedures, especially when handling low molecular weight substances, are discussed. The single steps of an interaction analysis combined with practical tips for evaluation, data processing, and interpretation of kinetic data are described in detail. In a practical example, a step-by-step procedure for the analysis of a low molecular weight compound interaction with serum protein, determined on a commercial SPR sensor, is presented.

Quantitative description of charge-carrier transport in a white organic light-emitting diode

NASA Astrophysics Data System (ADS)

Schober, M.; Anderson, M.; Thomschke, M.; Widmer, J.; Furno, M.; Scholz, R.; Lüssem, B.; Leo, K.

2011-10-01

We present a simulation model for the analysis of charge-carrier transport in organic thin-film devices, and apply it to a three-color white hybrid organic light-emitting diode (OLED) with fluorescent blue and phosphorescent red and green emission. We simulate a series of single-carrier devices, which reconstruct the OLED layer sequence step by step. Thereby, we determine the energy profiles for hole and electron transport, show how to discern bulk from interface limitation, and identify trap states.

Electrically driven spin qubit based on valley mixing

NASA Astrophysics Data System (ADS)

Huang, Wister; Veldhorst, Menno; Zimmerman, Neil M.; Dzurak, Andrew S.; Culcer, Dimitrie

2017-02-01

The electrical control of single spin qubits based on semiconductor quantum dots is of great interest for scalable quantum computing since electric fields provide an alternative mechanism for qubit control compared with magnetic fields and can also be easier to produce. Here we outline the mechanism for a drastic enhancement in the electrically-driven spin rotation frequency for silicon quantum dot qubits in the presence of a step at a heterointerface. The enhancement is due to the strong coupling between the ground and excited states which occurs when the electron wave function overcomes the potential barrier induced by the interface step. We theoretically calculate single qubit gate times tπ of 170 ns for a quantum dot confined at a silicon/silicon-dioxide interface. The engineering of such steps could be used to achieve fast electrical rotation and entanglement of spin qubits despite the weak spin-orbit coupling in silicon.

Electron source for a mini ion trap mass spectrometer

DOEpatents

Dietrich, D.D.; Keville, R.F.

1995-12-19

An ion trap is described which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10{sup 9} and commercial mass spectrometers requiring 10{sup 4} ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products. 10 figs.

Plasmonic SERS nanochips and nanoprobes for medical diagnostics and bio-energy applications

NASA Astrophysics Data System (ADS)

Ngo, Hoan T.; Wang, Hsin-Neng; Crawford, Bridget M.; Fales, Andrew M.; Vo-Dinh, Tuan

2017-02-01

The development of rapid, easy-to-use, cost-effective, high accuracy, and high sensitive DNA detection methods for molecular diagnostics has been receiving increasing interest. Over the last five years, our laboratory has developed several chip-based DNA detection techniques including the molecular sentinel-on-chip (MSC), the multiplex MSC, and the inverse molecular sentinel-on-chip (iMS-on-Chip). In these techniques, plasmonic surface-enhanced Raman scattering (SERS) Nanowave chips were functionalized with DNA probes for single-step DNA detection. Sensing mechanisms were based on hybridization of target sequences and DNA probes, resulting in a distance change between SERS reporters and the Nanowave chip's gold surface. This distance change resulted in change in SERS intensity, thus indicating the presence and capture of the target sequences. Our techniques were single-step DNA detection techniques. Target sequences were detected by simple delivery of sample solutions onto DNA probe-functionalized Nanowave chips and SERS signals were measured after 1h - 2h incubation. Target sequence labeling or washing to remove unreacted components was not required, making the techniques simple, easy-to-use, and cost effective. The usefulness of the techniques for medical diagnostics was illustrated by the detection of genetic biomarkers for respiratory viral infection and of dengue virus 4 DNA.

Au particle formation on the electron beam induced membrane

NASA Astrophysics Data System (ADS)

Choi, Seong Soo; Park, Myoung Jin; Han, Chul Hee; Oh, Sae-Joong; Kim, Sung-In; Park, Nam Kyou; Park, Doo-Jae; Choi, Soo Bong; Kim, Yong-Sang

2017-02-01

Recently the single molecules such as protein and deoxyribonucleic acid (DNA) have been successfully characterized by using a portable solidstate nanopore (MinION) with an electrical detection technique. However, there have been several reports about the high error rates of the fabricated nanopore device, possibly due to an electrical double layer formed inside the pore channel. The current DNA sequencing technology utilized is based on the optical detection method. In order to utilize the current optical detection technique, we will present the formation of the Au nano-pore with Au particle under the various electron beam irradiations. In order to provide the diffusion of Au atoms, a 2 keV electron beam irradiation has been performed During electron beam irradiations by using field emission scanning electron microscopy (FESEM), Au and C atoms would diffuse together and form the binary mixture membrane. Initially, the Au atoms diffused in the membrane are smaller than 1 nm, below the detection limit of the transmission electron microscopy (TEM), so that we are unable to observe the Au atoms in the formed membrane. However, after several months later, the Au atoms became larger and larger with expense of the smaller particles: Ostwald ripening. Furthermore, we also observe the Au crystalline lattice structure on the binary Au-C membrane. The formed Au crystalline lattice structures were constantly changing during electron beam imaging process due to Spinodal decomposition; the unstable thermodynamic system of Au-C binary membrane. The fabricated Au nanopore with an Au nanoparticle can be utilized as a single molecule nanobio sensor.

Imaging nanoscale spatial modulation of a relativistic electron beam with a MeV ultrafast electron microscope

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

Lu, Chao; Jiang, Tao; Liu, Shengguang

Here, an accelerator-based MeV ultrafast electron microscope (MUEM) has been proposed as a promising tool to the study structural dynamics at the nanometer spatial scale and the picosecond temporal scale. Here, we report experimental tests of a prototype MUEM where high quality images with nanoscale fine structures were recorded with a pulsed ~3 MeV picosecond electron beam. The temporal and spatial resolutions of the MUEM operating in the single-shot mode are about 4 ps (FWHM) and 100 nm (FWHM), corresponding to a temporal-spatial resolution of 4 × 10 –19 sm, about 2 orders of magnitude higher than that achieved withmore » state-of-the-art single-shot keV UEM. Using this instrument, we offer the demonstration of visualizing the nanoscale periodic spatial modulation of an electron beam, which may be converted into longitudinal density modulation through emittance exchange to enable production of high-power coherent radiation at short wavelengths. Our results mark a great step towards single-shot nanometer-resolution MUEMs and compact intense x-ray sources that may have widespread applications in many areas of science.« less

Low-energy transmission electron diffraction and imaging of large-area graphene

PubMed Central

Zhao, Wei; Xia, Bingyu; Lin, Li; Xiao, Xiaoyang; Liu, Peng; Lin, Xiaoyang; Peng, Hailin; Zhu, Yuanmin; Yu, Rong; Lei, Peng; Wang, Jiangtao; Zhang, Lina; Xu, Yong; Zhao, Mingwen; Peng, Lianmao; Li, Qunqing; Duan, Wenhui; Liu, Zhongfan; Fan, Shoushan; Jiang, Kaili

2017-01-01

Two-dimensional (2D) materials have attracted interest because of their excellent properties and potential applications. A key step in realizing industrial applications is to synthesize wafer-scale single-crystal samples. Until now, single-crystal samples, such as graphene domains up to the centimeter scale, have been synthesized. However, a new challenge is to efficiently characterize large-area samples. Currently, the crystalline characterization of these samples still relies on selected-area electron diffraction (SAED) or low-energy electron diffraction (LEED), which is more suitable for characterizing very small local regions. This paper presents a highly efficient characterization technique that adopts a low-energy electrostatically focused electron gun and a super-aligned carbon nanotube (SACNT) film sample support. It allows rapid crystalline characterization of large-area graphene through a single photograph of a transmission-diffracted image at a large beam size. Additionally, the low-energy electron beam enables the observation of a unique diffraction pattern of adsorbates on the suspended graphene at room temperature. This work presents a simple and convenient method for characterizing the macroscopic structures of 2D materials, and the instrument we constructed allows the study of the weak interaction with 2D materials. PMID:28879233

Low-energy transmission electron diffraction and imaging of large-area graphene.

PubMed

Zhao, Wei; Xia, Bingyu; Lin, Li; Xiao, Xiaoyang; Liu, Peng; Lin, Xiaoyang; Peng, Hailin; Zhu, Yuanmin; Yu, Rong; Lei, Peng; Wang, Jiangtao; Zhang, Lina; Xu, Yong; Zhao, Mingwen; Peng, Lianmao; Li, Qunqing; Duan, Wenhui; Liu, Zhongfan; Fan, Shoushan; Jiang, Kaili

2017-09-01

Two-dimensional (2D) materials have attracted interest because of their excellent properties and potential applications. A key step in realizing industrial applications is to synthesize wafer-scale single-crystal samples. Until now, single-crystal samples, such as graphene domains up to the centimeter scale, have been synthesized. However, a new challenge is to efficiently characterize large-area samples. Currently, the crystalline characterization of these samples still relies on selected-area electron diffraction (SAED) or low-energy electron diffraction (LEED), which is more suitable for characterizing very small local regions. This paper presents a highly efficient characterization technique that adopts a low-energy electrostatically focused electron gun and a super-aligned carbon nanotube (SACNT) film sample support. It allows rapid crystalline characterization of large-area graphene through a single photograph of a transmission-diffracted image at a large beam size. Additionally, the low-energy electron beam enables the observation of a unique diffraction pattern of adsorbates on the suspended graphene at room temperature. This work presents a simple and convenient method for characterizing the macroscopic structures of 2D materials, and the instrument we constructed allows the study of the weak interaction with 2D materials.

Imaging nanoscale spatial modulation of a relativistic electron beam with a MeV ultrafast electron microscope

DOE PAGES

Lu, Chao; Jiang, Tao; Liu, Shengguang; ...

2018-03-12

Here, an accelerator-based MeV ultrafast electron microscope (MUEM) has been proposed as a promising tool to the study structural dynamics at the nanometer spatial scale and the picosecond temporal scale. Here, we report experimental tests of a prototype MUEM where high quality images with nanoscale fine structures were recorded with a pulsed ~3 MeV picosecond electron beam. The temporal and spatial resolutions of the MUEM operating in the single-shot mode are about 4 ps (FWHM) and 100 nm (FWHM), corresponding to a temporal-spatial resolution of 4 × 10 –19 sm, about 2 orders of magnitude higher than that achieved withmore » state-of-the-art single-shot keV UEM. Using this instrument, we offer the demonstration of visualizing the nanoscale periodic spatial modulation of an electron beam, which may be converted into longitudinal density modulation through emittance exchange to enable production of high-power coherent radiation at short wavelengths. Our results mark a great step towards single-shot nanometer-resolution MUEMs and compact intense x-ray sources that may have widespread applications in many areas of science.« less

Site-Selection in Single-Molecule Junction for Highly Reproducible Molecular Electronics.

PubMed

Kaneko, Satoshi; Murai, Daigo; Marqués-González, Santiago; Nakamura, Hisao; Komoto, Yuki; Fujii, Shintaro; Nishino, Tomoaki; Ikeda, Katsuyoshi; Tsukagoshi, Kazuhito; Kiguchi, Manabu

2016-02-03

Adsorption sites of molecules critically determine the electric/photonic properties and the stability of heterogeneous molecule-metal interfaces. Then, selectivity of adsorption site is essential for development of the fields including organic electronics, catalysis, and biology. However, due to current technical limitations, site-selectivity, i.e., precise determination of the molecular adsorption site, remains a major challenge because of difficulty in precise selection of meaningful one among the sites. We have succeeded the single site-selection at a single-molecule junction by performing newly developed hybrid technique: simultaneous characterization of surface enhanced Raman scattering (SERS) and current-voltage (I-V) measurements. The I-V response of 1,4-benzenedithiol junctions reveals the existence of three metastable states arising from different adsorption sites. Notably, correlated SERS measurements show selectivity toward one of the adsorption sites: "bridge sites". This site-selectivity represents an essential step toward the reliable integration of individual molecules on metallic surfaces. Furthermore, the hybrid spectro-electric technique reveals the dependence of the SERS intensity on the strength of the molecule-metal interaction, showing the interdependence between the optical and electronic properties in single-molecule junctions.

Thread-like supercapacitors based on one-step spun nanocomposite yarns.

PubMed

Meng, Qinghai; Wang, Kai; Guo, Wei; Fang, Jin; Wei, Zhixiang; She, Xilin

2014-08-13

Thread-like electronic devices have attracted great interest because of their potential applications in wearable electronics. To produce high-performance, thread-like supercapacitors, a mixture of stable dispersions of single-walled carbon nanotubes and conducting polyaniline nanowires are prepared. Then, the mixture is spun into flexible yarns with a polyvinyl alcohol outer sheath by a one-step spinning process. The composite yarns show excellent mechanical properties and high electrical conductivities after sufficient washing to remove surfactants. After applying a further coating layer of gel electrolyte, two flexible yarns are twisted together to form a thread-like supercapacitor. The supercapacitor based on these two yarns (SWCNTs and PAniNWs) possesses a much higher specific capacitance than that based only on pure SWCNTs yarns, making it an ideal energy-storage device for wearable electronics. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Leucine/Pd-loaded (5,5) single-walled carbon nanotube matrix as a novel nanobiosensors for in silico detection of protein.

PubMed

Yoosefian, Mehdi; Etminan, Nazanin

2018-06-01

We have designed a novel nanobiosensor for in silico detecting proteins based on leucine/Pd-loaded single-walled carbon nanotube matrix. Density functional theory at the B3LYP/6-31G (d) level of theory was realized to analyze the geometrical and electronic structure of the proposed nanobiosensor. The solvent effects were investigated using the Tomasi's polarized continuum model. Atoms-in-molecules theory was used to study the nature of interactions by calculating the electron density ρ(r) and Laplacian at the bond critical points. Natural bond orbital analysis was performed to achieve a deep understanding of the nature of the interactions. The biosensor has potential application for high sensitive and rapid response to protein due to the chemical adsorption of L-leucine amino acid onto Pd-loaded single-walled carbon nanotube and reactive functional groups that can incorporate in hydrogen binding, hydrophobic interactions and van der Waals forces with the protein surface in detection process.

A novel electrochemical sensor for detecting hyperin with a nanocomposite of ZrO2-SDS-SWCNTs as decoration.

PubMed

Li, Shuo; Lei, Sheng; Yu, Qian; Zou, Lina; Ye, Baoxian

2018-08-01

A novel high-sensitive electrochemical sensor with glassy carbon electrode (GCE) as support for hyperin determination is successfully designed and constructed, and the well-shaped nano-meter modified material is synthesized via a one-step and facile route. Functionalized with surfactant sodium dodecyl sulfate (SDS), Single-Walled Carbon Nanotubes (SWCNTs) are synchronously grafted with ZrO 2 nanoparticles to develop into the as-prepared nano-composite (ZrO 2 -SDS-SWCNTs). Compared to the previous reports related with hyperin detection, the linear range gets wider and detection limit (LOD) becomes lower with the aid of this novel nano-composite modified glassy carbon electrode (ZrO 2 -SDS-SWCNTs/GCE). The crystalline phases and functionalization of the preparation process has been investigated by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) instrument analysis, respectively, and the micro-morphology of related modified materials is also visibly characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). In addition, electrochemical properties of the modified materials are comparably explored by means of impedance spectroscopy (EIS) and cyclic voltammograms (CV). According to the established calibration curve under optimized condition, the peak current (Differential pulse voltammetry (DPV) signal) keeps a linear relationship with hyperin concentration in the ranges of 1.0 × 10 -9 - 3.0 × 10 -7 mol L -1 , meanwhile detection limit reaches as low as 5 × 10 -10 mol L -1 (S/N = 3). As for practical applications, the proposed sensor has also worked well on sensitive hyperin determination in real species Abelmoschus manihot. Copyright © 2018 Elsevier B.V. All rights reserved.

Detection of Solar Energetic Electron, Proton and Heavy Ions by EPT-HET of Solar Orbiter: Calibration Results

NASA Astrophysics Data System (ADS)

Kulkarni, S. R.; Boden, S.; Elftmann, R.; Tammen, J.; Martin-Garcia, C.; Boettcher, S. I.; Seimetz, L.; Ravanbakhsh, A.; Mahesh, Y.; Schuster, B.; Wimmer-Schweingruber, R. F.; Rodriguez-Pacheco, J.

2017-12-01

The Energetic Particle Detector (EPD) suite for ESA's Solar Orbiter will provide key measurements to address particle acceleration at and near the Sun. The EPD suite consists of four sensors (STEP, SIS, EPT, and HET). The Electron Proton Telescope (EPT) is designed to cleanly separate and measure electrons in the energy range from 20 - 400 keV and protons from 20 - 7000 keV. The Solar Orbiter EPT electron measurements from 20 - 400 keV will cover the gap with some overlap between suprathermal electrons measured by STEP and high energy electrons measured by HET. The proton measurements from 20 -7000 keV will partially cover the gap between STEP and HET. The Electron and Proton Telescope relies on the magnet/foil-technique. The High-Energy Telescope (HET) will measure electrons from 300 keV up to about 30 MeV, protons from 10 -100 MeV, and heavy ions from 20 to 200 MeV/nuc by dE/dx -Total E technique. Thus, HET covers the energy range which is of specific interest for studies of the space environment and will perform the measurements needed to understand the origin of high-energy events at the Sun which occasionally accelerate particles to such high energies that they can penetrate the Earth's atmosphere and be measured at ground level. Here we present calibration results of EPT-HET which show that EPT-HET will function as planned.

Control of single-electron charging of metallic nanoparticles onto amorphous silicon surface.

PubMed

Weis, Martin; Gmucová, Katarína; Nádazdy, Vojtech; Capek, Ignác; Satka, Alexander; Kopáni, Martin; Cirák, Július; Majková, Eva

2008-11-01

Sequential single-electron charging of iron oxide nanoparticles encapsulated in oleic acid/oleyl amine envelope and deposited by the Langmuir-Blodgett technique onto Pt electrode covered with undoped hydrogenated amorphous silicon film is reported. Single-electron charging (so-called quantized double-layer charging) of nanoparticles is detected by cyclic voltammetry as current peaks and the charging effect can be switched on/off by the electric field in the surface region induced by the excess of negative/positive charged defect states in the amorphous silicon layer. The particular charge states in amorphous silicon are created by the simultaneous application of a suitable bias voltage and illumination before the measurement. The influence of charged states on the electric field in the surface region is evaluated by the finite element method. The single-electron charging is analyzed by the standard quantized double layer model as well as two weak-link junctions model. Both approaches are in accordance with experiment and confirm single-electron charging by tunnelling process at room temperature. This experiment illustrates the possibility of the creation of a voltage-controlled capacitor for nanotechnology.

Development of an Electronic Pediatric All-Cause Harm Measurement Tool Using a Modified Delphi Method.

PubMed

Stockwell, David Christopher; Bisarya, Hema; Classen, David C; Kirkendall, Eric S; Lachman, Peter I; Matlow, Anne G; Tham, Eric; Hyman, Dan; Lehman, Samuel M; Searles, Elizabeth; Muething, Stephen E; Sharek, Paul J

2016-12-01

To have impact on reducing harm in pediatric inpatients, an efficient and reliable process for harm detection is needed. This work describes the first step toward the development of a pediatric all-cause harm measurement tool by recognized experts in the field. An international group of leaders in pediatric patient safety and informatics were charged with developing a comprehensive pediatric inpatient all-cause harm measurement tool using a modified Delphi technique. The process was conducted in 5 distinct steps: (1) literature review of triggers (elements from a medical record that assist in identifying patient harm) for inclusion; (2) translation of triggers to likely associated harm, improving the ability for expert prioritization; (3) 2 applications of a modified Delphi selection approach with consensus criteria using severity and frequency of harm as well as detectability of the associated trigger as criteria to rate each trigger and associated harm; (4) developing specific trigger logic and relevant values when applicable; and (5) final vetting of the entire trigger list for pilot testing. Literature and expert panel review identified 108 triggers and associated harms suitable for consideration (steps 1 and 2). This list was pared to 64 triggers and their associated harms after the first of the 2 independent expert reviews. The second independent expert review led to further refinement of the trigger package, resulting in 46 items for inclusion (step 3). Adding in specific trigger logic expanded the list. Final review and voting resulted in a list of 51 triggers (steps 4 and 5). Application of a modified Delphi method on an expert-constructed list of 108 triggers, focusing on severity and frequency of harms as well as detectability of triggers in an electronic medical record, resulted in a final list of 51 pediatric triggers. Pilot testing this list of pediatric triggers to identify all-cause harm for pediatric inpatients is the next step to establish the appropriateness of each trigger for inclusion in a global pediatric safety measurement tool.

Deterministic Integration of Quantum Dots into on-Chip Multimode Interference Beamsplitters Using in Situ Electron Beam Lithography.

PubMed

Schnauber, Peter; Schall, Johannes; Bounouar, Samir; Höhne, Theresa; Park, Suk-In; Ryu, Geun-Hwan; Heindel, Tobias; Burger, Sven; Song, Jin-Dong; Rodt, Sven; Reitzenstein, Stephan

2018-04-11

The development of multinode quantum optical circuits has attracted great attention in recent years. In particular, interfacing quantum-light sources, gates, and detectors on a single chip is highly desirable for the realization of large networks. In this context, fabrication techniques that enable the deterministic integration of preselected quantum-light emitters into nanophotonic elements play a key role when moving forward to circuits containing multiple emitters. Here, we present the deterministic integration of an InAs quantum dot into a 50/50 multimode interference beamsplitter via in situ electron beam lithography. We demonstrate the combined emitter-gate interface functionality by measuring triggered single-photon emission on-chip with g (2) (0) = 0.13 ± 0.02. Due to its high patterning resolution as well as spectral and spatial control, in situ electron beam lithography allows for integration of preselected quantum emitters into complex photonic systems. Being a scalable single-step approach, it paves the way toward multinode, fully integrated quantum photonic chips.

Improved model for detection of homogeneous production batches of electronic components

NASA Astrophysics Data System (ADS)

Kazakovtsev, L. A.; Orlov, V. I.; Stashkov, D. V.; Antamoshkin, A. N.; Masich, I. S.

2017-10-01

Supplying the electronic units of the complex technical systems with electronic devices of the proper quality is one of the most important problems for increasing the whole system reliability. Moreover, for reaching the highest reliability of an electronic unit, the electronic devices of the same type must have equal characteristics which assure their coherent operation. The highest homogeneity of the characteristics is reached if the electronic devices are manufactured as a single production batch. Moreover, each production batch must contain homogeneous raw materials. In this paper, we propose an improved model for detecting the homogeneous production batches of shipped lot of electronic components based on implementing the kurtosis criterion for the results of non-destructive testing performed for each lot of electronic devices used in the space industry.

Ion time-of-flight determinations of doubly to singly ionized mercury ion ratios from a mercury electron bombardment discharge

NASA Technical Reports Server (NTRS)

Sellen, J. M., Jr.; Kemp, R. F.; Hall, D. F.

1973-01-01

Doubly to singly charged mercury ion ratios in electron bombardment ion thruster exhaust beams have been determined as functions of bombardment discharge potential, thrust beam current, thrust beam radial position, acceleration-deceleration voltage ratio, and propellant utilization fraction. A mathematical model for two-step ionization processes has been derived, and calculated ion ratios are compared to observed ratios. Production of Hg(++) appears to result primarily from sequential ionization of Hg(+) in the discharge. Experimental and analytical results are presented, and design, construction, and operation features of an electrostatic deflection ion time-of-flight analyzer for the determination of the above-mentioned ratios are reviewed.

Pellet injection research on the HT-6M and HT-7 tokamaks

NASA Astrophysics Data System (ADS)

Yang, Yu; Bao, Yi; Li, Jiangang; Gu, Xuemao; He, Yexi

1999-11-01

A multishot in situ pellet injection system has been constructed in the Institute of Plasma Physics. Single- and multi-pellet injection experiments were performed on the HT-6M and superconducting HT-7 tokamaks. The system proved to be convenient and reliable to operate. Pellets were fired into ohmically and LHCD and ICRF heated plasmas. Single pellet injection in ohmic discharge was found to increase the central density of HT-7 by about one half, while two pellet injection increased the central density in a step-like fashion by one half with each shot. Peaking of the electron density profile and a hollow electron temperature profile were obtained.

Single conducting polymer nanowire based conductometric sensors

NASA Astrophysics Data System (ADS)

Bangar, Mangesh Ashok

The detection of toxic chemicals, gases or biological agents at very low concentrations with high sensitivity and selectivity has been subject of immense interest. Sensors employing electrical signal readout as transduction mechanism offer easy, label-free detection of target analyte in real-time. Traditional thin film sensors inherently suffered through loss of sensitivity due to current shunting across the charge depleted/added region upon analyte binding to the sensor surface, due to their large cross sectional area. This limitation was overcome by use of nanostructure such as nanowire/tube as transducer where current shunting during sensing was almost eliminated. Due to their benign chemical/electrochemical fabrication route along with excellent electrical properties and biocompatibility, conducting polymers offer cost-effective alternative over other nanostructures. Biggest obstacle in using these nanostructures is lack of easy, scalable and cost-effective way of assembling these nanostructures on prefabricated micropatterns for device fabrication. In this dissertation, three different approaches have been taken to fabricate individual or array of single conducting polymer (and metal) nanowire based devices and using polymer by itself or after functionalization with appropriate recognition molecule they have been applied for gas and biochemical detection. In the first approach electrochemical fabrication of multisegmented nanowires with middle functional Ppy segment along with ferromagnetic nickel (Ni) and end gold segments for better electrical contact was studied. This multi-layered nanowires were used along with ferromagnetic contact electrode for controlled magnetic assembly of nanowires into devices and were used for ammonia gas sensing. The second approach uses conducting polymer, polypyrrole (Ppy) nanowires using simple electrophoretic alignment and maskless electrodeposition to anchor nanowire which were further functionalized with antibodies against cancer marker protein (Cancer Antigen, CA 125) using covalent immobilization for detection of CA 125 in buffer and human blood plasma. Third approach combined electrochemical deposition of conducting polymer and assembly steps into a single step fabrication & functionalization using e-beam lithographically patterned nano-channels. Using this method array of Ppy nanowires were fabricated. Further during fabrication step, by entrapping recognition molecule (avidin) biofunctionalization was achieved. Subsequently these sensors were used for detection of biotinylated single stranded DNA.

Dipole-resonance assisted isomerization in the electronic ground state using few-cycle infrared pulses.

PubMed

Skocek, Oliver; Uiberacker, Christoph; Jakubetz, Werner

2011-06-30

A computational investigation of HCN → HNC isomerization in the electronic ground state by one- and few-cycle infrared pulses is presented. Starting from a vibrationally pre-excited reagent state, isomerization yields of more than 50% are obtained using single one- to five-cycle pulses. The principal mechanism includes two steps of population transfer by dipole-resonance (DR), and hence, the success of the method is closely linked to the polarity of the system and, in particular, the stepwise change of the dipole moment from reactant to transition state and on to products. The yield drops massively if the diagonal dipole matrix elements are artificially set to zero. In detail, the mechanism includes DR-induced preparation of a delocalized vibrational wavepacket, which traverses the barrier region and is finally trapped in the product well by DR-dominated de-excitation. The excitation and de-excitation steps are triggered by pulse lobes of opposite field direction. As the number of optical cycles is increased, the leading field lobes prepare a vibrational superposition state by off-resonant ladder climbing, which is then subjected to the three steps of the principal isomerization mechanism. DR excitation is more efficient from a preformed vibrational wavepacket than from a molecular eigenstate. The entire process can be loosely described as Tannor-Kosloff-Rice type transfer mechanism on a single potential surface effected by a single pulse, individual field lobes assuming the roles of pump- and dump-pulses. Pre-excitation to a transient wavepacket can be enhanced by applying a separate, comparatively weak few-cycle prepulse, in which the prepulse prepares a vibrational wavepacket. The two-pulse setup corresponds to a double Tannor-Kosloff-Rice control scheme on a single potential surface.

Scanning ultrafast electron microscopy.

PubMed

Yang, Ding-Shyue; Mohammed, Omar F; Zewail, Ahmed H

2010-08-24

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.

Electrotunable artificial molecules based on van der Waals heterostructures

PubMed Central

Zhang, Zhuo-Zhi; Song, Xiang-Xiang; Luo, Gang; Deng, Guang-Wei; Mosallanejad, Vahid; Taniguchi, Takashi; Watanabe, Kenji; Li, Hai-Ou; Cao, Gang; Guo, Guang-Can; Nori, Franco; Guo, Guo-Ping

2017-01-01

Quantum confinement has made it possible to detect and manipulate single-electron charge and spin states. The recent focus on two-dimensional (2D) materials has attracted significant interests on possible applications to quantum devices, including detecting and manipulating either single-electron charging behavior or spin and valley degrees of freedom. However, the most popular model systems, consisting of tunable double-quantum-dot molecules, are still extremely difficult to realize in these materials. We show that an artificial molecule can be reversibly formed in atomically thin MoS2 sandwiched in hexagonal boron nitride, with each artificial atom controlled separately by electrostatic gating. The extracted values for coupling energies at different regimes indicate a single-electron transport behavior, with the coupling strength between the quantum dots tuned monotonically. Moreover, in the low-density regime, we observe a decrease of the conductance with magnetic field, suggesting the observation of Coulomb blockade weak anti-localization. Our experiments demonstrate for the first time the realization of an artificial quantum-dot molecule in a gated MoS2 van der Waals heterostructure, which could be used to investigate spin-valley physics. The compatibility with large-scale production, gate controllability, electron-hole bipolarity, and new quantum degrees of freedom in the family of 2D materials opens new possibilities for quantum electronics and its applications. PMID:29062893

Electronic Nose Testing Procedure for the Definition of Minimum Performance Requirements for Environmental Odor Monitoring

PubMed Central

Eusebio, Lidia; Capelli, Laura; Sironi, Selena

2016-01-01

Despite initial enthusiasm towards electronic noses and their possible application in different fields, and quite a lot of promising results, several criticalities emerge from most published research studies, and, as a matter of fact, the diffusion of electronic noses in real-life applications is still very limited. In general, a first step towards large-scale-diffusion of an analysis method, is standardization. The aim of this paper is describing the experimental procedure adopted in order to evaluate electronic nose performances, with the final purpose of establishing minimum performance requirements, which is considered to be a first crucial step towards standardization of the specific case of electronic nose application for environmental odor monitoring at receptors. Based on the experimental results of the performance testing of a commercialized electronic nose type with respect to three criteria (i.e., response invariability to variable atmospheric conditions, instrumental detection limit, and odor classification accuracy), it was possible to hypothesize a logic that could be adopted for the definition of minimum performance requirements, according to the idea that these are technologically achievable. PMID:27657086

Electronic Nose Testing Procedure for the Definition of Minimum Performance Requirements for Environmental Odor Monitoring.

PubMed

Eusebio, Lidia; Capelli, Laura; Sironi, Selena

2016-09-21

Despite initial enthusiasm towards electronic noses and their possible application in different fields, and quite a lot of promising results, several criticalities emerge from most published research studies, and, as a matter of fact, the diffusion of electronic noses in real-life applications is still very limited. In general, a first step towards large-scale-diffusion of an analysis method, is standardization. The aim of this paper is describing the experimental procedure adopted in order to evaluate electronic nose performances, with the final purpose of establishing minimum performance requirements, which is considered to be a first crucial step towards standardization of the specific case of electronic nose application for environmental odor monitoring at receptors. Based on the experimental results of the performance testing of a commercialized electronic nose type with respect to three criteria (i.e., response invariability to variable atmospheric conditions, instrumental detection limit, and odor classification accuracy), it was possible to hypothesize a logic that could be adopted for the definition of minimum performance requirements, according to the idea that these are technologically achievable.

Ultrafast Magnetization Manipulation Using Single Femtosecond Light and Hot-Electron Pulses.

PubMed

Xu, Yong; Deb, Marwan; Malinowski, Grégory; Hehn, Michel; Zhao, Weisheng; Mangin, Stéphane

2017-11-01

Current-induced magnetization manipulation is a key issue for spintronic applications. This manipulation must be fast, deterministic, and nondestructive in order to function in device applications. Therefore, single- electronic-pulse-driven deterministic switching of the magnetization on the picosecond timescale represents a major step toward future developments of ultrafast spintronic systems. Here, the ultrafast magnetization dynamics in engineered Gd x [FeCo] 1- x -based structures are studied to compare the effect of femtosecond laser and hot-electron pulses. It is demonstrated that a single femtosecond hot-electron pulse causes deterministic magnetization reversal in either Gd-rich and FeCo-rich alloys similarly to a femtosecond laser pulse. In addition, it is shown that the limiting factor of such manipulation for perpendicular magnetized films arises from the formation of a multidomain state due to dipolar interactions. By performing time-resolved measurements under various magnetic fields, it is demonstrated that the same magnetization dynamics are observed for both light and hot-electron excitation, and that the full magnetization reversal takes place within 40 ps. The efficiency of the ultrafast current-induced magnetization manipulation is enhanced due to the ballistic transport of hot electrons before reaching the GdFeCo magnetic layer. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural characterization and gas reactions of small metal particles by high resolution in-situ TEM (Transmission Electron Microscopy) and TED (Transmission Electron Diffraction)

NASA Technical Reports Server (NTRS)

Heinemann, K.

1987-01-01

The detection and size analysis of small metal particles supported on amorphous substrates becomes increasingly difficult when the particle size approaches that of the phase contrast background structures of the support. An approach of digital image analysis, involving Fourier transformation of the original image, filtering, and image reconstruction was studied with respect to the likelihood of unambiguously detecting particles of less than 1 nm diameter on amorphous substrates from a single electron micrograph.

High-Resolution “Fleezers”: Dual-Trap Optical Tweezers Combined with Single-Molecule Fluorescence Detection

PubMed Central

Whitley, Kevin D.; Comstock, Matthew J.; Chemla, Yann R.

2017-01-01

Recent advances in optical tweezers have greatly expanded their measurement capabilities. A new generation of hybrid instrument that combines nanomechanical manipulation with fluorescence detection—fluorescence optical tweezers, or “fleezers”—is providing a powerful approach to study complex macromolecular dynamics. Here, we describe a combined high-resolution optical trap/confocal fluorescence microscope that can simultaneously detect sub-nanometer displacements, sub-piconewton forces, and single-molecule fluorescence signals. The primary technical challenge to these hybrid instruments is how to combine both measurement modalities without sacrificing the sensitivity of either one. We present general design principles to overcome this challenge and provide detailed, step-by-step instructions to implement them in the construction and alignment of the instrument. Lastly, we present a set of protocols to perform a simple, proof-of-principle experiment that highlights the instrument capabilities. PMID:27844430

Spin injection in epitaxial MnGa(111)/GaN(0001) heterostructures

NASA Astrophysics Data System (ADS)

Zube, Christian; Malindretos, Joerg; Watschke, Lars; Zamani, Reza R.; Disterheft, David; Ulbrich, Rainer G.; Rizzi, Angela; Iza, Michael; Keller, Stacia; DenBaars, Steven P.

2018-01-01

Ferromagnetic MnGa(111) layers were grown on GaN(0001) by molecular beam epitaxy. MnGa/GaN Schottky diodes with a doping level of around n = 7 × 1018 cm-3 were fabricated to achieve single step tunneling across the metal/semiconductor junction. Below the GaN layer, a thin InGaN quantum well served as optical spin detector ("spin-LED"). For electron spin injection from MnGa into GaN and subsequent spin transport through a 45 nm (70 nm) thick GaN layer, we observe a circular polarization of 0.3% (0.2%) in the electroluminescence at 80 K. Interface mixing, spin polarization losses during electrical transport in the GaN layer, and spin relaxation in the InGaN quantum well are discussed in relation with the low value of the optically detected spin polarization.

Isothermal circular-strand-displacement polymerization of DNA and microRNA in digital microfluidic devices.

PubMed

Giuffrida, Maria Chiara; Zanoli, Laura Maria; D'Agata, Roberta; Finotti, Alessia; Gambari, Roberto; Spoto, Giuseppe

2015-02-01

Nucleic-acid amplification is a crucial step in nucleic-acid-sequence-detection assays. The use of digital microfluidic devices to miniaturize amplification techniques reduces the required sample volume and the analysis time and offers new possibilities for process automation and integration in a single device. The recently introduced droplet polymerase-chain-reaction (PCR) amplification methods require repeated cycles of two or three temperature-dependent steps during the amplification of the nucleic-acid target sequence. In contrast, low-temperature isothermal-amplification methods have no need for thermal cycling, thus requiring simplified microfluidic-device features. Here, the combined use of digital microfluidics and molecular-beacon (MB)-assisted isothermal circular-strand-displacement polymerization (ICSDP) to detect microRNA-210 sequences is described. MicroRNA-210 has been described as the most consistently and predominantly upregulated hypoxia-inducible factor. The nmol L(-1)-pmol L(-1) detection capabilities of the method were first tested by targeting single-stranded DNA sequences from the genetically modified Roundup Ready soybean. The ability of the droplet-ICSDP method to discriminate between full-matched, single-mismatched, and unrelated sequences was also investigated. The detection of a range of nmol L(-1)-pmol L(-1) microRNA-210 solutions compartmentalized in nanoliter-sized droplets was performed, establishing the ability of the method to detect as little as 10(-18) mol of microRNA target sequences compartmentalized in 20 nL droplets. The suitability of the method for biological samples was tested by detecting microRNA-210 from transfected K562 cells.

Clean-up of aqueous acetone vegetable extracts by solid-matrix partition for pyrethroid residue determination by gas chromatography-electron-capture detection.

PubMed

Di Muccio, A; Barbini, D A; Generali, T; Pelosi, P; Ausili, A; Vergori, F; Camoni, I

1997-03-21

Disposable, ready-to-use cartridges filled with macroporous diatomaceous material are used to carry out a partition clean-up that, in a single step, is capable of transferring pesticide residues from aqueous acetone extracts into light petroleum-dichloromethane (75:25, v/v). This procedure takes the place of some functions (such as separatory-funnel partition, drying over anhydrous sodium sulphate and partial adsorption clean-up) usually performed by separate steps in classical schemes. Fourteen pyrethroid pesticides, including tefluthrin, tetramethrin, cyphenothrin, cyfluthrin, flucythrinate, tau-fluvalinate, deltamethrin, bioallethrin, fenpropathrin, lambda-cyhalothrin, permethrin, alpha-cypermethrin, esfenvalerate and tralomethrin were determined using the described procedure with satisfactory recoveries for most of them, at spiking levels ranging from 0.08 to 0.82 mg/kg for the different compounds. Crops subjected to the described procedure included strawberry, apple, and orange gave extracts containing a mass of co-extractives that was between 5 and 30 mg. Compared with classical schemes, the described procedure is simple, less labour intensive, allows parallel handling of several extracts and does not require the preparation and maintenance of equipment. Troublesome emulsions such as those frequently observed in separation funnel partitioning do not occur.

A comparison of various surface charge transfer hole doping of graphene grown by chemical vapour deposition

NASA Astrophysics Data System (ADS)

Chandramohan, S.; Seo, Tae Hoon; Janardhanam, V.; Hong, Chang-Hee; Suh, Eun-Kyung

2017-10-01

Charge transfer doping is a renowned route to modify the electrical and electronic properties of graphene. Understanding the stability of potentially important charge-transfer materials for graphene doping is a crucial first step. Here we present a systematic comparison on the doping efficiency and stability of single layer graphene using molybdenum trioxide (MoO3), gold chloride (AuCl3), and bis(trifluoromethanesulfonyl)amide (TFSA). Chemical dopants proved to be very effective, but MoO3 offers better thermal stability and device fabrication compatibility. Single layer graphene films with sheet resistance values between 100 and 200 ohm/square were consistently produced by implementing a two-step growth followed by doping without compromising the optical transmittance.

One-step direct transfer of pristine single-walled carbon nanotubes for functional nanoelectronics.

PubMed

Wu, Chung Chiang; Liu, Chang Hua; Zhong, Zhaohui

2010-03-10

We report a one-step direct transfer technique for the fabrication of functional nanoelectronic devices using pristine single-walled carbon nanotubes (SWNTs). Suspended SWNTs grown by the chemical vapor deposition (CVD) method are aligned and directly transferred onto prepatterned device electrodes at ambient temperature. Using this technique, we successfully fabricated SWNT electromechanical resonators with gate-tunable resonance frequencies. A fully suspended SWNT p-n diode has also been demonstrated with the diode ideality factor equal to 1. Our method eliminates the organic residues on SWNTs resulting from conventional lithography and solution processing. The results open up opportunities for the fundamental study of electron transport physics in ultraclean SWNTs and for room temperature fabrication of novel functional devices based on pristine SWNTs.

Single electron relativistic clock interferometer

NASA Astrophysics Data System (ADS)

Bushev, P. A.; Cole, J. H.; Sholokhov, D.; Kukharchyk, N.; Zych, M.

2016-09-01

Although time is one of the fundamental notions in physics, it does not have a unique description. In quantum theory time is a parameter ordering the succession of the probability amplitudes of a quantum system, while according to relativity theory each system experiences in general a different proper time, depending on the system's world line, due to time dilation. It is therefore of fundamental interest to test the notion of time in the regime where both quantum and relativistic effects play a role, for example, when different amplitudes of a single quantum clock experience different magnitudes of time dilation. Here we propose a realization of such an experiment with a single electron in a Penning trap. The clock can be implemented in the electronic spin precession and its time dilation then depends on the radial (cyclotron) state of the electron. We show that coherent manipulation and detection of the electron can be achieved already with present day technology. A single electron in a Penning trap is a technologically ready platform where the notion of time can be probed in a hitherto untested regime, where it requires a relativistic as well as quantum description.

Potential applications of electron emission membranes in medicine

NASA Astrophysics Data System (ADS)

Bilevych, Yevgen; Brunner, Stefan E.; Chan, Hong Wah; Charbon, Edoardo; van der Graaf, Harry; Hagen, Cornelis W.; Nützel, Gert; Pinto, Serge D.; Prodanović, Violeta; Rotman, Daan; Santagata, Fabio; Sarro, Lina; Schaart, Dennis R.; Sinsheimer, John; Smedley, John; Tao, Shuxia; Theulings, Anne M. M. G.

2016-02-01

With a miniaturised stack of transmission dynodes, a noise free amplifier is being developed for the detection of single free electrons, with excellent time- and 2D spatial resolution and efficiency. With this generic technology, a new family of detectors for individual elementary particles may become possible. Potential applications of such electron emission membranes in medicine are discussed.

Deep learning and shapes similarity for joint segmentation and tracing single neurons in SEM images

NASA Astrophysics Data System (ADS)

Rao, Qiang; Xiao, Chi; Han, Hua; Chen, Xi; Shen, Lijun; Xie, Qiwei

2017-02-01

Extracting the structure of single neurons is critical for understanding how they function within the neural circuits. Recent developments in microscopy techniques, and the widely recognized need for openness and standardization provide a community resource for automated reconstruction of dendritic and axonal morphology of single neurons. In order to look into the fine structure of neurons, we use the Automated Tape-collecting Ultra Microtome Scanning Electron Microscopy (ATUM-SEM) to get images sequence of serial sections of animal brain tissue that densely packed with neurons. Different from other neuron reconstruction method, we propose a method that enhances the SEM images by detecting the neuronal membranes with deep convolutional neural network (DCNN) and segments single neurons by active contour with group shape similarity. We joint the segmentation and tracing together and they interact with each other by alternate iteration that tracing aids the selection of candidate region patch for active contour segmentation while the segmentation provides the neuron geometrical features which improve the robustness of tracing. The tracing model mainly relies on the neuron geometrical features and is updated after neuron being segmented on the every next section. Our method enables the reconstruction of neurons of the drosophila mushroom body which is cut to serial sections and imaged under SEM. Our method provides an elementary step for the whole reconstruction of neuronal networks.

Single-step fabrication of polydimethylsiloxane microwell arrays with long-lasting hydrophilic inner surfaces

NASA Astrophysics Data System (ADS)

Gowa Oyama, Tomoko; Barba, Bin Jeremiah Duenas; Hosaka, Yuji; Taguchi, Mitsumasa

2018-05-01

We propose a single-step fabrication method for polydimethylsiloxane (PDMS) cell-adhesive microwell arrays with long-lasting (>10 months in aqueous medium) hydrophilic inner surfaces without the need for any chemical treatment such as development. Irradiation of a PDMS film with a low-energy electron beam (55 kV) in air generated a ˜40-μm-thick hydrophilic silica-like layer on the PDMS surface, which was the key to the prolonged hydrophilicity. Moreover, the concomitant compaction of the irradiated area produced dozens-of-micrometers-deep concave wells. The hydrophilic microwells generated on the hydrophobic non-irradiated PDMS surface easily trapped nano-/picoliter droplets and cells/single-cells. In addition, the surfaces of the microwells offered stable and favorable cell-adherent environments. The method presented here can realize stable and reliable lab-on-chips and cater to the expanding demand in biological and medical applications.

Effect of bending and vacancies on the conductance of carbon nanotubes

NASA Astrophysics Data System (ADS)

Hansson, Anders; Paulsson, Magnus; Stafström, Sven

2000-09-01

Electron transport through nanotubes is studied theoretically using the Landauer formalism. The studies are carried out for finite metallic nanotubes that bridge two contacts pads. The current is observed to increase stepwise with the applied voltage. Each step corresponds to resonance tunneling including one single-particle eigenstate of the nanotube. Moderate bending of the nanotube results in a shift of the single-particle levels but the overall current remains essentially unaffected. For large bending, however, the π electron system becomes more disturbed, which introduces backscattering and a marked decrease in the conductivity along the tube. A single carbon vacancy in the nanotube is shown to have very small effect on the conductivity in the center of the metallic band whereas, by increasing the defect concentration the conductivity decreases in the same way as for the strongly bent tubes.

Demonstration of Quantum Entanglement between a Single Electron Spin Confined to an InAs Quantum Dot and a Photon

NASA Astrophysics Data System (ADS)

Schaibley, J. R.; Burgers, A. P.; McCracken, G. A.; Duan, L.-M.; Berman, P. R.; Steel, D. G.; Bracker, A. S.; Gammon, D.; Sham, L. J.

2013-04-01

The electron spin state of a singly charged semiconductor quantum dot has been shown to form a suitable single qubit for quantum computing architectures with fast gate times. A key challenge in realizing a useful quantum dot quantum computing architecture lies in demonstrating the ability to scale the system to many qubits. In this Letter, we report an all optical experimental demonstration of quantum entanglement between a single electron spin confined to a single charged semiconductor quantum dot and the polarization state of a photon spontaneously emitted from the quantum dot’s excited state. We obtain a lower bound on the fidelity of entanglement of 0.59±0.04, which is 84% of the maximum achievable given the timing resolution of available single photon detectors. In future applications, such as measurement-based spin-spin entanglement which does not require sub-nanosecond timing resolution, we estimate that this system would enable near ideal performance. The inferred (usable) entanglement generation rate is 3×103s-1. This spin-photon entanglement is the first step to a scalable quantum dot quantum computing architecture relying on photon (flying) qubits to mediate entanglement between distant nodes of a quantum dot network.

Demonstration of quantum entanglement between a single electron spin confined to an InAs quantum dot and a photon.

PubMed

Schaibley, J R; Burgers, A P; McCracken, G A; Duan, L-M; Berman, P R; Steel, D G; Bracker, A S; Gammon, D; Sham, L J

2013-04-19

The electron spin state of a singly charged semiconductor quantum dot has been shown to form a suitable single qubit for quantum computing architectures with fast gate times. A key challenge in realizing a useful quantum dot quantum computing architecture lies in demonstrating the ability to scale the system to many qubits. In this Letter, we report an all optical experimental demonstration of quantum entanglement between a single electron spin confined to a single charged semiconductor quantum dot and the polarization state of a photon spontaneously emitted from the quantum dot's excited state. We obtain a lower bound on the fidelity of entanglement of 0.59±0.04, which is 84% of the maximum achievable given the timing resolution of available single photon detectors. In future applications, such as measurement-based spin-spin entanglement which does not require sub-nanosecond timing resolution, we estimate that this system would enable near ideal performance. The inferred (usable) entanglement generation rate is 3×10(3) s(-1). This spin-photon entanglement is the first step to a scalable quantum dot quantum computing architecture relying on photon (flying) qubits to mediate entanglement between distant nodes of a quantum dot network.

Identification of the coupling step in Na(+)-translocating NADH:quinone oxidoreductase from real-time kinetics of electron transfer.

PubMed

Belevich, Nikolai P; Bertsova, Yulia V; Verkhovskaya, Marina L; Baykov, Alexander A; Bogachev, Alexander V

2016-02-01

Bacterial Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) uses a unique set of prosthetic redox groups-two covalently bound FMN residues, a [2Fe-2S] cluster, FAD, riboflavin and a Cys4[Fe] center-to catalyze electron transfer from NADH to ubiquinone in a reaction coupled with Na(+) translocation across the membrane. Here we used an ultra-fast microfluidic stopped-flow instrument to determine rate constants and the difference spectra for the six consecutive reaction steps of Vibrio harveyi Na(+)-NQR reduction by NADH. The instrument, with a dead time of 0.25 ms and optical path length of 1 cm allowed collection of visible spectra in 50-μs intervals. By comparing the spectra of reaction steps with the spectra of known redox transitions of individual enzyme cofactors, we were able to identify the chemical nature of most intermediates and the sequence of electron transfer events. A previously unknown spectral transition was detected and assigned to the Cys4[Fe] center reduction. Electron transfer from the [2Fe-2S] cluster to the Cys4[Fe] center and all subsequent steps were markedly accelerated when Na(+) concentration was increased from 20 μM to 25 mM, suggesting coupling of the former step with tight Na(+) binding to or occlusion by the enzyme. An alternating access mechanism was proposed to explain electron transfer between subunits NqrF and NqrC. According to the proposed mechanism, the Cys4[Fe] center is alternatively exposed to either side of the membrane, allowing the [2Fe-2S] cluster of NqrF and the FMN residue of NqrC to alternatively approach the Cys4[Fe] center from different sides of the membrane. Copyright © 2015 Elsevier B.V. All rights reserved.

Smartphones and e-tablets in perioperative medicine.

PubMed

Michard, Frederic

2017-10-01

Smartphones and electronic tablets (e-tablets) have become ubiquitous devices. Their ease of use, smartness, accessibility, mobility and connectivity create unique opportunities to improve quality of surgical care from prehabilitation to rehabilitation. Before surgery, digital applications (Apps), serious games and text messaging may help for a better control of risk factors (hypertension, overweight), for smoking cessation, and for optimizing adherence to preoperative recommendations (e.g., regarding anticoagulation or antihypertensive treatments). During surgery, Apps may help to rationalize fluid management and estimate blood loss. After surgery, smartphones and/or connected sensors (pulse oximeter, adhesive path, electronic tattoo, bioimpedance necklace) can be used to monitor body temperature, heart rate, heart rate variability (detection of cardiac arrhythmia), respiratory rate, arterial oxygen saturation and thoracic fluid content. Therefore, these tools have potential for the early detection of infectious, cardiac and respiratory complications in the wards and from home. When connected to echo probes, smartphones and e-tablets can also be used as ultrasound devices during central venous catheter insertion, for peripheral nerve blocks, and to perform echocardiography in patients developing cardiac complications. Finally, electronic checklists now exist as Apps to enhance communication between patients and healthcare professionals, and to track and record step by step each element of the surgical journey. Studies are now urgently needed to investigate whether this digital revolution can translate into a better outcome, an earlier detection of postoperative complications, a decrease in hospital readmissions and in health care costs.

Synchrotron Infrared Confocal Microspectroscopical Detection of Heterogeneity Within Chemically Modified Single Starch Granules

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

Wetzel, D.; Shi, Y; Reffner, J

This reports the first detection of chemical heterogeneity in octenyl succinic anhydride modified single starch granules using a Fourier transform infrared (FT-IR) microspectroscopical technique that combines diffraction-limited infrared microspectroscopy with a step size that is less than the mask projected spot size focused on the plane of the sample. The high spatial resolution was achieved with the combination of the application of a synchrotron infrared source and the confocal image plane masking system of the double-pass single-mask Continuum{reg_sign} infrared microscope. Starch from grains such as corn and wheat exists in granules. The size of the granules depends on the plantmore » producing the starch. Granules used in this study typically had a median size of 15 {micro}m. In the production of modified starch, an acid anhydride typically is reacted with OH groups of the starch polymer. The resulting esterification adds the ester carbonyl (1723 cm{sup -1}) organic functional group to the polymer and the hydrocarbon chain of the ester contributes to the CH{sub 2} stretching vibration to enhance the intensity of the 2927 cm{sup -1} band. Detection of the relative modifying population on a single granule was accomplished by ratioing the baseline adjusted peak area of the carbonyl functional group to that of a carbohydrate band. By stepping a confocally defined infrared beam as small as 5 {micro}m x 5 {micro}m across a starch granule 1 {micro}m at a time in both the x and y directions, the heterogeneity is detected with the highest possible spatial resolution.« less

Massively parallel unsupervised single-particle cryo-EM data clustering via statistical manifold learning

PubMed Central

Wu, Jiayi; Ma, Yong-Bei; Congdon, Charles; Brett, Bevin; Chen, Shuobing; Xu, Yaofang; Ouyang, Qi

2017-01-01

Structural heterogeneity in single-particle cryo-electron microscopy (cryo-EM) data represents a major challenge for high-resolution structure determination. Unsupervised classification may serve as the first step in the assessment of structural heterogeneity. However, traditional algorithms for unsupervised classification, such as K-means clustering and maximum likelihood optimization, may classify images into wrong classes with decreasing signal-to-noise-ratio (SNR) in the image data, yet demand increased computational costs. Overcoming these limitations requires further development of clustering algorithms for high-performance cryo-EM data processing. Here we introduce an unsupervised single-particle clustering algorithm derived from a statistical manifold learning framework called generative topographic mapping (GTM). We show that unsupervised GTM clustering improves classification accuracy by about 40% in the absence of input references for data with lower SNRs. Applications to several experimental datasets suggest that our algorithm can detect subtle structural differences among classes via a hierarchical clustering strategy. After code optimization over a high-performance computing (HPC) environment, our software implementation was able to generate thousands of reference-free class averages within hours in a massively parallel fashion, which allows a significant improvement on ab initio 3D reconstruction and assists in the computational purification of homogeneous datasets for high-resolution visualization. PMID:28786986

Massively parallel unsupervised single-particle cryo-EM data clustering via statistical manifold learning.

PubMed

Wu, Jiayi; Ma, Yong-Bei; Congdon, Charles; Brett, Bevin; Chen, Shuobing; Xu, Yaofang; Ouyang, Qi; Mao, Youdong

2017-01-01

Structural heterogeneity in single-particle cryo-electron microscopy (cryo-EM) data represents a major challenge for high-resolution structure determination. Unsupervised classification may serve as the first step in the assessment of structural heterogeneity. However, traditional algorithms for unsupervised classification, such as K-means clustering and maximum likelihood optimization, may classify images into wrong classes with decreasing signal-to-noise-ratio (SNR) in the image data, yet demand increased computational costs. Overcoming these limitations requires further development of clustering algorithms for high-performance cryo-EM data processing. Here we introduce an unsupervised single-particle clustering algorithm derived from a statistical manifold learning framework called generative topographic mapping (GTM). We show that unsupervised GTM clustering improves classification accuracy by about 40% in the absence of input references for data with lower SNRs. Applications to several experimental datasets suggest that our algorithm can detect subtle structural differences among classes via a hierarchical clustering strategy. After code optimization over a high-performance computing (HPC) environment, our software implementation was able to generate thousands of reference-free class averages within hours in a massively parallel fashion, which allows a significant improvement on ab initio 3D reconstruction and assists in the computational purification of homogeneous datasets for high-resolution visualization.

Effective Partnering of State Agencies to Achieve Early Hearing Detection and Intervention Benchmarks

ERIC Educational Resources Information Center

Corwin, Joanne

2011-01-01

Relative to Early Hearing Detection and Intervention (EHDI), New Mexico struggles with multiple points of referral into early intervention in the same way most states do. Referrals are not systematized through a single point of entry. The Step*Hi (statewide Parent-Infant) Program of the New Mexico School for the Deaf (NMSD) receives referrals from…

Label-free impedimetric immunosensor for sensitive detection of ochratoxin A.

PubMed

Radi, Abd-Elgawad; Muñoz-Berbel, Xavier; Lates, Vasilica; Marty, Jean-Louis

2009-03-15

A novel label-free electrochemical impedimetric immunosensor for sensitive detection of ochratoxin A (OTA) was reported. A two-step reaction protocol was elaborated to modify the gold electrode. The electrode was first derivatized by electrochemical reduction of in situ generated 4-carboxyphenyl diazonium salt (4-CPDS) in acidic aqueous solution yielded stable 4-carboxyphenyl (4-CP) monolayer. The ochratoxin A antibody was then immobilized making use of the carbodiimide chemistry. The steps of the immunosensor elaboration and the immunochemical reaction between ochratoxin A and the surface-bound antibody were interrogated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The impedance change, due to the specific immuno-interaction at the immunosensor surface was utilized to detect ochratoxin A. The increase in electron-transfer resistance (DeltaR(et)) values was linearly proportional to the concentration of OTA in the range of 1-20ngmL(-1), with a detection limit of 0.5ngmL(-1).

Highly Sensitive Bacteriophage-Based Detection of Brucella abortus in Mixed Culture and Spiked Blood

PubMed Central

Sergueev, Kirill V.; Filippov, Andrey A.; Nikolich, Mikeljon P.

2017-01-01

For decades, bacteriophages (phages) have been used for Brucella species identification in the diagnosis and epidemiology of brucellosis. Traditional Brucella phage typing is a multi-day procedure including the isolation of a pure culture, a step that can take up to three weeks. In this study, we focused on the use of brucellaphages for sensitive detection of the pathogen in clinical and other complex samples, and developed an indirect method of Brucella detection using real-time quantitative PCR monitoring of brucellaphage DNA amplification via replication on live Brucella cells. This assay allowed the detection of single bacteria (down to 1 colony-forming unit per milliliter) within 72 h without DNA extraction and purification steps. The technique was equally efficient with Brucella abortus pure culture and with mixed cultures of B. abortus and α-proteobacterial near neighbors that can be misidentified as Brucella spp., Ochrobactrum anthropi and Afipia felis. The addition of a simple short sample preparation step enabled the indirect phage-based detection of B. abortus in spiked blood, with the same high sensitivity. This indirect phage-based detection assay enables the rapid and sensitive detection of live B. abortus in mixed cultures and in blood samples, and can potentially be applied for detection in other clinical samples and other complex sample types. PMID:28604602

Rapid detection of single bacteria in unprocessed blood using Integrated Comprehensive Droplet Digital Detection

PubMed Central

Kang, Dong-Ku; Ali, M. Monsur; Zhang, Kaixiang; Huang, Susan S.; Peterson, Ellena; Digman, Michelle A.; Gratton, Enrico; Zhao, Weian

2014-01-01

Blood stream infection or sepsis is a major health problem worldwide, with extremely high mortality, which is partly due to the inability to rapidly detect and identify bacteria in the early stages of infection. Here we present a new technology termed ‘Integrated Comprehensive Droplet Digital Detection’ (IC 3D) that can selectively detect bacteria directly from milliliters of diluted blood at single-cell sensitivity in a one-step, culture- and amplification-free process within 1.5–4 h. The IC 3D integrates real-time, DNAzyme-based sensors, droplet microencapsulation and a high-throughput 3D particle counter system. Using Escherichia coli as a target, we demonstrate that the IC 3D can provide absolute quantification of both stock and clinical isolates of E. coli in spiked blood within a broad range of extremely low concentration from 1 to 10,000 bacteria per ml with exceptional robustness and limit of detection in the single digit regime. PMID:25391809

An Approach towards Ultrasound Kidney Cysts Detection using Vector Graphic Image Analysis

NASA Astrophysics Data System (ADS)

Mahmud, Wan Mahani Hafizah Wan; Supriyanto, Eko

2017-08-01

This study develops new approach towards detection of kidney ultrasound image for both with single cyst as well as multiple cysts. 50 single cyst images and 25 multiple cysts images were used to test the developed algorithm. Steps involved in developing this algorithm were vector graphic image formation and analysis, thresholding, binarization, filtering as well as roundness test. Performance evaluation to 50 single cyst images gave accuracy of 92%, while for multiple cysts images, the accuracy was about 86.89% when tested to 25 multiple cysts images. This developed algorithm may be used in developing a computerized system such as computer aided diagnosis system to help medical experts in diagnosis of kidney cysts.

Negative-ion formation in the explosives RDX, PETN, and TNT by using the reversal electron attachment detection technique

NASA Technical Reports Server (NTRS)

Boumsellek, S.; Alajajian, S. H.; Chutjian, A.

1992-01-01

First results of a beam-beam, single-collision study of negative-ion mass spectra produced by attachment of zero-energy electrons to the molecules of the explosives RDX, PETN, and TNT are presented. The technique used is reversal electron attachment detection (READ) wherein the zero-energy electrons are produced by focusing an intense electron beam into a shaped electrostatic field which reverses the trajectory of electrons. The target beam is introduced at the reversal point, and attachment occurs because the electrons have essentially zero longitudinal and radial velocity. The READ technique is used to obtain the 'signature' of molecular ion formation and/or fragmentation for each explosive. Present data are compared with results from atmospheric-pressure ionization and negative-ion chemical ionization methods.

Development of a highly sensitive real-time nested RT-PCR assay in a single closed tube for detection of enterovirus 71 in hand, foot, and mouth disease.

PubMed

Niu, Peihua; Qi, Shunxiang; Yu, Benzhang; Zhang, Chen; Wang, Ji; Li, Qi; Ma, Xuejun

2016-11-01

Enterovirus 71 (EV71) is one of the major causative agents of outbreaks of hand, foot, and mouth disease (HFMD). A commercial TaqMan probe-based real-time PCR assay has been widely used for the differential detection of EV71 despite its relatively high cost and failure to detect samples with a low viral load (Ct value > 35). In this study, a highly sensitive real-time nested RT-PCR (RTN RT-PCR) assay in a single closed tube for detection of EV71 in HFMD was developed. The sensitivity and specificity of this assay were evaluated using a reference EV71 stock and a panel of controls consisting of coxsackievirus A16 (CVA16) and common respiratory viruses, respectively. The clinical performance of this assay was evaluated and compared with those of a commercial TaqMan probe-based real-time PCR (qRT-PCR) assay and a traditional two-step nested RT-PCR assay. The limit of detection for the RTN RT-PCR assay was 0.01 TCID50/ml, with a Ct value of 38.3, which was the same as that of the traditional two-step nested RT-PCR assay and approximately tenfold lower than that of the qRT-PCR assay. When testing the reference strain EV71, this assay showed favorable detection reproducibility and no obvious cross-reactivity. The testing results of 100 clinical throat swabs from HFMD-suspected patients revealed that 41 samples were positive for EV71 by both RTN RT-PCR and traditional two-step nested RT-PCR assays, whereas only 29 were EV71 positive by qRT-PCR assay.

Evaluation of low-cost, objective instruments for assessing physical activity in 10-11-year-old children.

PubMed

Hart, Teresa L; Brusseau, Timothy; Kulinna, Pamela Hodges; McClain, James J; Tudor-Locke, Catrine

2011-12-01

This study compared step counts detected by four, low-cost, objective, physical-activity-assessment instruments and evaluated their ability to detect moderate-to-vigorous physical activity (MVPA) compared to the ActiGraph accelerometer (AG). Thirty-six 10-11-year-old children wore the NL-1000, Yamax Digiwalker SW 200, Omron HJ-151, and Walk4Life MVP concurrently with the AG during school hours on a single day. AG MVPA was derived from activity count data using previously validated cut points. Two of the evaluated instruments provided similar group mean MVPA and step counts compared to AG (dependent on cut point). Low-cost instruments may be useful for measurement of both MVPA and steps in children's physical activity interventions and program evaluation.

Automatic Feature Selection and Improved Classification in SICADA Counterfeit Electronics Detection

DTIC Science & Technology

2017-03-20

The SICADA methodology was developed to detect such counterfeit microelectronics by collecting power side channel data and applying machine learning...to identify counterfeits. This methodology has been extended to include a two-step automated feature selection process and now uses a one-class SVM...classifier. We describe this methodology and show results for empirical data collected from several types of Microchip dsPIC33F microcontrollers

Rapid detection of avian influenza virus a and subtype H5N1 by single step multiplex reverse transcription-polymerase chain reaction.

PubMed

Wei, Hui-Ling; Bai, Gui-Rong; Mweene, Aaron S; Zhou, Ying-Chun; Cong, Yan-Long; Pu, Juan; Wang, Shuai; Kida, Hiroshi; Liu, Jin-Hua

2006-06-01

Outbreaks of H5N1 highly pathogenic avian influenza (HPAI) virus caused great economic losses to the poultry industry and resulted in human deaths in Thailand and Viet Nam in 2004. Rapid typing and subtyping of H5N1 viruses, especially from clinical specimens, are desirable for taking prompt control measures to prevent the spread of the disease. Here, we developed a set of oligonucleotide primers able to detect, type and subtype H5 and N1 influenza viruses in a single step multiplex reverse transcription-polymerase chain reaction (RT-PCR). RNA was extracted from allantoic fluid or from specimens with guanidinium isothiocyanate reagent. Reverse transcription and PCR were carried out with a mixture of primers specific for influenza viruses of type A, subtype H5 and N1 in a single reaction system under identical conditions. The amplified DNA fragments were analyzed by agarose gel electrophoresis. All the H5N1 viruses tested in the study and the experimental specimens presented three specific bands by the method established here. The results presented here suggest that the method described below is rapid and specific and, therefore, could be valuable in the rapid detection of H5N1 influenza viruses in clinics.

Photoredox Catalysis Unlocks Single-Electron Elementary Steps in Transition Metal Catalyzed Cross-Coupling

PubMed Central

2016-01-01

Since initial reports, cross-coupling technologies employing photoredox catalysts to access novel reactivity have developed with increasing pace. In this Outlook, prominent examples from the recent literature are organized on the basis of the elementary transformation enabled by photoredox catalysis and are discussed in the context of relevant historical precedent in stoichiometric organometallic chemistry. This treatment allows mechanistic similarities inherent to odd-electron transition metal reactivity to be generalized to a set of lessons for future reaction development. PMID:27280163

Simulations of laser undulators

NASA Astrophysics Data System (ADS)

Milton, S. V.; Biedron, S. B.; Einstein, J. E.

2016-09-01

We perform a series of single-pass, one-D free-electron laser simulations based on an electron beam from a standard linear accelerator coupled with a so-called laser undulator, a specialized device that is more compact than a standard undulator based on magnetic materials. The longitudinal field profiles of such lasers undulators are intriguing as one must and can tailor the profile for the needs of creating the virtual undulator. We present and discuss several results of recent simulations and our future steps.

Interface and Electronic Characterization of Thin Epitaxial Co3O4 Films

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

Vaz, C.A.; Zhu, Y.; Wang, H.-Q.

2009-01-15

The interface and electronic structure of thin ({approx} 20-74 nm) Co{sub 3}O{sub 4}(1 1 0) epitaxial films grown by oxygen-assisted molecular beam epitaxy on MgAl{sub 2}O{sub 4}(1 1 0) single crystal substrates have been investigated by means of real and reciprocal space techniques. As-grown film surfaces are found to be relatively disordered and exhibit an oblique low energy electron diffraction (LEED) pattern associated with the O-rich CoO{sub 2} bulk termination of the (1 1 0) surface. Interface and bulk film structure are found to improve significantly with post-growth annealing at 820 K in air and display sharp rectangular LEED patterns,more » suggesting a surface stoichiometry of the alternative Co{sub 2}O{sub 2} bulk termination of the (1 1 0) surface. Non-contact atomic force microscopy demonstrates the presence of wide terraces separated by atomic steps in the annealed films that are not present in the as-grown structures; the step height of {approx}2.7 {angstrom} corresponds to two atomic layers and confirms a single termination for the annealed films, consistent with the LEED results. A model of the (1 x 1) surfaces that allows for compensation of the polar surfaces is presented.« less

Detection of gas molecules on single Mn adatom adsorbed graphyne: a DFT-D study

NASA Astrophysics Data System (ADS)

Lu, Zhansheng; Lv, Peng; Ma, Dongwei; Yang, Xinwei; Li, Shuo; Yang, Zongxian

2018-02-01

As one of the prominent applications in intelligent systems, gas sensing technology has attracted great interest in both industry and academia. In the current study, the pristine graphyne (GY) without and with a single Mn atom is investigated to detect the gas molecules (CO, CH4, CO2, NH3, NO and O2). The pristine GY is promising to detect O2 molecules because of its chemical adsorption on GY with large electron transfer. The great stability of the Mn/GY is found, and the Mn atom prefers to anchor at the alkyne ring as a single atom. Upon single Mn atom anchoring, the sensitivity and selectivity of GY based gas sensors is significantly improved for various molecules, except CH4. The recovery time of the Mn/GY after detecting the gas molecules may help to appraise the detection efficiency for the Mn/GY. The current study will help to understand the mechanism of detecting the gas molecules, and extend the potentially fascinating applications of GY-based materials.

The Energy Spectrum of Solar Energetic Electrons

NASA Astrophysics Data System (ADS)

Wang, L.; Yang, L.; Krucker, S.; Wimmer-Schweingruber, R. F.; Bale, S. D.

2015-12-01

Here we present a statistical survey of the energy spectrum of solar energetic electron events (SEEs) observed by the WIND 3DP instrument from 1995 though 2014. For SEEs with the minimum energy below 10 keV and the maximum energy above 100 keV, ~85% (~2%) have a double-power-law energy spectrum with a steepening (hardening) above the break energy, while ~13% have a single-power-law energy spectrum at all energies. The average spectral index is ~2.4 below the energy break and is ~4.0 above the energy break. For SEEs detected only at energies <10 keV (>20 keV), they generally show a single-power-law spectrum with the average index of ~3.0 (~3.3). The spectrum of SEEs detected only below 10 keV appears to get harder with increasing solar activity, but the spectrum of SEEs with higher-energy electrons shows no clear correlation with solar activity. We will also investigate whether the observed energy spectrum of SEEs at 1 AU mainly reflects the electron acceleration at the Sun or the electron transport in the interplanetary medium.

Development of a two-step high-resolution melting (HRM) analysis for screening sequence variants associated with resistance to the QoIs, benzimidazoles and dicarboximides in airborne inoculum of Botrytis cinerea.

PubMed

Chatzidimopoulos, Michael; Ganopoulos, Ioannis; Vellios, Evangelos; Madesis, Panagiotis; Tsaftaris, Athanasios; Pappas, Athanassios C

2014-11-01

A rapid, high-resolution melting (HRM) analysis protocol was developed to detect sequence variations associated with resistance to the QoIs, benzimidazoles and dicarboximides in Botrytis cinerea airborne inoculum. HRM analysis was applied directly in fungal DNA collected from air samplers with selective medium. Three and five different genotypes were detected and classified according to their melting profiles in BenA and bos1 genes associated with resistance to benzimidazoles and dicarboximides, respectively. The sensitivity of the methodology was evident in the case of the QoIs, where genotypes varying either by a single nucleotide polymorphism or an additional 1205-bp intron were separated accurately with a single pair of primers. The developed two-step protocol was completed in 82 min and showed reduced variation in the melting curves' formation. HRM analysis rapidly detected the major mutations found in greenhouse strains providing accurate data for successfully controlling grey mould. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Monitoring Single-Molecule Protein Dynamics with a Carbon Nanotube Transistor

NASA Astrophysics Data System (ADS)

Collins, Philip G.

2014-03-01

Nanoscale electronic devices like field-effect transistors have long promised to provide sensitive, label-free detection of biomolecules. Single-walled carbon nanotubes press this concept further by not just detecting molecules but also monitoring their dynamics in real time. Recent measurements have demonstrated this premise by monitoring the single-molecule processivity of three different enzymes: lysozyme, protein Kinase A, and the Klenow fragment of DNA polymerase I. With all three enzymes, single molecules tethered to nanotube transistors were electronically monitored for 10 or more minutes, allowing us to directly observe a range of activity including rare transitions to chemically inactive and hyperactive conformations. The high bandwidth of the nanotube transistors further allow every individual chemical event to be clearly resolved, providing excellent statistics from tens of thousands of turnovers by a single enzyme. Initial success with three different enzymes indicates the generality and attractiveness of the nanotube devices as a new tool to complement other single-molecule techniques. Research on transduction mechanisms provides the design rules necessary to further generalize this architecture and apply it to other proteins. The purposeful incorporation of just one amino acid is sufficient to fabricate effective, single molecule sensors from a wide range of enzymes or proteins.

Lewis Acid-Induced Change from Four- to Two-Electron Reduction of Dioxygen Catalyzed by Copper Complexes Using Scandium Triflate

PubMed Central

Kakuda, Saya; Rolle, Clarence; Ohkubo, Kei; Siegler, Maxime A.; Karlin, Kenneth D.; Fukuzumi, Shunichi

2015-01-01

Mononuclear copper complexes, [(tmpa)CuII(CH3CN)](ClO4)2 (1, tmpa = tris(2-pyridylmethyl)amine) and [(BzQ)CuII(H2O)2](ClO4)2 (2, BzQ = bis(2-quinolinylmethyl)benzylamine)], act as efficient catalysts for the selective two-electron reduction of O2 by ferrocene derivatives in the presence of scandium triflate (Sc(OTf)3), in acetone, whereas 1 catalyzes the four-electron reduction of O2 by the same reductant in the presence of Brønsted acids such as triflic acid. Following formation of the peroxo-bridged dicopper(II) complex [(tmpa)CuII(O2)CuII(tmpa)]2+, the two-electron reduced product of O2 with Sc3+ is observed to be scandium peroxide ([Sc3+(O22−)]+). In the presence of three equiv of hexamethylphosphoric triamide (HMPA), [Sc3+(O22−)]+ was oxidized by [Fe(bpy)3]3+ (bpy = 2,2′-bipyridine) to the known superoxide species [(HMPA)3Sc3+(O2•−)]2+ as detected by EPR spectroscopy. A kinetic study revealed that the rate-determining step of the catalytic cycle for the two-electron reduction of O2 with 1 is electron transfer from Fc* to 1 to give a cuprous complex which is highly reactive toward O2, whereas the rate-determining step with 2 is changed to the reaction of the cuprous complex with O2 following electron transfer from ferrocene derivatives to 2. The explanation for the change in catalytic O2-reaction stoichiometry from four-electron with Brønsted acids to two-electron reduction in the presence of Sc3+ and also for the change in the rate-determining step is clarified based on a kinetics interrogation of the overall catalytic cycle as well as each step of the catalytic cycle with study of the observed effects of Sc3+ on copper-oxygen intermediates. PMID:25659416

Pioneer Venus Orbiter planar retarding potential analyzer plasma experiment

NASA Technical Reports Server (NTRS)

Knudsen, W. C.; Bakke, J.; Spenner, K.; Novak, V.

1980-01-01

The retarding potential analyzer (RPA) on the Pioneer Venus Orbiter Mission measures most of the thermal plasma parameters within and near the Venusian ionosphere. Parameters include total ion concentration, concentrations of the more abundant ions, ion temperatures, ion drift velocity, electron temperature, and low-energy (0-50 eV) electron distribution function. Several functions not previously used in RPA's were developed and incorporated into this instrument to accomplish these measurements on a spinning spacecraft with a small bit rate. The more significant functions include automatic electrometer ranging with background current compensation; digital, quadratic retarding potential step generation for the ion and low-energy electron scans; a current sampling interval of 2 ms throughout all scans; digital logic inflection point detection and data selection; and automatic ram direction detection.

Single Protein Structural Analysis with a Solid-state Nanopore Sensor

NASA Astrophysics Data System (ADS)

Li, Jiali; Golovchenko, Jene; McNabb, David

2005-03-01

We report on the use of solid-state nanopore sensors to detect single polypeptides. These solid-state nanopores are fabricated in thin membranes of silicon nitride by ion beam sculpting...[1]. When an electrically biased nanopore is exposed to denatured proteins in ionic solution, discrete transient electronic signals: current blockages are observed. We demonstrate examples of such transient electronic signals for Bovine Serum Albumin (BSA) and human placental laminin M proteins in Guanidine hydrochloride solution, which suggest that these polypeptides are individually translocating through the nanopore during the detecting process. The amplitude of the current blockages is proportional to the bias voltage. No transient current blockages are observed when proteins are not present in the solution. To probe protein-folding state, pH and temperature dependence experiments are performed. The results demonstrate a solid-state nanopore sensor can be used to detect and analyze single polypeptide chains. Similarities and differences with signals obtained from double stranded DNA in a solid-state nanopore and single stranded DNA in a biological nanopore are discussed. [.1] Li, J., D. Stein, C. McMullan, D. Branton, M.J. Aziz, and J.A. Golovchenko, Ion-beam sculpting at nanometre length scales. Nature, 2001. 412(12 July): p. 166-169.

Electron spin polarization by isospin ordering in correlated two-layer quantum Hall systems.

PubMed

Tiemann, L; Wegscheider, W; Hauser, M

2015-05-01

Enhancement of the electron spin polarization in a correlated two-layer, two-dimensional electron system at a total Landau level filling factor of 1 is reported. Using resistively detected nuclear magnetic resonance, we demonstrate that the electron spin polarization of two closely spaced two-dimensional electron systems becomes maximized when interlayer Coulomb correlations establish spontaneous isospin ferromagnetic order. This correlation-driven polarization dominates over the spin polarizations of competing single-layer fractional quantum Hall states under electron density imbalances.

Hot-Electron Photon Counters for Detecting Terahertz Photons

NASA Technical Reports Server (NTRS)

Karasik, Boris; Sergeyev, Andrei

2005-01-01

A document proposes the development of hot-electron photon counters (HEPCs) for detecting terahertz photons in spaceborne far-infrared astronomical instruments. These would be superconducting- transition-edge devices: they would contain superconducting bridges that would have such low heat capacities that single terahertz photons would cause transient increases in their electron temperatures through the superconducting- transition range, thereby yielding measurable increases in electrical resistance. Single devices or imaging arrays of the devices would be fabricated as submicron-sized bridges made from films of disordered Ti (which has a superconducting- transition temperature of .0.35 K) between Nb contacts on bulk silicon or sapphire substrates. In operation, these devices would be cooled to a temperature of .0.3 K. The proposed devices would cost less to fabricate and operate, relative to integrating bolometers of equal sensitivity, which must be operated at a temperature of approx. = 0.1 K.

Effects of low-energy electron irradiation on formation of nitrogen–vacancy centers in single-crystal diamond

DOE PAGES

Schwartz, J.; Aloni, S.; Ogletree, D. F.; ...

2012-04-20

Exposure to beams of low-energy electrons (2-30 keV) in a scanning electron microscope locally induces formation of NV-centers without thermal annealing in diamonds that have been implanted with nitrogen ions. In this study, we find that non-thermal, electron-beam-induced NV-formation is about four times less efficient than thermal annealing. But NV-center formation in a consecutive thermal annealing step (800°C) following exposure to low-energy electrons increases by a factor of up to 1.8 compared to thermal annealing alone. Finally, these observations point to reconstruction of nitrogen-vacancy complexes induced by electronic excitations from low-energy electrons as an NV-center formation mechanism and identify localmore » electronic excitations as a means for spatially controlled room-temperature NV-center formation.« less

Splitting Fermi Surfaces and Heavy Electronic States in Non-Centrosymmetric U3Ni3Sn4

NASA Astrophysics Data System (ADS)

Maurya, Arvind; Harima, Hisatomo; Nakamura, Ai; Shimizu, Yusei; Homma, Yoshiya; Li, DeXin; Honda, Fuminori; Sato, Yoshiki J.; Aoki, Dai

2018-04-01

We report the single-crystal growth of the non-centrosymmetric paramagnet U3Ni3Sn4 by the Bridgman method and the Fermi surface properties detected by de Haas-van Alphen (dHvA) experiments. We have also investigated single-crystal U3Ni3Sn4 by single-crystal X-ray diffraction, magnetization, electrical resistivity, and heat capacity measurements. The angular dependence of the dHvA frequencies reveals many closed Fermi surfaces, which are nearly spherical in topology. The experimental results are in good agreement with local density approximation (LDA) band structure calculations based on the 5f-itinerant model. The band structure calculation predicts many Fermi surfaces, mostly with spherical shape, derived from 12 bands crossing the Fermi energy. To our knowledge, the splitting of Fermi surfaces due to the non-centrosymmetric crystal in 5f-electron systems is experimentally detected for the first time. The temperature dependence of the dHvA amplitude reveals a large cyclotron effective mass of up to 35 m0, indicating the heavy electronic state of U3Ni3Sn4 due to the proximity of the quantum critical point. From the field dependence of the dHvA amplitude, a mean free path of conduction electrons of up to 1950 Å is detected, reflecting the good quality of the grown crystal. The small splitting energy related to the antisymmetric spin-orbit interaction is most likely due to the large cyclotron effective mass.

New nucleic acid testing devices to diagnose infectious diseases in resource-limited settings.

PubMed

Maffert, P; Reverchon, S; Nasser, W; Rozand, C; Abaibou, H

2017-10-01

Point-of-care diagnosis based on nucleic acid testing aims to incorporate all the analytical steps, from sample preparation to nucleic acid amplification and detection, in a single device. This device needs to provide a low-cost, robust, sensitive, specific, and easily readable analysis. Microfluidics has great potential for handling small volumes of fluids on a single platform. Microfluidic technology has recently been applied to paper, which is already used in low-cost lateral flow tests. Nucleic acid extraction from a biological specimen usually requires cell filtration and lysis on specific membranes, while affinity matrices, such as chitosan or polydiacetylene, are well suited to concentrating nucleic acids for subsequent amplification. Access to electricity is often difficult in resource-limited areas, so the amplification step needs to be equipment-free. Consequently, the reaction has to be isothermal to alleviate the need for a thermocycler. LAMP, NASBA, HDA, and RPA are examples of the technologies available. Nucleic acid detection techniques are currently based on fluorescence, colorimetry, or chemiluminescence. For point-of-care diagnostics, the results should be readable with the naked eye. Nowadays, interpretation and communication of results to health professionals could rely on a smartphone, used as a telemedicine device. The major challenge of creating an "all-in-one" diagnostic test involves the design of an optimal solution and a sequence for each analytical step, as well as combining the execution of all these steps on a single device. This review provides an overview of available materials and technologies which seem to be adapted to point-of-care nucleic acid-based diagnosis, in low-resource areas.

A highly manufacturable 0.2 {mu}m AlGaAs/InGaAs PHEMT fabricated using the single-layer integrated-metal FET (SLIMFET) process

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

Havasy, C.K.; Quach, T.K.; Bozada, C.A.

1995-12-31

This work is the development of a single-layer integrated-metal field effect transistor (SLIMFET) process for a high performance 0.2 {mu}m AlGaAs/InGaAs pseudomorphic high electron mobility transistor (PHEMT). This process is compatible with MMIC fabrication and minimizes process variations, cycle time, and cost. This process uses non-alloyed ohmic contacts, a selective gate-recess etching process, and a single gate/source/drain metal deposition step to form both Schottky and ohmic contacts at the same time.

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

Le, Hai P.; Cambier, Jean -Luc

Here, we present a numerical model and a set of conservative algorithms for Non-Maxwellian plasma kinetics with inelastic collisions. These algorithms self-consistently solve for the time evolution of an isotropic electron energy distribution function interacting with an atomic state distribution function of an arbitrary number of levels through collisional excitation, deexcitation, as well as ionization and recombination. Electron-electron collisions, responsible for thermalization of the electron distribution, are also included in the model. The proposed algorithms guarantee mass/charge and energy conservation in a single step, and is applied to the case of non-uniform gridding of the energy axis in the phasemore » space of the electron distribution function. Numerical test cases are shown to demonstrate the accuracy of the method and its conservation properties.« less

Electronic drive and acquisition system for mass spectrometry

NASA Technical Reports Server (NTRS)

Schaefer, Rembrandt Thomas (Inventor); Chutjian, Ara (Inventor); Tran, Tuan (Inventor); Madzunkov, Stojan M. (Inventor); Thomas, John L. (Inventor); Mojarradi, Mohammad (Inventor); MacAskill, John (Inventor); Blaes, Brent R. (Inventor); Darrach, Murray R. (Inventor); Burke, Gary R. (Inventor)

2010-01-01

The present invention discloses a mixed signal RF drive electronics board that offers small, low power, reliable, and customizable method for driving and generating mass spectra from a mass spectrometer, and for control of other functions such as electron ionizer, ion focusing, single-ion detection, multi-channel data accumulation and, if desired, front-end interfaces such as pumps, valves, heaters, and columns.

Single-protein detection in crowded molecular environments in cryo-EM images

PubMed Central

Rickgauer, J Peter; Grigorieff, Nikolaus; Denk, Winfried

2017-01-01

We present an approach to study macromolecular assemblies by detecting component proteins’ characteristic high-resolution projection patterns, calculated from their known 3D structures, in single electron cryo-micrographs. Our method detects single apoferritin molecules in vitreous ice with high specificity and determines their orientation and location precisely. Simulations show that high spatial-frequency information and—in the presence of protein background—a whitening filter are essential for optimal detection, in particular for images taken far from focus. Experimentally, we could detect small viral RNA polymerase molecules, distributed randomly among binding locations, inside rotavirus particles. Based on the currently attainable image quality, we estimate a threshold for detection that is 150 kDa in ice and 300 kDa in 100 nm thick samples of dense biological material. DOI: http://dx.doi.org/10.7554/eLife.25648.001 PMID:28467302

Serial single molecule electron diffraction imaging: diffraction background of superfluid helium droplets

NASA Astrophysics Data System (ADS)

Zhang, Jie; He, Yunteng; Lei, Lei; Alghamdi, Maha; Oswalt, Andrew; Kong, Wei

2017-08-01

In an effort to solve the crystallization problem in crystallography, we have been engaged in developing a method termed "serial single molecule electron diffraction imaging" (SS-EDI). The unique features of SS-EDI are superfluid helium droplet cooling and field-induced orientation: together the two features constitute a molecular goniometer. Unfortunately, the helium atoms surrounding the sample molecule also contribute to a diffraction background. In this report, we analyze the properties of a superfluid helium droplet beam and its doping statistics, and demonstrate the feasibility of overcoming the background issue by using the velocity slip phenomenon of a pulsed droplet beam. Electron diffraction profiles and pair correlation functions of ferrocene-monomer-doped droplets and iodine-nanocluster-doped droplets are presented. The timing of the pulsed electron gun and the effective doping efficiency under different dopant pressures can both be controlled for size selection. This work clears any doubt of the effectiveness of superfluid helium droplets in SS-EDI, thereby advancing the effort in demonstrating the "proof-of-concept" one step further.

Patterned arrays of lateral heterojunctions within monolayer two-dimensional semiconductors

DOE PAGES

Mahjouri-Samani, Masoud; Lin, Ming-Wei; Wang, Kai; ...

2015-07-22

The formation of semiconductor heterojunctions and their high density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional (2D) crystalline semiconductors as building blocks in next generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate a process strategy for the formation of lithographically-patterned lateral semiconducting heterojunctions within a single 2D crystal. E-beam lithography is used to pattern MoSe 2 monolayer crystals with SiO 2, and the exposed locations are selectively and totally converted to MoS 2 using pulsed laser deposition (PLD) of sulfur in order to form MoSe 2/MoS 2 heterojunctions in predefinedmore » patterns. The junctions and conversion process are characterized by atomically resolved scanning transmission electron microscopy, photoluminescence, and Raman spectroscopy. This demonstration of lateral semiconductor heterojunction arrays within a single 2D crystal is an essential step for the lateral integration of 2D semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin circuitry.« less

Electron Flow through Proteins

PubMed Central

Gray, Harry B.; Winkler, Jay R.

2009-01-01

Electron transfers in photosynthesis and respiration commonly occur between metal-containing cofactors that are separated by large molecular distances. Employing laser flash-quench triggering methods, we have shown that 20-Å, coupling-limited FeII to RuIII and CuI to RuIII electron tunneling in Ru-modified cytochromes and blue copper proteins can occur on the microsecond timescale both in solutions and crystals. Redox equivalents can be transferred even longer distances by multistep tunneling, often called hopping, through intervening amino acid side chains. Our work has established that 20-Å hole hopping through an intervening tryptophan is two orders of magnitude faster than single-step electron tunneling in a Re-modified blue copper protein. PMID:20161522

Alternating electron and proton transfer steps in photosynthetic water oxidation

PubMed Central

Klauss, André; Haumann, Michael; Dau, Holger

2012-01-01

Water oxidation by cyanobacteria, algae, and plants is pivotal in oxygenic photosynthesis, the process that powers life on Earth, and is the paradigm for engineering solar fuel–production systems. Each complete reaction cycle of photosynthetic water oxidation requires the removal of four electrons and four protons from the catalytic site, a manganese–calcium complex and its protein environment in photosystem II. In time-resolved photothermal beam deflection experiments, we monitored apparent volume changes of the photosystem II protein associated with charge creation by light-induced electron transfer (contraction) and charge-compensating proton relocation (expansion). Two previously invisible proton removal steps were detected, thereby filling two gaps in the basic reaction-cycle model of photosynthetic water oxidation. In the S2 → S3 transition of the classical S-state cycle, an intermediate is formed by deprotonation clearly before electron transfer to the oxidant (). The rate-determining elementary step (τ, approximately 30 µs at 20 °C) in the long-distance proton relocation toward the protein–water interface is characterized by a high activation energy (Ea = 0.46 ± 0.05 eV) and strong H/D kinetic isotope effect (approximately 6). The characteristics of a proton transfer step during the S0 → S1 transition are similar (τ, approximately 100 µs; Ea = 0.34 ± 0.08 eV; kinetic isotope effect, approximately 3); however, the proton removal from the Mn complex proceeds after electron transfer to . By discovery of the transient formation of two further intermediate states in the reaction cycle of photosynthetic water oxidation, a temporal sequence of strictly alternating removal of electrons and protons from the catalytic site is established. PMID:22988080

Alternating electron and proton transfer steps in photosynthetic water oxidation.

PubMed

Klauss, André; Haumann, Michael; Dau, Holger

2012-10-02

Water oxidation by cyanobacteria, algae, and plants is pivotal in oxygenic photosynthesis, the process that powers life on Earth, and is the paradigm for engineering solar fuel-production systems. Each complete reaction cycle of photosynthetic water oxidation requires the removal of four electrons and four protons from the catalytic site, a manganese-calcium complex and its protein environment in photosystem II. In time-resolved photothermal beam deflection experiments, we monitored apparent volume changes of the photosystem II protein associated with charge creation by light-induced electron transfer (contraction) and charge-compensating proton relocation (expansion). Two previously invisible proton removal steps were detected, thereby filling two gaps in the basic reaction-cycle model of photosynthetic water oxidation. In the S(2) → S(3) transition of the classical S-state cycle, an intermediate is formed by deprotonation clearly before electron transfer to the oxidant (Y Z OX). The rate-determining elementary step (τ, approximately 30 µs at 20 °C) in the long-distance proton relocation toward the protein-water interface is characterized by a high activation energy (E(a) = 0.46 ± 0.05 eV) and strong H/D kinetic isotope effect (approximately 6). The characteristics of a proton transfer step during the S(0) → S(1) transition are similar (τ, approximately 100 µs; E(a) = 0.34 ± 0.08 eV; kinetic isotope effect, approximately 3); however, the proton removal from the Mn complex proceeds after electron transfer to . By discovery of the transient formation of two further intermediate states in the reaction cycle of photosynthetic water oxidation, a temporal sequence of strictly alternating removal of electrons and protons from the catalytic site is established.

Self-propelled motion of Au-Si droplets on Si(111) mediated by monoatomic step dissolution

NASA Astrophysics Data System (ADS)

Curiotto, S.; Leroy, F.; Cheynis, F.; Müller, P.

2015-02-01

By Low Energy Electron Microscopy, we show that the spontaneous motion of gold droplets on silicon (111) is chemically driven: the droplets tend to dissolve silicon monoatomic steps to reach the temperature-dependent Au-Si equilibrium stoichiometry. According to the droplet size, the motion details are different. In the first stages of Au deposition small droplets nucleate at steps and move continuously on single terraces. The droplets temporarily pin at each step they meet during their motion. During pinning, the growing droplets become supersaturated in Au. They depin from the steps when a notch nucleate on the upper step. Then the droplets climb up and locally dissolve the Si steps, leaving behind them deep tracks formed by notched steps. Measurements of the dissolution rate and the displacement lengths enable us to describe quantitatively the motion mechanism, also in terms of anisotropy of Si dissolution kinetics. Scaling laws for the droplet position as a function of time are proposed: x ∝ tn with 1/3 < n < 2/3.

Detecting Submicron Pattern Defects On Optical Photomasks Using An Enhanced El-3 Electron-Beam Lithography Tool

NASA Astrophysics Data System (ADS)

Simpson, R. A.; Davis, D. E.

1982-09-01

This paper describes techniques to detect submicron pattern defects on optical photomasks with an enhanced direct-write, electron-beam lithographic tool. EL-3 is a third generation, shaped spot, electron-beam lithography tool developed by IBM to fabricate semiconductor devices and masks. This tool is being upgraded to provide 100% inspection of optical photomasks for submicron pattern defects, which are subsequently repaired. Fixed-size overlapped spots are stepped over the mask patterns while a signal derived from the back-scattered electrons is monitored to detect pattern defects. Inspection does not require pattern recognition because the inspection scan patterns are derived from the original design data. The inspection spot is square and larger than the minimum defect to be detected, to improve throughput. A new registration technique provides the beam-to-pattern overlay required to locate submicron defects. The 'guard banding" of inspection shapes prevents mask and system tolerances from producing false alarms that would occur should the spots be mispositioned such that they only partially covered a shape being inspected. A rescanning technique eliminates noise-related false alarms and significantly improves throughput. Data is accumulated during inspection and processed offline, as required for defect repair. EL-3 will detect 0.5 um pattern defects at throughputs compatible with mask manufacturing.

Kinetic Monte Carlo Simulations and Molecular Conductance Measurements of the Bacterial Decaheme Cytochrome MtrF

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

Byun, H. S.; Pirbadian, S.; Nakano, Aiichiro

2014-09-05

Microorganisms overcome the considerable hurdle of respiring extracellular solid substrates by deploying large multiheme cytochrome complexes that form 20 nanometer conduits to traffic electrons through the periplasm and across the cellular outer membrane. Here we report the first kinetic Monte Carlo simulations and single-molecule scanning tunneling microscopy (STM) measurements of the Shewanella oneidensis MR-1 outer membrane decaheme cytochrome MtrF, which can perform the final electron transfer step from cells to minerals and microbial fuel cell anodes. We find that the calculated electron transport rate through MtrF is consistent with previously reported in vitro measurements of the Shewanella Mtr complex, asmore » well as in vivo respiration rates on electrode surfaces assuming a reasonable (experimentally verified) coverage of cytochromes on the cell surface. The simulations also reveal a rich phase diagram in the overall electron occupation density of the hemes as a function of electron injection and ejection rates. Single molecule tunneling spectroscopy confirms MtrF's ability to mediate electron transport between an STM tip and an underlying Au(111) surface, but at rates higher than expected from previously calculated heme-heme electron transfer rates for solvated molecules.« less

An impedimetric immunosensor for highly sensitive detection of IL-8 in human serum and saliva samples: A new surface modification method by 6-phosphonohexanoic acid for biosensing applications.

PubMed

Aydın, Elif Burcu; Sezgintürk, Mustafa Kemal

2018-08-01

In this study, we fabricated a sensitive and label-free impedimetric immunosensor based on 6-phosphonohexanoic acid (PHA) modified ITO electrode for detection of interleukin-8 (IL-8) in human serum and saliva. PHA was first employed to cancer biomarker sensing platform. Anti-IL-8 antibody was used as a biorecognition element and the detection principle of this immunosensor was based on monitoring specific interaction between anti-IL-8 antibody and IL-8 antigen. The morphological characterization of each electrode modification step was analyzed by scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) while electrochemical characterization was performed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and single frequency impedance (SFI) techniques. Moreover, the antibody immobilization on the electrode surface was proved Fourier-transform infrared spectroscopy (FTIR) and Raman Spectroscopy. This proposed impedimetric immunosensor exhibited good performances with a wide linear in the range from 0.02 pg/mL to 3 pg/mL as well as a relative low detection limit of 6 fg/mL. The impedimetric immunosensor had a good specificity, stability and reproducibility. This study proved that PHA was a suitable interface material to fabricate an electrochemical biosensor. Copyright © 2018 Elsevier Inc. All rights reserved.

Macromolecular Systems with MSA-Capped CdTe and CdTe/ZnS Core/Shell Quantum Dots as Superselective and Ultrasensitive Optical Sensors for Picric Acid Explosive.

PubMed

Dutta, Priyanka; Saikia, Dilip; Adhikary, Nirab Chandra; Sarma, Neelotpal Sen

2015-11-11

This work reports the development of highly fluorescent materials for the selective and efficient detection of picric acid explosive in the nanomolar range by fluorescence quenching phenomenon. Poly(vinyl alcohol) grafted polyaniline (PPA) and its nanocomposites with 2-mercaptosuccinic acid (MSA)-capped CdTe quantum dots (PPA-Q) and with MSA-capped CdTe/ZnS core/shell quantum dots (PPA-CSQ) are synthesized in a single step free radical polymerization reaction. The thermal stability and photo stability of the polymer increases in the order of PPA < PPA-Q < PPA-CSQ. The polymers show remarkably high selectivity and efficient sensitivity toward picric acid, and the quenching efficiency for PPA-CSQ reaches up to 99%. The detection limits of PPA, PPA-Q, and PPA-CSQ for picric acid are found to be 23, 1.6, and 0.65 nM, respectively, which are remarkably low. The mechanism operating in the quenching phenomenon is proposed to be a combination of a strong inner filter effect and ground state electrostatic interaction between the polymers and picric acid. A portable and cost-effective electronic device for the visual detection of picric acid by the sensory system is successfully fabricated. The device is further employed for quantitative detection of picric acid in real water samples.

E-DNA sensor of Mycobacterium tuberculosis based on electrochemical assembly of nanomaterials (MWCNTs/PPy/PAMAM).

PubMed

Miodek, Anna; Mejri, Nawel; Gomgnimbou, Michel; Sola, Christophe; Korri-Youssoufi, Hafsa

2015-09-15

Two-step electrochemical patterning methods have been employed to elaborate composite nanomaterials formed with multiwalled carbon nanotubes (MWCNTs) coated with polypyrrole (PPy) and redox PAMAM dendrimers. The nanomaterial has been demonstrated as a molecular transducer for electrochemical DNA detection. The nanocomposite MWCNTs-PPy has been formed by wrapping the PPy film on MWCNTs during electrochemical polymerization of pyrrole on the gold electrode. The MWCNTs-PPy layer was modified with PAMAM dendrimers of fourth generation (PAMAM G4) with covalent bonding by electro-oxidation method. Ferrocenyl groups were then attached to the surface as a redox marker. The electrochemical properties of the nanomaterial (MWCNTs-PPy-PAMAM-Fc) were studied using both square wave voltammetry and cyclic voltammetry to demonstrate efficient electron transfer. The nanomaterial shows high performance in the electrochemical detection of DNA hybridization leading to a variation in the electrochemical signal of ferrocene with a detection limit of 0.3 fM. Furthermore, the biosensor demonstrates ability for sensing DNA of rpoB gene of Mycobacterium tuberculosis in real PCR samples. Developed biosensor was suitable for detection of sequences with a single nucleotide polymorphism (SNP) T (TCG/TTG), responsible for resistance of M. tuberculosis to rifampicin drug, and discriminating them from wild-type samples without such mutation. This shows potential of such systems for further application in pathogens diagnostic and therapeutic purpose.

The energy spectra of solar flare electrons

NASA Technical Reports Server (NTRS)

Evenson, P. A.; Hovestadt, D.; Meyer, P.; Moses, D.

1985-01-01

A survey of 50 electron energy spectra from .1 to 100 MeV originating from solar flares was made by the combination of data from two spectrometers onboard the International Sun Earth Explorer-3 spacecraft. The observed spectral shapes of flare events can be divided into two classes through the criteria of fit to an acceleration model. This standard two step acceleration model, which fits the spectral shape of the first class of flares, involves an impulsive step that accelerates particles up to 100 keV and a second step that further accelerates these particles up to 100 MeV by a single shock. This fit fails for the second class of flares that can be characterized as having excessively hard spectra above 1 MeV relative to the predictions of the model. Correlations with soft X-ray and meter radio observations imply that the acceleration of the high energy particles in the second class of flares is dominated by the impulsive phase of the flares.

Thermal and Electronic Transport in Graphene-Based Nanostructures and Applications in Electrical Sensors

NASA Astrophysics Data System (ADS)

Ramnani, Pankaj Ghanshyam

It is a general consensus that silicon metal-oxide-semiconductor FET (MOSFET) is approaching its scaling limits due to issues including high power dissipation, short channel effects and degraded electrostatics. In recent years, a significant amount of research has been directed towards exploring novel materials like graphene and other two-dimensional atomic crystals to replace Si. Graphene is an ideal candidate owing to its exceptional properties including high carrier mobility (exceeding 15,000 cm2 V -1 s-1), high charge carrier concentration ( 1012 cm -2), low contact resistance due to tunable fermi level, excellent thermal conductivity ( 5000W m-1 K-1), optical transparency ( 97.7%) and flexibility. Despite all these intriguing properties, the absence of a bandgap in graphene has limited its potential applications owing to large off-state currents and low Ion/Ioff ratios observed in graphene-based field effect transistors (FETs). Additionally, most of these experimental studies are conducted using pristine graphene isolated by mechanical exfoliation of graphite, which is not a practical approach for large scale synthesis of graphene. In this dissertation, a scalable method of synthesizing high quality single-layer and bilayer graphene was developed using ambient pressure chemical vapor deposition (AP-CVD). The crystalline nature and physical properties were characterized using electron microscopy and spectroscopic techniques. We investigated the effects of point defects--typically introduced during material characterization and device fabrication steps--on thermal transport in CVD grown single-layer graphene. Furthermore, we investigated methods to engineer a bandgap in graphene by nanopatterning graphene into pseudo one-dimensional nanostructures called graphene nanoribbons (GNRs) using two different top-down approaches. The edge defects in GNRs, which limit carrier mobility and induce p-doping, were characterized using Raman spectroscopy and x-ray photoelectron spectroscopy (XPS), and thermal treatments to repair these defects were explored. Finally, the applications of these graphene-based nanostructures as FET-based electrical nano chemical/bio-sensors were explored. The GNR-FET device showed a significant increase in sensitivity for detection of NO 2 as compared to its graphene counterpart. Analogous to GNRs, single-walled carbon nanotubes (SWNTs) based chemiresistive sensors were also developed for detection of microRNA, a cancer biomarker, and detection of mercury ions in saliva samples.

Single walled carbon nanotube-based stochastic resonance device with molecular self-noise source

NASA Astrophysics Data System (ADS)

Fujii, Hayato; Setiadi, Agung; Kuwahara, Yuji; Akai-Kasaya, Megumi

2017-09-01

Stochastic resonance (SR) is an intrinsic noise usage system for small-signal sensing found in various living creatures. The noise-enhanced signal transmission and detection system, which is probabilistic but consumes low power, has not been used in modern electronics. We demonstrated SR in a summing network based on a single-walled carbon nanotube (SWNT) device that detects small subthreshold signals with very low current flow. The nonlinear current-voltage characteristics of this SWNT device, which incorporated Cr electrodes, were used as the threshold level of signal detection. The adsorption of redox-active polyoxometalate molecules on SWNTs generated additional noise, which was utilized as a self-noise source. To form a summing network SR device, a large number of SWNTs were aligned parallel to each other between the electrodes, which increased the signal detection ability. The functional capabilities of the present small-size summing network SR device, which rely on dense nanomaterials and exploit intrinsic spontaneous noise at room temperature, offer a glimpse of future bio-inspired electronic devices.

SNAP Assay Technology.

PubMed

O'Connor, Thomas P

2015-12-01

The most widely used immunoassay configuration is the enzyme-linked immunosorbent assay (ELISA) because the procedure produces highly sensitive and specific results and generally is easy to use. By definition, ELISAs are immunoassays used to detect a substance (typically an antigen or antibody) in which an enzyme is attached (conjugated) to one of the reactants and an enzymatic reaction is used to amplify the signal if the substance is present. Optimized ELISAs include several steps that are performed in sequence using a defined protocol that typically includes application of sample and an enzyme-conjugated antibody or antigen to an immobilized reagent, followed by wash and enzyme reaction steps. The SNAP assay is an in-clinic device that performs each of the ELISA steps in a timed sequential fashion with little consumer interface. The components and mechanical mechanism of the assay device are described. Detailed descriptions of features of the assay, which minimize nonspecific binding and enhance the ability to read results from weak-positive samples, are given. Basic principles used in assays with fundamentally different reaction mechanisms, namely, antigen-detection, antibody-detection, and competitive assays are given. Applications of ELISA technology, which led to the development of several multianalyte SNAP tests capable of testing for up to 6 analytes using a single-sample and a single-SNAP device are described. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Detection of canine distemper virus (CDV) through one step RT-PCR combined with nested PCR.

PubMed

Kim, Y H; Cho, K W; Youn, H Y; Yoo, H S; Han, H R

2001-04-01

A one step reverse transcription PCR (RT-PCR) combined nested PCR was set up to increase efficiency in the diagnosis of canine distemper virus (CDV) infection after developement of nested PCR. Two PCR primer sets were designed based on the sequence of nucleocapsid gene of CDV Onderstepoort strain. One-step RT-PCR with the outer primer pair was revealed to detect 10(2) PFU/ml. The sensitivity was increased hundredfold using the one-step RT-PCR combined with the nested PCR. Specificity of the PCR was also confirmed using other related canine virus and peripheral blood mononuclear cells (PBMC) and body secretes of healthy dogs. Of the 51 blood samples from dogs clinically suspected of CD, 45 samples were revealed as positive by one-step RT-PCR combined with nested PCR. However, only 15 samples were identified as positive with a single one step RT-PCR. Therefore approximately 60% increase in the efficiency of the diagnosis was observed by the combined method. These results suggested that one step RT-PCR combined with nested PCR could be a sensitive, specific, and practical method for diagnosis of CDV infection.

Two-dimensional simulation and modeling in scanning electron microscope imaging and metrology research.

PubMed

Postek, Michael T; Vladár, András E; Lowney, Jeremiah R; Keery, William J

2002-01-01

Traditional Monte Carlo modeling of the electron beam-specimen interactions in a scanning electron microscope (SEM) produces information about electron beam penetration and output signal generation at either a single beam-landing location, or multiple landing positions. If the multiple landings lie on a line, the results can be graphed in a line scan-like format. Monte Carlo results formatted as line scans have proven useful in providing one-dimensional information about the sample (e.g., linewidth). When used this way, this process is called forward line scan modeling. In the present work, the concept of image simulation (or the first step in the inverse modeling of images) is introduced where the forward-modeled line scan data are carried one step further to construct theoretical two-dimensional (2-D) micrographs (i.e., theoretical SEM images) for comparison with similar experimentally obtained micrographs. This provides an ability to mimic and closely match theory and experiment using SEM images. Calculated and/or measured libraries of simulated images can be developed with this technique. The library concept will prove to be very useful in the determination of dimensional and other properties of simple structures, such as integrated circuit parts, where the shape of the features is preferably measured from a single top-down image or a line scan. This paper presents one approach to the generation of 2-D simulated images and presents some suggestions as to their application to critical dimension metrology.

Mini ion trap mass spectrometer

DOEpatents

Dietrich, Daniel D.; Keville, Robert F.

1995-01-01

An ion trap which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10.sup.9 and commercial mass spectrometers requiring 10.sup.4 ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products.

Mini ion trap mass spectrometer

DOEpatents

Dietrich, D.D.; Keville, R.F.

1995-09-19

An ion trap is described which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10{sup 9} and commercial mass spectrometers requiring 10{sup 4} ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products. 10 figs.

Single Molecule Spectroscopy of Amino Acids and Peptides by Recognition Tunneling

PubMed Central

Zhao, Yanan; Ashcroft, Brian; Zhang, Peiming; Liu, Hao; Sen, Suman; Song, Weisi; Im, JongOne; Gyarfas, Brett; Manna, Saikat; Biswas, Sovan; Borges, Chad; Lindsay, Stuart

2014-01-01

The human proteome has millions of protein variants due to alternative RNA splicing and post-translational modifications, and variants that are related to diseases are frequently present in minute concentrations. For DNA and RNA, low concentrations can be amplified using the polymerase chain reaction, but there is no such reaction for proteins. Therefore, the development of single molecule protein sequencing is a critical step in the search for protein biomarkers. Here we show that single amino acids can be identified by trapping the molecules between two electrodes that are coated with a layer of recognition molecules and measuring the electron tunneling current across the junction. A given molecule can bind in more than one way in the junction, and we therefore use a machine-learning algorithm to distinguish between the sets of electronic ‘fingerprints’ associated with each binding motif. With this recognition tunneling technique, we are able to identify D, L enantiomers, a methylated amino acid, isobaric isomers, and short peptides. The results suggest that direct electronic sequencing of single proteins could be possible by sequentially measuring the products of processive exopeptidase digestion, or by using a molecular motor to pull proteins through a tunnel junction integrated with a nanopore. PMID:24705512

An electron paramagnetic resonance study on irradiated triphenylphosphinselenid single crystal

NASA Astrophysics Data System (ADS)

Aras, Erdal; Karatas, Ozgul; Meric, Yasemin; Abbass, Hind Kh; Birey, Mehmet; Kilic, Ahmet

2014-09-01

The single crystals of triphenylphosphinselenid [C18H15PSe] were produced by slow evaporation of concentrated ethyl acetate solutions. These single crystals were exposed to 60Co gamma (γ) rays with a dose speed of 0.980 kGy/h at the room temperature for 72 h. The free radical over the sample was observed using electron paramagnetic resonance (EPR)-X band spectrometer. The EPR spectra were recorded between 120 and 400 K. Furthermore, the sample irradiated was rotated in steps of 10° and analyzed for different orientations of the crystal in the magnetic field. Only one radical structure was determined on the molecule. The hyperfine constants of the sample were found to be anisotropic. The average values of these constants and value of g were calculated as following: g=2.007656, aSe=37.47 G, aP=27.44 G, aHa=17.28 G, and aHb=18.16 G.

A Demo opto-electronic power source based on single-walled carbon nanotube sheets.

PubMed

Hu, Chunhua; Liu, Changhong; Chen, Luzhuo; Meng, Chuizhou; Fan, Shoushan

2010-08-24

It is known that single-walled carbon nanotubes (SWNTs) strongly absorb light, especially in the near-infrared (NIR) region, and convert it into heat. In fact, SWNTs also have considerable ability to convert heat into electricity. In this work, we show that SWNT sheets made from as-grown SWNT arrays display a large positive thermoelectric coefficient (p-type). We designed a simple SWNT device to convert illuminating NIR light directly into a notable voltage output, which was verified by experimental tests. Furthermore, by a simple functionalization step, the p- to n-type transition was conveniently achieved for the SWNT sheets. By integrating p- and n-type elements in series, we constructed a novel NIR opto-electronic power source, which outputs a large voltage that sums over the output of every single element. Additionally, the output of the demo device has shown a good linear relationship with NIR light power density, favorable for IR sensors.

Hysteretic Four-Step Spin Crossover within a Three-Dimensional Porous Hofmann-like Material

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

Clements, John E.; Price, Jason R.; Neville, Suzanne M.

Materials that display multiple stepped spin crossover (SCO) transitions with accompanying hysteresis present the opportunity for ternary, quaternary, and quinary electronic switching and data storage but are rare in existence. Herein, we present the first report of a four-step hysteretic SCO framework. Single-crystal structure analysis of a porous 3D Hofmann-like material showed long-range ordering of spin states: HS, HS 0.67LS 0.33, HS 0.5LS 0.5, HS 0.33LS 0.67, and LS. These detailed structural studies provide insight into how multistep SCO materials can be rationally designed through control of host–host and host–guest interactions.

Discrete pre-processing step effects in registration-based pipelines, a preliminary volumetric study on T1-weighted images.

PubMed

Muncy, Nathan M; Hedges-Muncy, Ariana M; Kirwan, C Brock

2017-01-01

Pre-processing MRI scans prior to performing volumetric analyses is common practice in MRI studies. As pre-processing steps adjust the voxel intensities, the space in which the scan exists, and the amount of data in the scan, it is possible that the steps have an effect on the volumetric output. To date, studies have compared between and not within pipelines, and so the impact of each step is unknown. This study aims to quantify the effects of pre-processing steps on volumetric measures in T1-weighted scans within a single pipeline. It was our hypothesis that pre-processing steps would significantly impact ROI volume estimations. One hundred fifteen participants from the OASIS dataset were used, where each participant contributed three scans. All scans were then pre-processed using a step-wise pipeline. Bilateral hippocampus, putamen, and middle temporal gyrus volume estimations were assessed following each successive step, and all data were processed by the same pipeline 5 times. Repeated-measures analyses tested for a main effects of pipeline step, scan-rescan (for MRI scanner consistency) and repeated pipeline runs (for algorithmic consistency). A main effect of pipeline step was detected, and interestingly an interaction between pipeline step and ROI exists. No effect for either scan-rescan or repeated pipeline run was detected. We then supply a correction for noise in the data resulting from pre-processing.

Scanning ultrafast electron microscopy

PubMed Central

Yang, Ding-Shyue; Mohammed, Omar F.; Zewail, Ahmed H.

2010-01-01

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability. PMID:20696933

Test of the HAPD light sensor for the Belle II Aerogel RICH

NASA Astrophysics Data System (ADS)

Yusa, Y.; Adachi, I.; Dolenec, R.; Hayata, K.; Iori, S.; Iwata, S.; Kakuno, H.; Kataura, R.; Kawai, H.; Kindo, H.; Kobayashi, T.; Korpar, S.; Krizan, P.; Kumita, T.; Mrvar, M.; Nishida, S.; Ogawa, K.; Pestotnik, R.; Santelj, L.; Sumiyoshi, T.; Tabata, M.; Yonenaga, M.

2017-12-01

The Aerogel Ring-Imaging Cherenkov detector (ARICH) is being installed in the endcap region of Belle II spectrometer to identify particles from B meson decays by detecting the Cherenkov ring image from aerogel radiators. To detect single photons, high-sensitive photon detector which has wide effective area (∼70 mm × 70 mm), a Hybrid Avalanche Photo Detector (HAPD), has been developed in a collaboration with Hamamatsu K.K. The HAPD consists of hybrid structure of a vacuum tube and an avalanche photodiode (APD). It can be operated in 1.5 T magnetic field of the spectrometer and withstands the radiation levels expected in the Belle II experiment. There are two steps of electric pulse amplification: acceleration of photo-electron in electric field in the vacuum tube part and electron avalanche in the APD part resulting in total gain of order 105. For the ARICH, we use 420 HAPDs in total. Before installing them, we performed quality assessment studies such as measurements of dark current, noise level, signal-to-noise ratio and two-dimensional scan with laser illumination. We also measured quantum efficiency of the photocathode. During the HAPD performance tests in the magnetic field, we observed very large signal pulses which cause long dead time of the readout electronics in some of the HAPDs. We have carried out a number of studies to understand this phenomenon, and have found a way to mitigate it and suppress the degradation of the ARICH performance. In this report, we will show a summary of the HAPD performance and quality assessment measurements including validation in the magnetic field for all of the HAPDs manufactured for the ARICH in the Belle II.

Palladium-Catalyzed Asymmetric Allylic Alkylation of Electron-Deficient Pyrroles with Meso Electrophiles

PubMed Central

Osipov, Maksim; Dong, Guangbin

2012-01-01

Pyrroles can serve as competent nucleophiles with meso electrophiles in the Pd-catalyzed asymmetric allylic alkylation. The products from this transformation were obtained as a single regio- and diastereomer in high yield and enantiopurity. A nitropyrrole-containing nucleoside analogue was synthesized in 7 steps to demonstrate the synthetic utility of this transformation. PMID:22506671

Rapid and Sensitive Isothermal Detection of Nucleic-acid Sequence by Multiple Cross Displacement Amplification.

PubMed

Wang, Yi; Wang, Yan; Ma, Ai-Jing; Li, Dong-Xun; Luo, Li-Juan; Liu, Dong-Xin; Jin, Dong; Liu, Kai; Ye, Chang-Yun

2015-07-08

We have devised a novel amplification strategy based on isothermal strand-displacement polymerization reaction, which was termed multiple cross displacement amplification (MCDA). The approach employed a set of ten specially designed primers spanning ten distinct regions of target sequence and was preceded at a constant temperature (61-65 °C). At the assay temperature, the double-stranded DNAs were at dynamic reaction environment of primer-template hybrid, thus the high concentration of primers annealed to the template strands without a denaturing step to initiate the synthesis. For the subsequent isothermal amplification step, a series of primer binding and extension events yielded several single-stranded DNAs and single-stranded single stem-loop DNA structures. Then, these DNA products enabled the strand-displacement reaction to enter into the exponential amplification. Three mainstream methods, including colorimetric indicators, agarose gel electrophoresis and real-time turbidity, were selected for monitoring the MCDA reaction. Moreover, the practical application of the MCDA assay was successfully evaluated by detecting the target pathogen nucleic acid in pork samples, which offered advantages on quick results, modest equipment requirements, easiness in operation, and high specificity and sensitivity. Here we expounded the basic MCDA mechanism and also provided details on an alternative (Single-MCDA assay, S-MCDA) to MCDA technique.

Quasi-dynamic mode of nanomembranes for time-of-flight mass spectrometry of proteins.

PubMed

Park, Jonghoo; Kim, Hyunseok; Blick, Robert H

2012-04-21

Mechanical resonators realized on the nano-scale by now offer applications in mass-sensing of biomolecules with extraordinary sensitivity. The general idea is that perfect mechanical biosensors should be of extremely small size to achieve zeptogram sensitivity in weighing single molecules similar to a balance. However, the small scale and long response time of weighing biomolecules with a cantilever restrict their usefulness as a high-throughput method. Commercial mass spectrometry (MS) such as electro-spray ionization (ESI)-MS and matrix-assisted laser desorption/ionization (MALDI)-time of flight (TOF)-MS are the gold standards to which nanomechanical resonators have to live up to. These two methods rely on the ionization and acceleration of biomolecules and the following ion detection after a mass selection step, such as time-of-flight (TOF). Hence, the spectrum is typically represented in m/z, i.e. the mass to ionization charge ratio. Here, we describe the feasibility and mass range of detection of a new mechanical approach for ion detection in time-of-flight mass spectrometry, the principle of which is that the impinging ion packets excite mechanical oscillations in a silicon nitride nanomembrane. These mechanical oscillations are henceforth detected via field emission of electrons from the nanomembrane. Ion detection is demonstrated in MALDI-TOF analysis over a broad range with angiotensin, bovine serum albumin (BSA), and an equimolar protein mixture of insulin, BSA, and immunoglobulin G (IgG). We find an unprecedented mass range of operation of the nanomembrane detector.

High Sensitivity and High Detection Specificity of Gold-Nanoparticle-Grafted Nanostructured Silicon Mass Spectrometry for Glucose Analysis.

PubMed

Tsao, Chia-Wen; Yang, Zhi-Jie

2015-10-14

Desorption/ionization on silicon (DIOS) is a high-performance matrix-free mass spectrometry (MS) analysis method that involves using silicon nanostructures as a matrix for MS desorption/ionization. In this study, gold nanoparticles grafted onto a nanostructured silicon (AuNPs-nSi) surface were demonstrated as a DIOS-MS analysis approach with high sensitivity and high detection specificity for glucose detection. A glucose sample deposited on the AuNPs-nSi surface was directly catalyzed to negatively charged gluconic acid molecules on a single AuNPs-nSi chip for MS analysis. The AuNPs-nSi surface was fabricated using two electroless deposition steps and one electroless etching step. The effects of the electroless fabrication parameters on the glucose detection efficiency were evaluated. Practical application of AuNPs-nSi MS glucose analysis in urine samples was also demonstrated in this study.

Assessment of an electronic learning system for colon capsule endoscopy: a pilot study.

PubMed

Watabe, Hirotsugu; Nakamura, Tetsuya; Yamada, Atsuo; Kakugawa, Yasuo; Nouda, Sadaharu; Terano, Akira

2016-06-01

Training for colon capsule endoscopy (CCE) procedures is currently performed as a lecture and hands-on seminar. The aims of this pilot study were to assess the utility of an electronic learning system for CCE (ELCCE) designed for the Japanese Association for Capsule Endoscopy using an objective scoring engine, and to evaluate the efficacy of ELCCE on the acquisition of CCE reading competence. ELCCE is an Internet-based learning system with the following steps: step 1, introduction; step 2, CCE reading competence assessment test (CCAT), which evaluates the competence of CCE reading prior to training; step 3, learning reading theory; step 4, training with guidance; step 5, training without guidance; step 6, final assessment; and step 7, the same as step 2. The CCAT, step 5 and step 6 were scored automatically according to: lesion detection, diagnosis (location, size, shape of lesion), management recommendations, and quality of view. Ten trainee endoscopists were initially recruited (cohort 1), followed by a validating cohort of 11 trainee endoscopists (cohort 2). All but one participant finished ELCCE training within 7 weeks. In step 6, accuracy ranged from 53 to 98 % and was not impacted by step 2 pretest scores. The average CCAT scores significantly increased between step 2 pretest and step 7 in both cohorts, from 42 ± 18 % to 79 ± 15 % in cohort 1 (p = 0.0004), and from 52 ± 15 % to 79 ± 14 % in cohort 2 (p = 0.0003). ELCCE is useful and effective for improving CCE reading competence.

Development of a One-Step Duplex RT-PCR Method for the Simultaneous Detection of VP3/VP1 and VP1/P2B Regions of the Hepatitis A Virus.

PubMed

Kim, Mi-Ju; Lee, Shin-Young; Kim, Hyun-Joong; Lee, Jeong Su; Joo, In Sun; Kwak, Hyo Sun; Kim, Hae-Yeong

2016-08-28

The simultaneous detection and accurate identification of hepatitis A virus (HAV) is critical in food safety and epidemiological studies to prevent the spread of HAV outbreaks. Towards this goal, a one-step duplex reverse-transcription (RT)-PCR method was developed targeting the VP1/P2B and VP3/VP1 regions of the HAV genome for the qualitative detection of HAV. An HAV RT-qPCR standard curve was produced for the quantification of HAV RNA. The detection limit of the duplex RT-PCR method was 2.8 × 10(1) copies of HAV. The PCR products enabled HAV genotyping analysis through DNA sequencing, which can be applied for epidemiological investigations. The ability of this duplex RT-PCR method to detect HAV was evaluated with HAV-spiked samples of fresh lettuce, frozen strawberries, and oysters. The limit of detection of the one-step duplex RT-PCR for each food model was 9.4 × 10(2) copies/20 g fresh lettuce, 9.7 × 10(3) copies/20 g frozen strawberries, and 4.1 × 10(3) copies/1.5 g oysters. Use of a one-step duplex RT-PCR method has advantages such as shorter time, decreased cost, and decreased labor owing to the single amplification reaction instead of four amplifications necessary for nested RT-PCR.

Deterministic Integration of Quantum Dots into on-Chip Multimode Interference Beamsplitters Using in Situ Electron Beam Lithography

NASA Astrophysics Data System (ADS)

Schnauber, Peter; Schall, Johannes; Bounouar, Samir; Höhne, Theresa; Park, Suk-In; Ryu, Geun-Hwan; Heindel, Tobias; Burger, Sven; Song, Jin-Dong; Rodt, Sven; Reitzenstein, Stephan

2018-04-01

The development of multi-node quantum optical circuits has attracted great attention in recent years. In particular, interfacing quantum-light sources, gates and detectors on a single chip is highly desirable for the realization of large networks. In this context, fabrication techniques that enable the deterministic integration of pre-selected quantum-light emitters into nanophotonic elements play a key role when moving forward to circuits containing multiple emitters. Here, we present the deterministic integration of an InAs quantum dot into a 50/50 multi-mode interference beamsplitter via in-situ electron beam lithography. We demonstrate the combined emitter-gate interface functionality by measuring triggered single-photon emission on-chip with $g^{(2)}(0) = 0.13\\pm 0.02$. Due to its high patterning resolution as well as spectral and spatial control, in-situ electron beam lithography allows for integration of pre-selected quantum emitters into complex photonic systems. Being a scalable single-step approach, it paves the way towards multi-node, fully integrated quantum photonic chips.

Silk-molded flexible, ultrasensitive, and highly stable electronic skin for monitoring human physiological signals.

PubMed

Wang, Xuewen; Gu, Yang; Xiong, Zuoping; Cui, Zheng; Zhang, Ting

2014-03-05

Flexible and transparent E-skin devices are achieved by combining silk-molded micro-patterned polydimethylsiloxane (PDMS) with single-walled carbon nanotube (SWNT) ultrathin films. The E-skin sensing device demonstrates superior sensitivity, a very low detectable pressure limit, a fast response time, and a high stability for the detection of superslight pressures, which may broaden their potential use as cost-effective wearable electronics for healthcare applications. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theory for rates, equilibrium constants, and Brønsted slopes in F1-ATPase single molecule imaging experiments

PubMed Central

Volkán-Kacsó, Sándor; Marcus, Rudolph A.

2015-01-01

A theoretical model of elastically coupled reactions is proposed for single molecule imaging and rotor manipulation experiments on F1-ATPase. Stalling experiments are considered in which rates of individual ligand binding, ligand release, and chemical reaction steps have an exponential dependence on rotor angle. These data are treated in terms of the effect of thermodynamic driving forces on reaction rates, and lead to equations relating rate constants and free energies to the stalling angle. These relations, in turn, are modeled using a formalism originally developed to treat electron and other transfer reactions. During stalling the free energy profile of the enzymatic steps is altered by a work term due to elastic structural twisting. Using biochemical and single molecule data, the dependence of the rate constant and equilibrium constant on the stall angle, as well as the Børnsted slope are predicted and compared with experiment. Reasonable agreement is found with stalling experiments for ATP and GTP binding. The model can be applied to other torque-generating steps of reversible ligand binding, such as ADP and Pi release, when sufficient data become available. PMID:26483483

Development of a novel single tube nested PCR for enhanced detection of cytomegalovirus DNA from dried blood spots.

PubMed

Atkinson, C; Emery, V C; Griffiths, P D

2014-02-01

Newborn screening for congenital cytomegalovirus (CCMV) using dried blood spots (DBS) has been proposed because many developed countries have DBS screening programmes in place for other diseases. The aim of this study was to develop a rapid, single tube nested polymerase chain reaction (PCR) method for enhanced detection of CMV from DBS compared to existing (single target) real time PCRs. The new method was compared with existing real time PCRs for sensitivity and specificity. Overall sensitivity of the single target PCR assays in both asymptomatic and symptomatic infants with laboratory confirmed congenital CMV was 69% (CMV PCR or culture positive before day 21 of life). In contrast, the single tube nested assay had an increased sensitivity of 81% with100% specificity. Overall the assay detected CMV from a DBS equivalent to an original blood sample which contained 500IU/ml. In conclusion this single tube nested methodology allows simultaneous amplification and detection of CMV DNA in 1.5h removing the associated contamination risk of a two step nested PCR. Owing to its increased sensitivity, it has the potential to be used as a screening assay and ultimately allow early identification and intervention for children with congenital CMV. Copyright © 2013 Elsevier B.V. All rights reserved.

Anomalous high capacitance in a coaxial single nanowire capacitor.

PubMed

Liu, Zheng; Zhan, Yongjie; Shi, Gang; Moldovan, Simona; Gharbi, Mohamed; Song, Li; Ma, Lulu; Gao, Wei; Huang, Jiaqi; Vajtai, Robert; Banhart, Florian; Sharma, Pradeep; Lou, Jun; Ajayan, Pulickel M

2012-06-06

Building entire multiple-component devices on single nanowires is a promising strategy for miniaturizing electronic applications. Here we demonstrate a single nanowire capacitor with a coaxial asymmetric Cu-Cu(2)O-C structure, fabricated using a two-step chemical reaction and vapour deposition method. The capacitance measured from a single nanowire device corresponds to ~140 μF cm(-2), exceeding previous reported values for metal-insulator-metal micro-capacitors and is more than one order of magnitude higher than what is predicted by classical electrostatics. Quantum mechanical calculations indicate that this unusually high capacitance may be attributed to a negative quantum capacitance of the dielectric-metal interface, enhanced significantly at the nanoscale.

Atomic Step Formation on Sapphire Surface in Ultra-precision Manufacturing

PubMed Central

Wang, Rongrong; Guo, Dan; Xie, Guoxin; Pan, Guoshun

2016-01-01

Surfaces with controlled atomic step structures as substrates are highly relevant to desirable performances of materials grown on them, such as light emitting diode (LED) epitaxial layers, nanotubes and nanoribbons. However, very limited attention has been paid to the step formation in manufacturing process. In the present work, investigations have been conducted into this step formation mechanism on the sapphire c (0001) surface by using both experiments and simulations. The step evolutions at different stages in the polishing process were investigated with atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). The simulation of idealized steps was constructed theoretically on the basis of experimental results. It was found that (1) the subtle atomic structures (e.g., steps with different sawteeth, as well as steps with straight and zigzag edges), (2) the periodicity and (3) the degree of order of the steps were all dependent on surface composition and miscut direction (step edge direction). A comparison between experimental results and idealized step models of different surface compositions has been made. It has been found that the structure on the polished surface was in accordance with some surface compositions (the model of single-atom steps: Al steps or O steps). PMID:27444267

Atomic Step Formation on Sapphire Surface in Ultra-precision Manufacturing

NASA Astrophysics Data System (ADS)

Wang, Rongrong; Guo, Dan; Xie, Guoxin; Pan, Guoshun

2016-07-01

Surfaces with controlled atomic step structures as substrates are highly relevant to desirable performances of materials grown on them, such as light emitting diode (LED) epitaxial layers, nanotubes and nanoribbons. However, very limited attention has been paid to the step formation in manufacturing process. In the present work, investigations have been conducted into this step formation mechanism on the sapphire c (0001) surface by using both experiments and simulations. The step evolutions at different stages in the polishing process were investigated with atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). The simulation of idealized steps was constructed theoretically on the basis of experimental results. It was found that (1) the subtle atomic structures (e.g., steps with different sawteeth, as well as steps with straight and zigzag edges), (2) the periodicity and (3) the degree of order of the steps were all dependent on surface composition and miscut direction (step edge direction). A comparison between experimental results and idealized step models of different surface compositions has been made. It has been found that the structure on the polished surface was in accordance with some surface compositions (the model of single-atom steps: Al steps or O steps).

Smartphones and e-tablets in perioperative medicine

PubMed Central

2017-01-01

Smartphones and electronic tablets (e-tablets) have become ubiquitous devices. Their ease of use, smartness, accessibility, mobility and connectivity create unique opportunities to improve quality of surgical care from prehabilitation to rehabilitation. Before surgery, digital applications (Apps), serious games and text messaging may help for a better control of risk factors (hypertension, overweight), for smoking cessation, and for optimizing adherence to preoperative recommendations (e.g., regarding anticoagulation or antihypertensive treatments). During surgery, Apps may help to rationalize fluid management and estimate blood loss. After surgery, smartphones and/or connected sensors (pulse oximeter, adhesive path, electronic tattoo, bioimpedance necklace) can be used to monitor body temperature, heart rate, heart rate variability (detection of cardiac arrhythmia), respiratory rate, arterial oxygen saturation and thoracic fluid content. Therefore, these tools have potential for the early detection of infectious, cardiac and respiratory complications in the wards and from home. When connected to echo probes, smartphones and e-tablets can also be used as ultrasound devices during central venous catheter insertion, for peripheral nerve blocks, and to perform echocardiography in patients developing cardiac complications. Finally, electronic checklists now exist as Apps to enhance communication between patients and healthcare professionals, and to track and record step by step each element of the surgical journey. Studies are now urgently needed to investigate whether this digital revolution can translate into a better outcome, an earlier detection of postoperative complications, a decrease in hospital readmissions and in health care costs. PMID:29046768

Detailed analysis of complex single molecule FRET data with the software MASH

NASA Astrophysics Data System (ADS)

Hadzic, Mélodie C. A. S.; Kowerko, Danny; Börner, Richard; Zelger-Paulus, Susann; Sigel, Roland K. O.

2016-04-01

The processing and analysis of surface-immobilized single molecule FRET (Förster resonance energy transfer) data follows systematic steps (e.g. single molecule localization, clearance of different sources of noise, selection of the conformational and kinetic model, etc.) that require a solid knowledge in optics, photophysics, signal processing and statistics. The present proceeding aims at standardizing and facilitating procedures for single molecule detection by guiding the reader through an optimization protocol for a particular experimental data set. Relevant features were determined from single molecule movies (SMM) imaging Cy3- and Cy5-labeled Sc.ai5γ group II intron molecules synthetically recreated, to test the performances of four different detection algorithms. Up to 120 different parameterizations per method were routinely evaluated to finally establish an optimum detection procedure. The present protocol is adaptable to any movie displaying surface-immobilized molecules, and can be easily reproduced with our home-written software MASH (multifunctional analysis software for heterogeneous data) and script routines (both available in the download section of www.chem.uzh.ch/rna).

MEDIPIX: a VLSI chip for a GaAs pixel detector for digital radiology

NASA Astrophysics Data System (ADS)

Amendolia, S. R.; Bertolucci, E.; Bisogni, M. G.; Bottigli, U.; Ceccopieri, A.; Ciocci, M. A.; Conti, M.; Delogu, P.; Fantacci, M. E.; Maestro, P.; Marzulli, V.; Pernigotti, E.; Romeo, N.; Rosso, V.; Rosso, P.; Stefanini, A.; Stumbo, S.

1999-02-01

A GaAs pixel detector designed for digital mammography, equipped with a 36-channel single photon counting discrete read-out electronics, was tested using a test object developed for quality control purposes in mammography. Each pixel was 200×200 μm 2 large, and 200 μm deep. The choice of GaAs with respect to silicon (largely used in other applications and with a more established technique) has been made because of the much better detection efficiency at mammographic energies, combined with a very good charge collection efficiency achieved thanks to new ohmic contacts. This GaAs detector is able to perform a measurement of low-contrast details, with minimum contrast lower (nearly a factor two) than that typically achievable with standard mammographic film+screen systems in the same conditions of clinical routine. This should allow for an earlier diagnosis of breast tumour masses. Due to these encouraging results, the next step in the evolution of our imaging system based on GaAs detectors has been the development of a VLSI front-end prototype chip (MEDIPIX ) in order to cover a much larger diagnostic area. The chip reads 64×64 channels in single photon counting mode, each one 170 μm wide. Each channel contains also a test input where a signal can be simulated, injecting a known charge through a 16 f F capacitor. Fake signals have been injected via the test input measuring and equalizing minimum thresholds for all the channels. On an average, in most of the performing chips available up to now, we have found that it is possible to set a threshold as low as 1800 electrons with an RMS of 150 electrons (10 standard deviations lower than the 20 keV photon signal roughly equivalent to 4500 electrons). The detector, bump-bonded to the chip, will be tested and a ladder of detectors will be prepared to be able to scan large surface objects.

Rapid, single-step most-probable-number method for enumerating fecal coliforms in effluents from sewage treatment plants

NASA Technical Reports Server (NTRS)

Munoz, E. F.; Silverman, M. P.

1979-01-01

A single-step most-probable-number method for determining the number of fecal coliform bacteria present in sewage treatment plant effluents is discussed. A single growth medium based on that of Reasoner et al. (1976) and consisting of 5.0 gr. proteose peptone, 3.0 gr. yeast extract, 10.0 gr. lactose, 7.5 gr. NaCl, 0.2 gr. sodium lauryl sulfate, and 0.1 gr. sodium desoxycholate per liter is used. The pH is adjusted to 6.5, and samples are incubated at 44.5 deg C. Bacterial growth is detected either by measuring the increase with time in the electrical impedance ratio between the innoculated sample vial and an uninnoculated reference vial or by visual examination for turbidity. Results obtained by the single-step method for chlorinated and unchlorinated effluent samples are in excellent agreement with those obtained by the standard method. It is suggested that in automated treatment plants impedance ratio data could be automatically matched by computer programs with the appropriate dilution factors and most probable number tables already in the computer memory, with the corresponding result displayed as fecal coliforms per 100 ml of effluent.

[The Spectral Analysis of Laser-Induced Plasma in Laser Welding with Various Protecting Conditions].

PubMed

Du, Xiao; Yang, Li-jun; Liu, Tong; Jiao, Jiao; Wang, Hui-chao

2016-01-01

The shielding gas plays an important role in the laser welding process and the variation of the protecting conditions has an obvious effect on the welding quality. This paper studied the influence of the change of protecting conditions on the parameters of laser-induced plasma such as electron temperature and electron density during the laser welding process by designing some experiments of reducing the shielding gas flow rate step by step and simulating the adverse conditions possibly occurring in the actual Nd : YAG laser welding process. The laser-induced plasma was detected by a fiber spectrometer to get the spectral data. So the electron temperature of laser-induced plasma was calculated by using the method of relative spectral intensity and the electron density by the Stark Broadening. The results indicated that the variation of protecting conditions had an important effect on the electron temperature and the electron density in the laser welding. When the protecting conditions were changed, the average electron temperature and the average electron density of the laser-induced plasma would change, so did their fluctuation range. When the weld was in a good protecting condition, the electron temperature, the electron density and their fluctuation were all low. Otherwise, the values would be high. These characteristics would have contribution to monitoring the process of laser welding.

Real-time color image processing for forensic fiber investigations

NASA Astrophysics Data System (ADS)

Paulsson, Nils

1995-09-01

This paper describes a system for automatic fiber debris detection based on color identification. The properties of the system are fast analysis and high selectivity, a necessity when analyzing forensic fiber samples. An ordinary investigation separates the material into well above 100,000 video images to analyze. The system is based on standard techniques such as CCD-camera, motorized sample table, and IBM-compatible PC/AT with add-on-boards for video frame digitalization and stepping motor control as the main parts. It is possible to operate the instrument at full video rate (25 image/s) with aid of the HSI-color system (hue- saturation-intensity) and software optimization. High selectivity is achieved by separating the analysis into several steps. The first step is fast direct color identification of objects in the analyzed video images and the second step analyzes detected objects with a more complex and time consuming stage of the investigation to identify single fiber fragments for subsequent analysis with more selective techniques.

Fast electron transfer through a single molecule natively structured redox protein

NASA Astrophysics Data System (ADS)

Della Pia, Eduardo Antonio; Chi, Qijin; MacDonald, J. Emyr; Ulstrup, Jens; Jones, D. Dafydd; Elliott, Martin

2012-10-01

The electron transfer properties of proteins are normally measured as molecularly averaged ensembles. Through these and related measurements, proteins are widely regarded as macroscopically insulating materials. Using scanning tunnelling microscopy (STM), we present new measurements of the conductance through single-molecules of the electron transfer protein cytochrome b562 in its native conformation, under pseudo-physiological conditions. This is achieved by thiol (SH) linker pairs at opposite ends of the molecule through protein engineering, resulting in defined covalent contact between a gold surface and a platinum-iridium STM tip. Two different orientations of the linkers were examined: a long-axis configuration (SH-LA) and a short-axis configuration (SH-SA). In each case, the molecular conductance could be `gated' through electrochemical control of the heme redox state. Reproducible and remarkably high conductance was observed in this relatively complex electron transfer system, with single-molecule conductance values peaking around 18 nS and 12 nS for the SH-SA and SH-LA cytochrome b562 molecules near zero electrochemical overpotential. This strongly points to the important role of the heme co-factor bound to the natively structured protein. We suggest that the two-step model of protein electron transfer in the STM geometry requires a multi-electron transfer to explain such a high conductance. The model also yields a low value for the reorganisation energy, implying that solvent reorganisation is largely absent.The electron transfer properties of proteins are normally measured as molecularly averaged ensembles. Through these and related measurements, proteins are widely regarded as macroscopically insulating materials. Using scanning tunnelling microscopy (STM), we present new measurements of the conductance through single-molecules of the electron transfer protein cytochrome b562 in its native conformation, under pseudo-physiological conditions. This is achieved by thiol (SH) linker pairs at opposite ends of the molecule through protein engineering, resulting in defined covalent contact between a gold surface and a platinum-iridium STM tip. Two different orientations of the linkers were examined: a long-axis configuration (SH-LA) and a short-axis configuration (SH-SA). In each case, the molecular conductance could be `gated' through electrochemical control of the heme redox state. Reproducible and remarkably high conductance was observed in this relatively complex electron transfer system, with single-molecule conductance values peaking around 18 nS and 12 nS for the SH-SA and SH-LA cytochrome b562 molecules near zero electrochemical overpotential. This strongly points to the important role of the heme co-factor bound to the natively structured protein. We suggest that the two-step model of protein electron transfer in the STM geometry requires a multi-electron transfer to explain such a high conductance. The model also yields a low value for the reorganisation energy, implying that solvent reorganisation is largely absent. Electronic supplementary information (ESI) available: Experimental methods, DNA and protein sequences, additional STM statistical analysis and images, electrochemical data and It-z data analysis. See DOI: 10.1039/c2nr32131a

Carbon Nanotube Devices Engineered by Atomic Force Microscopy

NASA Astrophysics Data System (ADS)

Prisbrey, Landon

This dissertation explores the engineering of carbon nanotube electronic devices using atomic force microscopy (AFM) based techniques. A possible application for such devices is an electronic interface with individual biological molecules. This single molecule biosensing application is explored both experimentally and with computational modeling. Scanning probe microscopy techniques, such as AFM, are ideal to study nanoscale electronics. These techniques employ a probe which is raster scanned above a sample while measuring probe-surface interactions as a function of position. In addition to topographical and electrostatic/magnetic surface characterization, the probe may also be used as a tool to manipulate and engineer at the nanoscale. Nanoelectronic devices built from carbon nanotubes exhibit many exciting properties including one-dimensional electron transport. A natural consequence of onedimensional transport is that a single perturbation along the conduction channel can have extremely large effects on the device's transport characteristics. This property may be exploited to produce electronic sensors with single-molecule resolution. Here we use AFM-based engineering to fabricate atomic-sized transistors from carbon nanotube network devices. This is done through the incorporation of point defects into the carbon nanotube sidewall using voltage pulses from an AFM probe. We find that the incorporation of an oxidative defect leads to a variety of possible electrical signatures including sudden switching events, resonant scattering, and breaking of the symmetry between electron and hole transport. We discuss the relationship between these different electronic signatures and the chemical structure/charge state of the defect. Tunneling through a defect-induced Coulomb barrier is modeled with numerical Verlet integration of Schrodinger's equation and compared with experimental results. Atomic-sized transistors are ideal for single-molecule applications due to their sensitivity to electric fields with very small detection volumes. In this work we demonstrate these devices as single-molecule sensors to detect individual N-(3-Dimethylaminopropyl)- N'-ethylcarbodiimide (EDC) molecules in an aqueous environment. An exciting application of these sensors is to study individual macromolecules participating in biological reactions, or undergoing conformational change. However, it is unknown whether the associated electrostatic signals exceed detection limits. We report calculations which reveal that enzymatic processes, such as substrate binding and internal protein dynamics, are detectable at the single-molecule level using existing atomic-sized transistors. Finally, we demonstrate the use of AFM-based engineering to control the function of nanoelectronic devices without creating a point defect in the sidewall of the nanotube. With a biased AFM probe we write charge patterns on a silicon dioxide surface in close proximity to a carbon nanotube device. The written charge induces image charges in the nearby electronics, and can modulate the Fermi level in a nanotube by +/-1 eV. We use this technique to induce a spatially controlled doping charge pattern in the conduction channel, and thereby reconfigure a field-effect transistor into a pn junction. Other simple charge patterns could be used to create other devices. The doping charge persists for days and can be erased and rewritten, offering a new tool for prototyping nanodevices and optimizing electrostatic doping profiles.

Inkjet printing of single-crystal films.

PubMed

Minemawari, Hiromi; Yamada, Toshikazu; Matsui, Hiroyuki; Tsutsumi, Jun'ya; Haas, Simon; Chiba, Ryosuke; Kumai, Reiji; Hasegawa, Tatsuo

2011-07-13

The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. 'Printed electronics' is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials. However, because of the strong self-organizing tendency of the deposited materials, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid-air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C(8)-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4 cm(2) V(-1) s(-1). This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications.

Targeted next generation sequencing for the detection of ciprofloxacin resistance markers using molecular inversion probes

DTIC Science & Technology

2016-07-06

1 Targeted next-generation sequencing for the detection of ciprofloxacin resistance markers using molecular inversion probes Christopher P...development and evaluation of a panel of 44 single-stranded molecular inversion probes (MIPs) coupled to next-generation sequencing (NGS) for the...padlock and molecular inversion probes as upfront enrichment steps for use with NGS showed the specificity and multiplexability of these techniques

Protein structure determination by single-wavelength anomalous diffraction phasing of X-ray free-electron laser data

DOE PAGES

Nass, Karol; Meinhart, Anton; Barends, Thomas R. M.; ...

2016-03-09

Serial femtosecond crystallography (SFX) at X-ray free-electron lasers (XFELs) offers unprecedented possibilities for macromolecular structure determination of systems that are prone to radiation damage. However, phasing XFEL data de novo is complicated by the inherent inaccuracy of SFX data, and only a few successful examples, mostly based on exceedingly strong anomalous or isomorphous difference signals, have been reported. Here, it is shown that SFX data from thaumatin microcrystals can be successfully phased using only the weak anomalous scattering from the endogenous S atoms. Furthermore, a step-by-step investigation is presented of the particular problems of SAD phasing of SFX data, analysingmore » data from a derivative with a strong anomalous signal as well as the weak signal from endogenous S atoms.« less

A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

PubMed Central

Josefík, František; Svobodová, Markéta; Bertolasi, Valerio

2013-01-01

Summary Easily obtainable cyclic enaminones (piperidin-2-ylidenealkanones) can be transformed into substituted bicyclic pyridazinium tetrafluoroborates upon treatment with corresponding diazonium salts. The transformation can be performed either in a one-pot way or in a two-step process with the isolation of single azo-coupled enaminone as the intermediate. The former method is superior. Under the optimized conditions, a number of pyridazinium salts substituted with both electron-donating and electron-withdrawing substituents was easily synthesized. A mechanism of the formation of the pyridazinium salts is suggested. A partial drawback is the possibility of the formation of a mixture of products when using a different diazonium salt in each step due to a reversibility of the azo coupling. This can be suppressed by using a more reactive diazonium salt before a less reactive one. PMID:23946844

A biosensor for hydrogen peroxide detection based on electronic properties of carbon nanotubes

NASA Astrophysics Data System (ADS)

Majidi, Roya

2013-01-01

Density functional theory has been used to study the effect of hydrogen peroxide on the electronic properties of single walled carbon nanotubes. The metallic and semiconducting carbon nanotubes have been considered in the presence of different number of hydrogen peroxide. The results indicate that hydrogen peroxide has no significant effect on the metallic nanotube and these nanotubes remain to be metallic. In contrast, the electronic properties of the semiconducting nanotubes are so sensitive to hydrogen peroxide. The energy band gap of these nanotubes is decreased by increasing the number of hydrogen peroxide. The electronic sensivity of the carbon nanotubes to hydrogen peroxide opens new insights into developing biosensors based on the single walled carbon nanotubes.

Realization of a Cascaded Quantum System: Heralded Absorption of a Single Photon Qubit by a Single-Electron Charged Quantum Dot.

PubMed

Delteil, Aymeric; Sun, Zhe; Fält, Stefan; Imamoğlu, Atac

2017-04-28

Photonic losses pose a major limitation for the implementation of a quantum state transfer between nodes of a quantum network. A measurement that heralds a successful transfer without revealing any information about the qubit may alleviate this limitation. Here, we demonstrate the heralded absorption of a single photonic qubit, generated by a single neutral quantum dot, by a single-electron charged quantum dot that is located 5 m away. The transfer of quantum information to the spin degree of freedom takes place upon the emission of a photon; for a properly chosen or prepared quantum dot, the detection of this photon yields no information about the qubit. We show that this process can be combined with local operations optically performed on the destination node by measuring classical correlations between the absorbed photon color and the final state of the electron spin. Our work suggests alternative avenues for the realization of quantum information protocols based on cascaded quantum systems.

Iron single crystal growth from a lithium-rich melt

NASA Astrophysics Data System (ADS)

Fix, M.; Schumann, H.; Jantz, S. G.; Breitner, F. A.; Leineweber, A.; Jesche, A.

2018-03-01

α -Fe single crystals of rhombic dodecahedral habit were grown from a Li84N12Fe∼3 melt. Crystals of several millimeter along a side form at temperatures around T ≈ 800 ° C. Upon further cooling the growth competes with the formation of Fe-doped Li3N. The b.c.c. structure and good sample quality of α -Fe single crystals were confirmed by X-ray and electron diffraction as well as magnetization measurements and chemical analysis. A nitrogen concentration of 90 ppm was detected by means of carrier gas hot extraction. Scanning electron microscopy did not reveal any sign of iron nitride precipitates.

Applied Genomics: Data Mining Reveals Species-Specific Malaria Diagnostic Targets More Sensitive than 18S rRNA▿†‡

PubMed Central

Demas, Allison; Oberstaller, Jenna; DeBarry, Jeremy; Lucchi, Naomi W.; Srinivasamoorthy, Ganesh; Sumari, Deborah; Kabanywanyi, Abdunoor M.; Villegas, Leopoldo; Escalante, Ananias A.; Kachur, S. Patrick; Barnwell, John W.; Peterson, David S.; Udhayakumar, Venkatachalam; Kissinger, Jessica C.

2011-01-01

Accurate and rapid diagnosis of malaria infections is crucial for implementing species-appropriate treatment and saving lives. Molecular diagnostic tools are the most accurate and sensitive method of detecting Plasmodium, differentiating between Plasmodium species, and detecting subclinical infections. Despite available whole-genome sequence data for Plasmodium falciparum and P. vivax, the majority of PCR-based methods still rely on the 18S rRNA gene targets. Historically, this gene has served as the best target for diagnostic assays. However, it is limited in its ability to detect mixed infections in multiplex assay platforms without the use of nested PCR. New diagnostic targets are needed. Ideal targets will be species specific, highly sensitive, and amenable to both single-step and multiplex PCRs. We have mined the genomes of P. falciparum and P. vivax to identify species-specific, repetitive sequences that serve as new PCR targets for the detection of malaria. We show that these targets (Pvr47 and Pfr364) exist in 14 to 41 copies and are more sensitive than 18S rRNA when utilized in a single-step PCR. Parasites are routinely detected at levels of 1 to 10 parasites/μl. The reaction can be multiplexed to detect both species in a single reaction. We have examined 7 P. falciparum strains and 91 P. falciparum clinical isolates from Tanzania and 10 P. vivax strains and 96 P. vivax clinical isolates from Venezuela, and we have verified a sensitivity and specificity of ∼100% for both targets compared with a nested 18S rRNA approach. We show that bioinformatics approaches can be successfully applied to identify novel diagnostic targets and improve molecular methods for pathogen detection. These novel targets provide a powerful alternative molecular diagnostic method for the detection of P. falciparum and P. vivax in conventional or multiplex PCR platforms. PMID:21525225

Infrared-enhanced TV for fire detection

NASA Technical Reports Server (NTRS)

Hall, J. R.

1978-01-01

Closed-circuit television is superior to conventional smoke or heat sensors for detecting fires in large open spaces. Single TV camera scans entire area, whereas many conventional sensors and maze of interconnecting wiring might be required to get same coverage. Camera is monitored by person who would trip alarm if fire were detected, or electronic circuitry could process camera signal for fully-automatic alarm system.

One-step analysis of DNA/chitosan complexes by field-flow fractionation reveals particle size and free chitosan content.

PubMed

Ma, Pei Lian; Buschmann, Michael D; Winnik, Françoise M

2010-03-08

The composition of samples obtained upon complexation of DNA with chitosan was analyzed by asymmetrical flow field flow fractionation (AF4) with online UV-visible, multiangle light scattering (MALS), and dynamic light scattering (DLS) detectors. A chitosan labeled with rhodamine B to facilitate UV-vis detection of the polycation was complexed with DNA under conditions commonly used for transfection (chitosan glucosamine to DNA phosphate molar ratio of 5). AF4 analysis revealed that 73% of the chitosan-rhodamine remained free in the dispersion and that the DNA/chitosan complexes had a broad size distribution ranging from 20 to 160 nm in hydrodynamic radius. The accuracy of the data was assessed by comparison with data from batch-mode DLS and scanning electron microscopy. The AF4 combined with DLS allowed the characterization of small particles that were not detected by conventional batch-mode DLS. The AF4 analysis will prove to be an important tool in the field of gene therapy because it readily provides, in a single measurement, three important physicochemical parameters of the complexes: the amount of unbound polycation, the hydrodynamic size of the complexes, and their size distribution.

Bidirectional RNN for Medical Event Detection in Electronic Health Records.

PubMed

Jagannatha, Abhyuday N; Yu, Hong

2016-06-01

Sequence labeling for extraction of medical events and their attributes from unstructured text in Electronic Health Record (EHR) notes is a key step towards semantic understanding of EHRs. It has important applications in health informatics including pharmacovigilance and drug surveillance. The state of the art supervised machine learning models in this domain are based on Conditional Random Fields (CRFs) with features calculated from fixed context windows. In this application, we explored recurrent neural network frameworks and show that they significantly out-performed the CRF models.

Frequency bandwidth extension by use of multiple Zeeman field offsets for electron spin-echo EPR oxygen imaging of large objects

PubMed Central

Seifi, Payam; Epel, Boris; Sundramoorthy, Subramanian V.; Mailer, Colin; Halpern, Howard J.

2011-01-01

Purpose: Electron spin-echo (ESE) oxygen imaging is a new and evolving electron paramagnetic resonance (EPR) imaging (EPRI) modality that is useful for physiological in vivo applications, such as EPR oxygen imaging (EPROI), with potential application to imaging of multicentimeter objects as large as human tumors. A present limitation on the size of the object to be imaged at a given resolution is the frequency bandwidth of the system, since the location is encoded as a frequency offset in ESE imaging. The authors’ aim in this study was to demonstrate the object size advantage of the multioffset bandwidth extension technique.Methods: The multiple-stepped Zeeman field offset (or simply multi-B) technique was used for imaging of an 8.5-cm-long phantom containing a narrow single line triaryl methyl compound (trityl) solution at the 250 MHz imaging frequency. The image is compared to a standard single-field ESE image of the same phantom.Results: For the phantom used in this study, transverse relaxation (T2e) electron spin-echo (ESE) images from multi-B acquisition are more uniform, contain less prominent artifacts, and have a better signal to noise ratio (SNR) compared to single-field T2e images.Conclusions: The multi-B method is suitable for imaging of samples whose physical size restricts the applicability of the conventional single-field ESE imaging technique. PMID:21815379

Method and apparatus for detecting timing errors in a system oscillator

DOEpatents

Gliebe, Ronald J.; Kramer, William R.

1993-01-01

A method of detecting timing errors in a system oscillator for an electronic device, such as a power supply, includes the step of comparing a system oscillator signal with a delayed generated signal and generating a signal representative of the timing error when the system oscillator signal is not identical to the delayed signal. An LED indicates to an operator that a timing error has occurred. A hardware circuit implements the above-identified method.

Conservative algorithms for non-Maxwellian plasma kinetics

DOE PAGES

Le, Hai P.; Cambier, Jean -Luc

2017-12-08

Here, we present a numerical model and a set of conservative algorithms for Non-Maxwellian plasma kinetics with inelastic collisions. These algorithms self-consistently solve for the time evolution of an isotropic electron energy distribution function interacting with an atomic state distribution function of an arbitrary number of levels through collisional excitation, deexcitation, as well as ionization and recombination. Electron-electron collisions, responsible for thermalization of the electron distribution, are also included in the model. The proposed algorithms guarantee mass/charge and energy conservation in a single step, and is applied to the case of non-uniform gridding of the energy axis in the phasemore » space of the electron distribution function. Numerical test cases are shown to demonstrate the accuracy of the method and its conservation properties.« less

Separation and counting of single molecules through nanofluidics, programmable electrophoresis, and nanoelectrode-gated tunneling and dielectric detection

DOEpatents

Lee, James W.; Thundat, Thomas G.

2006-04-25

An apparatus for carrying out the separation, detection, and/or counting of single molecules at nanometer scale. Molecular separation is achieved by driving single molecules through a microfluidic or nanofluidic medium using programmable and coordinated electric fields. In various embodiments, the fluidic medium is a strip of hydrophilic material on nonconductive hydrophobic surface, a trough produced by parallel strips of hydrophobic nonconductive material on a hydrophilic base, or a covered passageway produced by parallel strips of hydrophobic nonconductive material on a hydrophilic base together with a nonconductive cover on the parallel strips of hydrophobic nonconductive material. The molecules are detected and counted using nanoelectrode-gated electron tunneling methods, dielectric monitoring, and other methods.

Mechanism of Nitrogenase H 2 Formation by Metal-Hydride Protonation Probed by Mediated Electrocatalysis and H/D Isotope Effects

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

Khadka, Nimesh; Milton, Ross D.; Shaw, Sudipta

Nitrogenase catalyzes the reduction of dinitrogen (N2) to ammonia (NH3) with obligatory reduction of protons (H+) to dihydrogen (H2) through a mechanism involving reductive elimination of two [Fe-H-Fe] bridging hydrides at its active site FeMo-cofactor. The overall rate-limiting step is associated with ATP-driven electron delivery from Fe protein, precluding isotope effect measurements on substrate reduction steps. Here, we use mediated bioelectrocatalysis to drive electron delivery to MoFe protein without Fe protein and ATP hydrolysis, thereby eliminating the normal rate-limiting step. The ratio of catalytic current in mixtures of H2O and D2O, the proton inventory, changes linearly with the D2O/H2O ratio,more » revealing that a single H/D is involved in the rate limiting step. Kinetic models, along with measurements that vary the electron/proton delivery rate and use different substrates, reveal that the rate-limiting step under these conditions is the H2 formation reaction. Altering the chemical environment around the active site FeMo-cofactor in the MoFe protein either by substituting nearby amino acids or transferring the isolated FeMo-cofactor into a different peptide matrix, changes the net isotope effect, but the proton inventory plot remains linear, consistent with an unchanging rate-limiting step. Density functional theory predicts a transition state for H2 formation where the proton from S-H+ moves to the hydride in Fe-H-, predicting the number and magnitude of the observed H/D isotope effect. This study not only reveals the mechanism of H2 formation, but also illustrates a strategy for mechanistic study that can be applied to other enzymes and to biomimetic complexes.« less

FPGA-Based, Self-Checking, Fault-Tolerant Computers

NASA Technical Reports Server (NTRS)

Some, Raphael; Rennels, David

2004-01-01

A proposed computer architecture would exploit the capabilities of commercially available field-programmable gate arrays (FPGAs) to enable computers to detect and recover from bit errors. The main purpose of the proposed architecture is to enable fault-tolerant computing in the presence of single-event upsets (SEUs). [An SEU is a spurious bit flip (also called a soft error) caused by a single impact of ionizing radiation.] The architecture would also enable recovery from some soft errors caused by electrical transients and, to some extent, from intermittent and permanent (hard) errors caused by aging of electronic components. A typical FPGA of the current generation contains one or more complete processor cores, memories, and highspeed serial input/output (I/O) channels, making it possible to shrink a board-level processor node to a single integrated-circuit chip. Custom, highly efficient microcontrollers, general-purpose computers, custom I/O processors, and signal processors can be rapidly and efficiently implemented by use of FPGAs. Unfortunately, FPGAs are susceptible to SEUs. Prior efforts to mitigate the effects of SEUs have yielded solutions that degrade performance of the system and require support from external hardware and software. In comparison with other fault-tolerant- computing architectures (e.g., triple modular redundancy), the proposed architecture could be implemented with less circuitry and lower power demand. Moreover, the fault-tolerant computing functions would require only minimal support from circuitry outside the central processing units (CPUs) of computers, would not require any software support, and would be largely transparent to software and to other computer hardware. There would be two types of modules: a self-checking processor module and a memory system (see figure). The self-checking processor module would be implemented on a single FPGA and would be capable of detecting its own internal errors. It would contain two CPUs executing identical programs in lock step, with comparison of their outputs to detect errors. It would also contain various cache local memory circuits, communication circuits, and configurable special-purpose processors that would use self-checking checkers. (The basic principle of the self-checking checker method is to utilize logic circuitry that generates error signals whenever there is an error in either the checker or the circuit being checked.) The memory system would comprise a main memory and a hardware-controlled check-pointing system (CPS) based on a buffer memory denoted the recovery cache. The main memory would contain random-access memory (RAM) chips and FPGAs that would, in addition to everything else, implement double-error-detecting and single-error-correcting memory functions to enable recovery from single-bit errors.

Demonstration of Single-Barium-Ion Sensitivity for Neutrinoless Double-Beta Decay Using Single-Molecule Fluorescence Imaging.

PubMed

McDonald, A D; Jones, B J P; Nygren, D R; Adams, C; Álvarez, V; Azevedo, C D R; Benlloch-Rodríguez, J M; Borges, F I G M; Botas, A; Cárcel, S; Carrión, J V; Cebrián, S; Conde, C A N; Díaz, J; Diesburg, M; Escada, J; Esteve, R; Felkai, R; Fernandes, L M P; Ferrario, P; Ferreira, A L; Freitas, E D C; Goldschmidt, A; Gómez-Cadenas, J J; González-Díaz, D; Gutiérrez, R M; Guenette, R; Hafidi, K; Hauptman, J; Henriques, C A O; Hernandez, A I; Hernando Morata, J A; Herrero, V; Johnston, S; Labarga, L; Laing, A; Lebrun, P; Liubarsky, I; López-March, N; Losada, M; Martín-Albo, J; Martínez-Lema, G; Martínez, A; Monrabal, F; Monteiro, C M B; Mora, F J; Moutinho, L M; Muñoz Vidal, J; Musti, M; Nebot-Guinot, M; Novella, P; Palmeiro, B; Para, A; Pérez, J; Querol, M; Repond, J; Renner, J; Riordan, S; Ripoll, L; Rodríguez, J; Rogers, L; Santos, F P; Dos Santos, J M F; Simón, A; Sofka, C; Sorel, M; Stiegler, T; Toledo, J F; Torrent, J; Tsamalaidze, Z; Veloso, J F C A; Webb, R; White, J T; Yahlali, N

2018-03-30

A new method to tag the barium daughter in the double-beta decay of ^{136}Xe is reported. Using the technique of single molecule fluorescent imaging (SMFI), individual barium dication (Ba^{++}) resolution at a transparent scanning surface is demonstrated. A single-step photobleach confirms the single ion interpretation. Individual ions are localized with superresolution (∼2  nm), and detected with a statistical significance of 12.9σ over backgrounds. This lays the foundation for a new and potentially background-free neutrinoless double-beta decay technology, based on SMFI coupled to high pressure xenon gas time projection chambers.

Demonstration of Single-Barium-Ion Sensitivity for Neutrinoless Double-Beta Decay Using Single-Molecule Fluorescence Imaging

NASA Astrophysics Data System (ADS)

McDonald, A. D.; Jones, B. J. P.; Nygren, D. R.; Adams, C.; Álvarez, V.; Azevedo, C. D. R.; Benlloch-Rodríguez, J. M.; Borges, F. I. G. M.; Botas, A.; Cárcel, S.; Carrión, J. V.; Cebrián, S.; Conde, C. A. N.; Díaz, J.; Diesburg, M.; Escada, J.; Esteve, R.; Felkai, R.; Fernandes, L. M. P.; Ferrario, P.; Ferreira, A. L.; Freitas, E. D. C.; Goldschmidt, A.; Gómez-Cadenas, J. J.; González-Díaz, D.; Gutiérrez, R. M.; Guenette, R.; Hafidi, K.; Hauptman, J.; Henriques, C. A. O.; Hernandez, A. I.; Hernando Morata, J. A.; Herrero, V.; Johnston, S.; Labarga, L.; Laing, A.; Lebrun, P.; Liubarsky, I.; López-March, N.; Losada, M.; Martín-Albo, J.; Martínez-Lema, G.; Martínez, A.; Monrabal, F.; Monteiro, C. M. B.; Mora, F. J.; Moutinho, L. M.; Muñoz Vidal, J.; Musti, M.; Nebot-Guinot, M.; Novella, P.; Palmeiro, B.; Para, A.; Pérez, J.; Querol, M.; Repond, J.; Renner, J.; Riordan, S.; Ripoll, L.; Rodríguez, J.; Rogers, L.; Santos, F. P.; dos Santos, J. M. F.; Simón, A.; Sofka, C.; Sorel, M.; Stiegler, T.; Toledo, J. F.; Torrent, J.; Tsamalaidze, Z.; Veloso, J. F. C. A.; Webb, R.; White, J. T.; Yahlali, N.; NEXT Collaboration

2018-03-01

A new method to tag the barium daughter in the double-beta decay of Xe 136 is reported. Using the technique of single molecule fluorescent imaging (SMFI), individual barium dication (Ba++ ) resolution at a transparent scanning surface is demonstrated. A single-step photobleach confirms the single ion interpretation. Individual ions are localized with superresolution (˜2 nm ), and detected with a statistical significance of 12.9 σ over backgrounds. This lays the foundation for a new and potentially background-free neutrinoless double-beta decay technology, based on SMFI coupled to high pressure xenon gas time projection chambers.

Recent advances in superconducting nanowire single photon detectors for single-photon imaging

NASA Astrophysics Data System (ADS)

Verma, V. B.; Allman, M. S.; Stevens, M.; Gerrits, T.; Horansky, R. D.; Lita, A. E.; Marsili, F.; Beyer, A.; Shaw, M. D.; Stern, J. A.; Mirin, R. P.; Nam, S. W.

2016-05-01

We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array, as well as characterization measurements are discussed.

Solid-phase microfibers based on polyethylene glycol modified single-walled carbon nanotubes for the determination of chlorinated organic carriers in textiles.

PubMed

Zhang, Wei-Ya; Sun, Yin; Wang, Cheng-Ming; Wu, Cai-Ying

2011-09-01

Based on polyethylene glycol modified single-walled carbon nanotubes, a novel sol-gel fiber coating was prepared and applied to the headspace microextraction of chlorinated organic carriers (COCs) in textiles by gas chromatography-electron capture detection. The preparation of polyethylene glycol modified single-walled carbon nanotubes and the sol-gel fiber coating process was stated and confirmed by infrared spectra, Raman spectroscopy, and scanning electron microscopy. Several parameters affecting headspace microextraction, including extraction temperature, extraction time, salting-out effect, and desorption time, were optimized by detecting 11 COCs in simulative sweat samples. Compared with the commercial solid-phase microextraction fibers, the sol-gel polyethylene glycol modified single-walled carbon nanotubes fiber showed higher extraction efficiency, better thermal stability, and longer life span. The method detection limits for COCs were in the range from 0.02 to 7.5 ng L(-1) (S/N = 3). The linearity of the developed method varied from 0.001 to 50 μg L(-1) for all analytes, with coefficients of correlation greater than 0.974. The developed method was successfully applied to the analysis of trace COCs in textiles, the recoveries of the analytes indicated that the developed method was considerably useful for the determination of COCs in ecological textile samples.

Room-temperature ultrafast nonlinear spectroscopy of a single molecule

NASA Astrophysics Data System (ADS)

Liebel, Matz; Toninelli, Costanza; van Hulst, Niek F.

2018-01-01

Single-molecule spectroscopy aims to unveil often hidden but potentially very important contributions of single entities to a system's ensemble response. Albeit contributing tremendously to our ever growing understanding of molecular processes, the fundamental question of temporal evolution, or change, has thus far been inaccessible, thus painting a static picture of a dynamic world. Here, we finally resolve this dilemma by performing ultrafast time-resolved transient spectroscopy on a single molecule. By tracing the femtosecond evolution of excited electronic state spectra of single molecules over hundreds of nanometres of bandwidth at room temperature, we reveal their nonlinear ultrafast response in an effective three-pulse scheme with fluorescence detection. A first excitation pulse is followed by a phase-locked de-excitation pulse pair, providing spectral encoding with 25 fs temporal resolution. This experimental realization of true single-molecule transient spectroscopy demonstrates that two-dimensional electronic spectroscopy of single molecules is experimentally within reach.

A Survey of the Use of Iterative Reconstruction Algorithms in Electron Microscopy

PubMed Central

Otón, J.; Vilas, J. L.; Kazemi, M.; Melero, R.; del Caño, L.; Cuenca, J.; Conesa, P.; Gómez-Blanco, J.; Marabini, R.; Carazo, J. M.

2017-01-01

One of the key steps in Electron Microscopy is the tomographic reconstruction of a three-dimensional (3D) map of the specimen being studied from a set of two-dimensional (2D) projections acquired at the microscope. This tomographic reconstruction may be performed with different reconstruction algorithms that can be grouped into several large families: direct Fourier inversion methods, back-projection methods, Radon methods, or iterative algorithms. In this review, we focus on the latter family of algorithms, explaining the mathematical rationale behind the different algorithms in this family as they have been introduced in the field of Electron Microscopy. We cover their use in Single Particle Analysis (SPA) as well as in Electron Tomography (ET). PMID:29312997

Tracking the ultrafast motion of a single molecule by femtosecond orbital imaging

PubMed Central

Yu, Ping; Repp, Jascha; Huber, Rupert

2017-01-01

Watching a single molecule move on its intrinsic time scale—one of the central goals of modern nanoscience—calls for measurements that combine ultrafast temporal resolution1–8 with atomic spatial resolution9–30. Steady-state experiments achieve the requisite spatial resolution, as illustrated by direct imaging of individual molecular orbitals using scanning tunnelling microscopy9–11 or the acquisition of tip-enhanced Raman and luminescence spectra with sub-molecular resolution27–29. But tracking the dynamics of a single molecule directly in the time domain faces the challenge that single-molecule excitations need to be confined to an ultrashort time window. A first step towards overcoming this challenge has combined scanning tunnelling microscopy with so-called ‘lightwave electronics”1–8, which uses the oscillating carrier wave of tailored light pulses to directly manipulate electronic motion on time scales faster even than that of a single cycle of light. Here we use such ultrafast terahertz scanning tunnelling microscopy to access a state-selective tunnelling regime, where the peak of a terahertz electric-field waveform transiently opens an otherwise forbidden tunnelling channel through a single molecular state and thereby removes a single electron from an individual pentacene molecule’s highest occupied molecular orbital within a time window shorter than one oscillation cycle of the terahertz wave. We exploit this effect to record ~100 fs snapshot images of the structure of the orbital involved, and to reveal through pump-probe measurements coherent molecular vibrations at terahertz frequencies directly in the time domain and with sub-angstrom spatial resolution. We anticipate that the combination of lightwave electronics1–8 and atomic resolution of our approach will open the door to controlling electronic motion inside individual molecules at optical clock rates. PMID:27830788

Virus Particle Detection by Convolutional Neural Network in Transmission Electron Microscopy Images.

PubMed

Ito, Eisuke; Sato, Takaaki; Sano, Daisuke; Utagawa, Etsuko; Kato, Tsuyoshi

2018-06-01

A new computational method for the detection of virus particles in transmission electron microscopy (TEM) images is presented. Our approach is to use a convolutional neural network that transforms a TEM image to a probabilistic map that indicates where virus particles exist in the image. Our proposed approach automatically and simultaneously learns both discriminative features and classifier for virus particle detection by machine learning, in contrast to existing methods that are based on handcrafted features that yield many false positives and require several postprocessing steps. The detection performance of the proposed method was assessed against a dataset of TEM images containing feline calicivirus particles and compared with several existing detection methods, and the state-of-the-art performance of the developed method for detecting virus was demonstrated. Since our method is based on supervised learning that requires both the input images and their corresponding annotations, it is basically used for detection of already-known viruses. However, the method is highly flexible, and the convolutional networks can adapt themselves to any virus particles by learning automatically from an annotated dataset.

Reaching the quantum limit of sensitivity in electron spin resonance

DOE PAGES

Bienfait, A.; Pla, J. J.; Kubo, Y.; ...

2015-12-14

The detection and characterization of paramagnetic species by electron spin resonance (ESR) spectroscopy is widely used throughout chemistry, biology and materials science, from in vivo imaging to distance measurements in spin-labelled proteins. ESR relies on the inductive detection of microwave signals emitted by the spins into a coupled microwave resonator during their Larmor precession. However, such signals can be very small, prohibiting the application of ESR at the nanoscale (for example, at the single-cell level or on individual nanoparticles). Here in this work, using a Josephson parametric microwave amplifier combined with high-quality-factor superconducting microresonators cooled at millikelvin temperatures, we improvemore » the state-of-the-art sensitivity of inductive ESR detection by nearly four orders of magnitude. We demonstrate the detection of 1,700 bismuth donor spins in silicon within a single Hahn echo with unit signal-to-noise ratio, reduced to 150 spins by averaging a single Carr-Purcell-Meiboom-Gill sequence. This unprecedented sensitivity reaches the limit set by quantum fluctuations of the electromagnetic field instead of thermal or technical noise, which constitutes a novel regime for magnetic resonance. In conclusion, the detection volume of our resonator is ~0.02nl, and our approach can be readily scaled down further to improve sensitivity, providing a new versatile toolbox for ESR at the nanoscale.« less

An iterative three-dimensional electron density imaging algorithm using uncollimated compton scattered x rays from a polyenergetic primary pencil beam.

PubMed

Van Uytven, Eric; Pistorius, Stephen; Gordon, Richard

2007-01-01

X-ray film-screen mammography is currently the gold standard for detecting breast cancer. However, one disadvantage is that it projects a three-dimensional (3D) object onto a two-dimensional (2D) image, reducing contrast between small lesions and layers of normal tissue. Another limitation is its reduced sensitivity in women with mammographically dense breasts. Computed tomography (CT) produces a 3D image yet has had a limited role in mammography due to its relatively high dose, low resolution, and low contrast. As a first step towards implementing quantitative 3D mammography, which may improve the ability to detect and specify breast tumors, we have developed an analytical technique that can use Compton scatter to obtain 3D information of an object from a single projection. Imaging material with a pencil beam of polychromatic x rays produces a characteristic scattered photon spectrum at each point on the detector plane. A comparable distribution may be calculated using a known incident x-ray energy spectrum, beam shape, and an initial estimate of the object's 3D mass attenuation and electron density. Our iterative minimization algorithm changes the initially arbitrary electron density voxel matrix to reduce regular differences between the analytically predicted and experimentally measured spectra at each point on the detector plane. The simulated electron density converges to that of the object as the differences are minimized. The reconstruction algorithm has been validated using simulated data produced by the EGSnrc Monte Carlo code system. We applied the imaging algorithm to a cylindrically symmetric breast tissue phantom containing multiple inhomogeneities. A preliminary ROC analysis scores greater than 0.96, which indicate that under the described simplifying conditions, this approach shows promise in identifying and localizing inhomogeneities which simulate 0.5 mm calcifications with an image voxel resolution of 0.25 cm and at a dose comparable to mammography.

One-Step Synthesis of Water-Soluble MoS2 Quantum Dots via a Hydrothermal Method as a Fluorescent Probe for Hyaluronidase Detection.

PubMed

Gu, Wei; Yan, Yinghan; Zhang, Cuiling; Ding, Caiping; Xian, Yuezhong

2016-05-11

In this work, a bottom-up strategy is developed to synthesize water-soluble molybdenum disulfide quantum dots (MoS2 QDs) through a simple, one-step hydrothermal method using ammonium tetrathiomolybdate [(NH4)2MoS4] as the precursor and hydrazine hydrate as the reducing agent. The as-synthesized MoS2 QDs are few-layered with a narrow size distribution, and the average diameter is about 2.8 nm. The resultant QDs show excitation-dependent blue fluorescence due to the polydispersity of the QDs. Moreover, the fluorescence can be quenched by hyaluronic acid (HA)-functionalized gold nanoparticles through a photoinduced electron-transfer mechanism. Hyaluronidase (HAase), an endoglucosidase, can cleave HA into proangiogenic fragments and lead to the aggregation of gold nanoparticles. As a result, the electron transfer is blocked and fluorescence is recovered. On the basis of this principle, a novel fluorescence sensor for HAase is developed with a linear range from 1 to 50 U/mL and a detection limit of 0.7 U/mL.

Plasmonic Optical Fiber Sensor Based on Double Step Growth of Gold Nano-Islands

PubMed Central

Vasconcelos, Helena

2018-01-01

It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO2) substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS) and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of ~60 nm/RIU was calculated, for the repeated dewetting, a value of ~186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency. PMID:29677108

Plasmonic Optical Fiber Sensor Based on Double Step Growth of Gold Nano-Islands.

PubMed

de Almeida, José M M M; Vasconcelos, Helena; Jorge, Pedro A S; Coelho, Luis

2018-04-20

It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO₂) substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS) and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of ~60 nm/RIU was calculated, for the repeated dewetting, a value of ~186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency.

The fifth electron in the fully reduced caa(3) from Thermus thermophilus is competent in proton pumping.

PubMed

Siletsky, Sergey A; Belevich, Ilya; Soulimane, Tewfik; Verkhovsky, Michael I; Wikström, Mårten

2013-01-01

The time-resolved kinetics of membrane potential generation coupled to oxidation of the fully reduced (five-electron) caa(3) cytochrome oxidase from Thermus thermophilus by oxygen was studied in a single-turnover regime. In order to calibrate the number of charges that move across the vesicle membrane in the different reaction steps, the reverse electron transfer from heme a(3) to heme a and further to the cytochrome c/Cu(A) has been resolved upon photodissociation of CO from the mixed valence enzyme in the absence of oxygen. The reverse electron transfer from heme a(3) to heme a and further to the cytochrome c/Cu(A) pair is resolved as a single transition with τ~40 μs. In the reaction of the fully reduced cytochrome caa(3) with oxygen, the first electrogenic phase (τ~30 μs) is linked to OO bond cleavage and generation of the P(R) state. The next electrogenic component (τ~50 μs) is associated with the P(R)→F transition and together with the previous reaction step it is coupled to translocation of about two charges across the membrane. The three subsequent electrogenic phases, with time constants of ~0.25 ms, ~1.4 ms and ~4 ms, are linked to the conversion of the binuclear center through the F→O(H)→E(H) transitions, and result in additional transfer of four charges through the membrane dielectric. This indicates that the delivery of the fifth electron from heme c to the binuclear center is coupled to pumping of an additional proton across the membrane. Copyright © 2012 Elsevier B.V. All rights reserved.

Single turnover studies of oxidative halophenol dehalogenation by horseradish peroxidase reveal a mechanism involving two consecutive one electron steps: toward a functional halophenol bioremediation catalyst.

PubMed

Sumithran, Suganya; Sono, Masanori; Raner, Gregory M; Dawson, John H

2012-12-01

Horseradish peroxidase (HRP) catalyzes the oxidative para-dechlorination of the environmental pollutant/carcinogen 2,4,6-trichlorophenol (2,4,6-TCP). A possible mechanism for this reaction is a direct oxygen atom transfer from HRP compound I (HRP I) to trichlorophenol to generate 2,6-dichloro 1,4-benzoquinone, a two-electron transfer process. An alternative mechanism involves two consecutive one-electron transfer steps in which HRP I is reduced to compound II (HRP II) and then to the ferric enzyme as first proposed by Wiese et al. [F.W. Wiese, H.C. Chang, R.V. Lloyd, J.P. Freeman, V.M. Samokyszyn, Arch. Environ. Contam. Toxicol. 34 (1998) 217-222]. To probe the mechanism of oxidative halophenol dehalogenation, the reactions between 2,4,6-TCP and HRP compounds I or II have been investigated under single turnover conditions (i.e., without excess H(2)O(2)) using rapid scan stopped-flow spectroscopy. Addition of 2,4,6-TCP to HRP I leads rapidly to HRP II and then more slowly to the ferric resting state, consistent with a mechanism involving two consecutive one-electron oxidations of the substrate via a phenoxy radical intermediate. HRP II can also directly dechlorinate 2,4,6-TCP as judged by rapid scan stopped-flow and mass spectrometry. This observation is particularly significant since HRP II can only carry out one-electron oxidations. A more detailed understanding of the mechanism of oxidative halophenol dehalogenation will facilitate the use of HRP as a halophenol bioremediation catalyst. Copyright © 2012 Elsevier Inc. All rights reserved.

Hybrid Electron Microscopy Normal Mode Analysis graphical interface and protocol.

PubMed

Sorzano, Carlos Oscar S; de la Rosa-Trevín, José Miguel; Tama, Florence; Jonić, Slavica

2014-11-01

This article presents an integral graphical interface to the Hybrid Electron Microscopy Normal Mode Analysis (HEMNMA) approach that was developed for capturing continuous motions of large macromolecular complexes from single-particle EM images. HEMNMA was shown to be a good approach to analyze multiple conformations of a macromolecular complex but it could not be widely used in the EM field due to a lack of an integral interface. In particular, its use required switching among different software sources as well as selecting modes for image analysis was difficult without the graphical interface. The graphical interface was thus developed to simplify the practical use of HEMNMA. It is implemented in the open-source software package Xmipp 3.1 (http://xmipp.cnb.csic.es) and only a small part of it relies on MATLAB that is accessible through the main interface. Such integration provides the user with an easy way to perform the analysis of macromolecular dynamics and forms a direct connection to the single-particle reconstruction process. A step-by-step HEMNMA protocol with the graphical interface is given in full details in Supplementary material. The graphical interface will be useful to experimentalists who are interested in studies of continuous conformational changes of macromolecular complexes beyond the modeling of continuous heterogeneity in single particle reconstruction. Copyright © 2014 Elsevier Inc. All rights reserved.

Development of binding assays in microfabricated picoliter vials: an assay for biotin.

PubMed

Grosvenor, A L; Feltus, A; Conover, R C; Daunert, S; Anderson, K W

2000-06-01

A homogeneous binding assay for the detection of biotin in picoliter vials was developed using the photoprotein aequorin as the label. The binding assay was based on the competition of free biotin with biotinylated aequorin (AEQ-biotin) for avidin. A sequential protocol was used, and modification of the assay to reduce the number of steps was examined. Results showed that detection limits on the order of 10(-14) mol of biotin were possible. Reducing the number of steps provided similar detection limits but only if the amount of avidin used was decreased. These binding assays based on picoliter volumes have potential applications in a variety of fields, including microanalysis and single-cell analysis, where the amount of sample is limited. In addition, these assays are suitable for the high-throughput screening of biopharmaceuticals.

Lability and Basicity of Bipyridine-Carboxylate-Phosphonate Ligand Accelerate Single-Site Water Oxidation by Ruthenium-Based Molecular Catalysts

DOE PAGES

Shaffer, David W.; Xie, Yan; Szalda, David J.; ...

2017-09-24

Here, a critical step in creating an artificial photosynthesis system for energy storage is designing catalysts that can thrive in an assembled device. Single-site catalysts have an advantage over bimolecular catalysts because they remain effective when immobilized. Hybrid water oxidation catalysts described here, combining the features of single-site bis-phosphonate catalysts and fast bimolecular bis-carboxylate catalysts, have reached turnover frequencies over 100 s –1, faster than both related catalysts under identical conditions. The new [(bpHc)Ru(L) 2] (bpH 2cH = 2,2'-bipyridine-6-phosphonic acid-6'-carboxylic acid, L = 4-picoline or isoquinoline) catalysts proceed through a single-site water nucleophilic attack pathway. The pendant phosphonate base mediatesmore » O–O bond formation via intramolecular atom-proton transfer with a calculated barrier of only 9.1 kcal/mol. Additionally, the labile carboxylate group allows water to bind early in the catalytic cycle, allowing intramolecular proton-coupled electron transfer to lower the potentials for oxidation steps and catalysis. That a single-site catalyst can be this fast lends credence to the possibility that the oxygen evolving complex adopts a similar mechanism.« less

Lability and Basicity of Bipyridine-Carboxylate-Phosphonate Ligand Accelerate Single-Site Water Oxidation by Ruthenium-Based Molecular Catalysts

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

Shaffer, David W.; Xie, Yan; Szalda, David J.

Here, a critical step in creating an artificial photosynthesis system for energy storage is designing catalysts that can thrive in an assembled device. Single-site catalysts have an advantage over bimolecular catalysts because they remain effective when immobilized. Hybrid water oxidation catalysts described here, combining the features of single-site bis-phosphonate catalysts and fast bimolecular bis-carboxylate catalysts, have reached turnover frequencies over 100 s –1, faster than both related catalysts under identical conditions. The new [(bpHc)Ru(L) 2] (bpH 2cH = 2,2'-bipyridine-6-phosphonic acid-6'-carboxylic acid, L = 4-picoline or isoquinoline) catalysts proceed through a single-site water nucleophilic attack pathway. The pendant phosphonate base mediatesmore » O–O bond formation via intramolecular atom-proton transfer with a calculated barrier of only 9.1 kcal/mol. Additionally, the labile carboxylate group allows water to bind early in the catalytic cycle, allowing intramolecular proton-coupled electron transfer to lower the potentials for oxidation steps and catalysis. That a single-site catalyst can be this fast lends credence to the possibility that the oxygen evolving complex adopts a similar mechanism.« less

GaSb-based single-mode distributed feedback lasers for sensing (Conference Presentation)

NASA Astrophysics Data System (ADS)

Gupta, James A.; Bezinger, Andrew; Lapointe, Jean; Poitras, Daniel; Aers, Geof C.

2017-02-01

GaSb-based tunable single-mode diode lasers can enable rapid, highly-selective and highly-sensitive absorption spectroscopy systems for gas sensing. In this work, single-mode distributed feedback (DFB) laser diodes were developed for the detection of various trace gases in the 2-3.3um range, including CO2, CO, HF, H2S, H2O and CH4. The lasers were fabricated using an index-coupled grating process without epitaxial regrowth, making the process significantly less expensive than conventional DFB fabrication. The devices are based on InGaAsSb/AlGaAsSb separate confinement heterostructures grown on GaSb by molecular beam epitaxy. DFB lasers were produced using a two step etch process. Narrow ridge waveguides were first defined by optical lithography and etched into the semiconductor. Lateral gratings were then defined on both sides of the ridge using electron-beam lithography and etched to produce the index-grating. Effective index modeling was used to optimize the ridge width, etch depths and the grating pitch to ensure single-lateral-mode operation and adequate coupling strength. The effective index method was further used to simulate the DFB laser emission spectrum, based on a transfer matrix model for light transmission through the periodic structure. The fabricated lasers exhibit single-mode operation which is tunable through the absorption features of the various target gases by adjustment of the drive current. In addition to the established open-path sensing applications, these devices have great potential for optoelectronic integrated gas sensors, making use of integrated photodetectors and possibly on-chip Si photonics waveguide structures.

Method of casting patterned dielectric structures

DOEpatents

Poco, John F.; Hrubesh, Lawrence W.

2001-01-01

A pattern of dielectric structures are formed directly on a substrate in a single step using sol-gel chemistry and molding procedures. The resulting dielectric structures are useful in vacuum applications for electronic devices. Porous, lightweight structures having a high aspect ratio that are suitable for use as spacers between the faceplate and baseplate of a field emission display can be manufactured using this method.

Microwave Plasma Based Single-Step Method for Generation of Carbon Nanostructures

DTIC Science & Technology

2013-07-01

Técnico, Technical University of Lisbon, Portugal 2 Mechanical and Aerospace Engeneering , Naval Postgraduate School, Monterey, CA 93943, U.S.A...Plasma environments constitute powerful tools in materials science due to their operation as thermal and chemical reactors. A microwave, atmospheric...applications include electronic devices, transparent conductive films, mechanical devices, chemical sensors, spintronic devices. Moreover, it shows enormous

Cathodic detection of H2O2 based on nanopyramidal gold surface with enhanced electron transfer of myoglobin.

PubMed

Xia, Peipei; Liu, Haiqing; Tian, Yang

2009-04-15

Direct and reversible electron transfer of myoglobin (Mb), for the first time, is achieved at nanopyramidal gold surface, which was fabricated by one-step electrodeposition, with redox formal potential of 0.21+/-0.01 V (vs. Ag/AgCl) and an apparent heterogeneous electron-transfer rate constant (k(s)) of 1.6+/-0.2 s(-1). Electrochemical investigation indicates that Mb is stably confined on the nanopyramidal gold surface and maintains electrocatalytic activity toward hydrogen peroxide (H(2)O(2)). The facilitated electron transfer combined with the intrinsic catalytical activity of Mb substantially construct the third-generation biosensor for H(2)O(2). The positive redox potential of Mb at the nanostructured gold electrode gives a strong basis for determination of H(2)O(2) with high selectivity. Besides this advantage, the present biosensor also exhibits quick response time, broad linear range, and good sensitivity. The dynamic detection linear range is from 1 microM to 1.4 mM with a detection limit of 0.5 microM at 3sigma. The striking analytical performance of the present biosensor, as well as the biocompatibility of gold nanostructures provided a potential for continuous, on-line detection of H(2)O(2) in the biological system.

Application of Organophosphonic Acids by One-Step Supercritical CO2 on 1D and 2D Semiconductors: Toward Enhanced Electrical and Sensing Performances.

PubMed

Bhartia, Bhavesh; Bacher, Nadav; Jayaraman, Sundaramurthy; Khatib, Salam; Song, Jing; Guo, Shifeng; Troadec, Cedric; Puniredd, Sreenivasa Reddy; Srinivasan, Madapusi Palavedu; Haick, Hossam

2015-07-15

Formation of dense monolayers with proven atmospheric stability using simple fabrication conditions remains a major challenge for potential applications such as (bio)sensors, solar cells, surfaces for growth of biological cells, and molecular, organic, and plastic electronics. Here, we demonstrate a single-step modification of organophosphonic acids (OPA) on 1D and 2D structures using supercritical carbon dioxide (SCCO2) as a processing medium, with high stability and significantly shorter processing times than those obtained by the conventional physisorption-chemisorption method (2.5 h vs 48-60 h).The advantages of this approach in terms of stability and atmospheric resistivity are demonstrated on various 2D materials, such as indium-tin-oxide (ITO) and 2D Si surfaces. The advantage of the reported approach on electronic and sensing devices is demonstrated by Si nanowire field effect transistors (SiNW FETs), which have shown a few orders of magnitude higher electrical and sensing performances, compared with devices obtained by conventional approaches. The compatibility of the reported approach with various materials and its simple implementation with a single reactor makes it easily scalable for various applications.

Single-step One-pot Synthesis of TiO2 Nanosheets Doped with Sulfur on Reduced Graphene Oxide with Enhanced Photocatalytic Activity.

PubMed

Wang, Weilin; Wang, Zhaofeng; Liu, Jingjing; Luo, Zhu; Suib, Steven L; He, Peng; Ding, Guqiao; Zhang, Zhengguo; Sun, Luyi

2017-04-21

A hybrid photocatalyst based on anatase TiO 2 was designed by doping TiO 2 with sulfur and incorporating reduced graphene oxide (TiO 2 -S/rGO hybrid), with an aim to narrow the band gap to potentially make use of visible light and decrease the recombination of excitons, respectively. This TiO 2 -S/rGO hybrid was successfully synthesized using a one-pot hydrothermal method via single-step reaction. The structure and morphology of the TiO 2 -S/rGO hybrid catalyst was carefully characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Its photocatalytic reactivity was evaluated by the degradation of methyl blue. The results showed that both the doping of sulfur and the introduction of rGO worked as designed, and the TiO 2 -S/rGO hybrid exhibited high photocatalytic activity under simulated sunlight. Considering both the facile and scalable reaction to synthesize TiO 2 -S/rGO hybrid, and its excellent photocatalytic performance, such TiO 2 -S/rGO hybrids are expect to find practical applications in environmental and energy sectors.

Single-step One-pot Synthesis of TiO2 Nanosheets Doped with Sulfur on Reduced Graphene Oxide with Enhanced Photocatalytic Activity

NASA Astrophysics Data System (ADS)

Wang, Weilin; Wang, Zhaofeng; Liu, Jingjing; Luo, Zhu; Suib, Steven L.; He, Peng; Ding, Guqiao; Zhang, Zhengguo; Sun, Luyi

2017-04-01

A hybrid photocatalyst based on anatase TiO2 was designed by doping TiO2 with sulfur and incorporating reduced graphene oxide (TiO2-S/rGO hybrid), with an aim to narrow the band gap to potentially make use of visible light and decrease the recombination of excitons, respectively. This TiO2-S/rGO hybrid was successfully synthesized using a one-pot hydrothermal method via single-step reaction. The structure and morphology of the TiO2-S/rGO hybrid catalyst was carefully characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Its photocatalytic reactivity was evaluated by the degradation of methyl blue. The results showed that both the doping of sulfur and the introduction of rGO worked as designed, and the TiO2-S/rGO hybrid exhibited high photocatalytic activity under simulated sunlight. Considering both the facile and scalable reaction to synthesize TiO2-S/rGO hybrid, and its excellent photocatalytic performance, such TiO2-S/rGO hybrids are expect to find practical applications in environmental and energy sectors.

Stepped-frequency GPR for utility line detection using polarization-dependent scattering

NASA Astrophysics Data System (ADS)

Jensen, Ole K.; Gregersen, Ole G.

2000-04-01

A GPR for detection of buried cables and pipes is developed by Ekko Dane Production in cooperation with Aalborg University. The appearance is a 'lawn mower' model including antennas, electronics and on-line data processing. A successful result is obtained by combining dedicated hardware and signal processing. The inherent signal to clutter ratio is bad, but making measurements at many polarization angles and subsequent signal processing improves the ratio. A simple model of the polarization dependence of the scattering from the target is used. The method is improved by combining the polarization filtering with averaging over small horizontal displacements. A stepped frequency measurement system is used. The method often implies long measurement times, but this problem is overcome by development of fast RF-electronics. Standard signal processors are used for real-time data processing. Several antenna array configurations are tested and optimized for low coupling between transmitter and receiver and for a short impulse response. A large number of tests have been made for different targets, e.g. metal cables and plastic pipes filled with air or water. Tests have been made under realistic ground conditions, including sand, wet clay, pavements and grass covered soil. The results show reliable detection even when the conditions are difficult.

Directional Sensitivity in Light-Mass Dark Matter Searches with Single-Electron-Resolution Ionization Detectors

NASA Astrophysics Data System (ADS)

Kadribasic, Fedja; Mirabolfathi, Nader; Nordlund, Kai; Sand, Andrea E.; Holmström, Eero; Djurabekova, Flyura

2018-03-01

We propose a method using solid state detectors with directional sensitivity to dark matter interactions to detect low-mass weakly interacting massive particles (WIMPs) originating from galactic sources. In spite of a large body of literature for high-mass WIMP detectors with directional sensitivity, no available technique exists to cover WIMPs in the mass range <1 GeV /c2 . We argue that single-electron-resolution semiconductor detectors allow for directional sensitivity once properly calibrated. We examine the commonly used semiconductor material response to these low-mass WIMP interactions.

The role of low-energy electrons in focused electron beam induced deposition: four case studies of representative precursors

PubMed Central

Thorman, Rachel M; Kumar T. P., Ragesh; Fairbrother, D Howard

2015-01-01

Summary Focused electron beam induced deposition (FEBID) is a single-step, direct-write nanofabrication technique capable of writing three-dimensional metal-containing nanoscale structures on surfaces using electron-induced reactions of organometallic precursors. Currently FEBID is, however, limited in resolution due to deposition outside the area of the primary electron beam and in metal purity due to incomplete precursor decomposition. Both limitations are likely in part caused by reactions of precursor molecules with low-energy (<100 eV) secondary electrons generated by interactions of the primary beam with the substrate. These low-energy electrons are abundant both inside and outside the area of the primary electron beam and are associated with reactions causing incomplete ligand dissociation from FEBID precursors. As it is not possible to directly study the effects of secondary electrons in situ in FEBID, other means must be used to elucidate their role. In this context, gas phase studies can obtain well-resolved information on low-energy electron-induced reactions with FEBID precursors by studying isolated molecules interacting with single electrons of well-defined energy. In contrast, ultra-high vacuum surface studies on adsorbed precursor molecules can provide information on surface speciation and identify species desorbing from a substrate during electron irradiation under conditions more representative of FEBID. Comparing gas phase and surface science studies allows for insight into the primary deposition mechanisms for individual precursors; ideally, this information can be used to design future FEBID precursors and optimize deposition conditions. In this review, we give a summary of different low-energy electron-induced fragmentation processes that can be initiated by the secondary electrons generated in FEBID, specifically, dissociative electron attachment, dissociative ionization, neutral dissociation, and dipolar dissociation, emphasizing the different nature and energy dependence of each process. We then explore the value of studying these processes through comparative gas phase and surface studies for four commonly-used FEBID precursors: MeCpPtMe3, Pt(PF3)4, Co(CO)3NO, and W(CO)6. Through these case studies, it is evident that this combination of studies can provide valuable insight into potential mechanisms governing deposit formation in FEBID. Although further experiments and new approaches are needed, these studies are an important stepping-stone toward better understanding the fundamental physics behind the deposition process and establishing design criteria for optimized FEBID precursors. PMID:26665061

The role of low-energy electrons in focused electron beam induced deposition: four case studies of representative precursors.

PubMed

Thorman, Rachel M; Kumar T P, Ragesh; Fairbrother, D Howard; Ingólfsson, Oddur

2015-01-01

Focused electron beam induced deposition (FEBID) is a single-step, direct-write nanofabrication technique capable of writing three-dimensional metal-containing nanoscale structures on surfaces using electron-induced reactions of organometallic precursors. Currently FEBID is, however, limited in resolution due to deposition outside the area of the primary electron beam and in metal purity due to incomplete precursor decomposition. Both limitations are likely in part caused by reactions of precursor molecules with low-energy (<100 eV) secondary electrons generated by interactions of the primary beam with the substrate. These low-energy electrons are abundant both inside and outside the area of the primary electron beam and are associated with reactions causing incomplete ligand dissociation from FEBID precursors. As it is not possible to directly study the effects of secondary electrons in situ in FEBID, other means must be used to elucidate their role. In this context, gas phase studies can obtain well-resolved information on low-energy electron-induced reactions with FEBID precursors by studying isolated molecules interacting with single electrons of well-defined energy. In contrast, ultra-high vacuum surface studies on adsorbed precursor molecules can provide information on surface speciation and identify species desorbing from a substrate during electron irradiation under conditions more representative of FEBID. Comparing gas phase and surface science studies allows for insight into the primary deposition mechanisms for individual precursors; ideally, this information can be used to design future FEBID precursors and optimize deposition conditions. In this review, we give a summary of different low-energy electron-induced fragmentation processes that can be initiated by the secondary electrons generated in FEBID, specifically, dissociative electron attachment, dissociative ionization, neutral dissociation, and dipolar dissociation, emphasizing the different nature and energy dependence of each process. We then explore the value of studying these processes through comparative gas phase and surface studies for four commonly-used FEBID precursors: MeCpPtMe3, Pt(PF3)4, Co(CO)3NO, and W(CO)6. Through these case studies, it is evident that this combination of studies can provide valuable insight into potential mechanisms governing deposit formation in FEBID. Although further experiments and new approaches are needed, these studies are an important stepping-stone toward better understanding the fundamental physics behind the deposition process and establishing design criteria for optimized FEBID precursors.

Probing the size of proteins with glass nanopores

NASA Astrophysics Data System (ADS)

Steinbock, L. J.; Krishnan, S.; Bulushev, R. D.; Borgeaud, S.; Blokesch, M.; Feletti, L.; Radenovic, A.

2014-11-01

Single molecule studies using nanopores have gained attention due to the ability to sense single molecules in aqueous solution without the need to label them. In this study, short DNA molecules and proteins were detected with glass nanopores, whose sensitivity was enhanced by electron reshaping which decreased the nanopore diameter and created geometries with a reduced sensing length. Further, proteins having molecular weights (MW) ranging from 12 kDa to 480 kDa were detected, which showed that their corresponding current peak amplitude changes according to their MW. In the case of the 12 kDa ComEA protein, its DNA-binding properties to an 800 bp long DNA molecule was investigated. Moreover, the influence of the pH on the charge of the protein was demonstrated by showing a change in the translocation direction. This work emphasizes the wide spectrum of detectable molecules using nanopores from glass nanocapillaries, which stand out because of their inexpensive, lithography-free, and rapid manufacturing process.Single molecule studies using nanopores have gained attention due to the ability to sense single molecules in aqueous solution without the need to label them. In this study, short DNA molecules and proteins were detected with glass nanopores, whose sensitivity was enhanced by electron reshaping which decreased the nanopore diameter and created geometries with a reduced sensing length. Further, proteins having molecular weights (MW) ranging from 12 kDa to 480 kDa were detected, which showed that their corresponding current peak amplitude changes according to their MW. In the case of the 12 kDa ComEA protein, its DNA-binding properties to an 800 bp long DNA molecule was investigated. Moreover, the influence of the pH on the charge of the protein was demonstrated by showing a change in the translocation direction. This work emphasizes the wide spectrum of detectable molecules using nanopores from glass nanocapillaries, which stand out because of their inexpensive, lithography-free, and rapid manufacturing process. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05001k

Revealing the Crystalline Integrity of Wafer-Scale Graphene on SiO2/Si: An Azimuthal RHEED Approach.

PubMed

Lu, Zonghuan; Sun, Xin; Xiang, Yu; Washington, Morris A; Wang, Gwo-Ching; Lu, Toh-Ming

2017-07-12

The symmetry of graphene is usually determined by a low-energy electron diffraction (LEED) method when the graphene is on the conductive substrates, but LEED cannot handle graphene transferred to SiO 2 /Si substrates due to the charging effect. While transmission electron microscopy can generate electron diffraction on post-transferred graphene, this method is too localized. Herein, we employed an azimuthal reflection high-energy electron diffraction (RHEED) method to construct the reciprocal space mapping and determine the symmetry of wafer-size graphene both pre- and post-transfer. In this work, single-crystalline Cu(111) films were prepared on sapphire(0001) and spinel(111) substrates with sputtering. Then the graphene was epitaxially grown on single-crystalline Cu(111) films with a low pressure chemical vapor deposition. The reciprocal space mapping using azimuthal RHEED confirmed that the graphene grown on Cu(111) films was single-crystalline, no matter the form of the monolayer or multilayer structure. While the Cu(111) film grown on sapphire(0001) may occasionally consist of 60° in-plane rotational twinning, the reciprocal space mapping revealed that the in-plane orientation of graphene grown atop was not affected. The proposed method for checking the crystalline integrity of the post-transferred graphene sheets is an important step in the realization of the graphene as a platform to fabricate electronic and optoelectronic devices.

Discrete pre-processing step effects in registration-based pipelines, a preliminary volumetric study on T1-weighted images

PubMed Central

2017-01-01

Pre-processing MRI scans prior to performing volumetric analyses is common practice in MRI studies. As pre-processing steps adjust the voxel intensities, the space in which the scan exists, and the amount of data in the scan, it is possible that the steps have an effect on the volumetric output. To date, studies have compared between and not within pipelines, and so the impact of each step is unknown. This study aims to quantify the effects of pre-processing steps on volumetric measures in T1-weighted scans within a single pipeline. It was our hypothesis that pre-processing steps would significantly impact ROI volume estimations. One hundred fifteen participants from the OASIS dataset were used, where each participant contributed three scans. All scans were then pre-processed using a step-wise pipeline. Bilateral hippocampus, putamen, and middle temporal gyrus volume estimations were assessed following each successive step, and all data were processed by the same pipeline 5 times. Repeated-measures analyses tested for a main effects of pipeline step, scan-rescan (for MRI scanner consistency) and repeated pipeline runs (for algorithmic consistency). A main effect of pipeline step was detected, and interestingly an interaction between pipeline step and ROI exists. No effect for either scan-rescan or repeated pipeline run was detected. We then supply a correction for noise in the data resulting from pre-processing. PMID:29023597

Using Quasiparticle Poisoning To Detect Photons

NASA Technical Reports Server (NTRS)

Echternach, Pierre; Day, Peter

2006-01-01

According to a proposal, a phenomenon associated with excitation of quasiparticles in certain superconducting quantum devices would be exploited as a means of detecting photons with exquisite sensitivity. The phenomenon could also be exploited to perform medium-resolution spectroscopy. The proposal was inspired by the observation that Coulomb blockade devices upon which some quantum logic gates are based are extremely sensitive to quasiparticles excited above the superconducting gaps in their leads. The presence of quasiparticles in the leads can be easily detected via the charge states. If quasiparticles could be generated in the leads by absorption of photons, then the devices could be used as very sensitive detectors of electromagnetic radiation over the spectral range from x-rays to submillimeter waves. The devices in question are single-Cooper-pair boxes (SCBs), which are mesoscopic superconducting devices developed for quantum computing. An SCB consists of a small superconducting island connected to a reservoir via a small tunnel junction and connected to a voltage source through a gate capacitor. An SCB is an artificial two-level quantum system, the Hamiltonian of which can be controlled by the gate voltage. One measures the expected value of the charge of the eigenvectors of this quantum system by use of a radio-frequency single-electron transistor. A plot of this expected value of charge as a function of gate voltage resembles a staircase that, in the ideal case, consists of steps of height 2 e (where e is the charge of one electron). Experiments have shown that depending on the parameters of the device, quasiparticles in the form of "broken" Cooper pairs present in the reservoir can tunnel to the island, giving rise to steps of 1 e. This effect is sometimes called "poisoning." Simulations have shown that an extremely small average number of quasiparticles can generate a 1-e periodic signal. In a device according to the proposal, this poisoning would be turned to advantage. Depending on the wavelength, an antenna or other component would be used to couple radiation into the reservoir, wherein the absorption of photons would break Cooper pairs, thereby creating quasiparticles that, in turn, would tunnel to the island, creating a 1-e signal. On the basis of conservative estimates of device parameters derived from experimental data and computational simulations that fit the data, it has been estimated that the noise equivalent power of a device according to the proposal could be as low as 6 10(exp -22) W/Hz(exp 1/2). It has also been estimated that the spectroscopic resolution (photon energy divided by increment of photon energy) of such a device in visible light would exceed 100.

Direct observation of single-charge-detection capability of nanowire field-effect transistors.

PubMed

Salfi, J; Savelyev, I G; Blumin, M; Nair, S V; Ruda, H E

2010-10-01

A single localized charge can quench the luminescence of a semiconductor nanowire, but relatively little is known about the effect of single charges on the conductance of the nanowire. In one-dimensional nanostructures embedded in a material with a low dielectric permittivity, the Coulomb interaction and excitonic binding energy are much larger than the corresponding values when embedded in a material with the same dielectric permittivity. The stronger Coulomb interaction is also predicted to limit the carrier mobility in nanowires. Here, we experimentally isolate and study the effect of individual localized electrons on carrier transport in InAs nanowire field-effect transistors, and extract the equivalent charge sensitivity. In the low carrier density regime, the electrostatic potential produced by one electron can create an insulating weak link in an otherwise conducting nanowire field-effect transistor, modulating its conductance by as much as 4,200% at 31 K. The equivalent charge sensitivity, 4 × 10(-5) e Hz(-1/2) at 25 K and 6 × 10(-5) e Hz(-1/2) at 198 K, is orders of magnitude better than conventional field-effect transistors and nanoelectromechanical systems, and is just a factor of 20-30 away from the record sensitivity for state-of-the-art single-electron transistors operating below 4 K (ref. 8). This work demonstrates the feasibility of nanowire-based single-electron memories and illustrates a physical process of potential relevance for high performance chemical sensors. The charge-state-detection capability we demonstrate also makes the nanowire field-effect transistor a promising host system for impurities (which may be introduced intentionally or unintentionally) with potentially long spin lifetimes, because such transistors offer more sensitive spin-to-charge conversion readout than schemes based on conventional field-effect transistors.

Measurement of intrahepatic pressure during radiofrequency ablation in porcine liver.

PubMed

Kawamoto, Chiaki; Yamauchi, Atsushi; Baba, Yoko; Kaneko, Keiko; Yakabi, Koji

2010-04-01

To identify the most effective procedures to avoid increased intrahepatic pressure during radiofrequency ablation, we evaluated different ablation methods. Laparotomy was performed in 19 pigs. Intrahepatic pressure was monitored using an invasive blood pressure monitor. Radiofrequency ablation was performed as follows: single-step standard ablation; single-step at 30 W; single-step at 70 W; 4-step at 30 W; 8-step at 30 W; 8-step at 70 W; and cooled-tip. The array was fully deployed in single-step methods. In the multi-step methods, the array was gradually deployed in four or eight steps. With the cooled-tip, ablation was performed by increasing output by 10 W/min, starting at 40 W. Intrahepatic pressure was as follows: single-step standard ablation, 154.5 +/- 30.9 mmHg; single-step at 30 W, 34.2 +/- 20.0 mmHg; single-step at 70 W, 46.7 +/- 24.3 mmHg; 4-step at 30 W, 42.3 +/- 17.9 mmHg; 8-step at 30 W, 24.1 +/- 18.2 mmHg; 8-step at 70 W, 47.5 +/- 31.5 mmHg; and cooled-tip, 114.5 +/- 16.6 mmHg. The radiofrequency ablation-induced area was spherical with single-step standard ablation, 4-step at 30 W, and 8-step at 30 W. Conversely, the ablated area was irregular with single-step at 30 W, single-step at 70 W, and 8-step at 70 W. The ablation time was significantly shorter for the multi-step method than for the single-step method. Increased intrahepatic pressure could be controlled using multi-step methods. From the shapes of the ablation area, 30-W 8-step expansions appear to be most suitable for radiofrequency ablation.

The electronic properties of SWNTs intercalated by electron acceptors

NASA Astrophysics Data System (ADS)

Chernysheva, M. V.; Kiseleva, E. A.; Verbitskii, N. I.; Eliseev, A. A.; Lukashin, A. V.; Tretyakov, Yu. D.; Savilov, S. V.; Kiselev, N. A.; Zhigalina, O. M.; Kumskov, A. S.; Krestinin, A. V.; Hutchison, J. L.

2008-05-01

Here we report synthesis of Chal@SWNT nanocomposites (where Chal=S, Se and Te) and the impact of the intercalated electron-acceptor compounds on the electronic properties of SWNTs. The chalcogens were introduced to the channels of single-walled carbon nanotubes by molten media technique via impregnation of pre-opened SWNTs with melted guest compounds in vacuum. HRTEM imaging confirms the filling of nanotube channels by continuous nanostructures of corresponding chalcogens. The strong influence of incorporated matter on the electronic properties of the SWNTs was detected by Raman spectroscopy.

Study on dioxygen reduction by mutational modifications of the hydrogen bond network leading from bulk water to the trinuclear copper center in bilirubin oxidase

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

Morishita, Hirotoshi; Kurita, Daisuke; Kataoka, Kunishige

2014-07-18

Highlights: • Proton transport pathway in bilirubin oxidase was mutated. • Two intermediates in the dioxygen reduction steps were trapped and characterized. • A specific glutamate for dioxygen reduction by multicopper oxidases was identified. - Abstract: The hydrogen bond network leading from bulk water to the trinuclear copper center in bilirubin oxidase is constructed with Glu463 and water molecules to transport protons for the four-electron reduction of dioxygen. Substitutions of Glu463 with Gln or Ala were attributed to virtually complete loss or significant reduction in enzymatic activities due to an inhibition of the proton transfer steps to dioxygen. The singlemore » turnover reaction of the Glu463Gln mutant afforded the highly magnetically interacted intermediate II (native intermediate) with a broad g = 1.96 electron paramagnetic resonance signal detectable at cryogenic temperatures. Reactions of the double mutants, Cys457Ser/Glu463Gln and Cys457Ser/Glu463Ala afforded the intermediate I (peroxide intermediate) because the type I copper center to donate the fourth electron to dioxygen was vacant in addition to the interference of proton transport due to the mutation at Glu463. The intermediate I gave no electron paramagnetic resonance signal, but the type II copper signal became detectable with the decay of the intermediate I. Structural and functional similarities between multicopper oxidases are discussed based on the present mutation at Glu463 in bilirubin oxidase.« less

Development and evaluation of an in-house single step loop-mediated isothermal amplification (SS-LAMP) assay for the detection of Mycobacterium tuberculosis complex in sputum samples from Moroccan patients.

PubMed

Bentaleb, El Mehdi; Abid, Mohammed; El Messaoudi, My Driss; Lakssir, Brahim; Ressami, El Mostafa; Amzazi, Saaïd; Sefrioui, Hassan; Ait Benhassou, Hassan

2016-09-27

Tuberculosis (TB) is a major global health problem and remains the leading cause of morbidity and mortality in developing countries. Routinely used TB diagnostic methods, in most endemic areas, are time-consuming, often less-sensitive, expensive and inaccessible to most patients. Therefore, there is an urgent need for the development of early, easy to use and effective diagnosis tools of TB, which can be effectively integrated into resource limited settings, to anticipate the early treatment and limit further spread of the disease. Over the last decade, Loop-mediated isothermal amplification (LAMP) assays have become a powerful tool for rapid diagnosis of infectious diseases because of the simplicity of device requirements. Indeed, LAMP is a simple, quick and cost effective Isothermal Nucleic Acid Amplification diagnostic test (INAAT) that has the potential to be used in TB endemic settings of resource-poor countries. In the present study, we have developed a simple and rapid TB molecular diagnostic test using a Single-Step Loop-mediated isothermal DNA amplification (SS-LAMP) method for the detection of Mycobacterium tuberculosis complex (MTBC) strains, with a simplified sample preparation procedure, eliminating DNA extraction prior to LAMP amplification, DNA initial denaturation and enzymatic inactivation steps during the amplification process. To perform our in-house SS-LAMP assay, a set of six specific primers was specifically designed to recognize eight distinct regions on the MTBC species-specific repetitive insertion sequence 6110 (IS6110). The amplification of the targeted DNA was carried out under isothermal conditions at 65 °C within 1 h. Our protocol was firstly optimized using 60 of confirmed MTBC isolates and a recombinant pGEMeasy-IS6110 vector for sensitivity testing. Thereafter, the assay was evaluated on liquefied sputum specimens collected from 157 Moroccan patients suspected of having TB. Our SS-LAMP developed assay was able to detect MTBC DNA directly from liquefied sputum samples without any prior DNA extraction, denaturation nor the final enzymatic inactivation step. When compared to routinely used Löwenstein Jensen (LJ) Culture method, our SS-LAMP assay is rapid and showed specificity and sensitivity of 99.14 % and 82.93 % respectively which are within the international standards. In addition, the limit of detection of our assay was found to be as little as 10 copies of bacterial DNA. To our knowledge, this is the first study using a single step LAMP (SS-LAMP) procedure as a rapid, easy to perform and cost effective testing for TB early detection. This innovative assay could be suitable for low-income countries with restricted health equipment facilities.

Graphene-Based Josephson-Junction Single-Photon Detector

NASA Astrophysics Data System (ADS)

Walsh, Evan D.; Efetov, Dmitri K.; Lee, Gil-Ho; Heuck, Mikkel; Crossno, Jesse; Ohki, Thomas A.; Kim, Philip; Englund, Dirk; Fong, Kin Chung

2017-08-01

We propose to use graphene-based Josephson junctions (GJJs) to detect single photons in a wide electromagnetic spectrum from visible to radio frequencies. Our approach takes advantage of the exceptionally low electronic heat capacity of monolayer graphene and its constricted thermal conductance to its phonon degrees of freedom. Such a system could provide high-sensitivity photon detection required for research areas including quantum information processing and radio astronomy. As an example, we present our device concepts for GJJ single-photon detectors in both the microwave and infrared regimes. The dark count rate and intrinsic quantum efficiency are computed based on parameters from a measured GJJ, demonstrating feasibility within existing technologies.

High-fidelity readout and control of a nuclear spin qubit in silicon.

PubMed

Pla, Jarryd J; Tan, Kuan Y; Dehollain, Juan P; Lim, Wee H; Morton, John J L; Zwanenburg, Floris A; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea

2013-04-18

Detection of nuclear spin precession is critical for a wide range of scientific techniques that have applications in diverse fields including analytical chemistry, materials science, medicine and biology. Fundamentally, it is possible because of the extreme isolation of nuclear spins from their environment. This isolation also makes single nuclear spins desirable for quantum-information processing, as shown by pioneering studies on nitrogen-vacancy centres in diamond. The nuclear spin of a (31)P donor in silicon is very promising as a quantum bit: bulk measurements indicate that it has excellent coherence times and silicon is the dominant material in the microelectronics industry. Here we demonstrate electrical detection and coherent manipulation of a single (31)P nuclear spin qubit with sufficiently high fidelities for fault-tolerant quantum computing. By integrating single-shot readout of the electron spin with on-chip electron spin resonance, we demonstrate quantum non-demolition and electrical single-shot readout of the nuclear spin with a readout fidelity higher than 99.8 percent-the highest so far reported for any solid-state qubit. The single nuclear spin is then operated as a qubit by applying coherent radio-frequency pulses. For an ionized (31)P donor, we find a nuclear spin coherence time of 60 milliseconds and a one-qubit gate control fidelity exceeding 98 percent. These results demonstrate that the dominant technology of modern electronics can be adapted to host a complete electrical measurement and control platform for nuclear-spin-based quantum-information processing.

The quantum dynamics of electronically nonadiabatic chemical reactions

NASA Technical Reports Server (NTRS)

Truhlar, Donald G.

1993-01-01

Considerable progress was achieved on the quantum mechanical treatment of electronically nonadiabatic collisions involving energy transfer and chemical reaction in the collision of an electronically excited atom with a molecule. In the first step, a new diabatic representation for the coupled potential energy surfaces was created. A two-state diabatic representation was developed which was designed to realistically reproduce the two lowest adiabatic states of the valence bond model and also to have the following three desirable features: (1) it is more economical to evaluate; (2) it is more portable; and (3) all spline fits are replaced by analytic functions. The new representation consists of a set of two coupled diabatic potential energy surfaces plus a coupling surface. It is suitable for dynamics calculations on both the electronic quenching and reaction processes in collisions of Na(3p2p) with H2. The new two-state representation was obtained by a three-step process from a modified eight-state diatomics-in-molecules (DIM) representation of Blais. The second step required the development of new dynamical methods. A formalism was developed for treating reactions with very general basis functions including electronically excited states. Our formalism is based on the generalized Newton, scattered wave, and outgoing wave variational principles that were used previously for reactive collisions on a single potential energy surface, and it incorporates three new features: (1) the basis functions include electronic degrees of freedom, as required to treat reactions involving electronic excitation and two or more coupled potential energy surfaces; (2) the primitive electronic basis is assumed to be diabatic, and it is not assumed that it diagonalizes the electronic Hamiltonian even asymptotically; and (3) contracted basis functions for vibrational-rotational-orbital degrees of freedom are included in a very general way, similar to previous prescriptions for locally adiabatic functions in various quantum scattering algorithms.

Retarding potential analyzer for the Pioneer-Venus Orbiter Mission

NASA Technical Reports Server (NTRS)

Knudsen, W. C.; Bakke, J.; Spenner, K.; Novak, V.

1979-01-01

The retarding potential analyzer on the Pioneer-Venus Orbiter Mission has been designed to measure most of the thermal plasma parameters within and near the Venusian ionosphere. Parameters include total ion concentration, concentrations of the more abundant ions, ion temperatures, ion drift velocity, electron temperature, and low-energy (0-50 eV) electron distribution function. To accomplish these measurements on a spinning vehicle with a small telemetry bit rate, several functions, including decision functions not previously used in RPA's, have been developed and incorporated into this instrument. The more significant functions include automatic electrometer ranging with background current compensation; digital, quadratic retarding potential step generation for the ion and low-energy electron scans; a current sampling interval of 2 ms throughout all scans; digital logic inflection point detection and data selection; and automatic ram direction detection. Extensive numerical simulation and plasma chamber tests have been conducted to verify adequacy of the design for the Pioneer Mission.

Patient identification errors: the detective in the laboratory.

PubMed

Salinas, Maria; López-Garrigós, Maite; Lillo, Rosa; Gutiérrez, Mercedes; Lugo, Javier; Leiva-Salinas, Carlos

2013-11-01

The eradication of errors regarding patients' identification is one of the main goals for safety improvement. As clinical laboratory intervenes in 70% of clinical decisions, laboratory safety is crucial in patient safety. We studied the number of Laboratory Information System (LIS) demographic data errors registered in our laboratory during one year. The laboratory attends a variety of inpatients and outpatients. The demographic data of outpatients is registered in the LIS, when they present to the laboratory front desk. The requests from the primary care centers (PCC) are made electronically by the general practitioner. A manual step is always done at the PCC to conciliate the patient identification number in the electronic request with the one in the LIS. Manual registration is done through hospital information system demographic data capture when patient's medical record number is registered in LIS. Laboratory report is always sent out electronically to the patient's electronic medical record. Daily, every demographic data in LIS is manually compared to the request form to detect potential errors. Fewer errors were committed when electronic order was used. There was great error variability between PCC when using the electronic order. LIS demographic data manual registration errors depended on patient origin and test requesting method. Even when using the electronic approach, errors were detected. There was a great variability between PCC even when using this electronic modality; this suggests that the number of errors is still dependent on the personnel in charge of the technology. © 2013.

The electronic band structures of gadolinium chalcogenides: a first-principles prediction for neutron detecting

NASA Astrophysics Data System (ADS)

Li, Kexue; Liu, Lei; Yu, Peter Y.; Chen, Xiaobo; Shen, D. Z.

2016-05-01

By converting the energy of nuclear radiation to excited electrons and holes, semiconductor detectors have provided a highly efficient way for detecting them, such as photons or charged particles. However, for detecting the radiated neutrons, those conventional semiconductors hardly behave well, as few of them possess enough capability for capturing these neutral particles. While the element Gd has the highest nuclear cross section, here for searching proper neutron-detecting semiconductors, we investigate theoretically the Gd chalcogenides whose electronic band structures have never been characterized clearly. Among them, we identify that γ-phase Gd2Se3 should be the best candidate for neutron detecting since it possesses not only the right bandgap of 1.76 eV for devices working under room temperature but also the desired indirect gap nature for charge carriers surviving longer. We propose further that semiconductor neutron detectors with single-neutron sensitivity can be realized with such a Gd-chalcogenide on the condition that their crystals can be grown with good quality.

The electronic band structures of gadolinium chalcogenides: a first-principles prediction for neutron detecting.

PubMed

Li, Kexue; Liu, Lei; Yu, Peter Y; Chen, Xiaobo; Shen, D Z

2016-05-11

By converting the energy of nuclear radiation to excited electrons and holes, semiconductor detectors have provided a highly efficient way for detecting them, such as photons or charged particles. However, for detecting the radiated neutrons, those conventional semiconductors hardly behave well, as few of them possess enough capability for capturing these neutral particles. While the element Gd has the highest nuclear cross section, here for searching proper neutron-detecting semiconductors, we investigate theoretically the Gd chalcogenides whose electronic band structures have never been characterized clearly. Among them, we identify that γ-phase Gd2Se3 should be the best candidate for neutron detecting since it possesses not only the right bandgap of 1.76 eV for devices working under room temperature but also the desired indirect gap nature for charge carriers surviving longer. We propose further that semiconductor neutron detectors with single-neutron sensitivity can be realized with such a Gd-chalcogenide on the condition that their crystals can be grown with good quality.

Theoretical aspects of femtosecond double-pump single-molecule spectroscopy. I. Weak-field regime.

PubMed

Palacino-González, Elisa; Gelin, Maxim F; Domcke, Wolfgang

2017-12-13

We present a theoretical description of double-pump femtosecond single-molecule signals with fluorescence detection. We simulate these signals in the weak-field regime for a model mimicking a chromophore with a Franck-Condon-active vibrational mode. We establish several signatures of these signals which are characteristic for the weak-field regime. The signatures include the quenching of vibrational beatings by electronic dephasing and a pronounced tilt of the phase-time profiles in the two-dimensional (2D) maps. We study how environment-induced slow modulations of the electronic dephasing and relevant chromophore parameters (electronic energy, orientation, vibrational frequency and relative shift of the potential energy surfaces) affect the signals.

Accurate modelling of single-particle cryo-EM images quantifies the benefits expected from using Zernike phase contrast

PubMed Central

Hall, R. J.; Nogales, E.; Glaeser, R. M.

2011-01-01

The use of a Zernike-type phase plate in biological cryo-electron microscopy allows the imaging, without using defocus, of what are predominantly phase objects. It is thought that such phase-plate implementations might result in higher quality images, free from the problems of CTF correction that occur when images must be recorded at extremely high values of defocus. In single-particle cryo-electron microscopy it is hoped that these improvements in image quality will facilitate work on structures that have proved difficult to study, either because of their relatively small size or because the structures are not completely homogeneous. There is still a need, however, to quantify how much improvement can be gained by using a phase plate for single-particle cryo-electron microscopy. We present a method for quantitatively modelling the images recorded with 200 keV electrons, for single particles embedded in vitreous ice. We then investigate what difference the use of a phase-plate device could have on the processing of single-particle data. We confirm that using a phase plate results in single-particle datasets in which smaller molecules can be detected, particles can be more accurately aligned and problems of heterogeneity can be more easily addressed. PMID:21463690

Solid-phase microextraction of methadone in urine samples by electrochemically co-deposited sol-gel/Cu nanocomposite fiber.

PubMed

Mohammadiazar, Sirwan; Hasanli, Fateme; Maham, Mehdi; Payami Samarin, Somayeh

2017-08-01

Electrochemically co-deposited sol-gel/Cu nanocomposites have been introduced as a novel, simple and single-step technique for preparation of solid-phase microextraction (SPME) coating to extract methadone (MDN) (a synthetic opioid) in urine samples. The porous surface structure of the sol-gel/Cu nanocomposite coating was revealed by scanning electron microscopy. Direct immersion SPME followed by HPLC-UV determination was employed. The factors influencing the SPME procedure, such as the salt content, desorption solvent type, pH and equilibration time, were optimized. The best conditions were obtained with no salt content, acetonitrile as desorption solvent type, pH 9 and 10 min equilibration time. The calibration graphs for urine samples showed good linearity. The detection limit was about 0.2 ng mL -1 . Also, the novel method for preparation of nanocomposite fiber was compared with previously reported techniques for MDN determination. The results show that the novel nanocomposite fiber has relatively high extraction efficiency. Copyright © 2016 John Wiley & Sons, Ltd.

Electrophoretic and field-effect graphene for all-electrical DNA array technology.

PubMed

Xu, Guangyu; Abbott, Jeffrey; Qin, Ling; Yeung, Kitty Y M; Song, Yi; Yoon, Hosang; Kong, Jing; Ham, Donhee

2014-09-05

Field-effect transistor biomolecular sensors based on low-dimensional nanomaterials boast sensitivity, label-free operation and chip-scale construction. Chemical vapour deposition graphene is especially well suited for multiplexed electronic DNA array applications, since its large two-dimensional morphology readily lends itself to top-down fabrication of transistor arrays. Nonetheless, graphene field-effect transistor DNA sensors have been studied mainly at single-device level. Here we create, from chemical vapour deposition graphene, field-effect transistor arrays with two features representing steps towards multiplexed DNA arrays. First, a robust array yield--seven out of eight transistors--is achieved with a 100-fM sensitivity, on par with optical DNA microarrays and at least 10 times higher than prior chemical vapour deposition graphene transistor DNA sensors. Second, each graphene acts as an electrophoretic electrode for site-specific probe DNA immobilization, and performs subsequent site-specific detection of target DNA as a field-effect transistor. The use of graphene as both electrode and transistor suggests a path towards all-electrical multiplexed graphene DNA arrays.

Uncovering many-body correlations in nanoscale nuclear spin baths by central spin decoherence

PubMed Central

Ma, Wen-Long; Wolfowicz, Gary; Zhao, Nan; Li, Shu-Shen; Morton, John J.L.; Liu, Ren-Bao

2014-01-01

Central spin decoherence caused by nuclear spin baths is often a critical issue in various quantum computing schemes, and it has also been used for sensing single-nuclear spins. Recent theoretical studies suggest that central spin decoherence can act as a probe of many-body physics in spin baths; however, identification and detection of many-body correlations of nuclear spins in nanoscale systems are highly challenging. Here, taking a phosphorus donor electron spin in a 29Si nuclear spin bath as our model system, we discover both theoretically and experimentally that many-body correlations in nanoscale nuclear spin baths produce identifiable signatures in decoherence of the central spin under multiple-pulse dynamical decoupling control. We demonstrate that under control by an odd or even number of pulses, the central spin decoherence is principally caused by second- or fourth-order nuclear spin correlations, respectively. This study marks an important step toward studying many-body physics using spin qubits. PMID:25205440

Monolayer optical memory cells based on artificial trap-mediated charge storage and release

NASA Astrophysics Data System (ADS)

Lee, Juwon; Pak, Sangyeon; Lee, Young-Woo; Cho, Yuljae; Hong, John; Giraud, Paul; Shin, Hyeon Suk; Morris, Stephen M.; Sohn, Jung Inn; Cha, Seungnam; Kim, Jong Min

2017-03-01

Monolayer transition metal dichalcogenides are considered to be promising candidates for flexible and transparent optoelectronics applications due to their direct bandgap and strong light-matter interactions. Although several monolayer-based photodetectors have been demonstrated, single-layered optical memory devices suitable for high-quality image sensing have received little attention. Here we report a concept for monolayer MoS2 optoelectronic memory devices using artificially-structured charge trap layers through the functionalization of the monolayer/dielectric interfaces, leading to localized electronic states that serve as a basis for electrically-induced charge trapping and optically-mediated charge release. Our devices exhibit excellent photo-responsive memory characteristics with a large linear dynamic range of ~4,700 (73.4 dB) coupled with a low OFF-state current (<4 pA), and a long storage lifetime of over 104 s. In addition, the multi-level detection of up to 8 optical states is successfully demonstrated. These results represent a significant step toward the development of future monolayer optoelectronic memory devices.

Influence of Substrate Bonding and Surface Morphology on Dynamic Organic Layer Growth: Perylenetetracarboxylic Dianhydride on Au(111).

PubMed

Schmidt, Thomas; Marchetto, Helder; Groh, Ullrich; Fink, Rainer H; Freund, Hans-Joachim; Umbach, Eberhard

2018-05-15

We investigated the dynamics of the initial growth of the first epitaxial layers of perylenetetracarboxylic dianhydride (PTCDA) on the Au(111) surface with high lateral resolution using the aberration-corrected spectro-microscope SMART. With this instrument, we could simultaneously study the different adsorption behaviors and layer growth on various surface areas consisting of either a distribution of flat (111) terraces, separated by single atomic steps ("ideal surface"), or on areas with a high density of step bunches and defects ("realistic surface"). The combined use of photoemission electron microscopy, low-energy electron microscopy, and μ-spot X-ray absorption provided a wealth of new information, showing that the growth of the archetype molecule PTCDA not only has similarities but also has significant differences when comparing Au(111) and Ag(111) substrate surfaces. For instance, under otherwise identical preparation conditions, we observed different growth mechanisms on different surface regions, depending on the density of step bunches. In addition, we studied the spatially resolved desorption behavior which also depends on the substrate morphology.

A phase contrast imaging–interferometer system for detection of multiscale electron density fluctuations on DIII-D

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

Davis, E. M.; Rost, J. C.; Porkolab, M.

2016-11-15

Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. This work describes the first-ever implementation of a combined PCI–interferometer. The combined system uses a single 10.6 μm probe beam, two interference schemes, and two detectors to measure electron density fluctuations at large spatiotemporal bandwidth (10 kHz

Scanned-probe detection of electron spin resonance from a nitroxide spin probe

PubMed Central

Moore, Eric W.; Lee, SangGap; Hickman, Steven A.; Wright, Sarah J.; Harrell, Lee E.; Borbat, Peter P.; Freed, Jack H.; Marohn, John A.

2009-01-01

We report an approach that extends the applicability of ultrasensitive force-gradient detection of magnetic resonance to samples with spin-lattice relaxation times (T 1) as short as a single cantilever period. To demonstrate the generality of the approach, which relies on detecting either cantilever frequency or phase, we used it to detect electron spin resonance from a T 1 = 1 ms nitroxide spin probe in a thin film at 4.2 K and 0.6 T. By using a custom-fabricated cantilever with a 4 μm-diameter nickel tip, we achieve a magnetic resonance sensitivity of 400 Bohr magnetons in a 1 Hz bandwidth. A theory is presented that quantitatively predicts both the lineshape and the magnitude of the observed cantilever frequency shift as a function of field and cantilever-sample separation. Good agreement was found between nitroxide T 1 's measured mechanically and inductively, indicating that the cantilever magnet is not an appreciable source of spin-lattice relaxation here. We suggest that the new approach has a number of advantages that make it well suited to push magnetic resonance detection and imaging of nitroxide spin labels in an individual macromolecule to single-spin sensitivity. PMID:20018707

Single-Molecule Spectroscopy and Imaging Over the Decades

PubMed Central

Moerner, W. E.; Shechtman, Yoav; Wang, Quan

2016-01-01

As of 2015, it has been 26 years since the first optical detection and spectroscopy of single molecules in condensed matter. This area of science has expanded far beyond the early low temperature studies in crystals to include single molecules in cells, polymers, and in solution. The early steps relied upon high-resolution spectroscopy of inhomogeneously broadened optical absorption profiles of molecular impurities in solids at low temperatures. Spectral fine structure arising directly from the position-dependent fluctuations of the number of molecules in resonance led to the attainment of the single-molecule limit in 1989 using frequency-modulation laser spectroscopy. In the early 1990's, a variety of fascinating physical effects were observed for individual molecules, including imaging of the light from single molecules as well as observations of spectral diffusion, optical switching and the ability to select different single molecules in the same focal volume simply by tuning the pumping laser frequency. In the room temperature regime, researchers showed that bursts of light from single molecules could be detected in solution, leading to imaging and microscopy by a variety of methods. Studies of single copies of the green fluorescent protein also uncovered surprises, especially the blinking and photoinduced recovery of emitters, which stimulated further development of photoswitchable fluorescent protein labels. All of these early steps provided important fundamentals underpinning the development of super-resolution microscopy based on single-molecule localization and active control of emitting concentration. Current thrust areas include extensions to three-dimensional imaging with high precision, orientational analysis of single molecules, and direct measurements of photodynamics and transport properties for single molecules trapped in solution by suppression of Brownian motion. Without question, a huge variety of studies of single molecules performed by many talented scientists all over the world have extended our knowledge of the nanoscale and microscopic mechanisms previously hidden by ensemble averaging. PMID:26616210

Nucleic acid detection system and method for detecting influenza

DOEpatents

Cai, Hong; Song, Jian

2015-03-17

The invention provides a rapid, sensitive and specific nucleic acid detection system which utilizes isothermal nucleic acid amplification in combination with a lateral flow chromatographic device, or DNA dipstick, for DNA-hybridization detection. The system of the invention requires no complex instrumentation or electronic hardware, and provides a low cost nucleic acid detection system suitable for highly sensitive pathogen detection. Hybridization to single-stranded DNA amplification products using the system of the invention provides a sensitive and specific means by which assays can be multiplexed for the detection of multiple target sequences.

Cucurbituril mediated single molecule detection and identification via recognition tunneling.

PubMed

Xiao, Bohuai; Liang, Feng; Liu, Simin; Im, JongOne; Li, Yunchuan; Liu, Jing; Zhang, Bintian; Zhou, Jianghao; He, Jin; Chang, Shuai

2018-06-08

Recognition tunneling (RT) is an emerging technique for investigating single molecules in a tunnel junction. We have previously demonstrated its capability of single molecule detection and identification, as well as probing the dynamics of intermolecular bonding at the single molecule level. Here by introducing cucurbituril as a new class of recognition molecule, we demonstrate a powerful platform for electronically investigating the host-guest chemistry at single molecule level. In this report, we first investigated the single molecule electrical properties of cucurbituril in a tunnel junction. Then we studied two model guest molecules, aminoferrocene and amantadine, which were encapsulated by cucurbituril. Small differences in conductance and lifetime can be recognized between the host-guest complexes with the inclusion of different guest molecules. By using a machine learning algorithm to classify the RT signals in a hyper dimensional space, the accuracy of guest molecule recognition can be significantly improved, suggesting the possibility of using cucurbituril molecule for single molecule identification. This work enables a new class of recognition molecule for RT technique and opens the door for detecting a vast variety of small molecules by electrical measurements.

TagDust2: a generic method to extract reads from sequencing data.

PubMed

Lassmann, Timo

2015-01-28

Arguably the most basic step in the analysis of next generation sequencing data (NGS) involves the extraction of mappable reads from the raw reads produced by sequencing instruments. The presence of barcodes, adaptors and artifacts subject to sequencing errors makes this step non-trivial. Here I present TagDust2, a generic approach utilizing a library of hidden Markov models (HMM) to accurately extract reads from a wide array of possible read architectures. TagDust2 extracts more reads of higher quality compared to other approaches. Processing of multiplexed single, paired end and libraries containing unique molecular identifiers is fully supported. Two additional post processing steps are included to exclude known contaminants and filter out low complexity sequences. Finally, TagDust2 can automatically detect the library type of sequenced data from a predefined selection. Taken together TagDust2 is a feature rich, flexible and adaptive solution to go from raw to mappable NGS reads in a single step. The ability to recognize and record the contents of raw reads will help to automate and demystify the initial, and often poorly documented, steps in NGS data analysis pipelines. TagDust2 is freely available at: http://tagdust.sourceforge.net .

Trimethylamine Sensors Based on Au-Modified Hierarchical Porous Single-Crystalline ZnO Nanosheets.

PubMed

Meng, Fanli; Zheng, Hanxiong; Sun, Yufeng; Li, Minqiang; Liu, Jinhuai

2017-06-22

It is of great significance for dynamic monitoring of foods in storage or during the transportation process through on-line detecting trimethylamine (TMA). Here, TMA were sensitively detected by Au-modified hierarchical porous single-crystalline ZnO nanosheets (HPSCZNs)-based sensors. The HPSCZNs were synthesized through a one-pot wet-chemical method followed by an annealing treatment. Polyethyleneimine (PEI) was used to modify the surface of the HPSCZNs, and then the PEI-modified samples were mixed with Au nanoparticles (NPs) sol solution. Electrostatic interactions drive Au nanoparticles loading onto the surface of the HPSCZNs. The Au-modified HPSCZNs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrum (EDS), respectively. The results show that Au-modified HPSCZNs-based sensors exhibit a high response to TMA. The linear range is from 10 to 300 ppb; while the detection limit is 10 ppb, which is the lowest value to our knowledge.

Trimethylamine Sensors Based on Au-Modified Hierarchical Porous Single-Crystalline ZnO Nanosheets

PubMed Central

Zheng, Hanxiong; Sun, Yufeng; Li, Minqiang; Liu, Jinhuai

2017-01-01

It is of great significance for dynamic monitoring of foods in storage or during the transportation process through on-line detecting trimethylamine (TMA). Here, TMA were sensitively detected by Au-modified hierarchical porous single-crystalline ZnO nanosheets (HPSCZNs)-based sensors. The HPSCZNs were synthesized through a one-pot wet-chemical method followed by an annealing treatment. Polyethyleneimine (PEI) was used to modify the surface of the HPSCZNs, and then the PEI-modified samples were mixed with Au nanoparticles (NPs) sol solution. Electrostatic interactions drive Au nanoparticles loading onto the surface of the HPSCZNs. The Au-modified HPSCZNs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrum (EDS), respectively. The results show that Au-modified HPSCZNs-based sensors exhibit a high response to TMA. The linear range is from 10 to 300 ppb; while the detection limit is 10 ppb, which is the lowest value to our knowledge. PMID:28640226

Experimental quasi-single-photon transmission from satellite to earth.

PubMed

Yin, Juan; Cao, Yuan; Liu, Shu-Bin; Pan, Ge-Sheng; Wang, Jin-Hong; Yang, Tao; Zhang, Zhong-Ping; Yang, Fu-Min; Chen, Yu-Ao; Peng, Cheng-Zhi; Pan, Jian-Wei

2013-08-26

Free-space quantum communication with satellites opens a promising avenue for global secure quantum network and large-scale test of quantum foundations. Recently, numerous experimental efforts have been carried out towards this ambitious goal. However, one essential step--transmitting single photons from the satellite to the ground with high signal-to-noise ratio (SNR) at realistic environments--remains experimental challenging. Here, we report a direct experimental demonstration of the satellite-ground transmission of a quasi-single-photon source. In the experiment, single photons (~0.85 photon per pulse) are generated by reflecting weak laser pulses back to earth with a cube-corner retro-reflector on the satellite CHAMP, collected by a 600-mm diameter telescope at the ground station, and finally detected by single-photon counting modules after 400-km free-space link transmission. With the help of high accuracy time synchronization, narrow receiver field-of-view and high-repetition-rate pulses (76 MHz), a SNR of better than 16:1 is obtained, which is sufficient for a secure quantum key distribution. Our experimental results represent an important step towards satellite-ground quantum communication.

78 FR 34990 - Application(s) for Duty-Free Entry of Scientific Instruments

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-11

... living organisms, cellular constructs, viruses, bacteria, and single-celled organisms, as well as... samples, and back-scattered electron detection of colloidal gold particles. Experiments will also require...

Chemoselective Hydrodehalogenation of Organic Halides Utilizing Two-Dimensional Anionic Electrons of Inorganic Electride [Ca2N]+·e^.

PubMed

Kim, Ye Ji; Kim, Sun Min; Yu, Chunghyeon; Yoo, YoungMin; Cho, Eun Jin; Yang, Jung Woon; Kim, Sung Wng

2017-01-31

Halogenated organic compounds are important anthropogenic chemicals widely used in chemical industry, biology, and pharmacology; however, the persistence and inertness of organic halides cause human health problems and considerable environmental pollution. Thus, the elimination or replacement of halogen atoms with organic halides has been considered a central task in synthetic chemistry. In dehalogenation reactions, the consecutive single-electron transfer from reducing agents generates the radical and corresponding carbanion and thus removes the halogen atom as the leaving group. Herein, we report a new strategy for an efficient chemoselective hydrodehalogenation through the formation of stable carbanion intermediates, which are simply achieved by using highly mobile two-dimensional electrons of inorganic electride [Ca 2 N] + ·e - with effective electron transfer ability. The consecutive single-electron transfer from inorganic electride [Ca 2 N] + ·e - stabilized free carbanions, which is a key step in achieving the selective reaction. Furthermore, a determinant more important than leaving group ability is the stability control of free carbanions according to the s character determined by the backbone structure. We anticipate that this approach may provide new insight into selective chemical formation, including hydrodehalogenation.

A versatile atomic force microscope integrated with a scanning electron microscope.

PubMed

Kreith, J; Strunz, T; Fantner, E J; Fantner, G E; Cordill, M J

2017-05-01

A versatile atomic force microscope (AFM), which can be installed in a scanning electron microscope (SEM), is introduced. The flexible design of the instrument enables correlated analysis for different experimental configurations, such as AFM imaging directly after nanoindentation in vacuum. In order to demonstrate the capabilities of the specially designed AFM installed inside a SEM, slip steps emanating around nanoindents in single crystalline brass were examined. This example showcases how the combination of AFM and SEM imaging can be utilized for quantitative dislocation analysis through the measurement of the slip step heights without the hindrance of oxide formation. Finally, an in situ nanoindentation technique is introduced, illustrating the use of AFM imaging during indentation experiments to examine plastic deformation occurring under the indenter tip. The mechanical indentation data are correlated to the SEM and AFM images to estimate the number of dislocations emitted to the surface.

Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses.

PubMed

Calegari, F; Ayuso, D; Trabattoni, A; Belshaw, L; De Camillis, S; Anumula, S; Frassetto, F; Poletto, L; Palacios, A; Decleva, P; Greenwood, J B; Martín, F; Nisoli, M

2014-10-17

In the past decade, attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules, and solids. Here, we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine and the subsequent detection of ultrafast dynamics on a sub-4.5-femtosecond temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules represents a crucial step forward in attosecond science, which is progressively moving toward the investigation of more and more complex systems. Copyright © 2014, American Association for the Advancement of Science.

Hydrated electrons react with high specificity with cisplatin bound to single-stranded DNA.

PubMed

Behmand, B; Cloutier, P; Girouard, S; Wagner, J R; Sanche, L; Hunting, D J

2013-12-19

Short oligonucleotides TTTTTGTGTTT and TTTTTTTGTTT in solution with and without cisplatin (cisPt) bound to the guanine bases were irradiated with γ-rays at doses varying from 0 to 2500 Gy. To determine the effect of hydrated electrons from water radiolysis on the oligonucleotides, we quenched (•)OH radicals with ethylenediaminetetraacetic acid (EDTA) and displaced oxygen, which reacts with hydrated electrons, by bubbling the solution with wet nitrogen. DNA strand breaks and platinum detachment were quantified by gel electrophoresis. Our results demonstrate that hydrated electrons react almost exclusively at the position of the cisPt adduct, where they induce cisPt detachment from one or both guanines in the oligonucleotide. Given the high yield of hydrated electrons in irradiated tissues, this reaction may be an important step in the mechanism of radiosensitization of DNA by cisPt.

Cyclic fatigue behavior of nickel-titanium dental rotary files in clinical simulated root canals.

PubMed

Chi, Chih-Wen; Li, Chun-Chieh; Lin, Chun-Pin; Shin, Chow-Shing

2017-04-01

Dental rotary instruments can be applied in multiple conditions of canals, but unpredictable fatigue fracture may happen. This study evaluated the fatigue lives of two batches of nickel-titanium (NiTi) dental rotary files operating in clinically simulated root canals. Single-step cyclic fatigue tests were carried out to assess the performance of two batches of NiTi files (ProTaper and ProFile) in nine combinations of simulated canals (cylinder radii 5 mm, 7.5 mm, and 10 mm, and insertion angles 20°, 40°, and 60°). Two-step cyclic fatigue tests were carried out in simulated root canals with the same radius by using the following two sets of insertion angles: (20°, 40°), (20°, 60°), (40°, 20°), and (60°, 20°). Fracture surfaces were observed by scanning electron microscopy. The single-step cyclic fatigue results showed that cyclic fatigue lives of the files decreased with increasing insertion angles or decreasing cylinder radius. The ProFile #25 .04 file was more fatigue resistant than the ProTaper F2 file. In two-step cyclic fatigue tests, the total fatigue lives were usually more than 100% when the files operated at a lower strain and then at a higher strain. By scanning electron microscopy, a larger area of fatigue striation corresponded to a longer fatigue life. Cyclic fatigue life can be influenced by the strains and geometries of files. The fatigue life was prolonged when the files operated at a lower strain and then at a higher strain. However, the fatigue life was shortened if the loading sequence was reversed. Copyright © 2016. Published by Elsevier B.V.

A modified single-tube one-step product-enhanced reverse transcriptase (mSTOS-PERT) assay with heparin as DNA polymerase inhibitor for specific detection of RTase activity.

PubMed

Fan, Xiao-Yong; Lü, Guo-Zhen; Wu, Li-Na; Chen, Jing-Hua; Xu, Wen-Qing; Zhao, Chun-Nü; Guo, Sheng-Qi

2006-12-01

Current regulations and recommendations proposed for the production of vaccines in continuous cell lines of any origin demand that these be free of exogenous viruses, particularly retroviruses. Recently, the ultra-sensitive product-enhanced reverse transcriptase (PERT) assay can be used to detect minute of reverse transcriptase (RTase) in single retroviral particle and is 10(6) times more sensitive than the conventional RTase assays. However, coincidental with this increase in sensitivity is an increase in false-positive reactions derived from contaminating cellular DNA polymerases, which are known to have RTase-like activities. To develop a modified single-tube one-step PERT (mSTOS-PERT) assay with improvements on decreasing significantly the level of false-positive reactions, and to evaluate the mSTOS-PERT assay for sensitivity and specificity. Ampliwaxtrade mark was used to compartmentalize the reverse transcription (RT) and PCR step in the same micro-tube with more efficiency and reproducibility, while maintaining the high sensitivity. The DNA amplification products were separated by 2% agarose gel electrophoresis, and then analyzed by non-isotopic Southern blot hybridization. A wide variety of cell lines used in biologicals production were detected to validate the improved mSTOS-PERT assay. The detection limit for the mSTOS-PERT assay was at least 10(-9)U, when using AMV-RTase as a positive control. Furthermore, heparin involvement in the RT step can eliminate completely the false-positive PERT signals which are exhibited by cellular polymerases such as DNA-dependent DNA polymerase alpha, gamma released by cell death. Most mammalian cells (MRC-5, Vero, WISH, 2BS, RK-13, MDCK, etc.) are PERT-negative in cell supernatants. Some PERT-positive signals in cell lysates were found to be introduced by the cellular DNA polymerases and could be inhibited specifically by heparin. Chick cells derived from either chick embryo fibroblasts (CEF) or allantoic fluid from SPF embryonated eggs, murine hybridoma cell SP2/0, etc., contained authentic RTase activities, which could not be inactivated by heparin. The improved mSTOS-PERT assay described here may distinguish the genuine RTase activity from cellular polymerases with high sensitivity and specificity, and is rapid and easy to perform to screen for the possible contamination of minute retroviruses in the cell substrates used in vaccine production.

Reflection symmetry detection using locally affine invariant edge correspondence.

PubMed

Wang, Zhaozhong; Tang, Zesheng; Zhang, Xiao

2015-04-01

Reflection symmetry detection receives increasing attentions in recent years. The state-of-the-art algorithms mainly use the matching of intensity-based features (such as the SIFT) within a single image to find symmetry axes. This paper proposes a novel approach by establishing the correspondence of locally affine invariant edge-based features, which are superior to the intensity based in the aspects that it is insensitive to illumination variations, and applicable to textureless objects. The locally affine invariance is achieved by simple linear algebra for efficient and robust computations, making the algorithm suitable for detections under object distortions like perspective projection. Commonly used edge detectors and a voting process are, respectively, used before and after the edge description and matching steps to form a complete reflection detection pipeline. Experiments are performed using synthetic and real-world images with both multiple and single reflection symmetry axis. The test results are compared with existing algorithms to validate the proposed method.

Loop-mediated isothermal amplification assay for detection and discrimination of Toxocara canis and Toxocara cati eggs directly from sand samples.

PubMed

Macuhova, K; Kumagai, T; Akao, N; Ohta, N

2010-12-01

We developed a novel and simple method, using loop-mediated isothermal amplification (LAMP), for the detection and discrimination of Toxocara canis and Toxocara cati eggs. The new method employs 4 steps: (1) concentration of Toxocara eggs in a small amount of sand; (2) dissolution of the proteinaceous membrane of eggs and simultaneously separation of them from the sand using NaClO treatment; (3) extraction of DNA using NaOH treatment; and (4) detection of T. canis / T. cati DNA using a LAMP assay. All these steps are fast, easy to perform, and do not require expensive equipment or reagents. The novel method was tested both experimentally and in a field study. In the laboratory, we could reliably detect as few as 3 T. canis eggs in artificially contaminated sand, if the experiment was repeated twice. In the field trial, we were able to detect T. cati DNA from 4 natural sandpits having moderate to heavy contamination, although not in a single lightly contaminated sandpit. All of the examined sandpits were found to be contaminated with eggs of T. cati, but none appeared to contain T. canis. Our new method could extract DNA from T. canis and T. cati eggs directly from sand samples as well as detect and distinguish these 2 species in a few easy steps, with markedly reduced time and expense.

47 CFR 1.10009 - What are the steps for electronic filing?

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false What are the steps for electronic filing? 1... International Bureau Filing System § 1.10009 What are the steps for electronic filing? (a) Step 1: Register for... an FRN, go to Step 2. (2) In order to process your electronic application, you must have an FRN. You...

Broadband Transmission EPR Spectroscopy

PubMed Central

Hagen, Wilfred R.

2013-01-01

EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9–10 GHz range. Most (bio)molecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin – nuclear spin interactions and electron spin – electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8–2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed. PMID:23555819

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.

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.

Digital Literature: Finding New Ways to Motivate Students to Read Brazilian Literature Electronic Books

ERIC Educational Resources Information Center

Barbosa, Vania Soares; Lima, Vera; Silva, Rejane; Silva, Willy; Soares, Ana Carolina; de Sousa, Aline

2012-01-01

This quantitative and qualitative study is aimed to diagnose and promote the use of new technologies in teaching literature reading in Public (State) Schools, assessing materials accessibility and computer skills. The research consisted of three distinct steps: (1) A survey to detect teachers' and students' computer skills, their use of computers…

Single-molecule comparison of DNA Pol I activity with native and analog nucleotides

NASA Astrophysics Data System (ADS)

Gul, Osman; Olsen, Tivoli; Choi, Yongki; Corso, Brad; Weiss, Gregory; Collins, Philip

2014-03-01

DNA polymerases are critical enzymes for DNA replication, and because of their complex catalytic cycle they are excellent targets for investigation by single-molecule experimental techniques. Recently, we studied the Klenow fragment (KF) of DNA polymerase I using a label-free, electronic technique involving single KF molecules attached to carbon nanotube transistors. The electronic technique allowed long-duration monitoring of a single KF molecule while processing thousands of template strands. Processivity of up to 42 nucleotide bases was directly observed, and statistical analysis of the recordings determined key kinetic parameters for the enzyme's open and closed conformations. Subsequently, we have used the same technique to compare the incorporation of canonical nucleotides like dATP to analogs like 1-thio-2'-dATP. The analog had almost no affect on duration of the closed conformation, during which the nucleotide is incorporated. On the other hand, the analog increased the rate-limiting duration of the open conformation by almost 40%. We propose that the thiolated analog interferes with KF's recognition and binding, two key steps that determine its ensemble turnover rate.

In situ hybridization at the electron microscope level: localization of transcripts on ultrathin sections of Lowicryl K4M-embedded tissue using biotinylated probes and protein A-gold complexes

PubMed Central

1986-01-01

A technique has been developed for localizing hybrids formed in situ on semi-thin and ultrathin sections of Lowicryl K4M-embedded tissue. Biotinylated dUTP (Bio-11-dUTP and/or Bio-16-dUTP) was incorporated into mitochondrial rDNA and small nuclear U1 probes by nick- translation. The probes were hybridized to sections of Drosophila ovaries and subsequently detected with an anti-biotin antibody and protein A-gold complex. On semi-thin sections, probe detection was achieved by amplification steps with anti-protein A antibody and protein A-gold with subsequent silver enhancement. At the electron microscope level, specific labeling was obtained over structures known to be the site of expression of the appropriate genes (i.e., either over mitochondria or over nuclei). The labeling pattern at the light microscope level (semi-thin sections) was consistent with that obtained at the electron microscope level. The described nonradioactive procedures for hybrid detection on Lowicryl K4M-embedded tissue sections offer several advantages: rapid signal detection: superior morphological preservation and spatial resolution; and signal-to-noise ratios equivalent to radiolabeling. PMID:3084498

One-step electrochemical deposition of a graphene-ZrO 2 nanocomposite: Preparation, characterization and application for detection of organophosphorus agents

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

Du, Dan; Liu, Juan; Zhang, Xiao-Yan

2011-04-27

This paper described the preparation, characterization, and electrochemical properties of a graphene-ZrO 2 nanocomposite (GZN) and its application for both the enrichment and detection of methyl parathion (MP). GZN was fabricated using electrochemical deposition and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), which showed the successful formation of nanocomposites. Due to the strong affinity to the phosphoric group and the fast electron-transfer kinetics of GZN, both the extraction and electrochemical detection of organophosphorus (OP) agents at the same GZN modified electrochemical sensor was possible. The combination of solid-phase extractionmore » and stripping voltammetric analysis allowed fast, sensitive, and selective determination of MP in garlic samples. The stripping response was highly linear over the MP concentrations ranging from 0.5 ng mL -1 to 100 ng mL -1, with a detection limit of 0.1 ng mL -1. This new nanocomposite-based electrochemical sensor provides an opportunity to develop a field-deployable, sensitive, and quantitative method for monitoring exposure to OPs.« less

Tremella-like graphene-Au composites used for amperometric determination of dopamine.

PubMed

Li, Cong; Zhao, Jingyu; Yan, Xiaoyi; Gu, Yue; Liu, Weilu; Tang, Liu; Zheng, Bo; Li, Yaru; Chen, Ruixue; Zhang, Zhiquan

2015-03-21

Electrochemical detection of dopamine (DA) plays an important role in medical diagnosis. In this paper, tremella-like graphene-Au (t-GN-Au) composites were synthesized by a one-step hydrothermal method for selective detection of DA. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy were used to characterize as-prepared t-GN-Au composites. The t-GN-Au composites were directly used for the determination of DA via cyclic voltammetry (CV) and the chronoamperometry (CA) technique. CA measurement gave a wide linear range from 0.8 to 2000 μM, and the detection limit of 57 nM (S/N = 3) for DA. The mechanism and the heterogeneous electron transfer kinetics of the DA oxidation were discussed in the light of rotating disk electrode (RDE) experiments. Moreover, the modified electrode was applied to the determination of DA in human urine and serum samples.

Demonstration of Single-Barium-Ion Sensitivity for Neutrinoless Double-Beta Decay Using Single-Molecule Fluorescence Imaging

DOE PAGES

McDonald, A. D.; Jones, B. J. P.; Nygren, D. R.; ...

2018-03-26

A new method to tag the barium daughter in the double beta decay ofmore » $$^{136}$$Xe is reported. Using the technique of single molecule fluorescent imaging (SMFI), individual barium dication (Ba$$^{++}$$) resolution at a transparent scanning surface has been demonstrated. A single-step photo-bleach confirms the single ion interpretation. Individual ions are localized with super-resolution ($$\\sim$$2~nm), and detected with a statistical significance of 12.9~$$\\sigma$$ over backgrounds. This lays the foundation for a new and potentially background-free neutrinoless double beta decay technology, based on SMFI coupled to high pressure xenon gas time projection chambers.« less

A space- and time-resolved single photon counting detector for fluorescence microscopy and spectroscopy

PubMed Central

Michalet, X.; Siegmund, O.H.W.; Vallerga, J.V.; Jelinsky, P.; Millaud, J.E.; Weiss, S.

2017-01-01

We have recently developed a wide-field photon-counting detector having high-temporal and high-spatial resolutions and capable of high-throughput (the H33D detector). Its design is based on a 25 mm diameter multi-alkali photocathode producing one photo electron per detected photon, which are then multiplied up to 107 times by a 3-microchannel plate stack. The resulting electron cloud is proximity focused on a cross delay line anode, which allows determining the incident photon position with high accuracy. The imaging and fluorescence lifetime measurement performances of the H33D detector installed on a standard epifluorescence microscope will be presented. We compare them to those of standard single-molecule detectors such as single-photon avalanche photodiode (SPAD) or electron-multiplying camera using model samples (fluorescent beads, quantum dots and live cells). Finally, we discuss the design and applications of future generation of H33D detectors for single-molecule imaging and high-throughput study of biomolecular interactions. PMID:29479130

A new fast detection system at the KWS-2 high-intensity SANS diffractometer of the JCNS at MLZ - prototype test

NASA Astrophysics Data System (ADS)

Radulescu, A.; Arend, N.; Drochner, M.; Ioffe, A.; Kemmerling, G.; Ossovyi, V.; Staringer, S.; Vehres, G.; McKinny, K.; Olechnowicz, B.; Yen, D.

2016-09-01

A new detection system based on an array of 3He tubes and innovative fast detection electronics was designed and produced by GE Reuter Stokes for the high-intensity small-angle neutron scattering diffractometer KWS-2, operated by the Jülich Centre for Neutron Science (JCNS) at the Heinz Meier-Leibnitz Zentrum (MLZ). The new detector consists of a panel array of 144 3He tubes and a new fast read-out electronics. The electronics is mounted in a closed case in the backside of the 3He tubes panel array and will operate at ambient atmosphere under cooling air stream. The new detection system is composed of eighteen 8-pack modules of 3He-tubes that work independently of one another (each unit has its own processor and electronics). Knowing beforehand the performance of one detector unit and of one single tube detector is prerequisite for tuning and maximizing the performance of the complete detection system. In this paper we present the results of the tests of the prototyped 8-pack of 3He-tubes and corresponding electronics, which have been carried out at the JCNS instruments KWS-2 (in high flux conditions) and TREFF.

Probing Dirac fermion dynamics in topological insulator Bi2Se3 films with a scanning tunneling microscope.

PubMed

Song, Can-Li; Wang, Lili; He, Ke; Ji, Shuai-Hua; Chen, Xi; Ma, Xu-Cun; Xue, Qi-Kun

2015-05-01

Scanning tunneling microscopy and spectroscopy have been used to investigate the femtosecond dynamics of Dirac fermions in the topological insulator Bi2Se3 ultrathin films. At the two-dimensional limit, bulk electrons become quantized and the quantization can be controlled by the film thickness at a single quintuple layer level. By studying the spatial decay of standing waves (quasiparticle interference patterns) off steps, we measure directly the energy and film thickness dependence of the phase relaxation length lϕ and inelastic scattering lifetime τ of topological surface-state electrons. We find that τ exhibits a remarkable (E - EF)(-2) energy dependence and increases with film thickness. We show that the features revealed are typical for electron-electron scattering between surface and bulk states.

Sustained change blindness to incremental scene rotation: a dissociation between explicit change detection and visual memory.

PubMed

Hollingworth, Andrew; Henderson, John M

2004-07-01

In a change detection paradigm, the global orientation of a natural scene was incrementally changed in 1 degree intervals. In Experiments 1 and 2, participants demonstrated sustained change blindness to incremental rotation, often coming to consider a significantly different scene viewpoint as an unchanged continuation of the original view. Experiment 3 showed that participants who failed to detect the incremental rotation nevertheless reliably detected a single-step rotation back to the initial view. Together, these results demonstrate an important dissociation between explicit change detection and visual memory. Following a change, visual memory is updated to reflect the changed state of the environment, even if the change was not detected.

Monolayer PtSe₂, a New Semiconducting Transition-Metal-Dichalcogenide, Epitaxially Grown by Direct Selenization of Pt.

PubMed

Wang, Yeliang; Li, Linfei; Yao, Wei; Song, Shiru; Sun, J T; Pan, Jinbo; Ren, Xiao; Li, Chen; Okunishi, Eiji; Wang, Yu-Qi; Wang, Eryin; Shao, Yan; Zhang, Y Y; Yang, Hai-tao; Schwier, Eike F; Iwasawa, Hideaki; Shimada, Kenya; Taniguchi, Masaki; Cheng, Zhaohua; Zhou, Shuyun; Du, Shixuan; Pennycook, Stephen J; Pantelides, Sokrates T; Gao, Hong-Jun

2015-06-10

Single-layer transition-metal dichalcogenides (TMDs) receive significant attention due to their intriguing physical properties for both fundamental research and potential applications in electronics, optoelectronics, spintronics, catalysis, and so on. Here, we demonstrate the epitaxial growth of high-quality single-crystal, monolayer platinum diselenide (PtSe2), a new member of the layered TMDs family, by a single step of direct selenization of a Pt(111) substrate. A combination of atomic-resolution experimental characterizations and first-principle theoretic calculations reveals the atomic structure of the monolayer PtSe2/Pt(111). Angle-resolved photoemission spectroscopy measurements confirm for the first time the semiconducting electronic structure of monolayer PtSe2 (in contrast to its semimetallic bulk counterpart). The photocatalytic activity of monolayer PtSe2 film is evaluated by a methylene-blue photodegradation experiment, demonstrating its practical application as a promising photocatalyst. Moreover, circular polarization calculations predict that monolayer PtSe2 has also potential applications in valleytronics.

Metals bioleaching from electronic waste by Chromobacterium violaceum and Pseudomonads sp.

PubMed

Pradhan, Jatindra Kumar; Kumar, Sudhir

2012-11-01

These days, electronic waste needs to be taken into consideration due to its materials content, but due to the heterogeneity of the metals present, reprocessing of electronic waste is quite limited. The bioleaching of metals from electronic waste was investigated by using cyanogenic bacterial strains (Chromobacterium violaceum, Pseudomonas aeruginosa and Pseudomonas fluorescens). A two-step bioleaching process was followed under cyanide-forming conditions for maximum metals mobilization. Both single and mixed cultures of cyanogenic bacteria were able to mobilize metals from electronic waste with different efficiencies. In all the flasks in which high metal mobilizations were observed, the consequent biomass productions were also high. Pseudomonas aeruginosa was applied in the bioleaching process for the first time and this achieved its bioleaching ability of mobilization of metals from electronic waste. Chromobacterium violaceum as a single culture and a mixture of C. violaceum and P. aeruginosa exhibited maximum metal mobilization. Chromobacterium violaceum was capable of leaching more than 79, 69, 46, 9 and 7% of Cu, Au, Zn, Fe and Ag, respectively at an electronic waste concentration of 1% w/v. Moreover, the mixture of C. violaceum and P. aeruginosa exhibited metals leaching of more than 83, 73, 49, 13 and 8% of total Cu, Au, Zn, Fe, and Ag, respectively. Precious metals were mobilized through bioleaching which might be considered as an industrial application for recycling of electronic waste in the near future.

Conceptual design and development of GEM based detecting system for tomographic tungsten focused transport monitoring

NASA Astrophysics Data System (ADS)

Chernyshova, M.; Czarski, T.; Malinowski, K.; Kowalska-Strzęciwilk, E.; Poźniak, K.; Kasprowicz, G.; Zabołotny, W.; Wojeński, A.; Kolasiński, P.; Mazon, D.; Malard, P.

2015-10-01

Implementing tungsten as a plasma facing material in ITER and future fusion reactors will require effective monitoring of not just its level in the plasma but also its distribution. That can be successfully achieved using detectors based on Gas Electron Multiplier (GEM) technology. This work presents the conceptual design of the detecting unit for poloidal tomography to be tested at the WEST project tokamak. The current stage of the development is discussed covering aspects which include detector's spatial dimensions, gas mixtures, window materials and arrangements inside and outside the tokamak ports, details of detector's structure itself and details of the detecting module electronics. It is expected that the detecting unit under development, when implemented, will add to the safe operation of tokamak bringing the creation of sustainable nuclear fusion reactors a step closer. A shorter version of this contribution is due to be published in PoS at: 1st EPS conference on Plasma Diagnostics

Cryo-EM image alignment based on nonuniform fast Fourier transform.

PubMed

Yang, Zhengfan; Penczek, Pawel A

2008-08-01

In single particle analysis, two-dimensional (2-D) alignment is a fundamental step intended to put into register various particle projections of biological macromolecules collected at the electron microscope. The efficiency and quality of three-dimensional (3-D) structure reconstruction largely depends on the computational speed and alignment accuracy of this crucial step. In order to improve the performance of alignment, we introduce a new method that takes advantage of the highly accurate interpolation scheme based on the gridding method, a version of the nonuniform fast Fourier transform, and utilizes a multi-dimensional optimization algorithm for the refinement of the orientation parameters. Using simulated data, we demonstrate that by using less than half of the sample points and taking twice the runtime, our new 2-D alignment method achieves dramatically better alignment accuracy than that based on quadratic interpolation. We also apply our method to image to volume registration, the key step in the single particle EM structure refinement protocol. We find that in this case the accuracy of the method not only surpasses the accuracy of the commonly used real-space implementation, but results are achieved in much shorter time, making gridding-based alignment a perfect candidate for efficient structure determination in single particle analysis.

Cryo-EM Image Alignment Based on Nonuniform Fast Fourier Transform

PubMed Central

Yang, Zhengfan; Penczek, Pawel A.

2008-01-01

In single particle analysis, two-dimensional (2-D) alignment is a fundamental step intended to put into register various particle projections of biological macromolecules collected at the electron microscope. The efficiency and quality of three-dimensional (3-D) structure reconstruction largely depends on the computational speed and alignment accuracy of this crucial step. In order to improve the performance of alignment, we introduce a new method that takes advantage of the highly accurate interpolation scheme based on the gridding method, a version of the nonuniform Fast Fourier Transform, and utilizes a multi-dimensional optimization algorithm for the refinement of the orientation parameters. Using simulated data, we demonstrate that by using less than half of the sample points and taking twice the runtime, our new 2-D alignment method achieves dramatically better alignment accuracy than that based on quadratic interpolation. We also apply our method to image to volume registration, the key step in the single particle EM structure refinement protocol. We find that in this case the accuracy of the method not only surpasses the accuracy of the commonly used real-space implementation, but results are achieved in much shorter time, making gridding-based alignment a perfect candidate for efficient structure determination in single particle analysis. PMID:18499351

Nanopore arrays in a silicon membrane for parallel single-molecule detection: DNA translocation

NASA Astrophysics Data System (ADS)

Zhang, Miao; Schmidt, Torsten; Jemt, Anders; Sahlén, Pelin; Sychugov, Ilya; Lundeberg, Joakim; Linnros, Jan

2015-08-01

Optical nanopore sensing offers great potential in single-molecule detection, genotyping, or DNA sequencing for high-throughput applications. However, one of the bottle-necks for fluorophore-based biomolecule sensing is the lack of an optically optimized membrane with a large array of nanopores, which has large pore-to-pore distance, small variation in pore size and low background photoluminescence (PL). Here, we demonstrate parallel detection of single-fluorophore-labeled DNA strands (450 bps) translocating through an array of silicon nanopores that fulfills the above-mentioned requirements for optical sensing. The nanopore array was fabricated using electron beam lithography and anisotropic etching followed by electrochemical etching resulting in pore diameters down to ∼7 nm. The DNA translocation measurements were performed in a conventional wide-field microscope tailored for effective background PL control. The individual nanopore diameter was found to have a substantial effect on the translocation velocity, where smaller openings slow the translocation enough for the event to be clearly detectable in the fluorescence. Our results demonstrate that a uniform silicon nanopore array combined with wide-field optical detection is a promising alternative with which to realize massively-parallel single-molecule detection.

Diffraction Techniques in Structural Biology

PubMed Central

Egli, Martin

2010-01-01

A detailed understanding of chemical and biological function and the mechanisms underlying the activities ultimately requires atomic-resolution structural data. Diffraction-based techniques such as single-crystal X-ray crystallography, electron microscopy and neutron diffraction are well established and have paved the road to the stunning successes of modern-day structural biology. The major advances achieved in the last 20 years in all aspects of structural research, including sample preparation, crystallization, the construction of synchrotron and spallation sources, phasing approaches and high-speed computing and visualization, now provide specialists and non-specialists alike with a steady flow of molecular images of unprecedented detail. The present chapter combines a general overview of diffraction methods with a step-by-step description of the process of a single-crystal X-ray structure determination experiment, from chemical synthesis or expression to phasing and refinement, analysis and quality control. For novices it may serve as a stepping-stone to more in-depth treatises of the individual topics. Readers relying on structural information for interpreting functional data may find it a useful consumer guide. PMID:20517991

Advantages offered by high average power picosecond lasers

NASA Astrophysics Data System (ADS)

Moorhouse, C.

2011-03-01

As electronic devices shrink in size to reduce material costs, device size and weight, thinner material thicknesses are also utilized. Feature sizes are also decreasing, which is pushing manufacturers towards single step laser direct write process as an attractive alternative to conventional, multiple step photolithography processes by eliminating process steps and the cost of chemicals. The fragile nature of these thin materials makes them difficult to machine either mechanically or with conventional nanosecond pulsewidth, Diode Pumped Solids State (DPSS) lasers. Picosecond laser pulses can cut materials with reduced damage regions and selectively remove thin films due to the reduced thermal effects of the shorter pulsewidth. Also, the high repetition rate allows high speed processing for industrial applications. Selective removal of thin films for OLED patterning, silicon solar cells and flat panel displays is discussed, as well as laser cutting of transparent materials with low melting point such as Polyethylene Terephthalate (PET). For many of these thin film applications, where low pulse energy and high repetition rate are required, throughput can be increased by the use of a novel technique to using multiple beams from a single laser source is outlined.

Contrast, size, and orientation-invariant target detection in infrared imagery

NASA Astrophysics Data System (ADS)

Zhou, Yi-Tong; Crawshaw, Richard D.

1991-08-01

Automatic target detection in IR imagery is a very difficult task due to variations in target brightness, shape, size, and orientation. In this paper, the authors present a contrast, size, and orientation invariant algorithm based on Gabor functions for detecting targets from a single IR image frame. The algorithms consists of three steps. First, it locates potential targets by using low-resolution Gabor functions which resist noise and background clutter effects, then, it removes false targets and eliminates redundant target points based on a similarity measure. These two steps mimic human vision processing but are different from Zeevi's Foveating Vision System. Finally, it uses both low- and high-resolution Gabor functions to verify target existence. This algorithm has been successfully tested on several IR images that contain multiple examples of military vehicles with different size and brightness in various background scenes and orientations.

In vitro and in vivo testing of a novel recessed-step catheter for reflux-free convection-enhanced drug delivery to the brain.

PubMed

Gill, T; Barua, N U; Woolley, M; Bienemann, A S; Johnson, D E; S O'Sullivan; Murray, G; Fennelly, C; Lewis, O; Irving, C; Wyatt, M J; Moore, P; Gill, S S

2013-09-30

The optimisation of convection-enhanced drug delivery (CED) to the brain is fundamentally reliant on minimising drug reflux. The aim of this study was to evaluate the performance of a novel reflux-resistant CED catheter incorporating a recessed-step and to compare its performance to previously described stepped catheters. The in vitro performance of the recessed-step catheter was compared to a conventional "one-step" catheter with a single transition in outer diameter (OD) at the catheter tip, and a "two-step" design comprising two distal transitions in OD. The volumes of distribution and reflux were compared by performing infusions of Trypan blue into agarose gels. The in vivo performance of the recessed-step catheter was then analysed in a large animal model by performing infusions of 0.2% Gadolinium-DTPA in Large White/Landrace pigs. The recessed-step catheter demonstrated significantly higher volumes of distribution than the one-step and two-step catheters (p=0.0001, one-way ANOVA). No reflux was detected until more than 100 ul had been delivered via the recessed-step catheter, whilst reflux was detected after infusion of only 25 ul via the 2 non-recessed catheters. The recessed-step design also showed superior reflux resistance to a conventational one-step catheter in vivo. Reflux-free infusions were achieved in the thalamus, putamen and white matter at a maximum infusion rate of 5 ul/min using the recessed-step design. The novel recessed-step catheter described in this study shows significant potential for the achievement of predictable high volume, high flow rate infusions whilst minimising the risk of reflux. Copyright © 2013 Elsevier B.V. All rights reserved.

RANKING TEM CAMERAS BY THEIR RESPONSE TO ELECTRON SHOT NOISE

PubMed Central

Grob, Patricia; Bean, Derek; Typke, Dieter; Li, Xueming; Nogales, Eva; Glaeser, Robert M.

2013-01-01

We demonstrate two ways in which the Fourier transforms of images that consist solely of randomly distributed electrons (shot noise) can be used to compare the relative performance of different electronic cameras. The principle is to determine how closely the Fourier transform of a given image does, or does not, approach that of an image produced by an ideal camera, i.e. one for which single-electron events are modeled as Kronecker delta functions located at the same pixels where the electrons were incident on the camera. Experimentally, the average width of the single-electron response is characterized by fitting a single Lorentzian function to the azimuthally averaged amplitude of the Fourier transform. The reciprocal of the spatial frequency at which the Lorentzian function falls to a value of 0.5 provides an estimate of the number of pixels at which the corresponding line-spread function falls to a value of 1/e. In addition, the excess noise due to stochastic variations in the magnitude of the response of the camera (for single-electron events) is characterized by the amount to which the appropriately normalized power spectrum does, or does not, exceed the total number of electrons in the image. These simple measurements provide an easy way to evaluate the relative performance of different cameras. To illustrate this point we present data for three different types of scintillator-coupled camera plus a silicon-pixel (direct detection) camera. PMID:23747527

Improving Signal-to-Noise Ratio in Scanning Transmission Electron Microscopy Energy-Dispersive X-Ray (STEM-EDX) Spectrum Images Using Single-Atomic-Column Cross-Correlation Averaging.

PubMed

Jeong, Jong Seok; Mkhoyan, K Andre

2016-06-01

Acquiring an atomic-resolution compositional map of crystalline specimens has become routine practice, thus opening possibilities for extracting subatomic information from such maps. A key challenge for achieving subatomic precision is the improvement of signal-to-noise ratio (SNR) of compositional maps. Here, we report a simple and reliable solution for achieving high-SNR energy-dispersive X-ray (EDX) spectroscopy spectrum images for individual atomic columns. The method is based on standard cross-correlation aided by averaging of single-column EDX maps with modifications in the reference image. It produces EDX maps with minimal specimen drift, beam drift, and scan distortions. Step-by-step procedures to determine a self-consistent reference map with a discussion on the reliability, stability, and limitations of the method are presented here.

Spins and photons: connecting quantum registers in diamond

NASA Astrophysics Data System (ADS)

Childress, Lily

2012-06-01

Long-lived electronic and nuclear spin states have made the nitrogen-vacancy (NV) defect in diamond a leading candidate for quantum information processing in the solid state. Multi-qubit quantum registers formed by single defects and nearby nuclear spins can currently be controlled and detected with high fidelity. Nevertheless, development of coherent connections between distant NVs remains an outstanding challenge. One advantage to working with solid-state defects is the opportunity to integrate them with microfabricated mechanical, electronic, or optical devices; in principle, such devices could mediate interactions between registers, turning them into nodes within a larger quantum network. In the last few months, several experiments have made key steps toward realizing a coherent quantum interface between individual NV centers using a mechanical quantum bus [1] or optical channels [2,3]. This talk will explore the current state of the art, and report on recent observation of two photon quantum interference between different gate-tunable defect centers [2]. These results pave the way towards measurement-based entanglement between remote NV centers and the realization of quantum networks with solid-state spins.[4pt] [1] Kolkowitz et al., Science 335, 1603 (2012)[2] Bernien et al., Phys. Rev. Lett. 108, 043604 (2012)[3] Sipahigil et al., http://lanl.arxiv.org/abs/1112.3975

A novel biotinylated lipid raft reporter for electron microscopic imaging of plasma membrane microdomains[S

PubMed Central

Krager, Kimberly J.; Sarkar, Mitul; Twait, Erik C.; Lill, Nancy L.; Koland, John G.

2012-01-01

The submicroscopic spatial organization of cell surface receptors and plasma membrane signaling molecules is readily characterized by electron microscopy (EM) via immunogold labeling of plasma membrane sheets. Although various signaling molecules have been seen to segregate within plasma membrane microdomains, the biochemical identity of these microdomains and the factors affecting their formation are largely unknown. Lipid rafts are envisioned as submicron membrane subdomains of liquid ordered structure with differing lipid and protein constituents that define their specific varieties. To facilitate EM investigation of inner leaflet lipid rafts and the localization of membrane proteins therein, a unique genetically encoded reporter with the dually acylated raft-targeting motif of the Lck kinase was developed. This reporter, designated Lck-BAP-GFP, incorporates green fluorescent protein (GFP) and biotin acceptor peptide (BAP) modules, with the latter allowing its single-step labeling with streptavidin-gold. Lck-BAP-GFP was metabolically biotinylated in mammalian cells, distributed into low-density detergent-resistant membrane fractions, and was readily detected with avidin-based reagents. In EM images of plasma membrane sheets, the streptavidin-gold-labeled reporter was clustered in 20–50 nm microdomains, presumably representative of inner leaflet lipid rafts. The utility of the reporter was demonstrated in an investigation of the potential lipid raft localization of the epidermal growth factor receptor. PMID:22822037

Iron oxide nanozyme catalyzed synthesis of fluorescent polydopamine for light-up Zn2+ detection

NASA Astrophysics Data System (ADS)

Liu, Biwu; Han, Xiao; Liu, Juewen

2016-07-01

Fluorescent polydopamine (FPD) is an interesting material with excellent biocompatibility. However, its preparation is currently a lengthy and potentially dangerous process. We herein employ magnetic iron oxide (Fe3O4) nanoparticles as a peroxidase-mimicking nanozyme to produce FPD under mild conditions. Different from previous protocols using multiple steps with up to 6% (~2 M) H2O2, this preparation takes place in a single step with just 5 mM H2O2 at room temperature. The oxidized product shows excitation-wavelength-dependent emission peaks, similar to previous reports. The reaction kinetics, pH, temperature, and ionic strength are individually optimized. Among a diverse range of other nanomaterials tested, including Fe2O3, CeO2, CoO, Co3O4, NiO, TiO2, gold nanoparticles, and graphene oxide, Fe2O3 and graphene oxide yielded relatively weak emission, while the rest of the materials failed to produce FPD. The Fe3O4 nanoparticles retained ~90% catalytic activity even after ten cycles of synthesis. Finally, Zn2+ can enhance the fluorescence of FPD under 360 nm excitation but not under 480 nm excitation, leading to a sensitive light-up sensor with a detection limit of 60 nM Zn2+. Therefore, this work has demonstrated not only a novel use of nanozymes, but also an interesting application of FPD.Fluorescent polydopamine (FPD) is an interesting material with excellent biocompatibility. However, its preparation is currently a lengthy and potentially dangerous process. We herein employ magnetic iron oxide (Fe3O4) nanoparticles as a peroxidase-mimicking nanozyme to produce FPD under mild conditions. Different from previous protocols using multiple steps with up to 6% (~2 M) H2O2, this preparation takes place in a single step with just 5 mM H2O2 at room temperature. The oxidized product shows excitation-wavelength-dependent emission peaks, similar to previous reports. The reaction kinetics, pH, temperature, and ionic strength are individually optimized. Among a diverse range of other nanomaterials tested, including Fe2O3, CeO2, CoO, Co3O4, NiO, TiO2, gold nanoparticles, and graphene oxide, Fe2O3 and graphene oxide yielded relatively weak emission, while the rest of the materials failed to produce FPD. The Fe3O4 nanoparticles retained ~90% catalytic activity even after ten cycles of synthesis. Finally, Zn2+ can enhance the fluorescence of FPD under 360 nm excitation but not under 480 nm excitation, leading to a sensitive light-up sensor with a detection limit of 60 nM Zn2+. Therefore, this work has demonstrated not only a novel use of nanozymes, but also an interesting application of FPD. Electronic supplementary information (ESI) available: Methods, TEM, ζ-potential, and original fluorescence spectra. See DOI: 10.1039/c6nr02584f

Gold-FISH: A correlative approach to microscopic imaging of single microbial cells in environmental samples

NASA Astrophysics Data System (ADS)

Schmidt, Hannes; Seki, David; Woebken, Dagmar; Eickhorst, Thilo

2017-04-01

Fluorescence in situ hybridization (FISH) is routinely used for the phylogenetic identification, detection, and quantification of single microbial cells environmental microbiology. Oligonucleotide probes that match the 16S rRNA sequence of target organisms are generally applied and the resulting signals are visualized via fluorescence microscopy. Consequently, the detection of the microbial cells of interest is limited by the resolution and the sensitivity of light microscopy where objects smaller than 0.2 µm can hardly be represented. Visualizing microbial cells at magnifications beyond light microscopy, however, can provide information on the composition and potential complexity of microbial habitats - the actual sites of nutrient cycling in soil and sediments. We present a recently developed technique that combines (1) the phylogenetic identification and detection of individual microorganisms by epifluorescence microscopy, with (2) the in situ localization of gold-labelled target cells on an ultrastructural level by SEM. Based on 16S rRNA targeted in situ hybridization combined with catalyzed reporter deposition, a streptavidin conjugate labeled with a fluorescent dye and nanogold particles is introduced into whole microbial cells. A two-step visualization process including an autometallographic enhancement of nanogold particles then allows for either fluorescence or electron microscopy, or a correlative application thereof. We will present applications of the Gold-FISH protocol to samples of marine sediments, agricultural soils, and plant roots. The detection and enumeration of bacterial cells in soil and sediment samples was comparable to CARD-FISH applications via fluorescence microscopy. Examples of microbe-surface interaction analysis will be presented on the basis of bacteria colonizing the rhizoplane of rice roots. In principle, Gold-FISH can be performed on any material to give a snapshot of microbe-surface interactions and provides a promising tool for the acquisition of correlative information on microorganisms within their respective habitats.

Electronic bypass of spinal lesions: activation of lower motor neurons directly driven by cortical neural signals.

PubMed

Li, Yan; Alam, Monzurul; Guo, Shanshan; Ting, K H; He, Jufang

2014-07-03

Lower motor neurons in the spinal cord lose supraspinal inputs after complete spinal cord injury, leading to a loss of volitional control below the injury site. Extensive locomotor training with spinal cord stimulation can restore locomotion function after spinal cord injury in humans and animals. However, this locomotion is non-voluntary, meaning that subjects cannot control stimulation via their natural "intent". A recent study demonstrated an advanced system that triggers a stimulator using forelimb stepping electromyographic patterns to restore quadrupedal walking in rats with spinal cord transection. However, this indirect source of "intent" may mean that other non-stepping forelimb activities may false-trigger the spinal stimulator and thus produce unwanted hindlimb movements. We hypothesized that there are distinguishable neural activities in the primary motor cortex during treadmill walking, even after low-thoracic spinal transection in adult guinea pigs. We developed an electronic spinal bridge, called "Motolink", which detects these neural patterns and triggers a "spinal" stimulator for hindlimb movement. This hardware can be head-mounted or carried in a backpack. Neural data were processed in real-time and transmitted to a computer for analysis by an embedded processor. Off-line neural spike analysis was conducted to calculate and preset the spike threshold for "Motolink" hardware. We identified correlated activities of primary motor cortex neurons during treadmill walking of guinea pigs with spinal cord transection. These neural activities were used to predict the kinematic states of the animals. The appropriate selection of spike threshold value enabled the "Motolink" system to detect the neural "intent" of walking, which triggered electrical stimulation of the spinal cord and induced stepping-like hindlimb movements. We present a direct cortical "intent"-driven electronic spinal bridge to restore hindlimb locomotion after complete spinal cord injury.

General methods for analysis of sequential "n-step" kinetic mechanisms: application to single turnover kinetics of helicase-catalyzed DNA unwinding.

PubMed

Lucius, Aaron L; Maluf, Nasib K; Fischer, Christopher J; Lohman, Timothy M

2003-10-01

Helicase-catalyzed DNA unwinding is often studied using "all or none" assays that detect only the final product of fully unwound DNA. Even using these assays, quantitative analysis of DNA unwinding time courses for DNA duplexes of different lengths, L, using "n-step" sequential mechanisms, can reveal information about the number of intermediates in the unwinding reaction and the "kinetic step size", m, defined as the average number of basepairs unwound between two successive rate limiting steps in the unwinding cycle. Simultaneous nonlinear least-squares analysis using "n-step" sequential mechanisms has previously been limited by an inability to float the number of "unwinding steps", n, and m, in the fitting algorithm. Here we discuss the behavior of single turnover DNA unwinding time courses and describe novel methods for nonlinear least-squares analysis that overcome these problems. Analytic expressions for the time courses, f(ss)(t), when obtainable, can be written using gamma and incomplete gamma functions. When analytic expressions are not obtainable, the numerical solution of the inverse Laplace transform can be used to obtain f(ss)(t). Both methods allow n and m to be continuous fitting parameters. These approaches are generally applicable to enzymes that translocate along a lattice or require repetition of a series of steps before product formation.

Radiation effects in cubic zirconia: A model system for ceramic oxides

NASA Astrophysics Data System (ADS)

Thomé, L.; Moll, S.; Sattonnay, G.; Vincent, L.; Garrido, F.; Jagielski, J.

2009-06-01

Ceramics are key engineering materials for electronic, space and nuclear industry. Some of them are promising matrices for the immobilization and/or transmutation of radioactive waste. Cubic zirconia is a model system for the study of radiation effects in ceramic oxides. Ion beams are very efficient tools for the simulation of the radiations produced in nuclear reactors or in storage form. In this article, we summarize the work made by combining advanced techniques (RBS/C, XRD, TEM, AFM) to study the structural modifications produced in ion-irradiated cubic zirconia single crystals. Ions with energies in the MeV-GeV range allow exploring the nuclear collision and electronic excitation regimes. At low energy, where ballistic effects dominate, the damage exhibits a peak around the ion projected range; it accumulates with a double-step process by the formation of a dislocation network. At high energy, where electronic excitations are favored, the damage profiles are rather flat up to several micrometers; the damage accumulation is monotonous (one step) and occurs through the creation and overlap of ion tracks. These results may be generalized to many nuclear ceramics.

Human Movement Recognition Based on the Stochastic Characterisation of Acceleration Data

PubMed Central

Munoz-Organero, Mario; Lotfi, Ahmad

2016-01-01

Human activity recognition algorithms based on information obtained from wearable sensors are successfully applied in detecting many basic activities. Identified activities with time-stationary features are characterised inside a predefined temporal window by using different machine learning algorithms on extracted features from the measured data. Better accuracy, precision and recall levels could be achieved by combining the information from different sensors. However, detecting short and sporadic human movements, gestures and actions is still a challenging task. In this paper, a novel algorithm to detect human basic movements from wearable measured data is proposed and evaluated. The proposed algorithm is designed to minimise computational requirements while achieving acceptable accuracy levels based on characterising some particular points in the temporal series obtained from a single sensor. The underlying idea is that this algorithm would be implemented in the sensor device in order to pre-process the sensed data stream before sending the information to a central point combining the information from different sensors to improve accuracy levels. Intra- and inter-person validation is used for two particular cases: single step detection and fall detection and classification using a single tri-axial accelerometer. Relevant results for the above cases and pertinent conclusions are also presented. PMID:27618063

Theory of Thermal Relaxation of Electrons in Semiconductors

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

Sadasivam, Sridhar; Chan, Maria K. Y.; Darancet, Pierre

2017-09-01

We compute the transient dynamics of phonons in contact with high energy ``hot'' charge carriers in 12 polar and non-polar semiconductors, using a first-principles Boltzmann transport framework. For most materials, we find that the decay in electronic temperature departs significantly from a single-exponential model at times ranging from 1 ps to 15 ps after electronic excitation, a phenomenon concomitant with the appearance of non-thermal vibrational modes. We demonstrate that these effects result from the slow thermalization within the phonon subsystem, caused by the large heterogeneity in the timescales of electron-phonon and phonon-phonon interactions in these materials. We propose a generalizedmore » 2-temperature model accounting for the phonon thermalization as a limiting step of electron-phonon thermalization, which captures the full thermal relaxation of hot electrons and holes in semiconductors. A direct consequence of our findings is that, for semiconductors, information about the spectral distribution of electron-phonon and phonon-phonon coupling can be extracted from the multi-exponential behavior of the electronic temperature.« less

Quantum Noise of Electron-Phonon Heat Current

NASA Astrophysics Data System (ADS)

Pekola, Jukka P.; Karimi, Bayan

2018-06-01

We analyze heat current fluctuations between electrons and phonons in a metal. In equilibrium we recover the standard result consistent with the fluctuation-dissipation theorem. Here we show that heat current noise at finite frequencies remains non-vanishing down to zero temperature. From the experimental point of view, it is a small effect and up to now elusive. We briefly discuss the impact of electron-phonon heat current fluctuations on calorimetry, particularly in the regime of single microwave-photon detection.

A New Single-Step PCR Assay for the Detection of the Zoonotic Malaria Parasite Plasmodium knowlesi

PubMed Central

Lucchi, Naomi W.; Poorak, Mitra; Oberstaller, Jenna; DeBarry, Jeremy; Srinivasamoorthy, Ganesh; Goldman, Ira; Xayavong, Maniphet; da Silva, Alexandre J.; Peterson, David S.; Barnwell, John W.; Kissinger, Jessica; Udhayakumar, Venkatachalam

2012-01-01

Background Recent studies in Southeast Asia have demonstrated substantial zoonotic transmission of Plasmodium knowlesi to humans. Microscopically, P. knowlesi exhibits several stage-dependent morphological similarities to P. malariae and P. falciparum. These similarities often lead to misdiagnosis of P. knowlesi as either P. malariae or P. falciparum and PCR-based molecular diagnostic tests are required to accurately detect P. knowlesi in humans. The most commonly used PCR test has been found to give false positive results, especially with a proportion of P. vivax isolates. To address the need for more sensitive and specific diagnostic tests for the accurate diagnosis of P. knowlesi, we report development of a new single-step PCR assay that uses novel genomic targets to accurately detect this infection. Methodology and Significant Findings We have developed a bioinformatics approach to search the available malaria parasite genome database for the identification of suitable DNA sequences relevant for molecular diagnostic tests. Using this approach, we have identified multi-copy DNA sequences distributed in the P. knowlesi genome. We designed and tested several novel primers specific to new target sequences in a single-tube, non-nested PCR assay and identified one set of primers that accurately detects P. knowlesi. We show that this primer set has 100% specificity for the detection of P. knowlesi using three different strains (Nuri, H, and Hackeri), and one human case of malaria caused by P. knowlesi. This test did not show cross reactivity with any of the four human malaria parasite species including 11 different strains of P. vivax as well as 5 additional species of simian malaria parasites. Conclusions The new PCR assay based on novel P. knowlesi genomic sequence targets was able to accurately detect P. knowlesi. Additional laboratory and field-based testing of this assay will be necessary to further validate its utility for clinical diagnosis of P. knowlesi. PMID:22363751

Development of new photon-counting detectors for single-molecule fluorescence microscopy.

PubMed

Michalet, X; Colyer, R A; Scalia, G; Ingargiola, A; Lin, R; Millaud, J E; Weiss, S; Siegmund, Oswald H W; Tremsin, Anton S; Vallerga, John V; Cheng, A; Levi, M; Aharoni, D; Arisaka, K; Villa, F; Guerrieri, F; Panzeri, F; Rech, I; Gulinatti, A; Zappa, F; Ghioni, M; Cova, S

2013-02-05

Two optical configurations are commonly used in single-molecule fluorescence microscopy: point-like excitation and detection to study freely diffusing molecules, and wide field illumination and detection to study surface immobilized or slowly diffusing molecules. Both approaches have common features, but also differ in significant aspects. In particular, they use different detectors, which share some requirements but also have major technical differences. Currently, two types of detectors best fulfil the needs of each approach: single-photon-counting avalanche diodes (SPADs) for point-like detection, and electron-multiplying charge-coupled devices (EMCCDs) for wide field detection. However, there is room for improvements in both cases. The first configuration suffers from low throughput owing to the analysis of data from a single location. The second, on the other hand, is limited to relatively low frame rates and loses the benefit of single-photon-counting approaches. During the past few years, new developments in point-like and wide field detectors have started addressing some of these issues. Here, we describe our recent progresses towards increasing the throughput of single-molecule fluorescence spectroscopy in solution using parallel arrays of SPADs. We also discuss our development of large area photon-counting cameras achieving subnanosecond resolution for fluorescence lifetime imaging applications at the single-molecule level.

Development of new photon-counting detectors for single-molecule fluorescence microscopy

PubMed Central

Michalet, X.; Colyer, R. A.; Scalia, G.; Ingargiola, A.; Lin, R.; Millaud, J. E.; Weiss, S.; Siegmund, Oswald H. W.; Tremsin, Anton S.; Vallerga, John V.; Cheng, A.; Levi, M.; Aharoni, D.; Arisaka, K.; Villa, F.; Guerrieri, F.; Panzeri, F.; Rech, I.; Gulinatti, A.; Zappa, F.; Ghioni, M.; Cova, S.

2013-01-01

Two optical configurations are commonly used in single-molecule fluorescence microscopy: point-like excitation and detection to study freely diffusing molecules, and wide field illumination and detection to study surface immobilized or slowly diffusing molecules. Both approaches have common features, but also differ in significant aspects. In particular, they use different detectors, which share some requirements but also have major technical differences. Currently, two types of detectors best fulfil the needs of each approach: single-photon-counting avalanche diodes (SPADs) for point-like detection, and electron-multiplying charge-coupled devices (EMCCDs) for wide field detection. However, there is room for improvements in both cases. The first configuration suffers from low throughput owing to the analysis of data from a single location. The second, on the other hand, is limited to relatively low frame rates and loses the benefit of single-photon-counting approaches. During the past few years, new developments in point-like and wide field detectors have started addressing some of these issues. Here, we describe our recent progresses towards increasing the throughput of single-molecule fluorescence spectroscopy in solution using parallel arrays of SPADs. We also discuss our development of large area photon-counting cameras achieving subnanosecond resolution for fluorescence lifetime imaging applications at the single-molecule level. PMID:23267185