These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

The effects of magnetic separation on cryopreserved bovine spermatozoa motility, viability and cryo-capacitation status.  

PubMed

Cryopreservation is a technique used to preserve cells for long-time storage. It is widely used in agriculture to store male gametes in liquid nitrogen. The aim of this study was to determine the optimum thawing temperature and time for samples subjected to annexin V magnetic-activated cell sorting (AnMACS) as the sperm preparation technique. Pooled semen samples from three ejaculates were divided into two groups. The treatment group was subjected both to AnMACS and to being cryopreserved, whilst the control group was cryopreserved directly without MACS. Post-thaw analysis was carried out for samples thawed at either 20°C for 13 s, 37°C for 30 s, 40°C for 7 s, 60°C for 6 s or 80°C for 5 s. Sperm kinematics, viability and capacitation status were determined for samples subjected to all thawing temperatures described. Results showed that thawing at 37°C for 13 s for MACS-processed samples was a superior option compared with other thawing procedures; there was a significant difference in P < 0.05 values for curvilinear velocity (VCL ?m/s) and sperm straightness (STR %) when samples were thawed at 40°C for 7 s, with fewer capacitated spermatozoa (P < 0.05) when samples were thawed at 37°C for 30 s, 40°C for 7 s or 60°C for 6 s. Hence, we can speculate that the use of AnMACS as the sperm preparation technique can somehow enhance sperm cryosurvival rate after cryopreservation, however the fertilization potential of these cells has yet to be determined. PMID:23237064

Faezah, S S M; Zuraina, F M Y; Farah, J H F; Khairul, O; Hilwani, N I; Iswadi, M I; Fang, C N; Zawawi, I; Abas, O M; Fatimah, S I

2014-08-01

2

The standard Instrumentation Feedthrough System for the LHC cryo-magnets  

E-print Network

For the LHC, 1232 dipole magnets and about 400 quadrupole magnets operating at 1.9 K are installed in arcs and dispersion suppressors. Each cryo-magnet assembly comprises the main magnet and several small corrector magnets. Each assembly is equipped with voltage taps, quench heaters and cryogenic instrumentation. The number of instrumentation wires serving each magnet assembly and passing from cold to ambient is between 36 and 40. An Instrumentation Feedthrough System (IFS) will electrically and mechanically connect the instrument wires to the outside of the vacuum vessel. The IFS has to satisfy several requirements: simplicity of integration, optimal access during tests and commissioning, voltage withstand and reliability during the lifetime of the machine. The heat load to superfluid helium must be minimized, and the long-term stability of the insulation vacuum should be preserved. The solution foresees an open stainless steel tube housing the wires connected between the magnet and the outside of the vacuum...

Bozzini, D

2002-01-01

3

Magnetic separation for soil decontamination  

SciTech Connect

High gradient magnetic separation (HGMS) is a physical separation process that is used to extract magnetic particles from mixtures. The technology is used on a large scale in the kaolin clay industry to whiten or brighten kaolin clay and increase its value. Because all uranium and plutonium compounds are slightly magnetic, HGMS can be used to separate these contaminants from non-magnetic soils. A Cooperative Research and Development Agreement (CRADA) was signed in 1992 between Los Alamos National Laboratory (LANL) and Lockheed Environmental Systems and Technologies Company (LESAT) to develop HGMS for soil decontamination. This paper reports progress and describes the HGMS technology.

Avens, L.R.; Worl, L.A.; deAguero, K.J.; Padilla, D.D.; Prenger, F.C.; Stewart, W.F.; Hill, D.D. [Los Alamos National Lab., NM (United States); Tolt, T.L. [Lockheed Environmental Systems and Technologies (United States)

1993-02-01

4

Magnetic separation for soil decontamination  

SciTech Connect

High gradient magnetic separation (HGMS) is a physical separation process that is used to extract magnetic particles from mixtures. The technology is used on a large scale in the kaolin clay industry to whiten or brighten kaolin clay and increase its value. Because all uranium and plutonium compounds are slightly magnetic, HGMS can be used to separate these contaminants from non-magnetic soils. A Cooperative Research and Development Agreement (CRADA) was signed in 1992 between Los Alamos National Laboratory (LANL) and Lockheed Environmental Systems and Technologies Company (LESAT) to develop HGMS for soil decontamination. This paper reports progress and describes the HGMS technology.

Avens, L.R.; Worl, L.A.; deAguero, K.J.; Padilla, D.D.; Prenger, F.C.; Stewart, W.F.; Hill, D.D. (Los Alamos National Lab., NM (United States)); Tolt, T.L. (Lockheed Environmental Systems and Technologies (United States))

1993-01-01

5

Continuous magnetic separator and process  

DOEpatents

A continuous magnetic separator and process for separating a slurry comprising magnetic particles into a clarified stream and a thickened stream. The separator has a container with a slurry inlet, an overflow outlet for the discharge of the clarified slurry stream, and an underflow outlet for the discharge of a thickened slurry stream. Magnetic particles in the slurry are attracted to, and slide down, magnetic rods within the container. The slurry is thus separated into magnetic concentrate and clarified slurry. Flow control means can be used to control the ratio of the rate of magnetic concentrate to the rate of clarified slurry. Feed control means can be used to control the rate of slurry feed to the slurry inlet.

Oder, Robin R. (Export, PA); Jamison, Russell E. (Lower Burrell, PA)

2008-04-22

6

Separation of magnetic field lines  

SciTech Connect

The field lines of magnetic fields that depend on three spatial coordinates are shown to have a fundamentally different behavior from those that depend on two coordinates. Unlike two-coordinate cases, a flux tube in a magnetic field that depends on all three spatial coordinates that has a circular cross section at one location along the tube characteristically has a highly distorted cross section at other locations. In an ideal evolution of a magnetic field, the current densities typically increase. Crudely stated, if the current densities increase by a factor {sigma}, the ratio of the long to the short distance across a cross section of a flux tube characteristically increases by e{sup 2{sigma}}, and the ratio of the longer distance to the initial radius increases as e{sup {sigma}}. Electron inertia prevents a plasma from isolating two magnetic field structures on a distance scale shorter than c/{omega}{sub pe}, which is about 10 cm in the solar corona, and reconnection must be triggered if {sigma} becomes sufficiently large. The radius of the sun, R{sub Circled-Dot-Operator }=7 Multiplication-Sign 10{sup 10}cm is about e{sup 23} times larger, so when {sigma} Greater-Than-Or-Equivalent-To 23, two lines separated by c/{omega}{sub pe} at one location can be separated by the full scale of any magnetic structures in the corona at another. The conditions for achieving a large exponentiation, {sigma}, are derived, and the importance of exponentiation is discussed.

Boozer, Allen H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

2012-11-15

7

Magnetic Separator Enhances Treatment Possibilities  

NASA Technical Reports Server (NTRS)

Since the earliest missions in space, NASA specialists have performed experiments in low gravity. Protein crystal growth, cell and tissue cultures, and separation technologies such as electrophoresis and magnetophoresis have been studied on Apollo 14, Apollo 16, STS-107, and many other missions. Electrophoresis and magnetophoresis, respectively, are processes that separate substances based on the electrical charge and magnetic field of a molecule or particle. Electrophoresis has been studied on over a dozen space shuttle flights, leading to developments in electrokinetics, which analyzes the effects of electric fields on mass transport (atoms, molecules, and particles) in fluids. Further studies in microgravity will continue to improve these techniques, which researchers use to extract cells for various medical treatments and research.

2008-01-01

8

Whole Mouse Cryo-Imaging  

PubMed Central

The Case cryo-imaging system is a section and image system which allows one to acquire micron-scale, information rich, whole mouse color bright field and molecular fluorescence images of an entire mouse. Cryo-imaging is used in a variety of applications, including mouse and embryo anatomical phenotyping, drug delivery, imaging agents, metastastic cancer, stem cells, and very high resolution vascular imaging, among many. Cryo-imaging fills the gap between whole animal in vivo imaging and histology, allowing one to image a mouse along the continuum from the mouse ? organ ? tissue structure ? cell ? sub-cellular domains. In this overview, we describe the technology and a variety of exciting applications. Enhancements to the system now enable tiled acquisition of high resolution images to cover an entire mouse. High resolution fluorescence imaging, aided by a novel subtraction processing algorithm to remove sub-surface fluorescence, makes it possible to detect fluorescently-labeled single cells. Multi-modality experiments in Magnetic Resonance Imaging and Cryo-imaging of a whole mouse demonstrate superior resolution of cryo-images and efficiency of registration techniques. The 3D results demonstrate the novel true-color volume visualization tools we have developed and the inherent advantage of cryo-imaging in providing unlimited depth of field and spatial resolution. The recent results continue to demonstrate the value cryo-imaging provides in the field of small animal imaging research. PMID:19756215

Wilson, David; Roy, Debashish; Steyer, Grant; Gargesha, Madhusudhana; Stone, Meredith; McKinley, Eliot

2009-01-01

9

A novel magnetic suspension cum linear actuator system for satellite cryo coolers  

SciTech Connect

Stirling cycle cryogenic coolers have been widely used for device cooling in satellites. Various types of magnetic bearings and linear actuators find application in such systems. The most widely used configurations have two-axis-radially-active suspension stations placed at either ends of a reciprocating shaft in the compression and expansion sections. Separate or integral liner motors are provided in each section for axial shaft movement. It may be noted that such configurations are rather complicated and less reliable because of the presence of numerous electro-mechanical components, sensors and electronic servo channels. In this paper, a simple and reliable scheme is suggested which axially stabilizes and linearly perturbs the piston so that the need for a separate motor for axial actuation can be totally dispensed with. The piston is radially supported by passive repulsive bearings. In the axial direction, a servo actuator balances'' the piston and also actuates it bi-directionally. Implemented of this bearing cum motor theme,'' reduces the number of electromechanical and electronic components required to operate the system and hence minimizes the chances of system failure. Apart from this, the system's power consumption is reduced and efficiency is improved as electrical heating losses caused by quiescent-operating currents are removed and electromagnetic losses on the moving parts are minimized. The necessary system parameters have been derived using finite element analysis techniques. Finally, the proposed design is validated by computer-aided system simulation.

Sivadasan, K.K. (Indian Space Research Organization, Trivandrum (India). ISRO Inertial Systems Unit)

1994-05-01

10

Particle acceleration at a reconnecting magnetic separator  

E-print Network

While the exact acceleration mechanism of energetic particles during solar flares is (as yet) unknown, magnetic reconnection plays a key role both in the release of stored magnetic energy of the solar corona and the magnetic restructuring during a flare. Recent work has shown that special field lines, called separators, are common sites of reconnection in 3D numerical experiments. To date, 3D separator reconnection sites have received little attention as particle accelerators. We investigate the effectiveness of separator reconnection as a particle acceleration mechanism for electrons and protons. We study the particle acceleration using a relativistic guiding-centre particle code in a time-dependent kinematic model of magnetic reconnection at a separator. The effect upon particle behaviour of initial position, pitch angle and initial kinetic energy are examined in detail, both for specific (single) particle examples and for large distributions of initial conditions. The separator reconnection model contains ...

Threlfall, J; Parnell, C E; Oskoui, S Eradat

2014-01-01

11

Magnetic separation in water pollution control  

Microsoft Academic Search

Magnetic separation as applied to waterborne contaminants is successful in reducing the solids content of a water sample and in removing the dissolved orthophosphate from the aqueous slurry. The contaminants are chemically associated with a magnetic seeding material, and subsequent removal of this seed sweeps the pollutants from the system. The advantage of this form of treatment over conventional techniques

CHRISTOPHER DE LATOUR

1973-01-01

12

HTS High Gradient Magnetic Separation system  

SciTech Connect

We report on the assembly, characterization and operation of a high temperature superconducting (HTS) magnetic separator. The magnet is made of 624 m of Silver/BSCCO superconducting wire and has overall dimensions of 18 cm OD, 15.5 cm height and 5 cm ID. The HTS current leads are designed to operate with the warm end at 75 K and the cold end cooled by a two stage Gifford-McMahon cryocooler. The upper stage of the cryocooler cools the thermal shield and two heat pipe thermal intercepts. The lower stage of the cryocooler cools the HTS magnet and the bottom end of the HTS current leads. The HTS magnet was initially characterized in liquid cryogens. We report on the current- voltage (I-V) characteristics of the HTS magnet at temperatures ranging from 15 to 40 K. At 40 K the magnet can generate a central field of 2.0 T at a current of 120 A.

Daugherty, M.A.; Coulter, J.Y.; Hults, W.L. [and others

1996-09-01

13

Development of magnetic separation system of magnetoliposomes  

NASA Astrophysics Data System (ADS)

The magnetic separation technology using sub-microsized ferromagnetic particle is indispensable in many areas of medical biosciences. For example, ferromagnetic particles (200-500 nm) are widely used for cell sorting in stem cell research with the use of cell surface-specific antigens. Nanosized ferromagnetic particles (10-20 nm) have been suggested as more suitable in drug delivery studies given their efficiency of tissue penetration, however, the magnetic separation method for them has not been established. One of the major reasons is that magnetic force acting on the object particles decreases drastically as a particle diameter becomes small. In this study, magnetic force acting on the targets was enhanced by the combination of superconducting magnet and the filter consisting of ferromagnetic particle. By doing so, we confirmed that Fe 3O 4 of 20 nm in diameter was trapped in the magnetic filter under an external magnetic field of 0.5 T. Fe 3O 4 encapsulated with phospholipid liposomes of 200 nm in diameter was also shown to be trapped as external magnetic field of 1.5 T, but not of 0.5 T. We also showed the result of particle trajectory calculation which emulated well the experimental data.

Nakao, R.; Matuo, Y.; Mishima, F.; Taguchi, T.; Maenosono, S.; Nishijima, S.

2009-10-01

14

Purification of condenser water in thermal power station by superconducting magnetic separation  

NASA Astrophysics Data System (ADS)

Thermal power station is made up of a steam turbine and a steam condenser which need a lot of water. The water of steam condenser should be replaced, since scales consisting of iron oxide mainly are accumulated on the surface of condenser pipes as it goes. Superconducting high gradient magnetic separation (HGMS) system has merits to remove paramagnetic substance like iron oxides because it can generate higher magnetic field strength than electromagnet or permanent magnet. In this paper, cryo-cooled Nb-Ti superconducting magnet that can generate up to 6 T was used for HGMS systems. Magnetic filters were designed by the analysis of magnetic field distribution at superconducting magnets. The result of X-ray analysis showed contaminants were mostly ?-Fe 2O 3 (hematite) and ?-Fe 2O 3 (maghemite). The higher magnetic field was applied up to 6 T, the more iron oxides were removed. As the wire diameter of magnetic filter decreased, the turbidity removal of the sample was enhanced.

Ha, D. W.; Kwon, J. M.; Baik, S. K.; Lee, Y. J.; Han, K. S.; Ko, R. K.; Sohn, M. H.; Seong, K. C.

2011-11-01

15

Multistage Magnetic Separator of Cells and Proteins  

NASA Technical Reports Server (NTRS)

The multistage electromagnetic separator for purifying cells and magnetic particles (MAGSEP) is a laboratory apparatus for separating and/or purifying particles (especially biological cells) on the basis of their magnetic susceptibility and magnetophoretic mobility. Whereas a typical prior apparatus based on similar principles offers only a single stage of separation, the MAGSEP, as its full name indicates, offers multiple stages of separation; this makes it possible to refine a sample population of particles to a higher level of purity or to categorize multiple portions of the sample on the basis of magnetic susceptibility and/or magnetophoretic mobility. The MAGSEP includes a processing unit and an electronic unit coupled to a personal computer. The processing unit includes upper and lower plates, a plate-rotation system, an electromagnet, an electromagnet-translation system, and a capture-magnet assembly. The plates are bolted together through a roller bearing that allows the plates to rotate with respect to each other. An interface between the plates acts as a seal for separating fluids. A lower cuvette can be aligned with as many as 15 upper cuvette stations for fraction collection during processing. A two-phase stepping motor drives the rotation system, causing the upper plate to rotate for the collection of each fraction of the sample material. The electromagnet generates a magnetic field across the lower cuvette, while the translation system translates the electromagnet upward along the lower cuvette. The current supplied to the electromagnet, and thus the magnetic flux density at the pole face of the electromagnet, can be set at a programmed value between 0 and 1,400 gauss (0.14 T). The rate of translation can be programmed between 5 and 2,000 m/s so as to align all sample particles in the same position in the cuvette. The capture magnet can be a permanent magnet. It is mounted on an arm connected to a stepping motor. The stepping motor rotates the arm to position the capture magnet above the upper cuvette into which a fraction of the sample is collected. The electronic unit includes a power switch, power-supply circuitry that accepts 110-Vac input power, an RS-232 interface, and status lights. The personal computer runs the MAGSEP software and controls the operation of the MAGSEP through the RS-232 interface. The status of the power, the translating electromagnet, the capture magnet, and the rotation of the upper plate are indicated in a graphical user interface on the computer screen.

Barton, Ken; Ainsworth, Mark; Daily, Bruce; Dunn, Scott; Metz, Bill; Vellinger, John; Taylor, Brock; Meador, Bruce

2005-01-01

16

Dual Magnetic Separator for TRI$?$P  

E-print Network

The TRI$\\mu$P facility, under construction at KVI, requires the production and separation of short-lived and rare isotopes. Direct reactions, fragmentation and fusion-evaporation reactions in normal and inverse kinematics are foreseen to produce nuclides of interest with a variety of heavy-ion beams from the superconducting cyclotron AGOR. For this purpose, we have designed, constructed and commissioned a versatile magnetic separator that allows efficient injection into an ion catcher, i.e., gas-filled stopper/cooler or thermal ionizer, from which a low energy radioactive beam will be extracted. The separator performance was tested with the production and clean separation of $^{21}$Na ions, where a beam purity of 99.5% could be achieved. For fusion-evaporation products, some of the features of its operation as a gas-filled recoil separator were tested.

G. P. A. Berg; O. C. Dermois; U. Dammalapati; P. Dendooven M. N. Harakeh; K. Jungmann; C. J. G. Onderwater; A. Rogachevskiy; M. Sohani; E. Traykov; L. Willmann; H. W. Wilschut

2005-09-09

17

Plasma separation from magnetic field lines in a magnetic nozzle  

NASA Technical Reports Server (NTRS)

This paper discusses conditions for separation of a plasma from the magnetic field of a magnetic nozzle. The analysis assumes a collisionless, quasineutral plasma, and therefore the results represent a lower bound on the amount of detachment possible for a given set of plasma conditions. We show that collisionless separation can occur because finite electron mass inhibits the flow of azimuthal currents in the nozzle. Separation conditions are governed by a parameter G which depends on plasma and nozzle conditions. Several methods of improving plasma detachment are presented, including moving the plasma generation zone downstream from the region of strongest magnetic field and using dual magnets to focus the plasma beam. Plasma detachment can be enhanced by manipulation of the nozzle configuration.

Kaufman, D. A.; Goodwin, D. G.; Sercel, J. C.

1993-01-01

18

Magnetic separation techniques in diagnostic microbiology.  

PubMed

The principles of magnetic separation aided by antibodies or other specific binding molecules have been used for isolation of specific viable whole organisms, antigens, or nucleic acids. Whereas growth on selective media may be helpful in isolation of a certain bacterial species, immunomagnetic separation (IMS) technology can isolate strains possessing specific and characteristic surface antigens. Further separation, cultivation, and identification of the isolate can be performed by traditional biochemical, immunologic, or molecular methods. PCR can be used for amplification and identification of genes of diagnostic importance for a target organism. The combination of IMS and PCR reduces the assay time to several hours while increasing both specificity and sensitivity. Use of streptavidin-coated magnetic beads for separation of amplified DNA fragments, containing both biotin and a signal molecule, has allowed for the conversion of the traditional PCR into an easy-to-read microtiter plate format. The bead-bound PCR amplicons can also easily be sequenced in an automated DNA sequencer. The latter technique makes it possible to obtain sequence data of 300 to 600 bases from 20 to 30 strains, starting with clinical samples, within 12 to 24 h. Sequence data can be used for both diagnostic and epidemiologic purposes. IMS has been demonstrated to be a useful method in diagnostic microbiology. Most recent publications describe IMS as a method for enhancing the specificity and sensitivity of other detection systems, such as PCR, and providing considerable savings in time compared with traditional diagnostic systems. The relevance to clinical diagnosis has, however, not yet been fully established for all of these new test principles. In the case of PCR, for example, the presence of specific DNA in a food sample does not demonstrate the presence of a live organism capable of inducing a disease. However, all tests offering increased sensitivity and specificity of detection, combined with reduced time of analysis, have to be seriously evaluated. PMID:8118790

Olsvik, O; Popovic, T; Skjerve, E; Cudjoe, K S; Hornes, E; Ugelstad, J; Uhlén, M

1994-01-01

19

The design of the drum separator with superconducting magnets  

SciTech Connect

This paper describes the open gradient drum type magnetic separator with superconducting magnet system to develop technologies for dry separation of low magnetic mineral raw material of 4-0 mm (medium size) up to 25-0 mm (coarse size). The separation zone is 1200 mm x 50 mm with the magnet system-wrap angle equal to 90{degree}, the magnetic field in the separation zone is at the level of 4.5 T, the average value of the magnetic forces is 120 T{sup 2}/m and the capacity is about 100 t/h. The results of the optimization and numerical calculations of thermophysical processes in magnetic and cryogenic systems are given. The technological developments of the design of some separator units are presented. The paper also presents the techno-economic indices of the separator application at the ore-mining operations.

Sidorenko, V.D.; Gerasimenko, I.A.; Kretinin, E.A. [Mekhanobrchermet Inst., Krivoy Rog (Ukraine). Lab. for Superconducting Technique and Technologies] [Mekhanobrchermet Inst., Krivoy Rog (Ukraine). Lab. for Superconducting Technique and Technologies; Zhelamsky, M.V.; Bondarchuk, E.N.; Rodin, I.Y.; Muratov, V.P. [Scientific and Research Inst. of Electrophysical Apparatus, St. Petersburg (Russian Federation)] [Scientific and Research Inst. of Electrophysical Apparatus, St. Petersburg (Russian Federation)

1996-07-01

20

Towards atomic resolution structural determination by single-particle cryo-electron microscopy  

PubMed Central

Recent advances in cryo-electron microscopy and single-particle reconstruction (collectively referred to as “cryoEM”) have made it possible to determine the three-dimensional (3D) structures of several macromolecular complexes at near-atomic resolution (~3.8 – 4.5 Å). These achievements were accomplished by overcoming challenges in sample handling, instrumentation, image processing, and model building. At near-atomic resolution, many detailed structural features can be resolved, such as the turns and deep grooves of helices, strand separation in ? sheets, and densities for loops and bulky amino acid side chains. Such structural data of the cytoplasmic polyhedrosis virus (CPV), the Epsilon 15 bacteriophage and the GroEL complex have provided valuable constraints for atomic model building using integrative tools, thus significantly enhancing the value of the cryoEM structures. The CPV structure revealed a drastic conformational change from a helix to a ? hairpin associated with RNA packaging and replication, coupling of RNA processing and release, and the long sought-after polyhedrin-binding domain. These latest advances in single-particle cryoEM provide exciting opportunities for the 3D structural determination of viruses and macromolecular complexes that are either too large or too heterogeneous to be investigated by conventional X-ray crystallography or nuclear magnetic resonance (NMR) methods. PMID:18403197

Zhou, Z. Hong

2009-01-01

21

Study on magnetic separation of nanosized ferromagnetic particles  

NASA Astrophysics Data System (ADS)

In recent researches in medicine and the pharmaceutical sciences, the magnetic separation technology using nanosized ferromagnetic particle is essential. For example, in the field of cell engineering, magnetic separation of nanosized ferromagnetic particles is necessary, but separation technology of nanosized particle using magnetic force has not been established. One of the reasons is that magnetic force acting on the object particles decreases as particle diameter becomes small, and makes magnetic separation difficult. In this study, magnetic force acting on the separation object was enlarged by the combination of superconducting magnet and the filter which consists of ferromagnetic particle. As a result of particle trajectory calculation and magnetic separation experiment, it was confirmed that the ferromagnetic particles of 15nm in diameter can be trapped in the magnetic filter under an external magnetic field of 0.5T. The ferromagnetic particles of 6nm in diameter which could not be separated under the same condition could also be trapped under 2.0T of external magnetic field.

Nakao, R.; Matuo, Y.; Mishima, F.; Taguchi, T.; Nishijima, S.

2009-03-01

22

Fundamental study of phosphor separation by controlling magnetic force  

NASA Astrophysics Data System (ADS)

The phosphor wastes consist of phosphors with different emission colors, green (LAP), red (YOX), blue (BAM) and white (HP). It is required to recover and reuse the rare earth phosphors with high market value. In this study, we tried to separate the phosphor using the magnetic separation by HTS bulk magnet utilizing the differences of magnetic susceptibility by the type of phosphors. We succeeded in the successive separation of HP with low market value from YOX and BAM including the rare earth using the magnetic Archimedes method. In this method, vertical and radial components of the magnetic force were used.

Wada, Kohei; Mishima, Fumihito; Akiyama, Yoko; Nishijima, Shigehiro

2013-11-01

23

Development of high gradient magnetic separation system under dry condition  

NASA Astrophysics Data System (ADS)

The interfusion of impurities such as metallic wear debris has been a problem in the manufacturing process of foods, medicines, and industrial products. Gravity separation system and membrane separation system has been used widely for powder separation, however magnetic separation system is much efficient to separate magnetic particles. Magnetic separation system under wet process is used conventionally, however, it has some demerit such as necessity of drying treatment after separation and difficulty of running the system in the cold region and so on. Thus, magnetic separation under dry process is prospective as alternative method. In this paper, we developed high gradient magnetic separation system (HGMS) under dry process. In dry HGMS system, powder coagulation caused by particle interaction is considerable. Powder coagulation causes a blockage of magnetic filters and results in decrease of separation performance of dry HGMS system. In order to investigate the effect of powder coagulation on separation performance, we conducted experiments with two kinds of powdered materials whose cohesive properties are different.

Nakai, Y.; Mishima, F.; Akiyama, Y.; Nishijima, S.

2010-11-01

24

Magnetic separation of micro-spheres from viscous biological fluids.  

SciTech Connect

A magnetically based detoxification system is being developed as a therapeutic tool for selective and rapid removal of biohazards, i.e. chemicals and radioactive substances, from human blood. One of the key components of this system is a portable magnetic separator capable of separating polymer-based magnetic nano/micro-spheres from arterial blood flow in an ex vivo unit. The magnetic separator consists of an array of alternating and parallel capillary tubing and magnetizable wires, which is exposed to an applied magnetic field created by two parallel permanent magnets such that the magnetic field is perpendicular to both the wires and the fluid flow. In this paper, the performance of this separator was evaluated via preliminary in vitro flow experiments using a separator unit consisting of single capillary glass tubing and two metal wires. Pure water, ethylene glycol-water solution (v:v = 39:61 and v:v = 49:51) and human whole blood were used as the fluids. The results showed that when the viscosity increased from 1.0 cp to 3.0 cp, the capture efficiency (CE) decreased from 90% to 56%. However, it is still feasible to obtain >90% CE in blood flow if the separator design is optimized to create higher magnetic gradients and magnetic fields in the separation area.

Chen, H.; Kaminski, M. D.; Xianqiao, L.; Caviness, P.; Torno, M.; Rosengart, A. J.; Dhar, P.; Chemical Engineering; Univ. of Chicago Pritzker School of Medicine; Illinois Inst. of Tech.

2007-02-21

25

Continuous cell separation using novel magnetic quadrupole flow sorter  

Microsoft Academic Search

A laboratory prototype of a flow cell sorter based on magnetic quadrupole field was built and evaluated. The magnetic force acting on magnetically labeled cells in such a field has a `centrifugal’ character which provides a basis for the design of a continuous separation process. The sorter was tested on a model cell system of human peripheral lymphocytes labeled with

Maciej Zborowski; Liping Sun; Lee R Moore; P Stephen Williams; Jeffrey J. Chalmers

1999-01-01

26

Microfluidic high gradient magnetic cell separation David W. Inglisa  

E-print Network

and by the selective attachment of magnetic beads has recently been demonstrated on microfluidic devices. We discuss is performed nearly every time blood is extracted from the body. In a centrifuge blood is separated along divided into two classes: using magnetic beads to select cell types, and using the native magnetic

27

Operating characteristics of superconducting high gradient magnetic separators  

Microsoft Academic Search

An 84 in. warm bore or operating bore superconducting high gradient magnetic separator has been designed and has been operational since May, 1986. It is used to process clay to improve its brightness. Since the magnetic force is proportional to the product of flux density and gradient, the included canister is packed with magnetic stainless steel wool. The effect of

J. A. Selvaggi

1989-01-01

28

Magnetic-based microfluidic platform for biomolecular separation.  

PubMed

A novel microfluidic platform for manipulation of micro/nano magnetic particles was designed, fabricated and tested for applications dealing with biomolecular separation. Recently, magnetic immunomagnetic cell separation has attracted a noticeable attention due to the high selectivity of such separation methods. Strong magnetic field gradients can be developed along the entire wire, and the miniaturized size of these current-carrying conductors strongly enhances the magnetic field gradient and therefore produces large, tunable and localized magnetic forces that can be applied on magnetic particles and confine them in very small spots. Further increases in the values of the generated magnetic field gradients can be achieved by employing miniaturized ferromagnetic structures (pillars) which can be magnetized by an external magnetic field or by micro-coils on the same chip. In this study, we demonstrate magnetic beads trapping, concentration, transportation and sensing in a liquid sample under continuous flow by employing high magnetic field gradients generated by novel multi-functional magnetic micro-devices. Each individual magnetic micro-device consists of the following components: 1. Cu micro-coils array embedded in the silicon substrate with high aspect ratio conductors for efficient magnetic field generation 2. Magnetic pillar(s) made of the magnetic alloy NiCoP for magnetic field focusing and magnetic field gradient enhancement. Each pillar is magnetized by its corresponding coil 3. Integrated sensing coil for magnetic beads detection 4. Microfluidic chamber containing all the previous components. Magnetic fields of about 0.1 T and field gradients of around 300 T/cm have been achieved, which allowed to develop a magnetic force of 3 x 10(-9) N on a magnetic particle with radius of 1 mum. This force is large enough to trap/move this particle as the required force to affect such particles in a liquid sample is on the order of approximately pN. Trapping rates of up to 80% were achieved. Furthermore, different micro-coil designs were realized which allowed various movement modes and with different step-sizes. These results demonstrate that such devices incorporated within a microfluidic system can provide significantly improved spatial resolution and force magnitude for quick, efficient and highly selective magnetic trapping, separation and transportation, and as such they are an excellent solution for miniaturized mu-total analysis systems. PMID:16688574

Ramadan, Qasem; Samper, Victor; Poenar, Daniel; Yu, Chen

2006-06-01

29

Electron spin separation without magnetic field.  

PubMed

A nanodevice capable of separating spins of two electrons confined in a quantum dot formed in a gated semiconductor nanowire is proposed. Two electrons confined initially in a single quantum dot in the singlet state are transformed into the system of two electrons confined in two spatially separated quantum dots with opposite spins. In order to separate the electrons' spins we exploit transitions between the singlet and the triplet state, which are induced by resonantly oscillating Rashba spin-orbit coupling strength. The proposed device is all electrically controlled and the electron spin separation can be realized within tens of picoseconds. The results are supported by solving numerically the quasi-one-dimensional time-dependent Schroedinger equation for two electrons, where the electron-electron correlations are taken into account in the exact manner. PMID:25106038

Paw?owski, J; Szumniak, P; Skubis, A; Bednarek, S

2014-08-27

30

Magnetically activated micromixers for separation membranes.  

PubMed

Presented here is a radically novel approach to reduce concentration polarization and, potentially, also fouling by colloids present in aqueous feeds: magnetically responsive micromixing membranes. Hydrophilic polymer chains, poly(2-hydroxyethyl methacrylate) (PHEMA), were grafted via controlled surface-initiated atom transfer radical polymerization (SI-ATRP) on the surface of polyamide composite nanofiltration (NF) membranes and then end-capped with superparamagnetic iron oxide magnetite (Fe(3)O(4)) nanoparticles. The results of all functionalization steps, that is, bromide ATRP initiator immobilization, SI-ATRP, conversion of PHEMA end groups from bromide to amine, and carboxyl-functional Fe(3)O(4) nanoparticle immobilization via peptide coupling, have been confirmed by X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM). These nanoparticles experience a magnetic force as well as a torque under an oscillating external magnetic field. It has been shown, using particle image velocimetry (PIV), that the resulting movement of the polymer brushes at certain magnetic field frequencies induces mixing directly above the membrane surface. Furthermore, it was demonstrated that with such membranes the NF performance could significantly be improved (increase of flux and salt rejection) by an oscillating magnetic field, which can be explained by a reduced concentration polarization in the boundary layer. However, the proof-of-concept presented here for the active alteration of macroscopic flow via surface-anchored micromixers based on polymer-nanoparticle conjugates has much broader implications. PMID:21462955

Himstedt, Heath H; Yang, Qian; Dasi, L Prasad; Qian, Xianghong; Wickramasinghe, S Ranil; Ulbricht, Mathias

2011-05-01

31

Ferritin conjugates as specific magnetic labels. Implications for cell separation.  

PubMed Central

Concanavalin A coupled to the naturally occurring iron storage protein ferritin is used to label rat erythrocytes and increase the cells' magnetic susceptibility. Labeled cells are introduced into a chamber containing spherical iron particles and the chamber is placed in a uniform 5.2 kG (gauss) magnetic field. The trajectory of cells in the inhomogeneous magnetic field around the iron particles and the polar distributions of cells bound to the iron particles compare well with the theoretical predictions for high gradient magnetic systems. On the basis of these findings we suggest that ferritin conjugated ligands can be used for selective magnetic separation of labeled cells. Images FIGURE 2 PMID:6743752

Odette, L L; McCloskey, M A; Young, S H

1984-01-01

32

Emerging magnetism and electronic phase separation at titanate interfaces  

NASA Astrophysics Data System (ADS)

The emergence of magnetism in otherwise nonmagnetic compounds and its underlying mechanisms have become the subject of intense research. Here we demonstrate that the nonmagnetic oxygen vacancies are responsible for an unconventional magnetic state common for titanate interfaces and surfaces. Using an effective multiorbital modeling, we find that the presence of localized vacancies leads to an interplay of ferromagnetic order in the itinerant t2g band and complex magnetic oscillations in the orbitally reconstructed eg band, which can be tuned by gate fields at oxide interfaces. The magnetic phase diagram includes highly fragmented regions of stable and phase-separated magnetic states forming beyond nonzero critical defect concentrations.

Pavlenko, N.; Kopp, T.; Mannhart, J.

2013-11-01

33

Physical separation of particles in magnetized fluidized beds  

Microsoft Academic Search

Magnetized fluidized bed stability is defined using relative amplitudes of pressure fluctuations. It is shown that transition velocities exist for different degrees of bed stability. Experimental results show that magnetically stabilized fluidized beds can be used to effect separation of particles by differences in particle penetration depth and settling velocity.

O. Harel; W. Resnick; Y. Zimmels

1990-01-01

34

Apparatus and method for continuous separation of magnetic particles from non-magnetic fluids  

DOEpatents

A magnetic separator vessel (1) for separating magnetic particles from non-magnetic fluid includes a separation chamber having an interior and exterior wall, a top and bottom portion; a magnet (3) having first and second poles (2) positioned adjacent to the exterior wall, wherein the first pole is substantially diametrically opposed to the second pole; a inlet port (5) is directed into the top portion of the separation chamber, wherein the inlet port (5) is positioned adjacent to one of the first and second poles (2), wherein the inlet port (5) is adapted to transfer a mixture into the separation chamber; an underflow port (6) in communication with the bottom portion, wherein the underflow port (6) is adapted to receive the magnetic particles; and an overflow port (9) in communication with the separation chamber, wherein the overflow port (9) is adapted to receive the non-magnetic fluid.

Oder, Robin R. (Export, PA); Jamison, Russell E. (Lower Burrell, PA)

2010-02-09

35

Feasibility study of iron mineral separation from red mud by high gradient superconducting magnetic separation  

Microsoft Academic Search

The disposal of bayer red mud tailings now seriously threats the environment safety. Reduction and recycling of red mud is now an urgent work in aluminum industry. High gradient superconducting magnetic separation (HGSMS) system was applied to separate the extreme fine RM particles (<100?m) into high iron content part and low iron content part. Two sorts of RM were fed

Yiran Li; Jun Wang; Xiaojun Wang; Baoqiang Wang; Zhaokun Luan

2011-01-01

36

Rare Cell Separation and Analysis by Magnetic Sorting  

PubMed Central

Summary The separation and or isolation of rare cells using magnetic forces is commonly used and growing in use ranging from simple sample prep for further studies to a FDA approved, clinical diagnostic test. This grown is the result of both the demand to obtain homogeneous rare cells for molecular analysis and the dramatic increases in the power of permanent magnets that even allow the separation of some unlabeled cells based on intrinsic magnetic moments, such as malaria parasite-infected red blood cells. PMID:21812408

Zborowski, Maciej; Chalmers, Jeffrey J.

2011-01-01

37

Development of cryogenic cooling system using a double GM cryo-cooler for NMR spectrometer  

Microsoft Academic Search

The sensitivity of nuclear magnetic resonance (NMR) spectrometer is limited by thermal noise. To increase the signal-noise-ratio (SNR), cryogenically cooled probes with cryo-coolers have been used. In order to cool RF coils in the probe below 10K, Gifford- McMahon\\/Joule-Thomson (G-M\\/J-T) cryo-coolers are used. But, the G-M\\/J-T cryo-coolers aren't suitable for a long time operation. On the other hand, G-M cryo-coolers

H Tanaka; Y Fukuda; M Okada; N Saho; K Saitoh; H Kitaguchi

2008-01-01

38

Simulation of recoil trajectories in gas-filled magnetic separators  

NASA Astrophysics Data System (ADS)

A computer code has been developed to simulate the production of heavy element compound nucleus recoils and their trajectories through gas-filled magnetic separators. The simulation is carried out in three steps: positions and trajectories of heavy element recoils in the target layer, propagation through remaining target material, and trajectories through the gas-filled separator. Separators with quite different magnetic configurations are modeled: the Berkeley gas-filled separator (BGS) and two magnetic configurations for the TransActinide separator and chemistry apparatus (TASCA). While computing trajectories through the gas-filled separator, special attention is paid to the charge exchange/equilibration and scattering in the gas. New features of these simulations include mixed He/H2/N2 gas operation and a gas density (pressure) effect. Numerical procedures used in the simulations are explained in detail. Results of the simulations are presented, showing the gas mixtures/pressures that result in the highest efficiency for collecting compound nucleus recoils at the focal plane of the gas-filled separator. Comparison between simulation and experimental results are presented for average recoil ion charge in various gases, focal plane image size, and magnetic rigidity dispersion.

Gregorich, K. E.

2013-05-01

39

Magnetic aqueous two-phase separation in preparative applications.  

PubMed

Magnetic aqueous two-phase separation is a new technique to speed up the separation of aqueous two-phase systems (Anal. Biochem. 1987, 167, 331-339). It is based on the addition of magnetically susceptible material (e.g. 1-micron iron oxide particles) which induces rapid phase separation when a mixed system is placed in a magnetic field. The technique has been applied to a number of two-phase systems. The time for phase separation was decreased by a factor of 5-240,000, with the largest improvement for systems containing high concentrations of protein and for systems with viscous or nearly isopycnic phases. An apparatus for preparative multistage extraction with magnetic separation was constructed and tested on glycolytic enzymes present in a yeast extract using a dextran/Cibacron blue-polyethylene glycol system. The presence of iron oxide particles did not adversely affect the extracted enzymes. An electromagnet-based apparatus for continuous phase separation on a larger scale was also designed. A phase system containing crude dextran and unpurified cell homogenate was effectively processed. The apparatus also allowed effective separation when the phase containing iron oxide particles was only a small fraction (4%) of the total phase system. PMID:1368542

Flygare, S; Wikström, P; Johansson, G; Larsson, P O

1990-02-01

40

Waste remediation using in situ magnetically assisted chemical separation  

SciTech Connect

The magnetically assisted chemical separation process (MACS) combines the selective and efficient separation afforded by chemical sorption with the magnetic recovery of ferromagnetic particles. This process is being developed for treating the underground storage tanks at Hanford. These waste streams contain cesium, strontium, and transuranics (TRU) that must be removed before this waste can be disposed of as grout. The separation process uses magnetic particles coated with either (1) a selective ion exchange material or an organic extractant containing solvent (for cesium and strontium removal) or (2) solvents for selective separation of TRU elements (e.g., TRUEX process). These coatings, by their chemical nature, selectively separate the contaminants onto the particles, which can then be recovered from the tank using a magnet. Once the particles are removed, the contaminants can either be left on the loaded particles and added to the glass feed slurry or stripped into a small volume of solution so that the extracting particles can be reused. The status of chemistry and separation process is discussed in this paper.

Nunez, L.; Buchholz, B.A.; Vandegrift, G.F.

1993-11-01

41

Magnetic micro-devices for separation and manipulation of biological components.  

E-print Network

??A scheme for magnetic based biomolecular separation, transportation and detection has been proposed, designed, fabricated and successfully demonstrated through a novel micro-fabricated magnetic system. Magnetic… (more)

Qasem Ramadan.

2008-01-01

42

Modeling high gradient magnetic separation from biological fluids.  

SciTech Connect

A proposed portable magnetic separator consists of an array of biocompatible capillary tubing and magnetizable wires immersed in an externally applied homogeneous magnetic field. While subject to the homogeneous magnetic field, the wires create high magnetic field gradients, which aid in the collection of blood-borne magnetic nanospheres from blood flow. In this study, a 3-D numerical model was created using COMSOL Multiphysics 3.2 software to determine the configuration of the wire-tubing array from two possible configurations, one being an array with rows alternating between wires and tubing, and the other being an array where wire and tubing alternate in two directions. The results demonstrated that the second configuration would actually capture more of the magnetic spheres. Experimental data obtained by our group support this numerical result.

Bockenfeld, D.; Chen, H.; Rempfer, D.; Kaminski, M. D.; Rosengart, A. J.; Chemical Engineering; Illinois Inst. of Tech.; Univ. of Chicago, Pritzker School of Medicine

2006-01-01

43

Inverted Linear Halbach Array for Separation of Magnetic Nanoparticles  

PubMed Central

A linear array of Nd-Fe-B magnets has been designed and constructed in an inverted Halbach configuration for use in separating magnetic nanoparticles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient in agreement with finite element modeling calculations. The magnet assembly has been combined with a flow channel for magnetic nanoparticle suspensions, such that for an appropriate distance away from the assembly, nanoparticles of higher moment aggregate and accumulate against the channel wall, with lower moment nanoparticles flowing unaffected. The device is demonstrated for iron oxide nanoparticles with diameters of ~ 5 and 20 nm. In comparison to other approaches, the inverted Halbach array is more amenable to modeling and to scaling up to preparative quantities of particles.

Ijiri, Y.; Poudel, C.; Williams, P.S.; Moore, L.R.; Orita, T.; Zborowski, M.

2014-01-01

44

Magnetic field analysis of high gradient magnetic separator via finite element analysis  

NASA Astrophysics Data System (ADS)

High Gradient Magnetic Separator (HGMS) uses matrix to make high magnetic field gradient so that ferro- or para-magnetic particles can be attracted to them by high magnetic force. The magnetic force generated by the field gradient is several thousand times larger than that by the magnetic flux density alone. So the HGMS shows excellent performance compared with other magnetic separators. These matrices are usually composed of stainless wires having high magnetization characteristics. This paper deals with superconducting HGMS which is aimed for purifying wastewater by using stainless steel matrix. Background magnetic field up to 6 T is generated by a superconducting solenoid and the stainless steel matrices are arranged inside of the solenoid. In order to calculate magnetic forces exerting on magnetic particles in wastewater, it is important to calculate magnetic field and magnetic field gradient those are proportional to the magnetic force acting on the particle. So we presents magnetic field distribution analysis result and estimates how many times of magnetic force will act on a particle when the matrix are arranged or not. Magnetic field is calculated in 3 dimensions by using Finite Element Method (FEM) and also compared with results obtained from 2 dimensional analysis.

Baik, S. K.; Ha, D. W.; Ko, R. K.; Kwon, J. M.

2012-10-01

45

Process to remove actinides from soil using magnetic separation  

DOEpatents

A process of separating actinide-containing components from an admixture including forming a slurry including actinide-containing components within an admixture, said slurry including a dispersion-promoting surfactant, adjusting the pH of the slurry to within a desired range, and, passing said slurry through a pretreated matrix material, said matrix material adapted to generate high magnetic field gradients upon the application of a strong magnetic field exceeding about 0.1 Tesla whereupon a portion of said actinide-containing components are separated from said slurry and remain adhered upon said matrix material is provided.

Avens, Larry R. (Los Alamos, NM); Hill, Dallas D. (Los Alamos, NM); Prenger, F. Coyne (Los Alamos, NM); Stewart, Walter F. (Las Cruces, NM); Tolt, Thomas L. (Los Alamos, NM); Worl, Laura A. (Los Alamos, NM)

1996-01-01

46

Separation of feeble magnetic particles with magneto-Archimedes levitation  

Microsoft Academic Search

Particles and solid substances with feeble magnetic susceptibility were levitated by magnetic fields with the aid of the “magneto-Archimedes levitation” method [Nature 393 (1998) 749]. A novel feature was found, namely that the initial particle mixture levitated underwent separation into each kind of the ingredient particle aggregates. The samples levitated were NaCl–KCl grain mixtures, and colored glass particles. The experiments

Y Ikezoe; T Kaihatsu; S Sakae; H Uetake; N Hirota; K Kitazawa

2002-01-01

47

Effect of reverse flotation on magnetic separation concentrates  

NASA Astrophysics Data System (ADS)

Reverse flotation studies on magnetite samples have revealed that the use of starch as a depressant of Fe-oxides has a hydrophilic effect on the surface of Fe-bearing silicates and significantly decreases Fe in the silica-rich stream when used in combination with an amine (Lilaflot D817M). In this study, the effect of reverse flotation on the optimization of products obtained from magnetic separation was investigated. Two different magnetic samples, zones 1 and 2, were milled to <75 ?m and then subjected to low intensity magnetic separation (LIMS). The LIMS test conducted on the <75 ?m shown an upgrade of 46.40wt% Fe, 28.40wt% SiO2 and 2.61wt% MnO for zone 1 and 47.60wt% Fe, 29.17wt% SiO2 and 0.50wt% MnO for zone 2. Further milling of the ore to <25 ?m resulted in a higher magnetic-rich product after magnetic separation. Reverse flotation tests were conducted on the agitated magnetic concentrate feed, and the result shows a significant upgrade of Fe compared to that obtained from the non-agitated feed. Iron concentrations greater than 69%, and SiO2 concentrations less than 2% with overall magnetite recoveries greater than 67% and 71% were obtained for zones 1 and 2, respectively.

Bada, S. O.; Afolabi, A. S.; Makhula, M. J.

2012-08-01

48

Coil geometry for efficient active compensation with separated magnetic shields  

NASA Astrophysics Data System (ADS)

We have already proposed a new method of magnetic shielding aiming for magnetocardiography, in which magnetic shells are separated and a new compensation scheme is employed to allow for wide space between them. Each magnetic shell that consists of a half of the cylinder (diameter=20 cm and length=60 cm) and two flanges at both ends of the half cylinder extending along the radial direction has a saddle coil on its outer surface with the coil's long straight section running parallel to the axis of the cylinder. In this paper, the relationship between the width of the long straight sections of the saddle coil and the efficiency of the active compensation is investigated by the finite element method (FEM) analysis and by experiments. A magnetic shield used in this study is a double shell structure where each shell is made of stacked amorphous tapes and the outer shell has a magnetic shaking coil for the enhancement of the permeability. We have found that for a given magnetic field, the compensation current necessary for a given magnetic field varies by a factor of 3 depending on the width of a saddle coil and that its value monotonically decreases with increasing the width. We have also confirmed that the phase delay of the compensation magnetic field experienced while it comes in the magnetic shell is small.

Nakashima, Yoshihiro; Sasada, Ichiro

2009-04-01

49

TREATMENT OF COMBINED SEWER OVERFLOWS BY HIGH GRADIENT MAGNETIC SEPARATION  

EPA Science Inventory

Seeded water treatment by high gradient magnetic separation techniques was carried out on combined storm overflows and raw sewage influents. Both bench-type and continuous pilot plant tests were performed to evaluate the effectiveness of the process in purifying waste waters. Cri...

50

Purification of Wastewater From Paper Factory by Superconducting Magnetic Separation  

Microsoft Academic Search

It is environmentally important to recycle the wastewater, since paper factories use a large amount of water and equivalent amount of wastewater is generated. Conventional water treatment facilities like precipitation process need large-scale equipment and wide space to purify the wastewater of paper factory. In case of massive waste water, high gradient magnetic separation (HGMS) parts are more effective to

Dong-Woo Ha; Tae-Hyung Kim; Myung-Hwan Sohn; Jun-Mo Kwon; Seung-Kyu Baik; Rock-Kil Ko; Sang-Soo Oh; Hong-Soo Ha; Ho-Sup Kim; Young-Hun Kim; Tae-Wook Ha

2010-01-01

51

Investigation of open-gradient magnetic separation for Illinois coal  

SciTech Connect

Open-gradient magnetic separation (OGMS) using superconducting quadrupole magnets is a novel coal-beneficiation technology offering high pyritic-sulfur removal from pulverized dry coal. The system operates in a continuous mode, uses no chemicals, and has an estimated power demand 75% lower than techniques using conventional electromagnets, while achieving magnetic separation forces up to 267% higher. Specifically applicable to finely ground coal (120 to 325 mesh), OGMS could encourage the commercialization of other developing coal technologies, such as coal-water slurries, fludized-bed combustion, and coal synfuels. Both the experimental program conducted by Argonne National Laboratory and the results of modeling in support of the experimental program are described. 11 refs., 9 figs.

Doctor, R.D.; Livengood, C.D.; Genens, L.E.; Swietlik, C.E.; Foote, K.

1987-01-01

52

D0 Cryo System ODH and Cryo Alarm System Response  

SciTech Connect

The D0 Cryo System is monitored by a computerized process control system and an ODH safety system. During steady state operations the cryo system will be unmanned and system experts will depend on communication systems for notification of system problems. The FIRUS system meets the minimum communication requirement and is supplemented with an autodialer which attempts to contact cryo operators by pager or phone. The RD/Safety Department requires the ODH monitor system to be connected to the labwide FIRUS system. which enables the Communications Center to receive alarms and notify the proper experts of the condition. The ODH system will have two alarm points. One for an ODH alarm and one for a system trouble alarm. The autodialer system has replaced a former cryo operations summation alarm point in the FIRUS system. This has freed space on the FIRUS system and has allowed the cryo experts more flexibility in setting up their own communication link. The FIRUS and the autodialer systems receive alarms and access lists of experts to call for notification of problems. Attempts to contact these experts will continue until the alarm or alarms is acknowledged.

Urbin, J.; Dixon, K.; /Fermilab

1990-04-05

53

Waste water purification by magnetic separation technique using HTS bulk magnet system  

NASA Astrophysics Data System (ADS)

We have investigated the feasibility of strong magnetic field generators composed of the high temperature superconducting (HTS) bulk magnet systems to the magnetic separation techniques for the waste water including thin emulsion bearing the cutting oil. Two types of the strong field generators were prepared by the face-to-face HTS bulk magnet systems, which emit the magnetic field density of 1 and 2 T in the open spaces between the magnetic poles activated by the pulsed field magnetization and the field cooling methods, respectively. A couple of water channels containing iron balls were settled in the strong field to trap the magnetized flocks in the waste water. The separation ratios of flocks containing 200 ppm magnetite powder were evaluated with respect to the flow rates of the waste water. The performances of bulk magnet system have kept showing values of around 100% until the flowing rate reached up to 18 l/min. This suggests that the magnetic separation by using bulk magnets is effective for the practical water purification systems.

Oka, T.; Kanayama, H.; Tanaka, K.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M.; Terasawa, T.; Itoh, Y.; Yabuno, R.

2009-10-01

54

Upgrading mixed polyolefin waste with magnetic density separation.  

PubMed

Polyolefin fractions are often end fractions resulting from the recycling of end-of-life consumer products. Polypropylene (PP) and polyethylene (PE) are present in such fractions as a mixture. For instance, the ratio of PP and PE in car scrap is 70:30 on average. However, the grade of the PP and PE should typically be better than 97% to be reused again as a high quality product. Density separation of the different polyolefins can be a solution. A promising separation technique is the inverse magnetic density separator (IMDS). This paper discusses the potential of shredder residue, one of the possible polyolefin's waste stream sources for the IMDS, in detail. Experiments with the separation of polyolefins with an IMDS prototype show both high grade and high recovery. The paper concludes with the economic opportunities of the IMDS in the recycling of polyolefins. PMID:19128952

Bakker, E J; Rem, P C; Fraunholcz, N

2009-05-01

55

[Development of new magnetic bead separation and purification instrument].  

PubMed

The article describes the development of new magnetic bead separation and purification instrument. The main application of the instrument is to capture tubercle bacillus from sputum. It is a pretreatment instrument and provides a new platform to help doctors to diagnose bacillary phthisis. Not only could it be used for tubercle bacillus capturing, but also for gene, protein and cell separating and purification. Because the controller of the instrument is 16-bit single chip microcomputer, the cost could be greatly reduced and it will be widely used in China. PMID:25241516

Xu, Yingyuan; Chen, Yi

2014-05-01

56

Dynamics of magnetic particles in cylindrical Halbach array: implications for magnetic cell separation and drug targeting.  

PubMed

Magnetic nanoparticles for therapy and diagnosis are at the leading edge of the rapidly developing field of bionanotechnology. In this study, we have theoretically studied motion of magnetic nano- as well as micro-particles in the field of cylindrical Halbach array of permanent magnets. Magnetic flux density was modeled as magnetostatic problem by finite element method and particle motion was described using system of ordinary differential equations--Newton law. Computations were done for nanoparticles Nanomag-D with radius 65 nm, which are often used in magnetic drug targeting, as well as microparticles DynaBeads-M280 with radius 1.4 microm, which can be used for magnetic separation. Analyzing snapshots of trajectories of hundred magnetite particles of each size in the water as well as in the air, we have found that optimally designed magnetic circuits of permanent magnets in quadrupolar Halbach array have substantially shorter capture time than simple blocks of permanent magnets commonly used in experiments, therefore, such a Halbach array may be useful as a potential source of magnetic field for magnetic separation and targeting of magnetic nanoparticles as well as microparticles for delivery of drugs, genes, and cells in various biomedical applications. PMID:20517710

Babinec, Peter; Krafcík, Andrej; Babincová, Melánia; Rosenecker, Joseph

2010-08-01

57

Oil-field wastewater purification by magnetic separation technique using a novel magnetic nanoparticle  

NASA Astrophysics Data System (ADS)

In the present work, oil-field wastewater purification through superconducting magnetic separation technique using a novel magnetic nanoparticle was investigated. The magnetic nanoparticle, which has a multi-shell structure with ferroferric oxide as core, dense nonporous silica as inter layer and mesoporous silica as outer layer, was synthesized by co-precipitation method. To functionalize the magnetic nanoparticle, plasma polymerization technique was adopted and poly methyl acrylate (PMA) was formed on the surface of the nanoparticle. The multi-shell structure of the nanoparticle was confirmed by transmission electron microscope (TEM) and the characteristic is measurable by FTIR. It is found that most of the pollutants (85% by turbidity or 84% by COD value) in the oil-field wastewater are removed through the superconducting magnetic separation technique using this novel magnetic nanoparticle.

Liu, Zhuonan; Yang, Huihui; Zhang, Hao; Huang, Chuanjun; Li, Laifeng

2012-12-01

58

Magnetic Separation for Nuclear Material Detection and Surveillance  

SciTech Connect

A high performance superconducting magnet is being developed for particle retrieval from field collected samples. Results show that maximum separation effectiveness is obtained when the matrix fiber diameter approaches the diameter of the particles to be captured. Experimentally, the authors obtained a single particle capture limit with 0.8{micro}m PuO{sub 2} particles with dodecane as a carrier fluid. The development of new matrix materials is being pursued through the controlled corrosion of stainless steel wool, or the deposition of nickel dendrites on the existing stainless steel matrix material. They have also derived a model from a continuity equation that uses empirically determined capture cross section values. This enables the prediction of high gradient magnetic separator performance for a variety of materials and applications. The model can be used to optimize the capture cross section and thus increase the capture efficiency.

Worl, L.A.; Devlin, D.; Hill, D.; Padilla, D.; Prenger, F.C.

1998-08-01

59

Differential magnetic catch and release: experimental parameters for controlled separation of magnetic nanoparticles.  

PubMed

Differential magnetic catch and release (DMCR) has been used as a method for the purification and separation of magnetic nanoparticles. DMCR separates nanoparticles in the mobile phase by magnetic trapping of magnetic nanoparticles against the wall of an open tubular capillary wrapped between two narrowly spaced electromagnetic poles. Using Au and CoFe(2)O(4) nanoparticles as model systems, the loading capacity of the 250 ?m diameter capillary is determined to be ?130 ?g, and is scalable to higher quantities with larger bore capillary. Peak resolution in DMCR is externally controlled by selection of the release time (R(t)) at which the magnetic flux density is removed, however, longer capture times are shown to reduce the capture yield. In addition, the magnetic nanoparticle capture yields are observed to depend on the nanoparticle diameter, mobile phase viscosity and velocity, and applied magnetic flux. Using these optimized parameters, three samples of CoFe(2)O(4) nanoparticles whose diameters are different by less than 10 nm are separated with excellent resolution and capture yield, demonstrating the capability of DMCR for separation and purification of magnetic nanoparticles. PMID:21562675

Beveridge, Jacob S; Stephens, Jason R; Williams, Mary Elizabeth

2011-06-21

60

Capture of metallic copper by high gradient magnetic separation system.  

PubMed

Valence copper was recovered from wastewater by chemical reduction and use of a high gradient magnetic separation (HGMS) system. Ammonia (NH3) and sodium dithionate (Na2S2O4) at a molar ratio of [Cu]:[NH3]:[Na2S2O4] = 1:4:3 at pH = 9.5 were used first to chemically reduce copper ion to metallic copper; the resultant metal solids were captured in an upflowing reactor space equipped with a permalloy matrix net under a high gradient magnetic field. The captured solids were predominantly 6-20 microm in diameter, with Cu2O and CuO present among the solids. Four treatment configurations with and without the use of magnetic field and metal alloy as the matrix net were tested and their effects evaluated: (1) no magnetic field or matrix, (2) no magnetic field but with matrix, (3) with magnetic field but no matrix, (4) with both magnetic field and matrix. At flow rates of 40, 60, 80 and 100 cm3/min, capture efficiencies for metallic copper in the absence of magnetic field were 87%, 86%, 63%, and 39%, respectively, and in the presence of magnetic field were 99%, 98%, 95%, and 93%, respectively. The HGMS was critical for a high capture efficiency, whereas a matrix net only marginally enhanced it. Additional tests with a larger reactor confirmed similarly high efficiencies of > 85%. The use of an alloy matrix appeared to be important when high flow rates are most likely to be employed in practical applications. PMID:22329132

Wu, Wan-I; Wu, Chung-Hsin; Hong, P K Andy; Lin, Cheng-Fang

2011-10-01

61

Cell separation in a microfluidic channel using magnetic microspheres  

Microsoft Academic Search

Magnetophoretic isolation of biological cells in a microfluidic environment has strong relevance in biomedicine and biotechnology.\\u000a A numerical analysis of magnetophoretic cell separation using magnetic microspheres in a straight and a T-shaped microfluidic\\u000a channel under the influence of a line dipole is presented. The effect of coupled particle–fluid interactions on the fluid\\u000a flow and particle trajectories are investigated under different

Nipu Modak; Amitava Datta; Ranjan Ganguly

2009-01-01

62

Magnetic Separation of Ferrite Sludge from a Wastewater Purification Process  

Microsoft Academic Search

The purification of wastewater containing dissolved metal ions by in situ precipitation gives rise to a sludge composed mainly of ferrites MeXFe3-xO4 (where Me represents the existing metal ions in the wastewater). Oxides, iron oxy-hydroxides and other impurities are also present in the sludge in smaller proportion. The present investigation proposes magnetic separation of the sludge to recover the ferrites

E. Barrado; F. Prieto; J. Ribas; F. A. López

1999-01-01

63

Charge separation in a magnetized plasma-sheath-lens  

NASA Astrophysics Data System (ADS)

Most of plasma processing technologies are based on radical-assisted ion-induced surface-modification where ions accumulate energy in the sheath, and then strike the surface modifying its properties in a desirable way. Plasma-sheath-lens is a three-dimensional potential distribution of customized shape, formed by the space charge surrounding a biased electrode-insulator interface. The discrete and modal focusing effects have been reveled for this type of electrostatic structures formed in plasma [1] and several applications including sheath thickness evaluation, negative ion detection and extraction of positive or negative ion beams have been developed. A non-magnetized plasma-sheath-lens act as a kinetic energy separator, but it is not mass sensitive. However, a magnetized plasma-sheath-lens exhibits mass separation, so that ions of different mass will impact the electrode at different locations on the biased electrode surface. The mass spectrum can be measured as the radial distribution of the ion current density over the plasma-sheath-lens's electrode. Relevant fluid and particles simulations of the magnetized plasma-sheath-lens structures and ion trajectories within them are presented for different plasma parameters and magnetic filed configurations. Practical aspects linked to the development of a new type of mass spectrometers are also investigated.[0pt] [1] E. Stamate and H. Sugai, Phys. Rev. Lett. (2005) 94, 125004

Stamate, Eugen

2009-10-01

64

Radiolysis and hydrolysis of magnetically assisted chemical separation particles  

SciTech Connect

The magnetically assisted chemical separation (MACS) process is designed to separate transuranic (TRU) elements out of high-level waste (HLW) or TRU waste. Magnetic microparticles (1--25 {mu}m) were coated with octyl (phenyl)N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) dissolved in tributyl phosphate (TBP) and tested for removing TRU elements from acidic nitrate solutions. The particles were contacted with nitric acid solutions and Hanford plutonium finishing plant (PFP) simulant, irradiated with a high intensity {sup 60}Co {gamma}-ray source, and evaluated for effectiveness in removing TRU elements from 2m HNO{sub 3} solutions. The resistance of the coatings and magnetic cores to radiolytic damage and hydrolytic degradation was investigated by irradiating samples of particles suspended in a variety of solutions with doses of up to 5 Mrad. Transmission electron microscopy (TEM), magnetic susceptibility measurements, and physical observations of the particles and suspension solutions were used to assess physical changes to the particles. Processes that affect the surface of the particles dramatically alter the binding sites for TRU in solution. Hydrolysis played a larger role than radiolysis in the degradation of the extraction capacity of the particles.

Buchholz, B.A.; Nunez, L.; Vandegrift, G.F.

1995-05-01

65

Kinetic approach for the purification of nucleotides with magnetic separation.  

PubMed

The isolation of ?-nicotinamide adenine dinucleotide is of great importance since it is widely used in different scientific and technologic fields such as biofuel cells, sensor technology, and hydrogen production. In order to isolate ?-nicotinamide adenine dinucleotide, first 3-aminophenyboronic acid functionalized magnetic nanoparticles were prepared to serve as a magnetic solid support and subsequently they were used for reversible adsorption/desorption of ?-nicotinamide adenine dinucleotide in a batch fashion. The loading capacity of the 3-aminophenyboronic acid functionalized nanoparticles for ?-nicotinamide adenine dinucleotide adsorption was 13.0 ?mol/g. Adsorption kinetic and isotherm studies showed that the adsorption process followed a pseudo-second-order kinetic model and the experimental data can be represented using Langmuir isotherm model. The 3-aminophenyboronic acid functionalized magnetic nanoparticles were proposed as an alternative support for the ?-nicotinamide adenine dinucleotide purification. The results elucidated the significance of magnetic separation as a fast, relatively simple, and low-cost technique. Furthermore, the magnetic supports can be reused at least five times for purification processes. PMID:25199632

Tural, Servet; Tural, Bilsen; Ece, Mehmet ?akir; Yetkin, Evren; Ozkan, Necati

2014-11-01

66

Automated cryo-electron microscopy  

Microsoft Academic Search

Cryo-electron microscopy is widely viewed as a uniquely powerful method for the study of membrane proteins and large macromolecular complexes - subjects that are viewed as extremely challenging or impossible to study using x-ray or NMR methods. Although the methodology of molecular microscopy has enormous potential, it is time consuming and labor intensive. Our group has done extensive work to

Clinton S. Potter; D. Fellmann; Ron A. Milligan; Jim Pulokas; C. Suloway; Yuanxin Zhu; A. Carragher

2002-01-01

67

Apparatus for magnetic separation of paramagnetic and diamagnetic material  

DOEpatents

The present invention relates to methods and apparatus for segregating paramagnetic from diamagnetic particles in particulate material and, in particular, to the open gradient magnetic separation of ash producing components and pyritic sulfur from coal. The apparatus includes a vertical cylinder and a rotatable vertical screw positioned within the cylinder, the screw having a helical blade angled downwardly and outwardly from the axis. Rotation of the vertical screw causes denser particles, which in the case of coal include pyritic sulfur and ash, which are paramagnetic, to migrate to the outside of the screw, and less dense particles, such as the low sulfur organic portion of the coal, which are diamagnetic, to migrate towards the center of the screw. A vibration mechanism attached to the screw causes the screw to vibrate during rotation, agitating and thereby accommodating further segregation of the particles. An open gradient magnetic field is applied circumferentially along the entire length of the screw by a superconducting quadropole magnet. The open gradient magnetic field further segregates the paramagnetic particles from the diamagnetic particles. The paramagnetic particles may then be directed from the cylinder into a first storage bin, and the diamagnetic particles, which are suitable for relatively clean combustion, may be directed into a second storage bin.

Doctor, Richard D. (Glen Ellyn, IL)

1988-01-01

68

Apparatus for magnetic separation of paramagnetic and diamagnetic material  

DOEpatents

The present invention relates to methods and apparatus for segregating paramagnetic from diamagnetic particles in particulate material and, in particular, to the open gradient magnetic separation of ash producing components and pyritic sulfur from coal. The apparatus includes a vertical cylinder and a rotatable vertical screw positioned within the cylinder, the screw having a helical blade angled downwardly and outwardly from the axis. Rotation of the vertical screw causes denser particles, which in the case of coal include pyritic sulfur and ash, which are paramagnetic, to migrate to the outside of the screw, and less dense particles, such as the low sulfur organic portion of the coal, which are diamagnetic, to migrate towards the center of the screw. A vibration mechanism attached to the screw causes the screw to vibrate during rotation, agitating and thereby accommodating further segregation of the particles. An open gradient magnetic field is applied circumferentially along the entire length of the screw by a superconducting quadrupole magnet. The open gradient magnetic field further segregates the paramagnetic-particles from the diamagnetic particles. The paramagnetic particles may then be directed from the cylinder into a first storage bin, and the diamagnetic particles, which are suitable for relatively clean combustion, may be directed into a second storage bin. 5 figs.

Doctor, R.D.

1986-07-24

69

Apparatus for magnetic separation of paramagnetic and diamagnetic material  

DOEpatents

The present invention relates to methods and apparatus for segregating paramagnetic from diamagnetic particles in particulate material and, in particular, to the open gradient magnetic separation of ash producing components and pyritic sulfur from coal. The apparatus includes a vertical cylinder and a rotatable vertical screw positioned within the cylinder, the screw having a helical blade angled downwardly and outwardly from the axis. Rotation of the vertical screw causes denser particles, which in the case of coal include pyritic sulfur and ash, which are paramagnetic, to migrate to the outside of the screw, and less dense particles, such as the low sulfur organic portion of the coal, which are diamagnetic, to migrate towards the center of the screw. A vibration mechanism attached to the screw causes the screw to vibrate during rotation, agitating and thereby accommodating further segregation of the particles. An open gradient magnetic field is applied circumferentially along the entire length of the screw by a superconducting quadrupole magnet. The open gradient magnetic field further segregates the paramagnetic particles from the diamagnetic particles. The paramagnetic particles may then be directed from the cylinder into a first storage bin, and the diamagnetic particles, which are suitable for relatively clean combustion, may be directed into a second storage bin. 5 figs.

Doctor, R.D.

1988-10-18

70

Haloing in bimodal magnetic colloids: the role of field induced phase separation , P.Kuzhir1  

E-print Network

separation, ferrofluid, magnetic colloids Abstract If a suspension of magnetic micron-sized and nano1 Haloing in bimodal magnetic colloids: the role of field induced phase separation C.Magnet1 , P technologies used in bio-analysis and water purification systems. 1. Introduction Bimodal colloidal mixtures

Boyer, Edmond

71

On-chip Magnetic Separation and Cell Encapsulation in Droplets†  

PubMed Central

The demand for high-throughput single cell assays is gaining importance because of the heterogeneity of many cell suspensions, even after significant initial sorting. These suspensions may display cell-to-cell variability at the gene expression level that could impact single cell functional genomics, cancer, stem-cell research and drug screening. The on-chip monitoring of individual cells in an isolated environment would prevent cross-contamination, provide high recovery yield, and enable study of biological traits at a single cell level. These advantages of on-chip biological experiments is a significant improvement for myriad of cell analyses over conventional methods, which require bulk samples providing only averaged information on cell metabolism. We report on a device that integrates mobile magnetic trap array with microfluidic technology to provide, combined functionality of separation of immunomagnetically labeled cells or magnetic beads and their encapsulation with reagents into pico-liter droplets. This scheme of simultaneous reagent delivery and compartmentalization of the cells immediately after sorting, all performed seamlessly within the same chip, offers unique advantages such as the ability to capture cell traits as originated from its native environment, reduced chance of contamination, minimal use and freshness of the reagent solution that reacts only with separated objects, and tunable encapsulation characteristics independent of the input flow. In addition to the demonstrated preliminary cell viability assay, the device can potentially be integrated with other up- or downstream on-chip modules to become a powerful single-cell analysis tool. PMID:23370785

Chen, Aaron; Byvank, Tom; Chang, Woo-Jin; Bharde, Atul; Vieira, Greg; Miller, Brandon; Chalmers, Jeffrey J.; Bashir, Rashid; Sooryakumar, Ratnasingham

2014-01-01

72

Study on magnetic separation for decontamination of cesium contaminated soil by using superconducting magnet  

NASA Astrophysics Data System (ADS)

The accident of Fukushima Daiichi nuclear power plant caused the diffusion of radioactive cesium over the wide area. We examined the possibility of applying magnetic separation method using the superconducting magnet, which can process a large amount of the soil in high speed, to the soil decontamination and volume reduction of the radioactive cesium contaminated soil. Clay minerals are classified as 2:1 and 1:1 types by the difference of their layer structures, and these types of minerals are respectively paramagnetic and diamagnetic including some exception. It is known that most of the radioactive cesium is strongly adsorbed on the clay, especially on 2:1 type clay minerals. It is expected that the method which can separate only 2:1 type clay minerals selectively from the mixture clay minerals can enormously contribute to the volume reduction of the contaminated soil. In this study, the components in the clay before and after separation were evaluated to estimate the magnetic separation efficiency by using X-ray diffraction. From the results, the decontamination efficiency and the volume reduction ratio were estimated in order to examine the appropriate separation conditions for the practical decontamination of the soil.

Igarashi, Susumu; Nomura, Naoki; Mishima, Fumihito; Akiyama, Yoko

2014-09-01

73

Fundamental study on magnetic separation of aquatic organisms for preservation of marine ecosystem  

NASA Astrophysics Data System (ADS)

Recently, destruction and disturbance of marine ecosystem have been caused by changes in global environment and transplants of farmed fishes and shellfishes. To solve the problems, water treatment techniques to kill or to remove aquatic organisms are necessary. In this study, application of magnetic separation for removal of the aquatic organisms was examined in order to establish the process with high-speed, compact device and low environmental load. Techniques of magnetic seeding and magnetic separation using superconducting magnet are important for high-speed processing of aquatic organisms. Magnetic seeding is to adhere separating object to the surface of ferromagnetic particles, and magnetic separation is to remove aquatic organisms with magnetic force. First, we confirmed the possibility of magnetic seeding of aquatic organisms, and then interaction between aquatic organisms and ferromagnetic particles was examined. Next, for practical application of magnetic separation system using superconducting magnet for removal of aquatic organisms, particle trajectories were simulated and magnetic separation experiment using superconducting magnet was performed in order to design magnetic separation system to achieve high separation efficiency.

Sakaguchi, F.; Akiyama, Y.; Izumi, Y.; Nishijima, S.

2009-10-01

74

Development of a high gradient magnetic separator using high temperature superconductors  

SciTech Connect

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). High-gradient magnetic separation (HGMS) is an application of superconducting magnet technology to the process of magnetic separation of solids from other solids, liquids, or gases. The production of both high magnetic fields and large field gradients using superconducting magnet technology has made it possible to separate a previously unreachable but large family of paramagnetic materials. It is possible to separate more than half of the elements in the periodic table using this method. Because HGMS is a physical separation process, no additional or mixed waste is generated. This project sought to develop a high-gradient magnetic separator using a high-temperature superconducting magnet.

Prenger, F.C.; Daney, D.; Daugherty, M.; Hill, D.

1996-09-01

75

The Development of the Separation Apparatus of Phosphor by Controlling the Magnetic Force  

NASA Astrophysics Data System (ADS)

The phosphor wastes contain the multiple kinds of rare-earth phosphors with high market value. Because of increasing demand for rare-earth, the technique to recover and reuse the rare-earth in the phosphor wastes is required. In this study, we focused on the difference of physical property such as magnetic susceptibility and density for each type of phosphor and tried to separate and recover the phosphors by using the magnetic separation technique utilizing the difference of the traction force to the magnet acting on the particles. Magneto-Archimedes method is method separation technique utilizi g the difference of magnetic susceptibility and density. We developed the magnetic separation apparatus by applying this technique. To develop the practical separation apparatus, the continuous process is required. Hence the fundamental experiment utilizing High Temperature Superconducting (HTS) Bulk Magnet which can generate the strong magnetic force was conducted. As a result, we succeeded the continuous separation of the phosphor wastes.

Wada, K.; Mishima, F.; Akiyama, Y.; Nishijima, S.

76

Development of superconducting high gradient magnetic separation system for highly viscous fluid for practical use  

NASA Astrophysics Data System (ADS)

In the industrial plants processing highly viscous fluid such as foods or industrial products, it is necessary to remove the metallic wear debris originating from pipe in manufacturing line which triggers quality loss. In this study, we developed a high gradient magnetic separation (HGMS) system which consists of superconducting magnet to remove the metallic wear debris. The magnetic separation experiment and the particle trajectory simulation were conducted with polyvinyl alcohol (PVA) as a model material (viscosity coefficient was 10 Pa s, which is 10,000 times higher than that in water). In order to develop a magnetic separation system for practical use, the particle trajectory simulation by using solenoidal superconducting magnet was conducted, and the possibility of the magnetic separation for removing ferromagnetic stainless steel (SUS) particles in highly viscous fluid of 10 Pa s was indicated. Based on the results, the number of filters to obtain required separation efficiency was examined to design the practical separation system.

Hayashi, S.; Mishima, F.; Akiyama, Y.; Nishijima, S.

2011-11-01

77

Cryo-compressed Hydrogen Storage. Tobias Brunner  

E-print Network

distribution along highways and in remote areas. Gaseous hydrogen distribution via pipelines in only-Infrastructure. Future filling station layout. Efficient compression and high scalability Cryo-compressed fuel g/L 70 MPa CGH2 1,5 kg/min (3 MW) CGH2 24 g/L 35 MPa Cryo-compressed tank compatible fuels #12;BMW

78

Method and apparatus for separating materials magnetically. [Patent application; iron pyrite from coal  

DOEpatents

Magnetic and nonmagnetic materials are separated by passing stream thereof past coaxial current-carrying coils which produce a magnetic field wherein intensity varies sharply with distance radially of the axis of the coils.

Hise, E.C. Jr.; Holman, A.S.; Friedlaender, F.J.

1980-11-06

79

The principles and operation of a very high intensity magnetic mineral separator  

Microsoft Academic Search

A magnetic separator is described which employs a superconducting quadrupole magnet. The magnet is installed in a vertical cylindrical cryostat with hollow central portion. The magnetic forces are substantially in the radial direction. The results of trial experiments are described with various configurations of mineral slurries and wash water streams. In the preferred configuration, mineral slurry travels around the outer

HENRY COHEN; JEREMY A. GOOD

1976-01-01

80

SUPERCONDUCTING OPEN-GRADIENT MAGNETIC SEPARATION FOR THE PRETREATMENT OF RADIOACTIVE OR MIXED WASTE VITRIFICATION FEEDS  

EPA Science Inventory

Scientists need to gain a better understanding of the magnetic separation processes that can be used to separate deleterious constituents (crystalline, amorphous, and colloidal) in vitrification feed streams for borosilicate glass production without adding chemicals or generating...

81

Application of high temperature superconductors to high-gradient magnetic separation  

SciTech Connect

High Gradient Magnetic Separation (HGMS) is a powerful technique which can be used to separate widely dispersed contaminants from a host material, This technology can separate magnetic solids from other solids, liquids or gases. As the name implies HGMS uses large magnetic field gradients to separate ferromagnetic and paramagnetic particles. HGMS separators usually consist of a high-field solenoid magnet, the bore of which contains a fine-structured, ferromagnetic matrix material. The matrix material locally distorts the magnetic field and creates large field gradients in the vicinity of the matrix elements. These elements then become trapping sites for magnetic particles and are the basis for the magnetic separation. In this paper we discuss the design and construction of a prototype HGMS unit using a magnet made with high temperature superconductors (HTS). The prototype consists of an outer vacuum vessel which contains the HTS solenoid magnet The magnet is surrounded by a thermal radiation shield and multilayer insulation (MLI) blankets. The magnet, thermal shield and current leads all operate in a vacuum and are cooled by a cryocooler. High temperature superconducting current leads are used to reduce the heat leak from the ambient environment to the HTS magnet.

Daugherty, M.A.; Prenger, F.C.; Hill, D.D.; Daney, D.E.; Worl, L.W.; Schake, A.R.; Padilla, D.D.

1994-06-01

82

An integrated microfluidic platform for magnetic microbeads separation and confinement  

Microsoft Academic Search

An innovative microfluidic platform for magnetic beads manipulation is introduced, consisting of novel microfabricated 3D magnetic devices positioned in a microfluidic chamber. Each magnetic device comprises of an embedded actuation micro-coil in various design versions, a ferromagnetic pillar, a magnetic backside plate and a sensing micro-coil. The various designs of the micro-coils enable efficient magnetic beads trapping and concentration in

Qasem Ramadan; Victor Samper; Daniel P. Poenar; Chen Yu

2006-01-01

83

[Actual modalities of separation by magnetic methods of active biological compounds, cells and pathogenic agents].  

PubMed

The paper presents an overview on magnetic techniques of bio-processing and some of their possible applications. These techniques are in fact direct, or more frequently, indirect magnetic means for separation of particulate substances. A brief presentation of direct and of the most important indirect methods (magnetic carrier and magnetic fluids technologies) is made. There are shown some of the possible applications of magnetic bio-processing in bio-technology and medicine: active biological compounds fixation, isolation and modification, cells and cells organelles separation, removal of xenobiotics, immuno-magnetic testing, pathogen microbes identification. PMID:12092161

Iacob, G; Brede?ean, O; Ciochin?, A D

2001-01-01

84

Cryo-electron tomography of bacterial viruses  

SciTech Connect

Bacteriophage particles contain both simple and complex macromolecular assemblages and machines that enable them to regulate the infection process under diverse environmental conditions with a broad range of bacterial hosts. Recent developments in cryo-electron tomography (cryo-ET) make it possible to observe the interactions of bacteriophages with their host cells under native-state conditions at unprecedented resolution and in three-dimensions. This review describes the application of cryo-ET to studies of bacteriophage attachment, genome ejection, assembly and egress. Current topics of investigation and future directions in the field are also discussed.

Guerrero-Ferreira, Ricardo C. [Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA 30322 (United States)] [Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA 30322 (United States); Wright, Elizabeth R., E-mail: erwrigh@emory.edu [Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA 30322 (United States)

2013-01-05

85

HIGH-GRADIENT MAGNETIC SEPARATION FOR REMOVAL OF SULFUR FROM COAL  

EPA Science Inventory

The report gives results of a thorough physical, chemical, and magnetic characterization of a Pennsylvania coal from the Upper Freeport seam. The powdered coal was then subjected to high-gradient magnetic separations, as a function of magnetic field and fluid velocity, in both a ...

86

Cryo-Electron Tomography of Rubella Virus  

PubMed Central

Rubella virus is the only member of the Rubivirus genus within the Togaviridae family and is the causative agent of the childhood disease known as rubella or German measles. Here, we report the use of cryo-electron tomography to examine the three-dimensional structure of rubella virions and compare their structure to that of Ross River virus, a togavirus belonging the genus Alphavirus. The ectodomains of the rubella virus glycoproteins, E1 and E2, are shown to be organized into extended rows of density, separated by 9 nm on the viral surface. We also show that the rubella virus nucleocapsid structure often forms a roughly spherical shell which lacks high density at its center. While many rubella virions are approximately spherical and have dimensions similar to that of the icosahedral Ross River virus, the present results indicate that rubella exhibits a large degree of pleomorphy. In addition, we used rotation function calculations and other analyses to show that approximately spherical rubella virions lack the icosahedral organization which characterizes Ross River and other alphaviruses. The present results indicate that the assembly mechanism of rubella virus, which has previously been shown to differ from that of the alphavirus assembly pathway, leads to an organization of the rubella virus structural proteins that is different from that of alphaviruses. PMID:22855483

Battisti, Anthony J.; Yoder, Joshua D.; Plevka, Pavel; Winkler, Dennis C.; Mangala Prasad, Vidya; Kuhn, Richard J.; Frey, Teryl K.; Steven, Alasdair C.

2012-01-01

87

Collection of Ni-bearing material from electroless plating waste by magnetic separation with HTS bulk magnet  

NASA Astrophysics Data System (ADS)

The magnetic separation experiment to collect the Ni compounds from the waste liquid of electroless plating processes was conducted in the open-gradient magnetic separation process with the high temperature superconducting bulk magnet system. The magnetic pole containing Gd-based bulk superconductors was activated to 3.45 T at 35 K in the static magnetic field of 5 T with use of a superconducting solenoid magnet. The coarse Ni-sulfate crystals were formed by adding the concentrated sulfuric acid to the Ni-phosphite precipitates which yielded from the plating waste liquid by controlling the temperature and the pH value. The open-gradient magnetic separation technique was employed to separate the Ni-sulfate crystals from the mixture of the Ni-sulfate and Ni-phosphite compounds by the difference between their magnetic properties. And we succeeded in collecting Ni-sulfate crystals preferentially to the Ni-phosphite by attracting them to the magnetic pole soon after the Ni-sulfate crystals began to grow.

Oka, T.; Fukazawa, H.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M.; Tsujimura, M.; Yokoyama, K.

2014-01-01

88

High Temperature Superconducting Reciprocating Magnetic Separator; Final Report  

Microsoft Academic Search

In 2001, under DOE's Superconductivity Partnership Initiative (SPI), E. I. du Pont de Nemours & Co. (Dupont) was awarded a cost-share contract to build a fully functional full-scale model high temperature superconducting reciprocating magnet unit specifically designed for the koalin clay industry. After competitive bidding, American Superconductor (AMSC) was selected to provide the coil for the magnet. Dupont performed the

James F. Maguire

2008-01-01

89

Highly Sensitive and Rapid Detection of Pseudomonas aeruginosa Based on Magnetic Enrichment and Magnetic Separation  

PubMed Central

A method for highly sensitive and rapid detection of Pseudomonas aeruginosa, based on magnetic enrichment and magnetic separation, is described in this paper. The magnetic nanoparticles (MNPs) were applied to adsorb genome DNA after the sample was lysed. The DNA binding MNPs were directly subjected to polymerase chain reaction (PCR) to amplify gyrB specific sequence of Pseudomonas aeruginosa. The biotin labeled PCR products were detected by chemiluminescence when they were successively incubated with the probes-modified MNPs and alkaline phosphatase (ALP) labeled streptavidin (SA). Agarose gel electrophoresis analyses approved the method of in situ PCR to be highly reliable. The factors which could affect the chemiluminiscence were studied in detail. The results showed that the MNPs of 400 nm in diameter are beneficial to the detection. The sequence length and the binding site of the probe with a target sequence have obvious effects on the detection. The optimal concentration of the probes, hybridization temperature and hybridization time were 10 ?M, 60 ºC and 60 mins, respectively. The method of in situ PCR based on MNPs can greatly improve the utilization rate of the DNA template ultimately enhancing the detection sensitivity. Experiment results proved that the primer and probe had high specificity, and Pseudomonas aeruginosa was successfully detected with detection limits as low as 10 cfu/mL by this method, while the detection of a single Pseudomonas aeruginosa can also be achieved. PMID:23424183

Tang, Yongjun; Zou, Jun; Ma, Chao; Ali, Zeeshan; Li, Zhiyang; Li, Xiaolong; Ma, Ninging; Mou, Xianbo; Deng, Yan; Zhang, Liming; Li, Kai; Lu, Guangming; Yang, Haowen; He, Nongyue

2013-01-01

90

Magnetic properties and loss separation in iron-silicone-MnZn ferrite soft magnetic composites  

SciTech Connect

This paper investigates the magnetic and structural properties of iron-based soft magnetic composites coated with silicone-MnZn ferrite hybrid. The organic silicone resin was added to improve the flexibility of the insulated iron powder and causes better adhesion between particles to increase the mechanical properties. Scanning electron microscopy and distribution maps show that the iron particle surface is covered with a thin layer of silicone-MnZn ferrite. Silicone-MnZn ferrite coated samples have higher permeability when compared with the non-magnetic silicone resin coated compacts. The real part of permeability increases by 34.18% when compared with the silicone resin coated samples at 20 kHz. In this work, a formula for calculating the total loss component by loss separation method is presented and finally the different parts of total losses are calculated. The results show that the eddy current loss coefficient is close to each other for the silicone-MnZn ferrite, silicone resin and MnZn ferrite coated samples (0.0078

Wu, Shen; Sun, Aizhi; Xu, Wenhuan; Zou, Chao; Yang, Jun; Dong, Juan [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing (China)

2013-12-16

91

Development of cryogenic cooling system using a double G-M cryo-cooler for NMR spectrometer  

NASA Astrophysics Data System (ADS)

The sensitivity of nuclear magnetic resonance (NMR) spectrometer is limited by thermal noise. To increase the signal-noise-ratio (SNR), cryogenically cooled probes with cryo-coolers have been used. In order to cool RF coils in the probe below 10K, Gifford- McMahon/Joule-Thomson (G-M/J-T) cryo-coolers are used. But, the G-M/J-T cryo-coolers aren't suitable for a long time operation. On the other hand, G-M cryo-coolers have high reliability. We designed a cryogenically cooled probe system using a double G-M cryo-cooler with an RF coil and preamplifiers that could be cooled below 5 and 50K, respectively. This probe system consists of a probe unit, a transfer unit and a cryo-cooling unit. The cryo-cooling unit consists of two G-M cryo-coolers, two counter-flow heat exchangers, helium gas lines, etc.,. Compressed helium gas is cooled by the cooling stages of G-M cryo-coolers and two heat exchangers. The cooled helium gas is supplied to the probe unit through the 2.5m long transfer unit which consists of a 45mm diameter flexible vacuum vessel containing four helium gas lines. Cold stages for the RF coil and the preamplifiers in the probe unit are cooled by the cryogenically cooled helium gas. Experimental results showed that the cold stage temperature for the RF coil and for preamplifiers after 12 hours was 5.29 and 40.3K, respectively.

Tanaka, H.; Fukuda, Y.; Okada, M.; Saho, N.; Saitoh, K.; Kitaguchi, H.

2008-02-01

92

Enhanced separation of magnetic and diamagnetic particles in a dilute Litao Liang, Cheng Zhang, and Xiangchun Xuan  

E-print Network

Enhanced separation of magnetic and diamagnetic particles in a dilute ferrofluid Litao Liang, Cheng://apl.aip.org/authors #12;Enhanced separation of magnetic and diamagnetic particles in a dilute ferrofluid Litao Liang,1) Traditional magnetic field-induced particle separations take place in water-based diamagnetic solutions, where

Xuan, Xiangchun "Schwann"

93

Removal of algal blooms from freshwater by the coagulation-magnetic separation method.  

PubMed

This research investigated the feasibility of changing waste into useful materials for water treatment and proposed a coagulation-magnetic separation technique. This technique was rapid and highly effective for clearing up harmful algal blooms in freshwater and mitigating lake eutrophication. A magnetic coagulant was synthesized by compounding acid-modified fly ash with magnetite (Fe(3)O(4)). Its removal effects on algal cells and dissolved organics in water were studied. After mixing, coagulation, and magnetic separation, the flocs obtained from the magnet surface were examined by SEM. Treated samples were withdrawn for the content determination of chlorophyll-a, turbidity, chemical oxygen demand (COD), total nitrogen, and total phosphorus. More than 99 % of algal cells were removed within 5 min after the addition of magnetic coagulant at optimal loadings (200 mg L(-1)). The removal efficiencies of COD, total nitrogen, and phosphorus were 93, 91, and 94 %, respectively. The mechanism of algal removal explored preliminarily showed that the magnetic coagulant played multiple roles in mesoporous adsorption, netting and bridging, as well as high magnetic responsiveness to a magnetic field. The magnetic-coagulation separation method can rapidly and effectively remove algae from water bodies and greatly mitigate eutrophication of freshwater using a new magnetic coagulant. The method has good performance, is low cost, can turn waste into something valuable, and provides reference and directions for future pilot and production scale-ups. PMID:22767355

Liu, Dan; Wang, Peng; Wei, Guanran; Dong, Wenbo; Hui, Franck

2013-01-01

94

Particle capture efficiency in a multi-wire model for high gradient magnetic separation  

NASA Astrophysics Data System (ADS)

High gradient magnetic separation (HGMS) is an efficient way to remove magnetic and paramagnetic particles, such as heavy metals, from waste water. As the suspension flows through a magnetized filter mesh, high magnetic gradients around the wires attract and capture the particles removing them from the fluid. We model such a system by considering the motion of a paramagnetic tracer particle through a periodic array of magnetized cylinders. We show that there is a critical Mason number (ratio of viscous to magnetic forces) below which the particle is captured irrespective of its initial position in the array. Above this threshold, particle capture is only partially successful and depends on the particle's entry position. We determine the relationship between the critical Mason number and the system geometry using numerical and asymptotic calculations. If a capture efficiency below 100% is sufficient, our results demonstrate how operating the HGMS system above the critical Mason number but with multiple separation cycles may increase efficiency.

Eisenträger, Almut; Vella, Dominic; Griffiths, Ian M.

2014-07-01

95

Transcranial Magnetic Stimulation in a Finger-tapping Task Separates Motor from Timing  

E-print Network

Transcranial Magnetic Stimulation in a Finger- tapping Task Separates Motor from Timing Mechanisms and of return to stability using error correction. The advent of transcranial magnetic stimulation (TMS) has by using precise pulses of transcranial mag- netic stimulation (TMS) applied to the primary motor cortex

Moses, Elisha

96

A method for perfonning magnetic mineral separations in a liquid 6s{inm  

Microsoft Academic Search

A method for performing magnetic separations of minerals in a liquid medium with the Franz separator is described. The method is successful for applications where only small sample weights (<200 mg) are available and the sieve size of the particles is small (<53p).

Gnecony R. LuuprtN

97

Correlative cryo-fluorescence and cryo-soft x-ray tomography of adherent cells at European synchrotrons.  

PubMed

Cryo-soft X-ray tomography (cryo-SXT) is a synchrotron-hosted imaging technique used to analyze the ultrastructure of intact, cryo-prepared cells. Correlation of cryo-fluorescence microscopy and cryo-SXT can be used to localize fluorescent proteins to organelles preserved close to native state. Cryo-correlative light and X-ray microscopy (cryo-CLXM) is particularly useful for the study of organelles that are susceptible to chemical fixation artifacts during sample preparation for electron microscopy. In our recent work, we used cryo-CLXM to characterize GFP-LC3-positive early autophagosomes in nutrient-starved HEK293A cells (Duke et al., 2013). Cup-shaped omegasomes were found to form at "hot-spots" on the endoplasmic reticulum. Furthermore, cryo-SXT image stacks revealed the presence of large complex networks of tubulated mitochondria in the starved cells, which would be challenging to model at this scale and resolution using light or electron microscopy. In this chapter, we detail the cryo-CLXM workflow that we developed and optimized for studying adherent mammalian cells. We show examples of data collected at the three European synchrotrons that currently host cryo-SXT microscopes, and describe how raw cryo-SXT datasets are processed into tomoX stacks, modeled, and correlated with cryo-fluorescence data to identify structures of interest. PMID:25287841

Carzaniga, Raffaella; Domart, Marie-Charlotte; Duke, Elizabeth; Collinson, Lucy M

2014-01-01

98

Separation of magnetically isolated TNF receptosomes from mitochondria.  

PubMed

We previously demonstrated that tumor necrosis factor receptor-1 (TNF-R1) initiates distinct TNF signaling pathways depending on the localization of the receptor. While TNF-R1 at the plasma membrane transmits proinflammatory and antiapoptotic signals, internalized TNF-R1 forms signaling endosomes (TNF receptosomes) that transmit proapoptotic signals. These findings were obtained by a novel technique for the isolation of morphologically intact endocytic vesicles containing magnetically labeled TNF-R1 complexes using a high-gradient, free-flow magnetic chamber. Since intact mitochondria appeared to be a major contaminating organelle in these preparations, we subsequently included a second purification step by iodixanol density centrifugation to obtain a mitochondria-free receptosome preparation. PMID:24377932

Tchikov, Vladimir; Fritsch, Jürgen; Schütze, Stefan

2014-01-01

99

Thinning of large mammalian cells for cryo-TEM characterization by cryo-FIB milling.  

PubMed

Focused ion beam milling at cryogenic temperatures (cryo-FIB) is a valuable tool that can be used to thin vitreous biological specimens for subsequent imaging and analysis by cryo-transmission electron microscopy (cryo-TEM) in a frozen-hydrated state. This technique offers the potential benefit of eliminating the mechanical artefacts that are typically found with cryo-ultramicrotomy. However, due to the additional complexity in transferring samples in and out of the FIB, contamination and devitrification of the amorphous ice is commonly encountered. To address these problems, we have designed a sample cryo-shuttle that directly and specifically accepts Polara TEM cartridges to simplify the transfer process between FIB and TEM. We optimized several parameters in the cryo-FIB and cryo-TEM processes using the quality of the samples' ice as an indicator and demonstrated high-quality milling with large mammalian cells. By comparing the results from HeLa cells to those from Escherichia coli cells, we discuss some of the artefacts and challenges we have encountered using this technique. PMID:22906009

Strunk, K M; Wang, K; Ke, D; Gray, J L; Zhang, P

2012-09-01

100

On-chip magnetic separation of superparamagnetic beads for integrated molecular analysis  

PubMed Central

We have demonstrated a postprocessed complementary metal oxide semiconductor (CMOS) integrated circuit (IC) capable of on-chip magnetic separation, i.e., removing via magnetic forces the nonspecifically bound magnetic beads from the detection area on the surface of the chip. Initially, 4.5 ?m wide superparamagnetic beads sedimenting out of solution due to gravity were attracted to the detection area by a magnetic concentration force generated by flowing current through a conductor embedded in the IC. After sedimentation, the magnetic beads that did not bind strongly to the functionalized surface of the IC through a specific biochemical complex were removed by a magnetic separation force generated by flowing current through another conductor placed laterally to the detection area. As the spherical bead pivoted on the surface of the chip, the lateral magnetic force was further amplified by mechanical leveraging, and 50 mA of current flowing through the separation conductor placed 18 ?m away from the bead resulted in 7.5 pN of tensile force on the biomolecular tether immobilizing the bead. This force proved high enough to break nonspecific interactions while leaving specific antibody-antigen bonds intact. A sandwich capture immunoassay on purified human immunoglobulin G showed strong correlation with a control enzyme linked immunosorbent assay and a detection limit of 10 ng?ml or 70 pM. The beads bound to the detection area after on-chip magnetic separation were detected optically. To implement a fully integrated molecular diagnostics platform, the on-chip magnetic separation functionality presented in this work can be readily combine with state-of-the art CMOS-based magnetic bead detection technology. PMID:20368988

Florescu, Octavian; Wang, Kevan; Au, Patrick; Tang, Jimmy; Harris, Eva; Beatty, P. Robert; Boser, Bernhard E.

2010-01-01

101

Measuring Thermal Conductivity and Moisture Absorption of Cryo-Insulation Materials  

NASA Technical Reports Server (NTRS)

NASA is seeking to develop thermal insulation material systems suitable for withstanding both extremely high temperatures encountered during atmospheric re-entry heating and aero- braking maneuvers, as well as extremely low temperatures existing in liquid fuel storage tanks. Currently, materials used for the high temperature insulation or Thermal Protection System (TPS) are different from the low temperature, or cryogenic insulation. Dual purpose materials are necessary to the development of reusable launch vehicles (RLV). The present Space Shuttle (or Space Transportation System, STS) employs TPS materials on the orbiter and cryo-insulation materials on the large fuel tank slung under the orbiter. The expensive fuel tank is jettisoned just before orbit is achieved and it burns up while re-entering over the Indian Ocean. A truly completely reusable launch vehicle must store aR cryogenic fuel internally. The fuel tanks will be located close to the outer surface. In fact the outer skin of the craft will probably also serve as the fuel tank enclosure, as in jet airliners. During a normal launch the combined TPS/cryo-insulation system will serve only as a low temperature insulator, since aerodynamic heating is relatively minimal during ascent to orbit. During re-entry, the combined TPS/cryo-insulation system will serve only as a high temperature insulator, since all the cryogenic fuel will have been expended in orbit. However, in the event of an.aborted launch or a forced/emergency early re-entry, the tanks will still contain fuel, and the TPS/cryo-insulation will have to serve as both low and high temperature insulation. Also, on long duration missions, such as to Mars, very effective cryo-insulation materials are needed to reduce bod off of liquid propellants, thereby reducing necessary tankage volume, weight, and cost. The conventional approach to obtaining both low and high temperature insulation, such as is employed for the X-33 and X-34 spacecraft, is to use separate TPS and cryo-insulation materials, which are connected by means of adhesives or stand-offs (spacers). Three concepts are being considered: (1) the TPS is bonded directly to the cryo-insulation which, in turn, is bonded to the exterior of the tank, (2) stand-offs are used to make a gap between the TPS and the cryo-insulation, which is bonded externally to the tank, (3) TPS is applied directly or with stand-offs to the exterior so the tank, and cryo-insulation is applied directly to the interior of the tank. Many potential problems are inherent in these approaches. For example, mismatch between coefficients of thermal expansion of the TPS and cryo-insulation, as well as aerodynamic loads, could lead to failure of the bond. Internal cryo-insulation must be prevent from entering the sump of the fuel turbo-pump. The mechanical integrity of the stand-off structure (if used) must withstand multiple missions. During ground hold (i.e., prior to launch) moisture condensation must be minimized in the gap between the cryo-insulation and the TPS. The longer term solution requires the development of a single material to act as cryo- insulation during ground hold and as TPS during re-entry. Such a material minimizes complexity and weight while improving reliability and reducing cost.

Lambert, Michael A.

1998-01-01

102

High Temperature Superconducting Reciprocating Magnetic Separator Final Report  

SciTech Connect

In 2001, under DOE's Superconductivity Partnership Initiative (SPI), E. I. du Pont de Nemours & Co. (Dupont) was awarded a cost-share contract to build a fully functional full-scale model high temperature superconducting reciprocating magnet unit specifically designed for the koalin clay industry. After competitive bidding, American Superconductor (AMSC) was selected to provide the coil for the magnet. Dupont performed the statement of work until September 2004, when it stopped work, with the concurrence of DOE, due to lack of federal funds. DOE had paid all invoices to that point, and Dupont had provided all cost share. At this same time, Dupont determined that this program did not fit with its corporate strategies and notified DOE that it was not interesting in resuming the program when funding became available. AMSC expressed interest in assuming performance of the Agreement to Dupont and DOE, and in March 2005, this project was transferred to AMSC by DOE amendment to the original contract and Novation Agreement between AMSC and Dupont. Design drawings and some hardware components and subassemblies were transferred to AMSC. However, no funding was obligated by DOE and AMSC never performed work on the project. This report contains a summary of the work performed by Dupont up to the September 04 timeframe.

James F. Maguire

2008-06-05

103

Removal of freshwater microalgae by a magnetic separation method  

NASA Astrophysics Data System (ADS)

Some species of microalgae, with high growth rate and high lipid content, appear to be attractive alternatives as a feedstock for biodiesel production. The high-energy input for harvesting biomass and removing the water from the algae makes current commercial microalgal biodiesel production cost expensive. The major techniques currently employed in microalgae harvesting and recovery include centrifugation, coagulation-flocculation, bio-flocculation, filtration and screening, gravity sedimentation, and flotation. The purpose of this study was to investigate the harvesting of microalgae cells by coagulation using magnetic activated carbon, magnetite (FeO4) nanoparticles, and common chemical coagulants. Scenedesmus rubescens was selected and cultivated in 10 L flasks under continuous artificial light. Samples were taken at different operation intervals. Jar tests were conducted to investigate the effect of adsorption of microalgae on the magnetic material. The removal efficiency of microalgae was affected by the coagulants dose, stirring time and speed, and the initial microalgae concentration. The recovery of microalgae was greater in cultures with high initial microalgae concentration compared to cultures with low microalgae concentrations.

Vergini, Sofia S.; Aravantinou, Andriana F.; Manariotis, Ioannis D.

2013-04-01

104

Metalizing reduction and magnetic separation of vanadium titano-magnetite based on hot briquetting  

NASA Astrophysics Data System (ADS)

To achieve high efficiency utilization of Panzhihua vanadium titano-magnetite, a new process of metalizing reduction and magnetic separation based on hot briquetting is proposed, and factors that affect the cold strength of the hot-briquetting products and the efficiency of reduction and magnetic separation are successively investigated through laboratory experiments. The relevant mechanisms are elucidated on the basis of microstructural observations. Experimental results show that the optimal process parameters for hot briquetting include a hot briquetting temperature of 475°C, a carbon ratio of 1.2, ore and coal particle sizes of less than 74 ?m. Additionally, with respect to metalizing reduction and magnetic separation, the rational parameters include a magnetic field intensity of 50 mT, a reduction temperature of 1350°C, a reduction time of 60 min, and a carbon ratio of 1.2. Under these above conditions, the crushing strength of the hot-briquetting agglomerates is 1480 N, and the recovery ratios of iron, vanadium, and titanium are as high as 91.19%, 61.82%, and 85.31%, respectively. The new process of metalizing reduction and magnetic separation based on hot briquetting demonstrates the evident technological advantages of high efficiency separation of iron from other valuable elements in the vanadium titano-magnetite.

Chen, Shuang-yin; Chu, Man-sheng

2014-03-01

105

Ferronickel enrichment by fine particle reduction and magnetic separation from nickel laterite ore  

NASA Astrophysics Data System (ADS)

Ferronickel enrichment and extraction from nickel laterite ore were studied through reduction and magnetic separation. Reduction experiments were performed using hydrogen and carbon monoxide as reductants at different temperatures (700-1000°C). Magnetic separation of the reduced products was conducted using a SLon-100 cycle pulsating magnetic separator (1.2 T). Composition analysis indicates that the nickel laterite ore contains a total iron content of 22.50wt% and a total nickel content of 1.91wt%. Its mineral composition mainly consists of serpentine, hortonolite, and goethite. During the reduction process, the grade of nickel and iron in the products increases with increasing reduction temperature. Although a higher temperature is more favorable for reduction, the temperature exceeding 1000°C results in sintering of the products, preventing magnetic separation. After magnetic separation, the maximum total nickel and iron concentrations are 5.43wt% and 56.86wt%, and the corresponding recovery rates are 84.38% and 53.76%, respectively.

Tang, Xiao-hui; Liu, Run-zao; Yao, Li; Ji, Zhi-jun; Zhang, Yan-ting; Li, Shi-qi

2014-10-01

106

Optimisation of magnetic separation: a case study for soil washing at a heavy metals polluted site.  

PubMed

Sandy loam soil polluted with heavy metals (As, Cu, Pb and Zn) from an ancient Mediterranean Pb mining and metallurgy site was treated by means of wet high-intensity magnetic separation to remove some of the pollutants therein. The treated fractions were chemically analysed and then subjected to magnetic characterisation, which determined the high-field specific (mass), magnetic susceptibility (?) and the specific (mass) saturation magnetisation (?S), through isothermal remanent magnetisation (IRM) curves. From the specific values of ? and ?S, a new expression to assess the performance of the magnetic separation operation was formulated and verified by comparison with the results obtained by traditional chemical analysis. The magnetic study provided valuable information for the exhaustive explanation of the operation, and the deduced mathematical expression was found to be appropriate to estimate the performance of the separation operation. From these results we determined that magnetic soil washing was effective for the treatment of the contaminated soil, concentrating the majority of the heavy metals and peaking its separation capacity at 60% of the maximum output voltage. PMID:24418067

Sierra, C; Martínez-Blanco, D; Blanco, Jesús A; Gallego, J R

2014-07-01

107

Magnetically assisted chemical separation (MACS) process: Preparation and optimization of particles for removal of transuranic elements  

SciTech Connect

The Magnetically Assisted Chemical Separation (MACS) process combines the selectivity afforded by solvent extractants with magnetic separation by using specially coated magnetic particles to provide a more efficient chemical separation of transuranic (TRU) elements, other radionuclides, and heavy metals from waste streams. Development of the MACS process uses chemical and physical techniques to elucidate the properties of particle coatings and the extent of radiolytic and chemical damage to the particles, and to optimize the stages of loading, extraction, and particle regeneration. This report describes the development of a separation process for TRU elements from various high-level waste streams. Polymer-coated ferromagnetic particles with an adsorbed layer of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) diluted with tributyl phosphate (TBP) were evaluated for use in the separation and recovery of americium and plutonium from nuclear waste solutions. Due to their chemical nature, these extractants selectively complex americium and plutonium contaminants onto the particles, which can then be recovered from the solution by using a magnet. The partition coefficients were larger than those expected based on liquid[liquid extractions, and the extraction proceeded with rapid kinetics. Extractants were stripped from the particles with alcohols and 400-fold volume reductions were achieved. Particles were more sensitive to acid hydrolysis than to radiolysis. Overall, the optimization of a suitable NMCS particle for TRU separation was achieved under simulant conditions, and a MACS unit is currently being designed for an in-lab demonstration.

Nunez, L.; Kaminski, M.; Bradley, C.; Buchholz, B.A.; Aase, S.B.; Tuazon, H.E.; Vandegrift, G.F. [Argonne National Lab., IL (United States); Landsberger, S. [Univ. of Illinois, Urbana, IL (United States)

1995-05-01

108

Setting up High Gradient Magnetic Separation for combating eutrophication of inland waters.  

PubMed

To find new approaches to devise technologies for handling with eutrophication of inland waters is a global challenge. Separation of the P from water under conditions of continuous flow is proposed as an alternative and effective method. This work is based on using highly magnetic particles as the seeding adsorbent material and their later removal from solution by High Gradient Magnetic Separation (HGMS). Contrast to other methods based on batch conditions, large volumes of water can be easily handled by HGMS because of decreasing retention times. This study identifies the best working conditions for removing P from solution by investigating the effects of a set of four different experimental variables: sonication time, flow rate (as it determines the retention time of particles in the magnetic field), magnetic field strength and the iron (Fe) particles/P concentration ratio. Additionally, the change of P removal efficiency with time (build up effect) and the possibility of reusing magnetic particles were also studied. Our results evidenced that while flow rate does not significantly affect P removal efficiency in the range 0.08-0.36 mL s(-1), sonication time, magnetic field strength and the Fe particles/P concentration ratio are the main factors controlling magnetic separation process. PMID:21255924

Merino-Martos, A; de Vicente, J; Cruz-Pizarro, L; de Vicente, I

2011-02-28

109

Evaluation of Cyanex 923-coated magnetic particles for the extraction and separation of lanthanides and actinides from nuclear waste streams  

Microsoft Academic Search

In the magnetically assisted chemical separation (MACS) process, tiny ferromagnetic particles coated with solvent extractant are used to selectively separate radionuclides and hazardous metals from aqueous waste streams. The contaminant-loaded particles are then recovered from the waste solutions using a magnetic field. The contaminants attached to the magnetic particles are subsequently removed using a small volume of stripping agent. In

B. S. Shaibu; M. L. P. Reddy; A. Bhattacharyya; V. K. Manchanda

2006-01-01

110

Particle Capture Efficiency in a Multi-Wire Model for High Gradient Magnetic Separation  

E-print Network

High gradient magnetic separation (HGMS) is an efficient way to remove magnetic and paramagnetic particles, such as heavy metals, from waste water. As the suspension flows through a magnetized filter mesh, high magnetic gradients around the wires attract and capture the particles, removing them from the fluid. We model such a system by considering the motion of a paramagnetic tracer particle through a periodic array of magnetized cylinders. We show that there is a critical Mason number (ratio of viscous to magnetic forces) below which the particle is captured irrespective of its initial position in the array. Above this threshold, particle capture is only partially successful and depends on the particle's entry position. We determine the relationship between the critical Mason number and the system geometry using numerical and asymptotic calculations. If a capture efficiency below 100% is sufficient, our results demonstrate how operating the HGMS system above the critical Mason number but with multiple separa...

Eisenträger, Almut; Griffiths, Ian M

2014-01-01

111

Imaging endosomes and autophagosomes in whole mammalian cells using correlative cryo-fluorescence and cryo-soft X-ray microscopy (cryo-CLXM)?  

PubMed Central

Cryo-soft X-ray tomography (cryo-SXT) is a powerful imaging technique that can extract ultrastructural information from whole, unstained mammalian cells as close to the living state as possible. Subcellular organelles including the nucleus, the Golgi apparatus and mitochondria have been identified by morphology alone, due to the similarity in contrast to transmission electron micrographs. In this study, we used cryo-SXT to image endosomes and autophagosomes, organelles that are particularly susceptible to chemical fixation artefacts during sample preparation for electron microscopy. We used two approaches to identify these compartments. For early and recycling endosomes, which are accessible to externally-loaded markers, we used an anti-transferrin receptor antibody conjugated to 10 nm gold particles. For autophagosomes, which are not accessible to externally-applied markers, we developed a correlative cryo-fluorescence and cryo-SXT workflow (cryo-CLXM) to localise GFP-LC3 and RFP-Atg9. We used a stand-alone cryo-fluorescence stage in the home laboratory to localise the cloned fluorophores, followed by cryo-soft X-ray tomography at the synchrotron to analyse cellular ultrastructure. We mapped the 3D ultrastructure of the endocytic and autophagic structures, and discovered clusters of omegasomes arising from ‘hotspots’ on the ER. Thus, immunogold markers and cryo-CLXM can be used to analyse cellular processes that are inaccessible using other imaging modalities. PMID:24238600

Duke, Elizabeth M.H.; Razi, Minoo; Weston, Anne; Guttmann, Peter; Werner, Stephan; Henzler, Katja; Schneider, Gerd; Tooze, Sharon A.; Collinson, Lucy M.

2014-01-01

112

[The outlook for human blood component separation and the treatment of cancerous tumors by magnetic methods].  

PubMed

This work presents in brief some expectations related to the solution of certain biomedical problems by using a non-conventional physical method: The high-gradient magnetic separation (HGMS). At first a short presentation of the HGMS method is given and then its application in separation of the human blood components is reported. The up to date intensely studied method with magnetic carriers is then described. Among other things, this method enables the cancer tumors treatment by intracavity radiotherapy, drug targeting, and diagnosis exploration. PMID:10756959

Iacob, G; Ciochin?, A D

1999-01-01

113

Separation and detection of multiple pathogens in a food matrix by magnetic SERS nanoprobes  

Microsoft Academic Search

A rapid and sensitive method was developed here for separation and detection of multiple pathogens in food matrix by magnetic\\u000a surface-enhanced Raman scattering (SERS) nanoprobes. Silica-coated magnetic probes (MNPs@SiO2) of ?100 nm in diameter were first prepared via the reverse microemulsion method using cetyltrimethylammonium bromide as\\u000a a surfactant and tetraethyl orthosilicate as the silica precursor. The as-prepared MNPs@SiO2 were functionalized with

Yuling Wang; Sandeep Ravindranath; Joseph Irudayaraj

2011-01-01

114

Practical workflow for cryo focused-ion-beam milling of tissues and cells for cryo-TEM tomography.  

PubMed

Vitreous freezing offers a way to study cells and tissue in a near-native state by cryo-transmission electron microscopy (cryo-TEM), which is important when structural information at the macromolecular level is required. Many cells - especially those in tissue - are too thick to study intact in the cryo-TEM. Cryo focused-ion-beam (cryo-FIB) milling is being used in a few laboratories to thin vitreously frozen specimens, thus avoiding the artifacts and difficulties of cryo-ultramicrotomy. However, the technique is challenging because of the need to avoid devitrification and frost accumulation during the entire process, from the initial step of freezing to the final step of loading the specimen into the cryo-TEM. We present a robust workflow that makes use of custom fixtures and devices that can be used for high-pressure-frozen bulk tissue samples as well as for samples frozen on TEM grids. PMID:24211822

Hsieh, Chyongere; Schmelzer, Thomas; Kishchenko, Gregory; Wagenknecht, Terence; Marko, Michael

2014-01-01

115

Mechanical and Electrical Properties of Cryo-worked Cu  

NASA Astrophysics Data System (ADS)

For manufacturing the magnets of fusion machines pure copper of both high mechanical resistance and electrical conductivity is required. Though high purity copper guarantees high electrical conductivity, its mechanical properties may be not suitable for the applications in tokamaks. In this view, a new procedure developed for obtaining high purity copper with excellent mechanical strength is described in this work. Samples of oxygen free copper (OFC) have been worked by pressing in liquid nitrogen (77 K). It has been verified that the mechanical properties of the worked metal are strongly dependent on the strain rate. Very low strain rates permitted to attain values of tensile yield strength (550 MPa) significantly higher than those obtained by traditional cold-working at room temperature (450 MPa). The electrical conductivity of the cryo-worked Cu decreases with the tensile yield strength even though the hardest samples of tensile yield strength of 550 MPa exhibit still acceptable values of conductivity (about 94 % IACS at room temperature).

Bettinali, Livio; Tosti, Silvano; Pizzuto, Aldo

2014-01-01

116

Separation and enrichment of enantiopure from racemic compounds using magnetic levitation.  

PubMed

Crystallization of a solution with high enantiomeric excess can generate a mixture of crystals of the desired enantiomer and the racemic compound. Using a mixture of S-/RS-ibuprofen crystals as a model, we demonstrated that magnetic levitation (MagLev) is a useful technique for analysis, separation and enantioenrichment of chiral/racemic products. PMID:24875274

Yang, Xiaochuan; Wong, Shin Yee; Bwambok, David K; Atkinson, Manza B J; Zhang, Xi; Whitesides, George M; Myerson, Allan S

2014-07-18

117

Magnetic separation of colloidal nanoparticle mixtures using a material specific peptide.  

PubMed

A material specific peptide bound to Fe2O3 facilitates the selective sequestration of Au from a colloidal mixture of Au and CdS nanoparticles; the Au-Fe2O3 precipitate can then be magnetically separated from the colloidal CdS, and the Au nanoparticles can be recovered upon release from the Fe2O3. PMID:23661051

Essinger-Hileman, Elizabeth R; Popczun, Eric J; Schaak, Raymond E

2013-06-18

118

APPLICATION OF HIGH-GRADIENT MAGNETIC SEPARATION TO FINE PARTICLE CONTROL  

EPA Science Inventory

The report gives results of an assessment of the potential use of high-gradient magnetic separation (HGMS) as a means of collecting gas stream particulates. The assessment included both experiments and analyses of theoretical models. Phase I included evaluations of theoretical ex...

119

Two-dimensional plasma expansion in a magnetic nozzle: Separation due to electron inertia  

SciTech Connect

A previous axisymmetric model of the supersonic expansion of a collisionless, hot plasma in a divergent magnetic nozzle is extended here in order to include electron-inertia effects. Up to dominant order on all components of the electron velocity, electron momentum equations still reduce to three conservation laws. Electron inertia leads to outward electron separation from the magnetic streamtubes. The progressive plasma filling of the adjacent vacuum region is consistent with electron-inertia being part of finite electron Larmor radius effects, which increase downstream and eventually demagnetize the plasma. Current ambipolarity is not fulfilled and ion separation can be either outwards or inwards of magnetic streamtubes, depending on their magnetization. Electron separation penalizes slightly the plume efficiency and is larger for plasma beams injected with large pressure gradients. An alternative nonzero electron-inertia model [E. Hooper, J. Propul. Power 9, 757 (1993)] based on cold plasmas and current ambipolarity, which predicts inwards electron separation, is discussed critically. A possible competition of the gyroviscous force with electron-inertia effects is commented briefly.

Ahedo, Eduardo; Merino, Mario [Universidad Politecnica de Madrid, 28040 Madrid (Spain)

2012-08-15

120

Removal of less biodegradable dissolved organic matters in water by superconducting magnetic separation with magnetic mesoporous carbon  

NASA Astrophysics Data System (ADS)

Less biodegradable dissolved organic matters in water as typified by humic substances are known as precursors of carcinogenic trihalomethanes, and are removed about 60% by current advanced water treatments. However, further increase of the removal ratio is demand. In this study, magnetic mesoporous carbon (MMPC), which can adsorb the substances physically and be efficiently collected by using superconducting high gradient magnetic separation (HGMS), has been synthesized with coconut-shell-based activated carbon and ferric nitrate solution by the gas activation method. The MMPC has the maximum magnetization value of 30.7 emu/g and an adsorption ability of 87% to 10 mg/L humic acid in a short time. The standard MMPC having a magnetization of 6.43 emu/g was able to be separated at magnetic field of 2 T. Used MMPC regained the adsorption ability to 93.1% by N 2 reactivation heat treatment. These results show promise for application of current water treatments by superconducting HGMS, which is suitable for high-speed water treatment without secondary wastes.

Kondo, K.; Jin, T.; Miura, O.

2010-11-01

121

Correlated cryo-fluorescence and cryo-electron microscopy with high spatial precision and improved sensitivity.  

PubMed

Performing fluorescence microscopy and electron microscopy on the same sample allows fluorescent signals to be used to identify and locate features of interest for subsequent imaging by electron microscopy. To carry out such correlative microscopy on vitrified samples appropriate for structural cryo-electron microscopy it is necessary to perform fluorescence microscopy at liquid-nitrogen temperatures. Here we describe an adaptation of a cryo-light microscopy stage to permit use of high-numerical aperture objectives. This allows high-sensitivity and high-resolution fluorescence microscopy of vitrified samples. We describe and apply a correlative cryo-fluorescence and cryo-electron microscopy workflow together with a fiducial bead-based image correlation procedure. This procedure allows us to locate fluorescent bacteriophages in cryo-electron microscopy images with an accuracy on the order of 50 nm, based on their fluorescent signal. It will allow the user to precisely and unambiguously identify and locate objects and events for subsequent high-resolution structural study, based on fluorescent signals. PMID:24275379

Schorb, Martin; Briggs, John A G

2014-08-01

122

Cryo-electron Tomography of Neurospora Mitochondria  

Microsoft Academic Search

Cryo-electron tomography was used to study the structural organization of whole frozen-hydrated mitochondria from Neurospora crassa. Unlike mitochondria from many other species and tissues, in this case the cristae form a three-dimensional network of interconnected lamellae. Basically, the three-dimensional structure of ice-embedded mitochondria from this species is consistent with previous descriptions of mitochondria prepared by chemical fixation and resin embedding.

Daniela Nicastro; Achilleas S. Frangakis; Dieter Typke; Wolfgang Baumeister

2000-01-01

123

Laboratory cryo soft X-ray microscopy.  

PubMed

Lens-based water-window X-ray microscopy allows two- and three-dimensional (2D and 3D) imaging of intact unstained cells in their near-native state with unprecedented contrast and resolution. Cryofixation is essential to avoid radiation damage to the sample. Present cryo X-ray microscopes rely on synchrotron radiation sources, thereby limiting the accessibility for a wider community of biologists. In the present paper we demonstrate water-window cryo X-ray microscopy with a laboratory-source-based arrangement. The microscope relies on a ?=2.48-nm liquid-jet high-brightness laser-plasma source, normal-incidence multilayer condenser optics, 30-nm zone-plate optics, and a cryo sample chamber. We demonstrate 2D imaging of test patterns, and intact unstained yeast, protozoan parasites and mammalian cells. Overview 3D information is obtained by stereo imaging while complete 3D microscopy is provided by full tomographic reconstruction. The laboratory microscope image quality approaches that of the synchrotron microscopes, but with longer exposure times. The experimental image quality is analyzed from a numerical wave-propagation model of the imaging system and a path to reach synchrotron-like exposure times in laboratory microscopy is outlined. PMID:22119891

Hertz, H M; von Hofsten, O; Bertilson, M; Vogt, U; Holmberg, A; Reinspach, J; Martz, D; Selin, M; Christakou, A E; Jerlström-Hultqvist, J; Svärd, S

2012-02-01

124

?-Detected NMR Search for Magnetic Phase Separation in Epitaxial GaAs:Mn  

NASA Astrophysics Data System (ADS)

To test for the microscopic magnetic phase separation in the dilute magnetic semiconductor Ga1-xMnxAs sug-gested by low energy muon spin rotation measurements[1], we present a detailed analysis of the amplitudes of the 8Li ?-detected nuclear magnetic resonance in an epitaxially grown thin film of x = 5.4% Mn doped GaAs on a semi-insulating GaAs substrate with magnetic transition temperature TC =72 K. The spectrum at 100 K corresponds to 73% of the full room temperature amplitude, and at 60 K to about 62%. The 11% loss of signal through the magnetic tran-sition is much smaller than that ? 50% found by low energy ?SR[1], and may be entirely due to an amplitude change intrinsic to GaAs. This lack of evidence for phase separation is, however, consistent with the full volume fraction magnetism found by a second low energy ?SR measurement on a different sample using weak transverse field[2].

Song, Q.; Chow, K. H.; Miller, R. I.; Fan, I.; Hossain, M. D.; Kiefl, R. F.; Morris, G. D.; Kreitzman, S. R.; Levy, C. D. P.; Parolin, T. J.; Pearson, M. R.; Salman, Z.; Saadaoui, H.; Smadella, M.; Wang, D.; Yu, K. M.; Liu, X.; Furdyna, J. K.; MacFarlane, W. A.

125

Magnetic materials as sorbents for metal/metalloid preconcentration and/or separation. A review.  

PubMed

The use of magnetic materials in solid phase extraction has received considerable attention in recent years taking into account many advantages arising from the inherent characteristics of magnetic particles. Magnetic solid phase extraction (MSPE) methodology overcomes problems such as column packing and phase separation, which can be easily performed by applying an external magnetic field. The use of magnetic particles in automatic systems is growing over the last few years making the on-line operation of MSPE a promising technique in the frame of green chemistry. This article aims to provide all recent progress in the research of novel magnetic materials as sorbents for metal preconcentration and determination coupled with different detection systems as well as their implementation in sequential injection and microfluidic systems. In addition, a description of preparation, characterization as well as applications of various types of magnetic materials, either with organic or inorganic coating of the magnetic core, is presented. Concluding remarks and future trends are also commented. PMID:23856225

Giakisikli, Georgia; Anthemidis, Aristidis N

2013-07-30

126

Cryo-electron tomography of cells: connecting structure and function  

PubMed Central

Cryo-electron tomography (cryo-ET) allows the visualization of cellular structures under close-to-life conditions and at molecular resolution. While it is inherently a static approach, yielding structural information about supramolecular organization at a certain time point, it can nevertheless provide insights into function of the structures imaged, in particular, when supplemented by other approaches. Here, we review the use of experimental methods that supplement cryo-ET imaging of whole cells. These include genetic and pharmacological manipulations, as well as correlative light microscopy and cryo-ET. While these methods have mostly been used to detect and identify structures visualized in cryo-ET or to assist the search for a feature of interest, we expect that in the future they will play a more important role in the functional interpretation of cryo-tomograms. PMID:18566823

Lucic, Vladan; Leis, Andrew

2008-01-01

127

Measurement of the adhesion force between particles for high gradient magnetic separation of pneumatic conveyed powder products  

NASA Astrophysics Data System (ADS)

In the industrial plants such as foods, medicines or industrial materials, there are big amount of issues on contamination by metallic wear debris originated from pipes of manufacturing lines. In this study, we developed a high gradient magnetic separation system (HGMS) under the dry process by using superconducting magnet to remove the ferromagnetic particles. One of the major problems of dry HGMS systems is, however, the blockage of magnetic filter caused by particle coagulation or deposition. In order to actualize the magnetic separation without blockage, we introduced pneumatic conveyance system as a new method to feed the powder. It is important to increase the drag force acting on the sufficiently dispersed particles, which require strong magnetic fields. To generate the strong magnetic fields, HGMS technique was examined which consists of a magnetic filter and a superconducting solenoid magnet. As a result of the magnetic separation experiment, it was shown that the separation efficiency changes due to the difference of the cohesive property of the particles. On the basis of the result, the adhesion force which acts between the ferromagnetic particles and the medium particles used for the magnetic separation was measured by Atomic Force Microscope (AFM), and cohesion of particles was studied from the aspect of interparticle interaction. We assessed a suitable flow velocity for magnetic separation according to the cohesive property of each particle based on the result.

Senkawa, K.; Nakai, Y.; Mishima, F.; Akiyama, Y.; Nishijima, S.

2011-11-01

128

Isolation of Osteoprogenitors from Human Jaw Periosteal Cells: A Comparison of Two Magnetic Separation Methods  

PubMed Central

Human jaw periosteum tissue contains osteoprogenitors that have potential for tissue engineering applications in oral and maxillofacial surgeries. To isolate osteoprogenitor cells from heterogeneous cell populations, we used the specific mesenchymal stem cell antigen-1 (MSCA-1) antibody and compared two magnetic separation methods. We analyzed the obtained MSCA-1+ and MSCA-1? fractions in terms of purity, yield of positive/negative cells and proliferative and mineralization potentials. The analysis of cell viability after separation revealed that the EasySep method yielded higher viability rates, whereas the flow cytometry results showed a higher purity for the MACS-separated cell fractions. The mineralization capacity of the osteogenic induced MSCA-1+ cells compared with the MSCA-1? controls using MACS was 5-fold higher, whereas the same comparison after EasySep showed no significant differences between both fractions. By analyzing cell proliferation, we detected a significant difference between the proliferative potential of the osteogenic cells versus untreated cells after the MACS and EasySep separations. The differentiated cells after MACS separation adjusted their proliferative capacity, whereas the EasySep-separated cells failed to do so. The protein expression analysis showed small differences between the two separation methods. Our findings suggest that MACS is a more suitable separation method to isolate osteoprogenitors from the entire jaw periosteal cell population. PMID:23094035

Olbrich, Marcus; Rieger, Melanie; Reinert, Siegmar; Alexander, Dorothea

2012-01-01

129

Separation Nanotechnology of Diethylenetriaminepentaacetic Acid Bonded Magnetic Nanoparticles for Spent Nuclear Fuel  

SciTech Connect

A nanomagnetic separation method based on Diethylenetriaminepentaacetic acid (DTPA) conjugated with magnetic nanoparticles (MNPs) is studied for application in spent nuclear fuel separation. The high affinity of DTPA towards actinides aids in separation from the highly acidic medium of nuclear waste. The solubility and magnetization of particles at low pH is protected by encapsulating them in silica layer. Surface functionalization of silica coated particles with polyamines enhances the loading capacity of the chelators on MNPs. The particles were characterized before and after surface modification using transmission electron microscopy (TEM), helium ion microscopy (HIM), Fourier transform-infrared (FT-IR) spectrometry, and X-ray diffractometry. The coated and uncoated samples were studied using vibrating sample magnetometer (VSM) to understand the change in magnetic properties due to the influence of the surface functionalization. The hydrodynamic size and surface charge of the particles are investigated using Dynamic Light Scattering (DLS). The uptake behavior of Am(III), Pu(IV), U(VI), and Np(V) from 0.1M NaNO3 solution was investigated. The sorption result shows the strong affinity of DTPA towards Am(III) and Pu(IV) by extracting 97% and 80% of actinides, respectively. The high removal efficiency and fast uptake of actinides make the chelator conjugated MNPs an effective method for spent nuclear fuel separation.

Kaur, Maninder [Idaho Univ., Moscow, ID (United States); Johnson, Andrew [Idaho Univ., Moscow, ID (United States); Tian, Guoxin [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Jiang, Weilin [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Rao, Linfeng [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Paszczynski, Andrzej [Idaho Univ., Moscow, ID (United States); Qiang, You [Center for Advanced Energy Studies, Idaho Falls, ID (United States); Idaho Univ., Moscow, ID (United States)

2013-01-15

130

Measurement of the magnetic interaction between two bound electrons of two separate ions.  

PubMed

Electrons have an intrinsic, indivisible, magnetic dipole aligned with their internal angular momentum (spin). The magnetic interaction between two electronic spins can therefore impose a change in their orientation. Similar dipolar magnetic interactions exist between other spin systems and have been studied experimentally. Examples include the interaction between an electron and its nucleus and the interaction between several multi-electron spin complexes. The challenge in observing such interactions for two electrons is twofold. First, at the atomic scale, where the coupling is relatively large, it is often dominated by the much larger Coulomb exchange counterpart. Second, on scales that are substantially larger than the atomic, the magnetic coupling is very weak and can be well below the ambient magnetic noise. Here we report the measurement of the magnetic interaction between the two ground-state spin-1/2 valence electrons of two (88)Sr(+) ions, co-trapped in an electric Paul trap. We varied the ion separation, d, between 2.18 and 2.76 micrometres and measured the electrons' weak, millihertz-scale, magnetic interaction as a function of distance, in the presence of magnetic noise that was six orders of magnitude larger than the magnetic fields the electrons apply on each other. The cooperative spin dynamics was kept coherent for 15 seconds, during which spin entanglement was generated, as verified by a negative measured value of -0.16 for the swap entanglement witness. The sensitivity necessary for this measurement was provided by restricting the spin evolution to a decoherence-free subspace that is immune to collective magnetic field noise. Our measurements show a d(-3.0(4)) distance dependence for the coupling, consistent with the inverse-cube law. PMID:24943952

Kotler, Shlomi; Akerman, Nitzan; Navon, Nir; Glickman, Yinnon; Ozeri, Roee

2014-06-19

131

Measurement of the magnetic interaction between two bound electrons of two separate ions  

NASA Astrophysics Data System (ADS)

Electrons have an intrinsic, indivisible, magnetic dipole aligned with their internal angular momentum (spin). The magnetic interaction between two electronic spins can therefore impose a change in their orientation. Similar dipolar magnetic interactions exist between other spin systems and have been studied experimentally. Examples include the interaction between an electron and its nucleus and the interaction between several multi-electron spin complexes. The challenge in observing such interactions for two electrons is twofold. First, at the atomic scale, where the coupling is relatively large, it is often dominated by the much larger Coulomb exchange counterpart. Second, on scales that are substantially larger than the atomic, the magnetic coupling is very weak and can be well below the ambient magnetic noise. Here we report the measurement of the magnetic interaction between the two ground-state spin-1/2 valence electrons of two 88Sr+ ions, co-trapped in an electric Paul trap. We varied the ion separation, d, between 2.18 and 2.76 micrometres and measured the electrons' weak, millihertz-scale, magnetic interaction as a function of distance, in the presence of magnetic noise that was six orders of magnitude larger than the magnetic fields the electrons apply on each other. The cooperative spin dynamics was kept coherent for 15 seconds, during which spin entanglement was generated, as verified by a negative measured value of -0.16 for the swap entanglement witness. The sensitivity necessary for this measurement was provided by restricting the spin evolution to a decoherence-free subspace that is immune to collective magnetic field noise. Our measurements show a d-3.0(4) distance dependence for the coupling, consistent with the inverse-cube law.

Kotler, Shlomi; Akerman, Nitzan; Navon, Nir; Glickman, Yinnon; Ozeri, Roee

2014-06-01

132

Magnetic Field Separation Around Planets Using an Adjoint-Method Approach  

NASA Astrophysics Data System (ADS)

The two spacecraft of the BepiColombo mission will reach planet Mercury in 2022. The magnetometers on-board these polar orbiting spacecraft will provide a detailed map of the magnetic field in Mercury's environment. Unfortunately, a separation of the magnetic field into internal and external parts using the classical Gauss-algorithm is not possible due to strong electric currents in the orbit region of the spacecraft. These currents are due to the interaction of the solar wind with Mercury's planetary magnetic field. We use an MHD code to simulate this interaction process. This requires a first choice of Mercury's planetary field which is used and modified until the simulation results fit to the actual measurements. This optimization process is carried out most efficiently using an adjoint-method. The adjoint-method is well known for its low computational cost in order to determine sensitivities required for the minimization. In a first step, the validity of our approach to separate magnetic field contributions into internal and external parts is demonstrated using synthetic generated data. Furthermore, we apply our approach to satellite measurements of the Earth's magnetic field. We can compare the results with the well known planetary field of the Earth to prove practical suitability.

Nabert, Christian; Glassmeier, Karl-Heinz; Heyner, Daniel; Othmer, Carsten

133

Preparation of thermosensitive polymer magnetic particles and their application in protein separations.  

PubMed

This paper presents a kind of thermoresponsive polymeric magnetic particles for protein separations. The magnetofluids were directly encapsulated in hollow particles constructed by self-assembly of rod-coil poly(ethylene glycol)-poly(N-isopropylacrylamide)/?-cyclodextrin (PEG-PNIPAM/?-CD) complexes. The resulting particles showed reversible protein absorption/desorption capacity because the reversible thermo-sensitivity of PNIPAM. Above the lower critical solution temperature (LCST) of PNIPAM, these particles showed high absorptive capacities and adsorption was done at lower temperature. The protein-laden particles are readily removed from the feed solution in a magnetic field. PMID:25222511

Luo, Ling; Zhang, Hong-Su; Liu, Yan; Ha, Wei; Li, Luo-Hao; Gong, Xiao-Lei; Li, Bang-Jing; Zhang, Sheng

2014-12-01

134

Review and evaluation of extractants for strontium removal using magnetically assisted chemical separation  

SciTech Connect

A literature review on extractants for strontium removal was initially performed at Northern Illinois University to assess their potential in magnetically assisted chemical separation. A series of potential strontium extractants was systematically evaluated there using radioanalytical methods. Initial experiments were designed to test the uptake of strontium from nitric acid using several samples of magnetic extractant particles that were coated with various crown ether ligands. High partition coefficient (K{sub d}) values for stimulant tank waste were obtained. Further studies demonstrated that the large partitioning was due to uncoated particles.

Bauer, C.B.; Rogers, R.D. [Northern Illinois Univ., De Kalb, IL (United States). Dept. of Chemistry; Nunez, L.; Ziemer, M.D.; Pleune, T.T.; Vandegrift, G.F. [Argonne National Lab., IL (United States)

1995-11-01

135

Just in Time-Selection: A Rapid Semiautomated SELEX of DNA Aptamers Using Magnetic Separation and BEAMing.  

PubMed

A semiautomated two-step method for in vitro selection of DNA aptamers using magnetic separation and solid-phase emulsion polymerase chain reaction has been developed. The application of a magnetic separator allows the simultaneous processing of up to 12 SELEXs (systematic evolution of ligands by exponential enrichment) with different targets or buffer conditions. Using a magnetic separator and covalent target immobilization on magnetic beads, the selection process was simplified and the substeps of aptamer/target incubation, washing, and elution of the aptamers were merged into one automated procedure called "FISHing". Without further processing the resulting FISHing eluates are suitable for BEAMing (beads, emulsion, amplification, and magnetics), which includes the amplification by emPCR (emulsion polymerase chain reaction) and strand separation by the implementation of covalently immobilized reverse primers on magnetic beads. The novel selection process has been proved and validated by selecting and characterization of aptamers to the wine fining agent lysozyme. PMID:25286022

Hünniger, Tim; Wessels, Hauke; Fischer, Christin; Paschke-Kratzin, Angelika; Fischer, Markus

2014-11-01

136

Selective separation of lambdacyhalothrin by porous/magnetic molecularly imprinted polymers prepared by Pickering emulsion polymerization.  

PubMed

Porous/magnetic molecularly imprinted polymers (PM-MIPs) were prepared by Pickering emulsion polymerization. The reaction was carried out in an oil/water emulsion using magnetic halloysite nanotubes as the stabilizer instead of a toxic surfactant. In the oil phase, the imprinting process was conducted by radical polymerization of functional and cross-linked monomers, and porogen chloroform generated steam under the high reaction temperature, which resulted in some pores decorated with easily accessible molecular binding sites within the as-made PM-MIPs. The characterization demonstrated that the PM-MIPs were porous and magnetic inorganic-polymer composite microparticles with magnetic sensitivity (M(s) = 0.7448 emu/g), thermal stability (below 473 K) and magnetic stability (over the pH range of 2.0-8.0). The PM-MIPs were used as a sorbent for the selective binding of lambdacyhalothrin (LC) and rapidly separated under an external magnetic field. The Freundlich isotherm model gave a good fit to the experimental data. The adsorption kinetics of the PM-MIPs was well described by pseudo-second-order kinetics, indicating that the chemical process could be the rate-limiting step in the adsorption of LC. The selective recognition experiments exhibited the outstanding selective adsorption effect of the PM-MIPs for target LC. Moreover, the PM-MIPs regeneration without significant loss in adsorption capacity was demonstrated by at least four repeated cycles. PMID:23894024

Hang, Hui; Li, Chunxiang; Pan, Jianming; Li, Linzi; Dai, Jiangdong; Dai, Xiaohui; Yu, Ping; Feng, Yonghai

2013-10-01

137

SERS-Fluorescence Joint Spectral Encoded Magnetic Nanoprobes for Multiplex Cancer Cell Separation.  

PubMed

A new kind of cancer cell separation method is demonstrated, using surface-enhanced Raman scattering (SERS) and fluorescence dual-encoded magnetic nanoprobes. The designed nanoprobes can realize SERS-fluorescence joint spectral encoding (SFJSE) and greatly improve the multiplexing ability. The nanoprobes have four main components, that is, the magnetic core, SERS generator, fluorescent agent, and targeting antibody. These components are assembled with a multi-layered structure to form the nanoprobes. Specifically, silica-coated magnetic nanobeads (MBs) are used as the inner core. Au core-Ag shell nanorods (Au@Ag NRs) are employed as the SERS generators and attached on the silica-coated MBs. After burying these Au@Ag NRs with another silica layer, CdTe quantum dots (QDs), that is, the fluorescent agent, are anchored onto the silica layer. Finally, antibodies are covalently linked to CdTe QDs. SFJSE is fulfilled by using different Raman molecules and QDs with different emission wavelengths. By utilizing four human cancer cell lines and one normal cell line as the model cells, the nanoprobes can specifically and simultaneously separate target cancer cells from the normal ones. This SFJSE-based method greatly facilitates the multiplex, rapid, and accurate cancer cell separation, and has a prosperous potential in high-throughput analysis and cancer diagnosis. PMID:24862088

Wang, Zhuyuan; Zong, Shenfei; Chen, Hui; Wang, Chunlei; Xu, Shuhong; Cui, Yiping

2014-11-01

138

Study on a novel POM-based magnetic photocatalyst: Photocatalytic degradation and magnetic separation  

Microsoft Academic Search

The photocatalytic performance of a novel polyoxometalate (POM)-based magnetic photocatalyst was studied by photocatalytic degradation of a model compound (formic acid) in an annular fluidized bed photoreactor. Degradation rate, apparent quantum efficiency, and energy efficiency were evaluated and compared with suspended TiO2 fine particles (Degussa P25) and quartz sand supported TiO2 photocatalysts. All degradation experiments were conducted under fully irradiated

Wei Qiu; Ying Zheng; Katy A. Haralampides

2007-01-01

139

Detection of Cronobacter species in powdered infant formula by probe-magnetic separation PCR.  

PubMed

Cronobacter species are opportunistic foodborne pathogens associated with serious infections in preterm neonates and infants. Based on the epidemiological research, infant formula products are considered to be the main source of infections from this organism. Therefore, accurate methods are required for detection of Cronobacter species. In this study, the specific probe and primers for detection of this organism were designed and verified. The probe-magnetic beads were prepared for sequence capture, followed by PCR assay to detect the target gene. This probe-magnetic separation PCR assay could detect as few as 10(3) cfu/mL of Cronobacter in artificially contaminated infant formulas in less than 4 h. The combination of magnetic beads and PCR showed the potential for the detection of Cronobacter in infant formulas and may have applications in the dairy industry. PMID:25108865

Xu, Feng; Li, Peng; Ming, Xing; Yang, Dong; Xu, Hengyi; Wu, Xiaoli; Shah, Nagendra P; Wei, Hua

2014-10-01

140

Cesium separation from contaminated milk using magnetic particles containing crystalline silicotitantes.  

SciTech Connect

The Chernobyl nuclear reactor disaster in 1986 contaminated vast regions of prime grazing land. Subsequently, milk produced in the region has been contaminated with small amounts of the long-lived fission product cesium-137, and the Ukraine is seeking to deploy a simple separation process that will remove the Cs and preserve the nutritional value of the milk. Tiny magnetic particles containing crystalline silicotitanates (CST) have been manufactured and tested to this end. The results show that partitioning efficiency is optimized with low ratios of particle mass to volume. To achieve 90% Cs decontamination in a single-stage process, <3 g of magnetic CST per l milk is sufficient with a 30-min mixing time. A two-stage process would utilize <0.4 g/l per stage. The modeling of the magnetic CST system described herein can be achieved rather simply which is important for deployment in the affected Ukraine region.

Nunez, L.; Kaminski, M.; Chemical Engineering

2000-11-01

141

The use of multifunctional magnetic mesoporous core/shell heteronanostructures in a biomolecule separation system.  

PubMed

A multifunctional magnetic mesoporous core/shell heteronanostructure (designated as Fe(3)O(4)@NiSiO(3)) has been designed and constructed that combined the capacity of effective protein purification from protein mixture and selective low molecule weight (MW) biomolecule enrichment. The nanoparticle is composed by magnetite nanoparticle with immobilized metal ion surface and solid porous shell which presents a number of important features, such as controllable shell thickness, uniform pore size and excellent magnetism. By taking advantages of the high affinity of Ni(2+) on the shell surface toward His-tagged proteins and the fast response toward an assistant magnet, the heteronanoparticles can be applied to selectively bind to and magnetically separate of His-tagged proteins from a cell lysate of E. coli. Additionally, owing to the homogeneous 3D mesopores on the nickel silicate shell, the heteronanoparticles can selectively capture low MW biomolecules from complex mixture. Significantly, it is expected that this approach can be extended to other biomolecule separation and enrichment systems by changing the immobilized surface and the pore size. PMID:21481453

Liu, Zhen; Li, Meng; Yang, Xinjian; Yin, Meili; Ren, Jinsong; Qu, Xiaogang

2011-07-01

142

Conjugates of magnetic nanoparticle-actinide specific chelator for radioactive waste separation.  

PubMed

A novel nanotechnology for the separation of radioactive waste that uses magnetic nanoparticles (MNPs) conjugated with actinide specific chelators (MNP-Che) is reviewed with a focus on design and process development. The MNP-Che separation process is an effective way of separating heat generating minor actinides (Np, Am, Cm) from spent nuclear fuel solution to reduce the radiological hazard. It utilizes coated MNPs to selectively adsorb the contaminants onto their surfaces, after which the loaded particles are collected using a magnetic field. The MNP-Che conjugates can be recycled by stripping contaminates into a separate, smaller volume of solution, and then become the final waste form for disposal after reusing number of times. Due to the highly selective chelators, this remediation method could be both simple and versatile while allowing the valuable actinides to be recovered and recycled. Key issues standing in the way of large-scale application are stability of the conjugates and their dispersion in solution to maintain their unique properties, especially large surface area, of MNPs. With substantial research progress made on MNPs and their surface functionalization, as well as development of environmentally benign chelators, this method could become very flexible and cost-effective for recycling used fuel. Finally, the development of this nanotechnology is summarized and its future direction is discussed. PMID:24070142

Kaur, Maninder; Zhang, Huijin; Martin, Leigh; Todd, Terry; Qiang, You

2013-11-01

143

Conjugates of Magnetic Nanoparticle -- Actinide Specific Chelator for Radioactive Waste Separation  

SciTech Connect

A novel nanotechnology for the separation of radioactive waste that uses magnetic nanoparticles (MNPs) conjugated with actinide specific chelators (MNP-Che) is reviewed with a focus on design and process development. The MNP-Che separation process is an effective way of separating heat generating minor actinides (Np, Am, Cm) from spent nuclear fuel solution to reduce the radiological hazard. It utilizes coated MNPs to selectively adsorb the contaminants onto their surfaces, after which the loaded particles are collected using a magnetic field. The MNP-Che conjugates can be recycled by stripping contaminates into a separate, smaller volume of solution, and then become the final waste form for disposal after reusing number of times. Due to the highly selective chelators, this remediation method could be both simple and versatile while allowing the valuable actinides to be recovered and recycled. Key issues standing in the way of large-scale application are stability of the conjugates and their dispersion in solution to maintain their unique properties, especially large surface area, of MNPs. With substantial research progress made on MNPs and their surface functionalization, as well as development of environmentally benign chelators, this method could become very flexible and cost-effective for recycling used fuel. Finally, the development of this nanotechnology is summarized and its future direction is discussed.

Maninder Kaur; Huijin Zhang; Leigh Martin; Terry Todd; You Qiang

2013-11-01

144

ATOMIC RESOLUTION CRYO ELECTRON MICROSCOPY OF MACROMOLECULAR COMPLEXES  

PubMed Central

Single-particle cryo electron microscopy (cryoEM) is a technique for determining three-dimensional (3D) structures from projection images of molecular complexes preserved in their “native,” noncrystalline state. Recently, atomic or near-atomic resolution structures of several viruses and protein assemblies have been determined by single-particle cryoEM, allowing ab initio atomic model building by following the amino acid side chains or nucleic acid bases identifiable in their cryoEM density maps. In particular, these cryoEM structures have revealed extended arms contributing to molecular interactions that are otherwise not resolved by the conventional structural method of X-ray crystallography at similar resolutions. High-resolution cryoEM requires careful consideration of a number of factors, including proper sample preparation to ensure structural homogeneity, optimal configuration of electron imaging conditions to record high-resolution cryoEM images, accurate determination of image parameters to correct image distortions, efficient refinement and computation to reconstruct a 3D density map, and finally appropriate choice of modeling tools to construct atomic models for functional interpretation. This progress illustrates the power of cryoEM and ushers it into the arsenal of structural biology, alongside conventional techniques of X-ray crystallography and NMR, as a major tool (and sometimes the preferred one) for the studies of molecular interactions in supramolecular assemblies or machines. PMID:21501817

ZHOU, Z. HONG

2013-01-01

145

Cryo-Electron Tomography for Structural Characterization of Macromolecular Complexes  

PubMed Central

Cryo-electron tomography (cryo-ET) is an emerging 3-D reconstruction technology that combines the principles of tomographic 3-D reconstruction with the unmatched structural preservation of biological material embedded in vitreous ice. Cryo-ET is particularly suited to investigating cell-biological samples and large macromolecular structures that are too polymorphic to be reconstructed by classical averaging-based 3-D reconstruction procedures. This unit aims to make cryo-ET accessible to newcomers and discusses the specialized equipment required, as well as the relevant advantages and hurdles associated with sample preparation by vitrification and cryo-ET. Protocols describe specimen preparation, data recording and 3-D data reconstruction for cryo-ET, with a special focus on macromolecular complexes. A step-by-step procedure for specimen vitrification by plunge freezing is provided, followed by the general practicalities of tilt-series acquisition for cryo-ET, including advice on how to select an area appropriate for acquiring a tilt series. A brief introduction to the underlying computational reconstruction principles applied in tomography is described, along with instructions for reconstructing a tomogram from cryo-tilt series data. Finally, a method is detailed for extracting small subvolumes containing identical macromolecular structures from tomograms for alignment and averaging as a means to increase the signal-to-noise ratio and eliminate missing wedge effects inherent in tomographic reconstructions. PMID:21842467

Cope, Julia; Heumann, John; Hoenger, Andreas

2011-01-01

146

A lysozyme and magnetic bead based method of separating intact bacteria.  

PubMed

As a response to environmental stress, bacterial cells can enter a physiological state called viable but noncultivable (VBNC). In this state, bacteria fail to grow on routine bacteriological media. Consequently, standard methods of contamination detection based on bacteria cultivation fail. Although they are not growing, the cells are still alive and are able to reactivate their metabolism. The VBNC state and low bacterial densities are big challenges for cultivation-based pathogen detection in drinking water and the food industry, for example. In this context, a new molecular-biological separation method for bacteria using point-mutated lysozymes immobilised on magnetic beads for separating bacteria is described. The immobilised mutated lysozymes on magnetic beads serve as bait for the specific capture of bacteria from complex matrices or water due to their remaining affinity for bacterial cell wall components. Beads with bacteria can be separated using magnetic racks. To avoid bacterial cell lysis by the lysozymes, the protein was mutated at amino acid position 35, leading to the exchange of the catalytic glutamate for alanine (LysE35A) and glutamine (LysE35Q). As proved by turbidity assay with reference bacteria, the muramidase activity was knocked out. The mutated constructs were expressed by the yeast Pichia pastoris and secreted into expression medium. Protein enrichment and purification were carried out by SO(3)-functionalised nanoscale cationic exchanger particles. For a proof of principle, the proteins were biotinylated and immobilised on streptavidin-functionalised, fluorescence dye-labelled magnetic beads. These constructs were used for the successful capture of Syto9-marked Microccocus luteus cells from cell suspension, as visualised by fluorescence microscopy, which confirmed the success of the strategy. PMID:21574057

Diler, Ebru; Obst, Ursula; Schmitz, Katja; Schwartz, Thomas

2011-07-01

147

Nanomagnetism of Core-Shell Magnetic Nanoparticles and Application in Spent Nuclear Fuel Separation  

NASA Astrophysics Data System (ADS)

This dissertation presents the study on novel core-shell magnetic nanoparticles (NPs) with unique magnetic properties. Understanding the fundamental physics of antiferromagnetic - ferromagnetic interactions is essential to apply in different applications. Chromium (Cr) doped and undoped core-shell iron/iron-oxide NPs have been synthesized using cluster deposition system and studied with respect to their nanostructures, morphologies, sizes, chemical composition and magnetic properties. The room-temperature magnetic properties of Fe based NPs shows the strong dependence of intra/inter-particle interaction on NP size. The Cr-doped Fe NP shows the origin of sigma-FeCr phase at very low Cr concentration (2 at.%) unlike others reported at high Cr content and interaction reversal from dipolar to exchange interaction. A theoretical model of watermelon is constructed based on the experimental results and core-shell NP system in order to explain the physics of exchange interaction in Cr-doped Fe particles. The magnetic nanoparticle---chelator separation nanotechnology is investigated for spent nuclear fuel recycling and is reported 97% and 80% of extraction for Am(III) and Pu(IV) actinides respectively. If the long-term heat generating actinides such as Am(III) can be efficiently removed from the used fuel raffinates, the volume of material that can be placed in a given amount of repository space can be significantly increased. As it is a simple, versatile, compact, and cost efficient process that minimizes secondary waste and improves storage performance.

Tarsem Singh, Maninder Kaur

148

Development of magnetic separation methods of analysis: magnetic field flow fractionation  

E-print Network

Tagging Of Bov1ne Serum Albumin By Nickel Ions And Magnetic FFF Ana lys1s Sam le Ni A lied Ma . Field Dro Retention Time 1. BSA 0 2. BSA 3. N1 + BSA -5. 0 X 10 M 4. Ni + BSA -5. 0 X 10 M 200 G 200 G 24. 0 min 24. 0 min 24. 0 m1n 25. 5 min... Bell Inc. , Model 640 Gaussmeter Detector ? Standard HPLC ultrav1olet detector (254 nm excitation wavelength) with 8 ul cell volume and 20 ul injection port volume BSA Concentrat1on - 1. 0 X 10 M in I and 2; 5 X 10 M in 3 and 4. 28 Table II lists...

Garcia-Ramirez, Jaime

2012-06-07

149

Magnetic Field Distribution of Permanent Magnet Magnetized by Static Magnetic Field Generated by HTS Bulk Magnet  

Microsoft Academic Search

Demagnetized rare earth magnets (Nd-Fe-B) can be fully magnetized by scanning them in the intense static fields over 3 T of a HTS bulk magnet which was cooled to the temperature range lower than 77K with use of cryo-coolers and activated by the field of 5 T. We precisely examined the magnetic field distributions of magnetized permanent magnets. The magnetic

Tetsuo Oka; Nobutaka Kawasaki; Satoshi Fukui; Jun Ogawa; Takao Sato; Toshihisa Terasawa; Yoshitaka Itoh; Ryohei Yabuno

2012-01-01

150

Near-surface epigenetic magnetic indicators of buried hydrocarbons and separation of spurious signals  

SciTech Connect

Significant geochemical alteration zones occurring over buried hydrocarbon deposits can be recognized and mapped by geophysical methods. The authors believe near-surface secondary magnetic minerals formed as a result of seeping hydrocarbons and associated compounds interacting with constituents of the overlying rocks. A new method is described to identify anomalous magnetic signatures associated with this mineralization, and to differentiate that signal from cultural interference and other surface shallow, and intermediate-depth geologic sources. Using low-altitude, high-sensitivity aeromagnetic data, the separation involves detailed spectral analysis, subsequent band-pass filtering, and analytic signal transformation of the filtered data. Depicted in contour form, the analytic signal minimizes spatial aliasing and allows us to map the areal distribution of subtle, near-surface anomalies related to probable epigenetic magnetic mineralization. This method is illustrated using data from the Arctic National Wildlife Refuge and Cook Inlet, Alaska, and from offshore Texas, where high-resolution seismic data support the aeromagnetic interpretation and suggest important structural controls. Correlations of published detailed gravimeter and low-altitude aeromagnetic data at the Cement oil field, Oklahoma, were coupled with interactive modeling studies. Except for the obvious extreme high wave-number spikes, cultural contamination cannot be responsible for the high wave-number signal there, and the epigenetic magnetic mineralization may be more extensive vertically than originally suggested.

Donovan, T.J.; O'Brien, D.P.; Bryan, J.G.; Shepherd, M.A.

1986-05-01

151

Desulphurization of lignites by slow, fast, and flash pyrolysis and high intensity dry magnetic separation  

SciTech Connect

Slow, fast and flash pyrolysis followed by high intensity dry magnetic (HIDM) separation experiments were conducted to obtain improved solid fuels. Pyrolysis experiments were performed in three different apparatus, and important parameters of processes, temperature, particle size, residence time and heating rate were studied to determine the optimum conditions. Desulphurization of lignites by flash pyrolysis is more successful than slow and fast pyrolysis. At optimum conditions of pyrolysis, up to 58.15, 60.24, and 62.31% sulphur reductions were obtained in slow, fast and flash pyrolysis, respectively. Char, obtained from the pyrolysis experiments, was further cleaned by a Permroll HIDM separator. Sulphur reduction enhanced up to 82.68, 84.40, and 86.55% in the char of slow, fast and flash pyrolysis, respectively.

Koca, H.; Kockar, O.M.; Koca, S. [Anadolu University, Eskisehir (Turkey). Porsuk Technical College

2007-07-01

152

High magnetic field far-infrared spectroscopy of spatially separated electron-hole layers  

NASA Astrophysics Data System (ADS)

Cyclotron resonance (CR) experiments have been performed on InAs/GaSb structures, in which InAs (electron) and GaSb (hole) layers are separated by AlSb barriers. Our data reveal that properties of InAs/GaSb systems with AlSb barriers thinner than 1.5 nm are entirely determined by interlayer tunneling and the CR features in such samples can be explained by hybridization between states in the InAs conduction band and in the GaSb valence band. The hybridization gap has been estimated from CR spectra for two samples with different degrees of electron-hole coupling. The CR spectra of widely separated electron-hole layers (with barriers thicker than 2 nm) are characterized by pronounced spin splitting. In addition to multiple spin-split CR lines new lines have been observed at high magnetic fields (11-13 T).

Vasilyev, Yu. B.; Suchalkin, S. D.; Klitzing, K. v.; Meltser, B. Ya.; Ivanov, S. V.; Kop'ev, P. S.

1998-12-01

153

High gradient magnetic separation of iron oxide minerals from soil clays  

E-print Network

. The titanium oxide minerals, anatase and rutile, were identified by peaks at 3. 52A and 3. 25A respectively (Hutton, 1977). In many D 0 cases, the 3. 52A anatase peak could not be resolved from the 3. 57A kaolinite peak until the kaolinite peak... was destroyed by heating at 550'C. The 3. 52A and 3. 25A peaks are the strongest peaks for anatase and rutile and are the only ones normally observed in routine x-ray diffraction analysis. 25 RESULTS AND DISCUSSION Effectiveness of Magnetic Separation...

Schulze, Darrell Gene

2012-06-07

154

TREATMENT OF COMBINED SEWER OVERFLOWS BY HIGH GRADIENT MAGNETIC SEPARATION. ON-SITE TESTING WITH MOBILE PILOT PLANT TRAILER  

EPA Science Inventory

Seeded water treatment using a SALA high gradient magnetic separator pilot plant system was conducted on combined sewer overflows and raw sewage at SALA Magnetics in Cambridge, MA and at on-site locations in the Boston area. Special emphasis was placed on specific design and oper...

155

Method and apparatus for separating gases based on electrically and magnetically enhanced monolithic carbon fiber composite sorbents  

DOEpatents

A method for separating gases or other fluids involves placing a magnetic field on a monolithic carbon fiber composite sorption material to more preferentially attract certain gases or other fluids to the sorption material to which a magnetic field is applied. This technique may be combined with the known "pressure swing adsorption" technique utilizing the same sorption material.

Judkins, Roddie R. (9917 Rainbow Dr., Knoxville, TN 37922); Burchell, Timothy D. (109 Greywood Pl., Oak Ridge, TN 37830)

1999-01-01

156

Method and apparatus for separating gases based on electrically and magnetically enhanced monolithic carbon fiber composite sorbents  

DOEpatents

A method for separating gases or other fluids involves placing a magnetic field on a monolithic carbon fiber composite sorption material to more preferentially attract certain gases or other fluids to the sorption material to which a magnetic field is applied. This technique may be combined with the known pressure swing adsorption'' technique utilizing the same sorption material. 1 fig.

Judkins, R.R.; Burchell, T.D.

1999-07-20

157

Quantification of Non-Specific Binding of Magnetic Micro and Nano particles using Cell Tracking Velocimetry: Implication for magnetic cell separation and detection  

PubMed Central

The maturation of magnetic cell separation technology places increasing demands on magnetic cell separation performance. While a number of factors can cause suboptimal performance, one of the major challenges can be non-specific binding of magnetic nano or micro particles to non-targeted cells. Depending on the type of separation, this non-specific binding can have a negative effect on the final purity, the recovery of the targeted cells, or both. In this work, we quantitatively demonstrate that non-specific binding of magnetic nanoparticles can impart a magnetization to cells such that these cells can be retained in a separation column and thus negatively impact the purity of the final product and the recovery of the desired cells. Through experimental data and theoretical arguments, we demonstrate that the number of MACS magnetic particles needed to impart a magnetization that is sufficient to causes non-targeted cells to be retained in the column to be on the order of 500 to 1,000 nanoparticles. This number of non-specifically bound particles was demonstrated experimentally with an instrument, cell tracking velocimeter, CTV, and it is demonstrated that the sensitivity of the CTV instrument for Fe atoms contained in magnetic nanoparticles on the order of 1 × 10?15 g/mL of Fe. PMID:20014141

Chalmers, J.J.; Xiong, Y.; Jin, X.; Shao, M.; Tong, X.; Farag, S.; Zborowski, M.

2012-01-01

158

A novel bubbling-assisted exfoliating method preparation of magnetically separable ?-Fe2O3/graphene recyclable photocatalysts  

NASA Astrophysics Data System (ADS)

A facile and novel bubbling-assisted exfoliating method was developed for the preparation of ?-Fe2O3/graphene composite, which showed desirable photocatalytic activity toward methyl orange with excellent cycling abilities and the possible growth mechanism was discussed. Photocatalytic and magnetic properties measurements show that the composite has excellent recyclable degradation efficiency and soft magnetic parameters, which makes the composite magnetically separable in a suspension system and can be recycled without significant loss of catalytic activity.

Zhang, Lili; Hu, Hongrui; Wu, Mingzai; Yu, Xinxin; Sun, Zhaoqi; Li, Guang; Liu, Xiansong; Zheng, Xiuwen

2014-06-01

159

Magnetic network model including loss separation and Preisach principles for the evaluation of core losses in devices  

NASA Astrophysics Data System (ADS)

In this paper, a method is developed to calculate the core loss in a switched reluctance machine. The magnetic circuit of the motor is described as a magnetic network. The electromagnetic behavior of each magnetic network element takes into account the iron loss using the Preisach model and the principle of loss separation. Using the numerical routines, the local core loss in the different motor sections is calculated. The global core loss is compared with the experimentally determined core loss.

Dupré, Luc; Sergeant, Peter; Vandenbossche, Lode

2005-05-01

160

Synthesis of magnetic ion-imprinted composites and selective separation and preconcentration of U(VI).  

PubMed

The U(VI) magnetic ion-imprinted composite (MIIC) with a uniform core-shell structure for the selective separation and preconcentration of U(VI) was prepared by copolymerization of a ternary complex of uranyl ions with 4-vinylpyridine (4-VP) and acrylamide in the presence of 2,2'-azobisisobutyronitrile. The sorption of U(VI) on the MIIC from aqueous solution was evaluated. The maximum sorption capacity of MIIC for U(VI) was 354.85 mg g(-1), which was much higher than that of the magnetic nonimprinted composite. The MIIC could be recovered by desorbing the U(VI)-loaded MIIC with 0.5 mol L(-1) HNO3, and the surface morphology of MIIC after five consecutive sorption/desorption cycles was significantly damaged. The competitive sorption experiments showed that the MIIC had a desirable selectivity for U(VI) over a range of competing metal ions. The MIIC may be a promising sorbent material for the selective separation and preconcentration of U(VI). PMID:24667936

Liu, Mancheng; Chen, Changlun; Wen, Tao; Wang, Xiangke

2014-05-21

161

Synthesis of teicoplanin-modified hybrid magnetic mesoporous silica nanoparticles and their application in chiral separation of racemic compounds.  

PubMed

Teicoplanin-conjugated mesoporous silica magnetic nanoparticles (TE-MSMNPs) were fabricated as novel chiral magnetic nano-selectors. Successful preparation of the functional magnetic mesoporous materials was achieved by grafting teicoplanin on N-(2-aminoethyl)-3-aminopropyltrimethoxysilane-modified mesoporous silica Fe3O4 magnetic nanoparticles (AEAPTMS-MSMNPs), and this was confirmed by various characterization techniques. The synthesized magnetic nanoparticles were regularly spherical and uniformly mesoporous with an average diameter of around 600 nm and a mean pore size of about 3.9 nm, respectively. These versatile magnetic nanoparticles were effective in a direct chiral separation of five racemic compounds in phosphate buffer. Much stronger interactions were observed with the (+)-enantiomers than with the (-)-enantiomers. After washing with water and ethanol by sonication, TE-MSMNPs could be reused at least three times with little efficiency loss. The functional magnetic mesoporous nanoparticles were easily separated from the racemic solutions using an external magnetic field. These magnetic nano-materials are suitable for enantiomer separations. PMID:23541694

Wu, Jingwei; Su, Ping; Huang, Jun; Wang, Siming; Yang, Yi

2013-06-01

162

Imaging of magnetic colloids under the influence of magnetic field by cryogenic transmission electron microscopy  

NASA Astrophysics Data System (ADS)

The application of superparamagnetic nanoparticles for in vivo magnetic resonance imaging (MRI) under external ac magnetic field has attracted considerable research efforts in recent years. However, it is unclear how superparamagnetic nanostructures arrange themselves in fluidic environment under external magnetic field. Here, we report direct visualization of the effect of applied magnetic field to the ferrofluids (about 6 nm superparamagnetic magnetite (Fe3O4) nanoparticle "colloidal" suspension) using the cryogenic transmission electron microscopy (cryo-TEM). While long dipole chains (up to millimeter range) of the magnetite along the magnetic lines are found in samples dried inside the magnetic field, only short dipole chains (within tens of nanometer scale) with random orientations are observed in the wet sample observed by cryo-TEM. In the wet sample, aggregations of medium-length dipole chains (up to hundreds of nanometer) can be observed at the areas where the nanoparticles are "solidified" when phase separation occurs. In situ formation of flux-closure rings is observed at the edge where vitreous ice sublimes due to high-energy electron radiation that leaves magnetite nanoparticles isolated in the vacuum. Such observations may help elucidate the nature of magnetic field-induced assembly in fluidic environment as in the physiological aqueous conditions in MRI and related applications.

Wu, Jinsong; Aslam, M.; Dravid, Vinayak P.

2008-08-01

163

Development of high gradient magnetic separation system for removing the metallic wear debris to be present in highly viscous fluid  

NASA Astrophysics Data System (ADS)

In the industrial plants processing highly viscous fluid such as foods or industrial materials, there is an issue of contamination by metallic wear debris originating from pipe of manufacturing line. It is necessary to remove the metallic wear debris in highly viscous fluid, since these debris causes quality loss. In this study, we developed a high gradient magnetic separation system by using superconducting magnet to remove the metallic wear debris. The particle trajectory simulation and the magnetic separation experiment were conducted with polyvinyl alcohol as a model material. As a result, ca. 100% and 92.2% of the separation efficiency was achieved respectively for the highly viscous fluid of 1 Pa s and 6 Pa s in viscosity, with 14 and 30 mesh magnetic filters.

Hayashi, S.; Mishima, F.; Akiyama, Y.; Nishijima, S.

2010-11-01

164

Imaging helical nano-filament and modulated smectic phases of bent shaped liquid crystals by cryo-TEM  

NASA Astrophysics Data System (ADS)

Recently we showed that cryo-TEM can be used to visualize smectic layers of thermotropic liquid crystals. Here we describe cryo-TEM studies of the nanofilaments (B4 phase) and the modulated smectic layers (B7 phase ) of various bent shaped liquid crystal compounds. In the B4 phase a periodic array of about 15 nm wide bands of parallel stripes, separated by a distance equal to the layer spacing, appear with a periodicity of about 120 nm corresponding to the half pitch of the nanofilaments. As cryo-TEM shows only layers that are parallel to the electron beam, these results indicate grains of straight layers twisted along the filament axis compose the nano-filaments. In the B7 phase cryo-TEM not only can visualize the smectic layers, but also the periodic modulation indicating defects with less dense molecular packing. In addition we observe a labyrinth structure with curvature radii in the 150 nm ranges. These results yield information complementary to freeze fracture TEM and X-ray observations.

Zhang, Cuiyu; Sawade, Hans; Weissflog, Wolfgang; Jakli, Antal

2013-03-01

165

Experimental cryo-irrigation of the knee joint  

Microsoft Academic Search

Experiments have been carried out to test the feasibility of using cryo-irrigation as a means of ablating the synovium in the rheumatoid knee joint. Cryo-irrigation was performed by a cooling machine and pump, which circulated cold 200\\/10 centistoke (cSt) silicone through the knee joint of rabbits anaesthetised with intravenous (IV) 'Saffan'. Fluid left the joint at -5 to -10 degrees

S C Chen; B Helal; P A Revell; R Brocklehurst; H L Currey

1986-01-01

166

Cryo-electron tomography of cells: connecting structure and function  

Microsoft Academic Search

Cryo-electron tomography (cryo-ET) allows the visualization of cellular structures under close-to-life conditions and at molecular\\u000a resolution. While it is inherently a static approach, yielding structural information about supramolecular organization at\\u000a a certain time point, it can nevertheless provide insights into function of the structures imaged, in particular, when supplemented\\u000a by other approaches. Here, we review the use of experimental methods

Vladan Lu?i?; Andrew Leis; Wolfgang Baumeister

2008-01-01

167

CryoWEB: Web software for the documentation of the cryo-preserved material in animal gene banks  

PubMed Central

Many countries in the world have set up national domestic conservation programmes and collections of long-term storage of cryo-preserved animal genetic material. We have developed a web based software ? CryoWEB for the documentation of such collections. The software is generally applicable to all livestock breeds, independent of the donor's species and the type of preserved material. The software can record basic herd?book information for the donor animal, the structure of the storage facilities, description of the stored samples and their distribution within the gene bank. It also traces the movements of the sample vessels within the storage facilities and the usage of sample units. The outputs implemented in CryoWEB address the informational needs of the gene bank manager in her everyday tasks. Availability CryoWEB is publicly available athttp://cryoweb.tzv.fal.de PMID:21364801

Duchev, Zhivko; Cong, Truong Van Chi; Groeneveld, Eildert

2010-01-01

168

Optimized high gradient magnetic separation for isolation of Plasmodium-infected red blood cells  

PubMed Central

Background Highly purified infected red blood cells (irbc), or highly synchronized parasite cultures, are regularly required in malaria research. Conventional isolation and synchronization rely on density and osmotic fragility of irbc, respectively. High gradient magnetic separation (HGMS) offers an alternative based on intrinsic magnetic properties of irbc, avoiding exposure to chemicals and osmotic stress. Successful HGMS concentration in malaria research was previously reported using polymer coated columns, while HGMS depletion has not been described yet. This study presents a new approach to both HGMS concentration and depletion in malaria research, rendering polymer coating unnecessary. Methods A dipole magnet generating a strong homogenous field was custom assembled. Polypropylene syringes were fitted with one-way stopcocks and filled with stainless steel wool. Rbc from Plasmodium falciparum cultures were resuspended in density and viscosity optimized HGMS buffers and HGMS processed. Purification and depletion results were analysed by flow cytometer and light microscopy. Viability was evaluated by calculating the infection rate after re-culturing of isolates. Results In HGMS concentration, purity of irbc isolates from asynchronous cultures consistently ranged from 94.8% to 98.4% (mean 95.7%). With further optimization, over 90% of isolated irbc contained segmented schizonts. Processing time was less than 45 min. Reinfection rates ranged from 21.0% to 56.4%. In HGMS depletion, results were comparable to treatment with sorbitol, as demonstrated by essentially identical development of cultures. Conclusion The novel HGMS concentration procedure achieves high purities of segmented stage irbc from standard asynchronous cultures, and is the first HGMS depletion alternative to sorbitol lysis. It represents a simple and highly efficient alternative to conventional irbc concentration and synchronization methods. PMID:20122252

2010-01-01

169

Blood progenitor cell separation from clinical leukapheresis product by magnetic nanoparticle binding and magnetophoresis.  

PubMed

Positive selection of CD34+ blood progenitor cells from circulation has been reported to improve patient recovery in applications of autologous transplantation. Current magnetic separation methods rely on cell capture and release on solid supports rather than sorting from flowing suspensions, which limits the range of therapeutic applications and the process scale up. We tested CD34+ cell immunomagnetic labeling and isolation from fresh leukocyte fraction of peripheral blood (leukapheresis) using the continuous quadrupole magnetic flow sorter (QMS), consisting of a flow channel (SHOT, Greenville, IN) and a quadrupole magnet with a maximum field intensity (B(o)) of 1.42 T and a mean force field strength (S(m)) of 1.45 x 10(8) TA/m(2). Both the sample magnetophoretic mobility (m) and the inlet and outlet flow patterns highly affect the QMS performance. Seven commercial progenitor cell labeling reagent combinations were quantitatively evaluated by measuring magnetophoretic mobility of a high CD34 expression cell line, KG-1a, using the cell tracking velocimeter (CTV). The CD34 Progenitor Cell Isolation Kit (Miltenyi Biotec, Bergisch Gladbach, Germany) showed the strongest labeling of KG-1a cells and was selected for progenitor cell enrichment from 11 fresh and 11 cryopreserved clinical leukapheresis samples derived from different donors. The CD34+ cells were isolated with a purity of 60-96%, a recovery of 18-60%, an enrichment rate of 12-169, and a throughput of (1.7-9.3) x 10(4) cells/s. The results also showed a highly regular dependence of the QMS performance on the flow conditions that agreed with the theoretical predictions based on the CD34+ cell magnetophoretic mobility. PMID:17009321

Jing, Ying; Moore, Lee R; Williams, P Stephen; Chalmers, Jeffrey J; Farag, Sherif S; Bolwell, Brian; Zborowski, Maciej

2007-04-15

170

Cryo-electron microscopy of extracellular vesicles in fresh plasma  

PubMed Central

Introduction Extracellular vesicles (EV) are phospholipid bilayer-enclosed vesicles recognized as new mediators in intercellular communication and potential biomarkers of disease. They are found in many body fluids and mainly studied in fractions isolated from blood plasma in view of their potential in medicine. Due to the limitations of available analytical methods, morphological information on EV in fresh plasma is still rather limited. Objectives To image EV and determine the morphology, structure and size distribution in fresh plasma by cryo-electron microscopy (cryo-EM). Methods Fresh citrate- and ethylenediaminetetraacetic acid (EDTA)-anticoagulated plasma or EV isolated from these plasmas were rapidly cryo-immobilized by vitrification and visualized by cryo-EM. Results EV isolated from fresh plasma were highly heterogeneous in morphology and size and mostly contain a discernible lipid bilayer (lipid vesicles). In fresh plasma there were 2 types of particles with a median diameter of 30 nm (25–260 nm). The majority of these particles are electron dense particles which most likely represent lipoproteins. The minority are lipid vesicles, either electron dense or electron lucent, which most likely represent EV. Lipid vesicles were occasionally observed in close proximity of platelets in citrate and EDTA-anticoagulated platelet-rich plasma. Cryo-electron tomography (cryo-ET) was employed to determine the 3D structure of platelet secretory granules. Conclusions Cryo-EM is a powerful technique that enables the characterization of EV in fresh plasma revealing structural details and considerable morphological heterogeneity. Only a small proportion of the submicron structures in fresh plasma are lipid vesicles representing EV. PMID:24455109

Yuana, Yuana; Koning, Roman I.; Kuil, Maxim E.; Rensen, Patrick C. N.; Koster, Abraham J.; Bertina, Rogier M; Osanto, Susanne

2013-01-01

171

Superfluidity and quantum vortices in systems with pairing of spatially separated electrons and holes in crossed magnetic and electric fields  

Microsoft Academic Search

The low-temperature behavior of two-dimensional systems with pairing spatially separated electrons and holes is studied. We predict a transition to a superfluid state of a dilute gas of electron-hole pairs in a strong magnetic field normal to conducting layers. In the superfluid phase the crossed electric and magnetic fields are shown to create planar vortices where the pairs rotate in

S. I. Shevchenko

1998-01-01

172

Cryo-balloon catheter localization in fluoroscopic images  

NASA Astrophysics Data System (ADS)

Minimally invasive catheter ablation has become the preferred treatment option for atrial fibrillation. Although the standard ablation procedure involves ablation points set by radio-frequency catheters, cryo-balloon catheters have even been reported to be more advantageous in certain cases. As electro-anatomical mapping systems do not support cryo-balloon ablation procedures, X-ray guidance is needed. However, current methods to provide support for cryo-balloon catheters in fluoroscopically guided ablation procedures rely heavily on manual user interaction. To improve this, we propose a first method for automatic cryo-balloon catheter localization in fluoroscopic images based on a blob detection algorithm. Our method is evaluated on 24 clinical images from 17 patients. The method successfully detected the cryoballoon in 22 out of 24 images, yielding a success rate of 91.6 %. The successful localization achieved an accuracy of 1.00 mm +/- 0.44 mm. Even though our methods currently fails in 8.4 % of the images available, it still offers a significant improvement over manual methods. Furthermore, detecting a landmark point along the cryo-balloon catheter can be a very important step for additional post-processing operations.

Kurzendorfer, Tanja; Brost, Alexander; Jakob, Carolin; Mewes, Philip W.; Bourier, Felix; Koch, Martin; Kurzidim, Klaus; Hornegger, Joachim; Strobel, Norbert

2013-03-01

173

CryoEDM: A cryogenic experiment to measure the neutron electric dipole moment  

NASA Astrophysics Data System (ADS)

CryoEDM is an experiment that aims to measure the electric dipole moment (EDM) of the neutron to a precision of 10 -28 e cm. A description of CryoEDM, the apparatus, technologies and commissioning is presented.

van der Grinten, M. G. D.; CryoEDM Collaboration; Balashov, S. N.; Francis, V.; Green, K.; Iaydjiev, P. S.; Ivanov, S. N.; Khazov, A.; Tucker, M. A. H.; Wark, D. L.; Davidson, A.; Hardiman, M.; Harris, P. G.; Katsika, K.; Pendlebury, J. M.; Peeters, S. J. M.; Shiers, D. B.; Smith, P.; Townsley, C.; Wardell, I.; Clarke, C.; Henry, S.; Kraus, H.; McCann, M.; Geltenbort, P.; Yoshiki, Y.

2009-12-01

174

In situ magnetic separation of antibody fragments from Escherichia coli in complex media  

PubMed Central

Background In situ magnetic separation (ISMS) has emerged as a powerful tool to overcome process constraints such as product degradation or inhibition of target production. In the present work, an integrated ISMS process was established for the production of his-tagged single chain fragment variable (scFv) D1.3 antibodies (“D1.3”) produced by E. coli in complex media. This study investigates the impact of ISMS on the overall product yield as well as its biocompatibility with the bioprocess when metal-chelate and triazine-functionalized magnetic beads were used. Results Both particle systems are well suited for separation of D1.3 during cultivation. While the triazine beads did not negatively impact the bioprocess, the application of metal-chelate particles caused leakage of divalent copper ions in the medium. After the ISMS step, elevated copper concentrations above 120 mg/L in the medium negatively influenced D1.3 production. Due to the stable nature of the model protein scFv D1.3 in the biosuspension, the application of ISMS could not increase the overall D1.3 yield as was shown by simulation and experiments. Conclusions We could demonstrate that triazine-functionalized beads are a suitable low-cost alternative to selectively adsorb D1.3 fragments, and measured maximum loads of 0.08 g D1.3 per g of beads. Although copper-loaded metal-chelate beads did adsorb his-tagged D1.3 well during cultivation, this particle system must be optimized by minimizing metal leakage from the beads in order to avoid negative inhibitory effects on growth of the microorganisms and target production. Hereby, other types of metal chelate complexes should be tested to demonstrate biocompatibility. Such optimized particle systems can be regarded as ISMS platform technology, especially for the production of antibodies and their fragments with low stability in the medium. The proposed model can be applied to design future ISMS experiments in order to maximize the overall product yield while the amount of particles being used is minimized as well as the number of required ISMS steps. PMID:23688064

2013-01-01

175

Fluorescence cryo-microscopy: current challenges and prospects  

PubMed Central

Studying biological structures with fine details does not only require a microscope with high resolution, but also a sample preparation process that preserves the structures in a near-native state. Live-cell imaging is restricted mostly to the field of light microscopy. For studies requiring much higher resolution, fast freezing techniques (vitrification) are successfully used to immobilize the sample in a near-native state for imaging with electron and X-ray cryo-microscopy. Fluorescence cryo-microscopy combines imaging of vitrified samples with the advantages of fluorescence labeling of biological structures. Technical considerations as well as the behavior of fluorophores at low temperatures have to be taken into account for developing or adapting super-resolution methods under cryo conditions to exploit the full potential of this technique. PMID:24951858

Kaufmann, Rainer; Hagen, Christoph; Grunewald, Kay

2014-01-01

176

Optimization of sample cooling temperature for redox cryo-imaging.  

PubMed

Cryo-imaging techniques have been widely used to measure the metabolic state of tissues by capturing reduced nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) autofluorescence. However, NADH and FAD fluorescence is sensitive to changes in temperature, which may result in unreliable redox ratio calculations. Here, the relationship between the measured redox ratio and sample surface temperature was analyzed using a standard phantom solution and biological tissues. The results indicated that a temperature < - 100°C was a suitable cryo-imaging temperature window in which redox ratio measuring was immune to temperature fluctuations. These results may serve as a reference for designing and optimizing redox cryo-imaging experiments for quantitatively mapping the metabolic state of biological samples. PMID:25147959

Wang, Anle; Yuan, Jing; Luo, Weihua; Liu, Mengmeng; Luo, Qingming

2014-08-01

177

Magnetically separable nanocomposites with photocatalytic activity under visible light for the selective transformation of biomass-derived platform molecules  

EPA Science Inventory

Novel magnetically separable TiO2-guanidine-(Ni,Co)Fe2O4 nanomaterials were prepared and characterised by a series of techniques including XRD, SEM, TEM, N2 physisorption as well as XPS and subsequently tested for their photocatalytic activities in the selective transformation of...

178

CRUCIAL: CryoSat+ Land and Inland Water  

NASA Astrophysics Data System (ADS)

The CryoSat-2 SIRAL altimeter presents a unique opportunity for inland water height retrieval. In order to maximise the potential of this new dataset the ESA CRUCIAL (CryoSat+ Land and Inland Water) contract has been set up to investigate the application of CryoSat-2 data over land and inland water. When operating in SAR mode CryoSat-2 obtains waveforms at an unprecedented resolution alongtrack, allowing far smaller inland water targets then previously possible to be acquired. Prior work performed with the Envisat Individual echoes has shown that a high Pulse Repetition Frequency (PRF) allows successful measurements to be obtained from river targets as small as 25m across. SAR Full Bit Rate (FBR) data are acquired over the Mekong River area, including the Mekong Delta itself. This region provides the ideal test-bed for obtaining small target inland water measurements and early results of FBR waveform reconstruction and analysis are presented within this paper. Whilst FBR data over land are available in a few test regions, over much of the Earth's land surface measurements are acquired in Low Resolution Mode. These data are comparable to those obtained by conventional altimeters, such as ERS-2 and EnviSat. The non-repeat orbit of CryoSat-2 presents a new challenge to inland water measurement by satellite radar altimetry, as repeat time-series are no longer possible. However, CryoSat-2 data produce stage measurements from along the course of rivers more regularly than the 35-days of previous ESA missions. New methodologies must be investigated to allow hydrologists to harness the full benefit of these new data. This paper presents initial findings of investigations over major river systems captured in LRM mode and a first look at results over the Mekong area from SAR FBR. This additional data will also be used to enhance and improve the Altimetry Corrected Elevations (ACE2) Global Digital Elevation Models.

Berry, Philippa; Smith, Richard; Salloway, Mark; Lucas, Bruno Manuel; Dinardo, Salvatore; Benveniste, Jérôme

2013-04-01

179

Cryo-imaging in a toxicological study on mouse fetuses  

NASA Astrophysics Data System (ADS)

We applied the Case cryo-imaging system to detect signals of developmental toxicity in transgenic mouse fetuses resulting from maternal exposure to a developmental environmental toxicant (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD). We utilized a fluorescent transgenic mouse model that expresses Green Fluorescent Protein (GFP) exclusively in smooth muscles under the control of the smooth muscle gamma actin (SMGA) promoter (SMGA/EGFP mice kindly provided by J. Lessard, U. Cincinnati). Analysis of cryo-image data volumes, comprising of very high-resolution anatomical brightfield and molecular fluorescence block face images, revealed qualitative and quantitative morphological differences in control versus exposed fetuses. Fetuses randomly chosen from pregnant females euthanized on gestation day (GD) 18 were either manually examined or cryo-imaged. For cryo-imaging, fetuses were embedded, frozen and cryo-sectioned at 20 ?m thickness and brightfield color and fluorescent block-face images were acquired with an in-plane resolution of ~15 ?m. Automated 3D volume visualization schemes segmented out the black embedding medium and blended fluorescence and brightfield data to produce 3D reconstructions of all fetuses. Comparison of Treatment groups TCDD GD13, TCDD GD14 and control through automated analysis tools highlighted differences not observable by prosectors performing traditional fresh dissection. For example, severe hydronephrosis, suggestive of irreversible kidney damage, was detected by cryoimaging in fetuses exposed to TCDD. Automated quantification of total fluorescence in smooth muscles revealed suppressed fluorescence in TCDD-exposed fetuses. This application demonstrated that cryo-imaging can be utilized as a routine high-throughput screening tool to assess the effects of potential toxins on the developmental biology of small animals.

Roy, Debashish; Gargesha, Madhusudhana; Sloter, Eddie; Watanabe, Michiko; Wilson, David

2010-03-01

180

The fine structure of Entamoeba histolytica processed by cryo-fixation and cryo-substitution.  

PubMed

Recently, the use of cryo-fixation followed by freeze-substitution has been shown to produce a better ultrastructural preservation of cellular components due to the rapidity of the fixation procedure and the lack of distortion during dehydration. When these techniques are applied to study the fine structure of axenically cultured trophozoites of E. histolytica, an improved preservation of cytoplasmic and nuclear components was found. The surface coat of the parasite appears much thicker and uniform than in conventionally treated samples. Also, the ground substance of the cytoplasm is packed with fibrogranular material, which is usually extracted by chemical fixation. The extremely fast fixation procedure allows the visualization of fusion and/or fission processes of cytoplasmic vacuoles and vesicles. Nuclear microtubules and cytoplasmic microfilaments are clearly identified. Low-temperature techniques allow not only a better preservation of the cell structure of E. histolytica parasites, but will also facilitate considerably future immunoelectronmicroscopical studies. PMID:1340327

González-Robles, A; Martínez-Palomo, A

1992-01-01

181

On-chip magnetic separation and encapsulation of cells in droplets.  

PubMed

Single cell study is gaining importance because of the cell-to-cell variation that exists within cell population, even after significant initial sorting. Analysis of such variation at the gene expression level could impact single cell functional genomics, cancer, stem-cell research, and drug screening. The on-chip monitoring of individual cells in an isolated environment would prevent cross-contamination, provide high recovery yield, and enable study of biological traits at a single cell level. These advantages of on-chip biological experiments is a significant improvement for a myriad of cell analyses methods, compared to conventional methods, which require bulk samples and provide only averaged information on cell structure and function. We report on a device that integrates a mobile magnetic trap array with microfluidic technology to provide the possibility of separation of immunomagnetically labeled cells and their encapsulation with reagents into picoliter droplets for single cell analysis. The simultaneous reagent delivery and compartmentalization of the cells immediately following sorting are all performed seamlessly within the same chip. These steps offer unique advantages such as the ability to capture cell traits as originated from its native environment, reduced chance of contamination, minimal use of the reagents, and tunable encapsulation characteristics independent of the input flow. Preliminary assay on cell viability demonstrates the potential for the device to be integrated with other up- or downstream on-chip modules to become a powerful single-cell analysis tool. PMID:23370785

Chen, Aaron; Byvank, Tom; Chang, Woo-Jin; Bharde, Atul; Vieira, Greg; Miller, Brandon L; Chalmers, Jeffrey J; Bashir, Rashid; Sooryakumar, Ratnasingham

2013-03-21

182

Synthesis, characterization and photocatalytic activity of magnetically separable hexagonal Ni/ZnO nanostructure.  

PubMed

The hexagonal zinc oxide coated nickel (Ni/ZnO) nanostructure photocatalyst has successfully been prepared by the reduction of nickel chloride hexahydrate using hydrazine hydrate through the solvothermal process at 140 °C followed by surface modification of the product by the reflux method at 110 °C for 1 h. The X-ray diffraction (XRD) pattern showed that the 'as prepared' sample consists of face centered cubic Ni and hexagonal wurtzite ZnO without any traces of impurity. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images confirmed the formation of nickel nanoparticles under solvothermal conditions. These nickel nanoparticles, when subjected to reflux, formed the hexagonal zinc oxide coated nickel nanostructure. Fourier transform infrared (FTIR) spectra, photoluminescence (PL) and Raman studies also confirmed the presence of zinc oxide in the hybrid nanostructure. The growth mechanism for the development of the hexagonal zinc oxide coated nickel (Ni/ZnO) nanostructure has also been proposed. The appearance of the hysteresis loop, in the as-prepared Ni/ZnO hybrid nanostructure, demonstrated its ferromagnetic character at room temperature. The hexagonal Ni/ZnO nanostructure also acts as an efficient photocatalyst in the degradation of methylene blue under ultraviolet light irradiation. It is observed that the catalytic efficiency of the hybrid nanocatalyst is better compared to pure zinc oxide. Most importantly, the Ni/ZnO catalyst could also be easily separated, simply by applying an external magnetic field, and reused. PMID:22975724

Senapati, Samarpita; Srivastava, Suneel K; Singh, Shiv B

2012-10-21

183

Chemical interferences when using high gradient magnetic separation for phosphate removal: consequences for lake restoration.  

PubMed

A promising method for lake restoration is the treatment of lake inlets through the specific adsorption of phosphate (P) on strongly magnetizable particles (Fe) and their subsequent removal using in-flow high gradient magnetic separation (HGMS) techniques. In this work, we report an extensive investigation on the chemical interferences affecting P removal efficiencies in natural waters from 20 Mediterranean ponds and reservoirs. A set of three treatments were considered based on different Fe particles/P concentration ratios. High P removal efficiencies (>80%) were found in freshwater lakes (conductivities<600 ? S cm(-1)). However, a significant reduction in P removal was observed for extremely high mineralized waters. Correlation analysis showed that major cations (Mg(2+), Na(+) and K(+)) and anions (SO(4)(2-) and Cl(-)) played an essential role in P removal efficiency. Comparison between different treatments have shown that when increasing P and Fe concentrations at the same rate or when increasing Fe concentrations for a fixed P concentration, there exist systematic reductions in the slope of the regression lines relating P removal efficiency and the concentration of different chemical variables. These results evidence a general reduction in the chemical competition between P and other ions for adsorption sites on Fe particles. Additional analyses also revealed a reduction in water color, dissolved organic carbon (DOC) and reactive silicate (Si) concentrations with the addition of Fe microparticles. PMID:21741173

de Vicente, I; Merino-Martos, A; Guerrero, F; Amores, V; de Vicente, J

2011-09-15

184

A paper-based surface-enhanced resonance Raman spectroscopic (SERRS) immunoassay using magnetic separation and enzyme-catalyzed reaction.  

PubMed

In this study, a novel paper-based SERRS immunoassay based on magnetic separation and alkaline phosphatase (ALP) enzyme catalyzed hydrolysis reaction was developed. By using modified antibodies conjugated to magnetic beads, capture of mouse IgG followed by addition of ALP-labeled antibodies would form a sandwich-like immunoconjugate. After magnetic separation, 5-bromo-4-chloro-3-indolyl phosphate (BCIP), a low SERRS active compound, was added as the substrate for ALP to generate a high SERRS response. Detection was conducted on a silver colloid/PVP/filter paper SERS substrate by spotting a pre-aggregated silver colloid sol onto polyvinyl pyrrolidone (PVP) modified filter paper using a semi-automatic TLC sample applicator. The optimization of the highly SERS active paper-based substrate, dynamic hydrolysis process of BCIP, quantitative detection of IgG, and selectivity of the assay was studied in detail. By taking advantage of magnetic separation in order to decrease the background interference, the selective enzyme reaction involved in producing a highly SERRS active product could detect mouse IgG from 1 to 500 ng mL(-1) with a LOD of 0.33 ng mL(-1). PMID:23486763

Chen, Yuanyuan; Cheng, Hanwen; Tram, Kha; Zhang, Shengfeng; Zhao, Yanhua; Han, Liyang; Chen, Zengping; Huan, Shuangyan

2013-05-01

185

Superconducting open-gradient magnetic separation for the pretreatment of radioactive or mixed waste vitrification feeds. 1997 annual progress report  

SciTech Connect

'Vitrification has been selected as a final waste form technology in the US for long-term storage of high-level radioactive wastes (HLW). However, a foreseeable problem during vitrification in some waste feed streams lies in the presence of elements (e.g., transition metals) in the HLW that may cause instabilities in the final glass product. The formation of spinel compounds, such as Fe{sub 3}O{sub 4} and FeCrO{sub 4}, results in glass phase separation and reduces vitrifier lifetime, and durability of the final waste form. A superconducting open gradient magnetic separation (OGMS) system maybe suitable for the removal of the deleterious transition elements (e.g. Fe, Co, and Ni) and other elements (lanthanides) from vitrification feed streams due to their ferromagnetic or paramagnetic nature. The OGMS systems are designed to deflect and collect paramagnetic minerals as they interact with a magnetic field gradient. This system has the potential to reduce the volume of HLW for vitrification and ensure a stable product. In order to design efficient OGMS and High gradient magnetic separation (HGMS) processes, a fundamental understanding of the physical and chemical properties of the waste feed streams is required. Using HLW simulant and radioactive fly ash and sludge samples from the Savannah River Technology Center, Rocky Flats site, and the Hanford reservation, several techniques were used to characterize and predict the separation capability for a superconducting OGMS system.'

Doctor, R.; Nunez, L. [Argonne National Lab., IL (US); Cicero-Herman, C.A. [Westinghouse Savannah River Co., Aiken, SC (US). Savannah River Technology Center; Ritter, J.A. [Univ. of South Carolina, Columbia, SC (US). Chemical Engineering Dept.; Landsberger, S. [Univ. of Texas, Austin, TX (US). Nuclear Engineering Dept.

1997-01-01

186

Correlative Cryo-electron Tomography and Optical Microscopy of Cells  

PubMed Central

The biological processes occurring in a cell are complex and dynamic, and to achieve a comprehensive understanding of the molecular mechanisms underlying these processes, both temporal and spatial information is required. While cryo-electron tomography (cryoET) provides three-dimensional (3D) still pictures of near-native state cells and organelles at molecular resolution, fluorescence light microscopy (fLM) offers movies of dynamic cellular processes in living cells. Combining and integrating these two commonly used imaging modalities (termed correlative microscopy) provides a powerful means to not only expand the imaging scale and resolution but also to complement the dynamic information available from optical microscopy with the molecular-level, 3D ultrastructure detail provided by cryoET. As such, a correlative approach performed on a given specimen can provide high resolution snapshots of dynamic cellular events. In this article, I review recent advances in correlative light microscopy and cryoET and discuss major findings made available by applying this method. PMID:23962486

Zhang, Peijun

2013-01-01

187

Navigation for fluoroscopy-guided cryo-balloon ablation procedures of atrial fibrillation  

NASA Astrophysics Data System (ADS)

Atrial fibrillation (AFib), the most common arrhythmia, has been identified as a major cause of stroke. The current standard in interventional treatment of AFib is the pulmonary vein isolation (PVI). PVI is guided by fluoroscopy or non-fluoroscopic electro-anatomic mapping systems (EAMS). Either classic point-to-point radio-frequency (RF)- catheter ablation or so-called single-shot-devices like cryo-balloons are used to achieve electrically isolation of the pulmonary veins and the left atrium (LA). Fluoroscopy-based systems render overlay images from pre-operative 3-D data sets which are then merged with fluoroscopic imaging, thereby adding detailed 3-D information to conventional fluoroscopy. EAMS provide tracking and visualization of RF catheters by means of electro-magnetic tracking. Unfortunately, current navigation systems, fluoroscopy-based or EAMS, do not provide tools to localize and visualize single shot devices like cryo-balloon catheters in 3-D. We present a prototype software for fluoroscopy-guided ablation procedures that is capable of superimposing 3-D datasets as well as reconstructing cyro-balloon catheters in 3-D. The 3-D cyro-balloon reconstruction was evaluated on 9 clinical data sets, yielded a reprojected 2-D error of 1.72 mm +/- 1.02 mm.

Bourier, Felix; Brost, Alexander; Kleinoeder, Andreas; Kurzendorfer, Tanja; Koch, Martin; Kiraly, Attila; Schneider, Hans-Juergen; Hornegger, Joachim; Strobel, Norbert; Kurzidim, Klaus

2012-02-01

188

Separation and correlation of structural and magnetic roughness in a Ni thin film by polarized off-specular neutron reflectometry  

NASA Astrophysics Data System (ADS)

Diffuse (off-specular) neutron and x-ray reflectometry has been used extensively for the determination of interface morphology in solids and liquids. For neutrons, a novel possibility is off-specular reflectometry with polarized neutrons to determine the morphology of a magnetic interface. There have been few such attempts due to the lower brilliance of neutron sources, though magnetic interaction of neutrons with atomic magnetic moments is much easier to comprehend and easily tractable theoretically. We have obtained a simple and physically meaningful expression, under the Born approximation, for analyzing polarized diffuse (off-specular) neutron reflectivity (PDNR) data. For the first time PDNR data from a Ni film have been analyzed and separate chemical and magnetic morphologies have been quantified. Also specular polarized neutron reflectivity measurements have been carried out to measure the magnetic moment density profile of the Ni film. The fit to PDNR data results in a longer correlation length for in-plane magnetic roughness than for chemical (structural) roughness. The magnetic interface is smoother than the chemical interface.

Singh, Surendra; Basu, Saibal

2009-02-01

189

Towards an electro-magnetic field separation of deposited material implemented in an ion beam sputter process  

SciTech Connect

Nowadays, Ion Beam Sputter (IBS) processes are very well optimized on an empirical basis. To achieve further progresses, a modification of the IBS process by guiding the coating material using an axial magnetic field and an additional electrical field has been studied. The electro-magnetic (EM) field leads to a significant change in plasma properties and deposition rate distributions, whereas an increase in deposition rate along the centerline of the axial EM field around 150% was observed. These fundamental studies on the prototype are the basis for the development of an applicable and workable design of a separation device.

Malobabic, Sina; Jupe, Marco; Ristau, Detlev [Laser Component Department, Laser Zentrum Hannover e.V., Hollerithallee 8, 30149 Hannover (Germany) [Laser Component Department, Laser Zentrum Hannover e.V., Hollerithallee 8, 30149 Hannover (Germany); Quest: Centre of Quantum Engineering and Space-Time Research, Leibniz Universitaet Hannover, Hannover (Germany)

2013-06-03

190

Microfluidically Cryo-Cooled Planar Coils for Magnetic Resonance Imaging  

E-print Network

finger becomes single fluidic channel. ........................................... 68 26. (a) Capacitance of the PPT capacitor when filling water and mineral oil as dielectric fluid through the microchannels placed between two metal plates and (b) Q... factor of the PPT capacitor. ................................................................. 70 27. (a) Capacitance of the IDT capacitor when filling water, mineral oil and BSTO-oil mixture as dielectric fluid through the capacitor and (b) Q factor...

Koo, Chiwan

2013-08-09

191

Fast characterisation of cell-derived extracellular vesicles by nanoparticles tracking analysis, cryo-electron microscopy, and Raman tweezers microspectroscopy  

PubMed Central

The joint use of 3 complementary techniques, namely, nanoparticle tracking analysis (NTA), cryo-electron microscopy (Cryo-EM) and Raman tweezers microspectroscopy (RTM), is proposed for a rapid characterisation of extracellular vesicles (EVs) of various origins. NTA is valuable for studying the size distribution and concentration, Cryo-EM is outstanding for the morphological characterisation, including observation of vesicle heterogeneity, while RTM provides the global chemical composition without using any exogenous label. The capabilities of this approach are evaluated on the example of cell-derived vesicles of Dictyostelium discoideum, a convenient general model for eukaryotic EVs. At least 2 separate species differing in chemical composition (relative amounts of DNA, lipids and proteins, presence of carotenoids) were found for each of the 2 physiological states of this non-pathogenic microorganism, that is, cell growth and starvation-induced aggregation. These findings demonstrate the specific potency of RTM. In addition, the first Raman spectra of human urinary exosomes are reported, presumably constituting the primary step towards Raman characterisation of EVs for the purpose of human diseases diagnoses. PMID:24009887

Tatischeff, Irene; Larquet, Eric; Falcon-Perez, Juan M.; Turpin, Pierre-Yves; Kruglik, Sergei G.

2012-01-01

192

Separation Anxiety  

NSDL National Science Digital Library

In this activity, learners discover the primary physical properties used to separate pure substances from mixtures. Learners use test tubes, beakers, magnets, and other tools to separate a mixture of sand, iron filings, salt, popcorn kernels, and poppyseeds. This activity introduces learners to the basic properties of size, magnetism, density and solubility while emphasizing that chemistry involves separating out substances either to understand what they are or to use the pure components to create new substances.

Yu, Julie

2007-01-01

193

GEOPHYSICS, VOL. 63, NO. 2 (MARCH-APRIL 1998); P. 431439, 13 FIGS. Separation of regional and residual magnetic field data  

E-print Network

underground sources. The targets for specific surveys are often small-scale structures buried at shallow and residual magnetic field data Yaoguo Li and Douglas W. Oldenburg ABSTRACT Wepresentamethodforseparatingregionalandresid- ual magnetic fields using a 3-D magnetic inversion al- gorithm. The separation is achieved

Oldenburg, Douglas W.

194

Beam-energy dependence of charge separation along the magnetic field in Au+Au collisions at RHIC.  

PubMed

Local parity-odd domains are theorized to form inside a quark-gluon plasma which has been produced in high-energy heavy-ion collisions. The local parity-odd domains manifest themselves as charge separation along the magnetic field axis via the chiral magnetic effect. The experimental observation of charge separation has previously been reported for heavy-ion collisions at the top RHIC energies. In this Letter, we present the results of the beam-energy dependence of the charge correlations in Au+Au collisions at midrapidity for center-of-mass energies of 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV from the STAR experiment. After background subtraction, the signal gradually reduces with decreased beam energy and tends to vanish by 7.7 GeV. This implies the dominance of hadronic interactions over partonic ones at lower collision energies. PMID:25126911

Adamczyk, L; Adkins, J K; Agakishiev, G; Aggarwal, M M; Ahammed, Z; Alekseev, I; Alford, J; Anson, C D; Aparin, A; Arkhipkin, D; Aschenauer, E C; Averichev, G S; Banerjee, A; Beavis, D R; Bellwied, R; Bhasin, A; Bhati, A K; Bhattarai, P; Bichsel, H; Bielcik, J; Bielcikova, J; Bland, L C; Bordyuzhin, I G; Borowski, W; Bouchet, J; Brandin, A V; Brovko, S G; Bültmann, S; Bunzarov, I; Burton, T P; Butterworth, J; Caines, H; Calderón de la Barca Sánchez, M; Cebra, D; Cendejas, R; Cervantes, M C; Chaloupka, P; Chang, Z; Chattopadhyay, S; Chen, H F; Chen, J H; Chen, L; Cheng, J; Cherney, M; Chikanian, A; Christie, W; Chwastowski, J; Codrington, M J M; Contin, G; Cramer, J G; Crawford, H J; Cui, X; Das, S; Davila Leyva, A; De Silva, L C; Debbe, R R; Dedovich, T G; Deng, J; Derevschikov, A A; Derradi de Souza, R; Dhamija, S; di Ruzza, B; Didenko, L; Dilks, C; Ding, F; Djawotho, P; Dong, X; Drachenberg, J L; Draper, J E; Du, C M; Dunkelberger, L E; Dunlop, J C; Efimov, L G; Engelage, J; Engle, K S; Eppley, G; Eun, L; Evdokimov, O; Eyser, O; Fatemi, R; Fazio, S; Fedorisin, J; Filip, P; Finch, E; Fisyak, Y; Flores, C E; Gagliardi, C A; Gangadharan, D R; Garand, D; Geurts, F; Gibson, A; Girard, M; Gliske, S; Greiner, L; Grosnick, D; Gunarathne, D S; Guo, Y; Gupta, A; Gupta, S; Guryn, W; Haag, B; Hamed, A; Han, L-X; Haque, R; Harris, J W; Heppelmann, S; Hirsch, A; Hoffmann, G W; Hofman, D J; Horvat, S; Huang, B; Huang, H Z; Huang, X; Huck, P; Humanic, T J; Igo, G; Jacobs, W W; Jang, H; Judd, E G; Kabana, S; Kalinkin, D; Kang, K; Kauder, K; Ke, H W; Keane, D; Kechechyan, A; Kesich, A; Khan, Z H; Kikola, D P; Kisel, I; Kisiel, A; Koetke, D D; Kollegger, T; Konzer, J; Koralt, I; Kotchenda, L; Kraishan, A F; Kravtsov, P; Krueger, K; Kulakov, I; Kumar, L; Kycia, R A; Lamont, M A C; Landgraf, J M; Landry, K D; Lauret, J; Lebedev, A; Lednicky, R; Lee, J H; LeVine, M J; Li, C; Li, W; Li, X; Li, X; Li, Y; Li, Z M; Lisa, M A; Liu, F; Ljubicic, T; Llope, W J; Lomnitz, M; Longacre, R S; Luo, X; Ma, G L; Ma, Y G; Madagodagettige Don, D M M D; Mahapatra, D P; Majka, R; Margetis, S; Markert, C; Masui, H; Matis, H S; McDonald, D; McShane, T S; Minaev, N G; Mioduszewski, S; Mohanty, B; Mondal, M M; Morozov, D A; Mustafa, M K; Nandi, B K; Nasim, Md; Nayak, T K; Nelson, J M; Nigmatkulov, G; Nogach, L V; Noh, S Y; Novak, J; Nurushev, S B; Odyniec, G; Ogawa, A; Oh, K; Ohlson, A; Okorokov, V; Oldag, E W; Olvitt, D L; Pachr, M; Page, B S; Pal, S K; Pan, Y X; Pandit, Y; Panebratsev, Y; Pawlak, T; Pawlik, B; Pei, H; Perkins, C; Peryt, W; Pile, P; Planinic, M; Pluta, J; Poljak, N; Porter, J; Poskanzer, A M; Pruthi, N K; Przybycien, M; Pujahari, P R; Putschke, J; Qiu, H; Quintero, A; Ramachandran, S; Raniwala, R; Raniwala, S; Ray, R L; Riley, C K; Ritter, H G; Roberts, J B; Rogachevskiy, O V; Romero, J L; Ross, J F; Roy, A; Ruan, L; Rusnak, J; Rusnakova, O; Sahoo, N R; Sahu, P K; Sakrejda, I; Salur, S; Sandweiss, J; Sangaline, E; Sarkar, A; Schambach, J; Scharenberg, R P; Schmah, A M; Schmidke, W B; Schmitz, N; Seger, J; Seyboth, P; Shah, N; Shahaliev, E; Shanmuganathan, P V; Shao, M; Sharma, B; Shen, W Q; Shi, S S; Shou, Q Y; Sichtermann, E P; Singaraju, R N; Skoby, M J; Smirnov, D; Smirnov, N; Solanki, D; Sorensen, P; Spinka, H M; Srivastava, B; Stanislaus, T D S; Stevens, J R; Stock, R; Strikhanov, M; Stringfellow, B; Sumbera, M; Sun, X; Sun, X M; Sun, Y; Sun, Z; Surrow, B; Svirida, D N; Symons, T J M; Szelezniak, M A; Takahashi, J; Tang, A H; Tang, Z; Tarnowsky, T; Thomas, J H; Timmins, A R; Tlusty, D; Tokarev, M; Trentalange, S; Tribble, R E; Tribedy, P; Trzeciak, B A; Tsai, O D; Turnau, J; Ullrich, T; Underwood, D G; Van Buren, G; van Nieuwenhuizen, G; Vandenbroucke, M; Vanfossen, J A; Varma, R; Vasconcelos, G M S; Vasiliev, A N; Vertesi, R; Videbæk, F; Viyogi, Y P; Vokal, S; Voloshin, S A; Vossen, A; Wada, M; Wang, F; Wang, G; Wang, H; Wang, J S; Wang, X L; Wang, Y; Wang, Y; Webb, G; Webb, J C; Westfall, G D; Wieman, H; Wissink, S W; Witt, R; Wu, Y F; Xiao, Z; Xie, W; Xin, K; Xu, H; Xu, J; Xu, N; Xu, Q H; Xu, Y; Xu, Z; Yan, W; Yang, C; Yang, Y; Yang, Y; Ye, Z; Yepes, P; Yi, L; Yip, K; Yoo, I-K; Yu, N; Zawisza, Y; Zbroszczyk, H; Zha, W; Zhang, J B; Zhang, J L; Zhang, S; Zhang, X P; Zhang, Y; Zhang, Z P; Zhao, F; Zhao, J; Zhong, C; Zhu, X; Zhu, Y H; Zoulkarneeva, Y; Zyzak, M

2014-08-01

195

Beam-energy dependence of charge separation along the magnetic field in Au+Au collisions at RHIC  

E-print Network

Local parity-odd domains are theorized to form inside a Quark-Gluon-Plasma (QGP) which has been produced in high-energy heavy-ion collisions. The local parity-odd domains manifest themselves as charge separation along the magnetic field axis via the chiral magnetic effect (CME). The experimental observation of charge separation has previously been reported for heavy-ion collisions at the top RHIC energies. In this paper, we present the results of the beam-energy dependence of the charge correlations in Au+Au collisions at midrapidity for center-of-mass energies of 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV from the STAR experiment. After background subtraction, the signal gradually reduces with decreased beam energy, and tends to vanish by 7.7 GeV. The implications of these results for the CME will be discussed.

STAR Collaboration; L. Adamczyk; J. K. Adkins; G. Agakishiev; M. M. Aggarwal; Z. Ahammed; I. Alekseev; J. Alford; C. D. Anson; A. Aparin; D. Arkhipkin; E. C. Aschenauer; G. S. Averichev; A. Banerjee; D. R. Beavis; R. Bellwied; A. Bhasin; A. K. Bhati; P. Bhattarai; H. Bichsel; J. Bielcik; J. Bielcikova; L. C. Bland; I. G. Bordyuzhin; W. Borowski; J. Bouchet; A. V. Brandin; S. G. Brovko; S. Bültmann; I. Bunzarov; T. P. Burton; J. Butterworth; H. Caines; M. Calderón de la Barca Sánchez; D. Cebra; R. Cendejas; M. C. Cervantes; P. Chaloupka; Z. Chang; S. Chattopadhyay; H. F. Chen; J. H. Chen; L. Chen; J. Cheng; M. Cherney; A. Chikanian; W. Christie; J. Chwastowski; M. J. M. Codrington; G. Contin; J. G. Cramer; H. J. Crawford; X. Cui; S. Das; A. Davila Leyva; L. C. De Silva; R. R. Debbe; T. G. Dedovich; J. Deng; A. A. Derevschikov; R. Derradi de Souza; S. Dhamija; B. di Ruzza; L. Didenko; C. Dilks; F. Ding; P. Djawotho; X. Dong; J. L. Drachenberg; J. E. Draper; C. M. Du; L. E. Dunkelberger; J. C. Dunlop; L. G. Efimov; J. Engelage; K. S. Engle; G. Eppley; L. Eun; O. Evdokimov; O. Eyser; R. Fatemi; S. Fazio; J. Fedorisin; P. Filip; E. Finch; Y. Fisyak; C. E. Flores; C. A. Gagliardi; D. R. Gangadharan; D. Garand; F. Geurts; A. Gibson; M. Girard; S. Gliske; L. Greiner; D. Grosnick; D. S. Gunarathne; Y. Guo; A. Gupta; S. Gupta; W. Guryn; B. Haag; A. Hamed; L-X. Han; R. Haque; J. W. Harris; S. Heppelmann; A. Hirsch; G. W. Hoffmann; D. J. Hofman; S. Horvat; B. Huang; H. Z. Huang; X. Huang; P. Huck; T. J. Humanic; G. Igo; W. W. Jacobs; H. Jang; E. G. Judd; S. Kabana; D. Kalinkin; K. Kang; K. Kauder; H. W. Ke; D. Keane; A. Kechechyan; A. Kesich; Z. H. Khan; D. P. Kikola; I. Kisel; A. Kisiel; D. D. Koetke; T. Kollegger; J. Konzer; I. Koralt; L. K. Kosarzewski; L. Kotchenda; A. F. Kraishan; P. Kravtsov; K. Krueger; I. Kulakov; L. Kumar; R. A. Kycia; M. A. C. Lamont; J. M. Landgraf; K. D. Landry; J. Lauret; A. Lebedev; R. Lednicky; J. H. Lee; M. J. LeVine; C. Li; W. Li; X. Li; X. Li; Y. Li; Z. M. Li; M. A. Lisa; F. Liu; T. Ljubicic; W. J. Llope; M. Lomnitz; R. S. Longacre; X. Luo; G. L. Ma; Y. G. Ma; D. M. M. D. Madagodagettige Don; D. P. Mahapatra; R. Majka; S. Margetis; C. Markert; H. Masui; H. S. Matis; D. McDonald; T. S. McShane; N. G. Minaev; S. Mioduszewski; B. Mohanty; M. M. Mondal; D. A. Morozov; M. K. Mustafa; B. K. Nandi; Md. Nasim; T. K. Nayak; J. M. Nelson; G. Nigmatkulov; L. V. Nogach; S. Y. Noh; J. Novak; S. B. Nurushev; G. Odyniec; A. Ogawa; K. Oh; A. Ohlson; V. Okorokov; E. W. Oldag; D. L. Olvitt Jr.; M. Pachr; B. S. Page; S. K. Pal; Y. X. Pan; Y. Pandit; Y. Panebratsev; T. Pawlak; B. Pawlik; H. Pei; C. Perkins; W. Peryt; P. Pile; M. Planinic; J. Pluta; N. Poljak; K. Poniatowska; J. Porter; A. M. Poskanzer; N. K. Pruthi; M. Przybycien; P. R. Pujahari; J. Putschke; H. Qiu; A. Quintero; S. Ramachandran; R. Raniwala; S. Raniwala; R. L. Ray; C. K. Riley; H. G. Ritter; J. B. Roberts; O. V. Rogachevskiy; J. L. Romero; J. F. Ross; A. Roy; L. Ruan; J. Rusnak; O. Rusnakova; N. R. Sahoo; P. K. Sahu; I. Sakrejda; S. Salur; J. Sandweiss; E. Sangaline; A. Sarkar; J. Schambach; R. P. Scharenberg; A. M. Schmah; W. B. Schmidke; N. Schmitz; J. Seger; P. Seyboth; N. Shah; E. Shahaliev; P. V. Shanmuganathan; M. Shao; B. Sharma; W. Q. Shen; S. S. Shi; Q. Y. Shou; E. P. Sichtermann; R. N. Singaraju; M. J. Skoby; D. Smirnov; N. Smirnov; D. Solanki; P. Sorensen; H. M. Spinka; B. Srivastava; T. D. S. Stanislaus; J. R. Stevens; R. Stock; M. Strikhanov; B. Stringfellow; M. Sumbera; X. Sun; X. M. Sun; Y. Sun; Z. Sun; B. Surrow; D. N. Svirida; T. J. M. Symons; M. A. Szelezniak; J. Takahashi; A. H. Tang; Z. Tang; T. Tarnowsky; J. H. Thomas; A. R. Timmins; D. Tlusty; M. Tokarev; S. Trentalange; R. E. Tribble; P. Tribedy; B. A. Trzeciak; O. D. Tsai; J. Turnau; T. Ullrich; D. G. Underwood; G. Van Buren; G. van Nieuwenhuizen; M. Vandenbroucke; J. A. Vanfossen, Jr.; R. Varma; G. M. S. Vasconcelos; A. N. Vasiliev; R. Vertesi; F. Videbæk; Y. P. Viyogi; S. Vokal; A. Vossen; M. Wada; F. Wang; G. Wang; H. Wang; J. S. Wang; X. L. Wang; Y. Wang; Y. Wang; G. Webb; J. C. Webb; G. D. Westfall; H. Wieman; S. W. Wissink; R. Witt; Y. F. Wu; Z. Xiao; W. Xie; K. Xin; H. Xu; J. Xu; N. Xu; Q. H. Xu; Y. Xu; Z. Xu; W. Yan; C. Yang; Y. Yang; Y. Yang; Z. Ye; P. Yepes; L. Yi; K. Yip; I-K. Yoo; N. Yu; Y. Zawisza; H. Zbroszczyk; W. Zha; J. B. Zhang; J. L. Zhang; S. Zhang; X. P. Zhang; Y. Zhang; Z. P. Zhang; F. Zhao; J. Zhao; C. Zhong; X. Zhu; Y. H. Zhu; Y. Zoulkarneeva; M. Zyzak

2014-04-05

196

CryoSat Plus For Oceans: an ESA Project for CryoSat-2 Data Exploitation Over Ocean  

NASA Astrophysics Data System (ADS)

The ESA CryoSat-2 mission is the first space mission to carry a space-borne radar altimeter that is able to operate in the conventional pulsewidth-limited (LRM) mode and in the novel Synthetic Aperture Radar (SAR) mode. Although the prime objective of the Cryosat-2 mission is dedicated to monitoring land and marine ice, the SAR mode capability of the Cryosat-2 SIRAL altimeter also presents the possibility of demonstrating significant potential benefits of SAR altimetry for ocean applications, based on expected performance enhancements which include improved range precision and finer along track spatial resolution. With this scope in mind, the "CryoSat Plus for Oceans" (CP4O) Project, dedicated to the exploitation of CryoSat-2 Data over ocean, supported by the ESA STSE (Support To Science Element) programme, brings together an expert European consortium comprising: DTU Space, isardSAT, National Oceanography Centre , Noveltis, SatOC, Starlab, TU Delft, the University of Porto and CLS (supported by CNES),. The objectives of CP4O are: - to build a sound scientific basis for new scientific and operational applications of Cryosat-2 data over the open ocean, polar ocean, coastal seas and for sea-floor mapping. - to generate and evaluate new methods and products that will enable the full exploitation of the capabilities of the Cryosat-2 SIRAL altimeter , and extend their application beyond the initial mission objectives. - to ensure that the scientific return of the Cryosat-2 mission is maximised. In particular four themes will be addressed: -Open Ocean Altimetry: Combining GOCE Geoid Model with CryoSat Oceanographic LRM Products for the retrieval of CryoSat MSS/MDT model over open ocean surfaces and for analysis of mesoscale and large scale prominent open ocean features. Under this priority the project will also foster the exploitation of the finer resolution and higher SNR of novel CryoSat SAR Data to detect short spatial scale open ocean features. -High Resolution Polar Ocean Altimetry: Combination of GOCE Geoid Model with CryoSat Oceanographic SAR Products over polar oceans for the retrieval of CryoSat MSS/MDT and currents circulations system improving the polar tides models and studying the coupling between blowing wind and current pattern. -High Resolution Coastal Zone Altimetry: Exploitation of the finer resolution and higher SNR of novel CryoSat SAR Data to get the radar altimetry closer to the shore exploiting the SARIn mode for the discrimination of off-nadir land targets (e.g. steep cliffs) in the radar footprint from nadir sea return. -High Resolution Sea-Floor Altimetry: Exploitation of the finer resolution and higher SNR of novel CryoSat SAR Data to resolve the weak short-wavelength sea surface signals caused by sea-floor topography elements and to map uncharted sea-mounts/trenches. One of the first project activities is the consolidation of preliminary scientific requirements for the four themes under investigation. This paper will present the CP4O project content and objectives and will address the first initial results from the on-going work to define the scientific requirements.

Benveniste, J.; Cotton, D.; Clarizia, M.; Roca, M.; Gommenginger, C. P.; Naeije, M. C.; Labroue, S.; Picot, N.; Fernandes, J.; Andersen, O. B.; Cancet, M.; Dinardo, S.; Lucas, B. M.

2012-12-01

197

Synthesis and performance of novel magnetically separable nanospheres of titanium dioxide photocatalyst with egg-like structure.  

PubMed

A magnetically separable photocatalyst TiO(2)/SiO(2)/NiFe(2)O(4) (TSN) nanosphere with egg-like structure was prepared by a unique process that combined a liquid catalytic phase transformation method, reverse micelle technique and chemical precipitation means. The prepared photocatalyst shows high photocatalytic activity for the degradation of methyl orange in water. The magnetic property measurements indicate that the photocatalyst possesses a superparamagnetic nature. It can be separated from water when an external magnetic field is added and redispersed into water solution after the external magnetic field is eliminated. It is one of the promising photocatalysts for wastewater treatment. A transmission electron microscope (TEM) and an x-ray diffractometer (XRD) were used to characterize the structure of the TSN photocatalyst. The results indicate that nickel ferrite core nanoparticles were completely encapsulated into monodisperse silica nanospheres as carrier, and titania nanoparticle aggregates were coated onto the surface of SN nanospheres, forming an imperfect TiO(2) shell for photocatalysis. The SiO(2) layer between the NiFe(2)O(4) core and the TiO(2) shell effectively prevents the injection of charges from TiO(2) particles to NiFe(2)O(4), which gives rise to an increase in photocatalytic activity. Moreover, the recycled TSN exhibits good repeatability of the photocatalytic activity. PMID:21817681

Xu, Shihong; Shangguan, Wenfeng; Yuan, Jian; Chen, Mingxia; Shi, Jianwei; Jiang, Zhi

2008-03-01

198

Correspondence between neutron depolarization and higher order magnetic susceptibility to investigate ferromagnetic clusters in phase separated systems.  

PubMed

It is a tough task to distinguish a short-range ferromagnetically correlated cluster-glass phase from a canonical spin-glass-like phase in many magnetic oxide systems using conventional magnetometry measurements. As a case study, we investigate the magnetic ground state of La0.85Sr0.15CoO3, which is often debated based on phase separation issues. We report the results of two samples of La0.85Sr0.15CoO3 (S-1 and S-2) prepared under different conditions. Neutron depolarization, higher harmonic ac susceptibility and magnetic relaxation studies were carried out along with conventional magnetometry measurements to differentiate subtle changes at the microscopic level. There is no evidence of ferromagnetic correlation in the sample S-2 attributed to a spin-glass phase, and this is compounded by the lack of existence of a second order component of higher harmonic ac susceptibility and neutron depolarization. A magnetic relaxation experiment at different temperatures complements the spin glass characteristic in S-2. All these signal a sharp variance when we consider the cluster-glass-like phase (phase separated) in S-1, especially when prepared from an improper chemical synthesis process. This shows that the nonlinear ac susceptibility is a viable tool to detect ferromagnetic clusters such as those the neutron depolarization study can reveal. PMID:24275331

Manna, Kaustuv; Samal, D; Bera, A K; Elizabeth, Suja; Yusuf, S M; Kumar, P S Anil

2014-01-01

199

Optimization of human corneal endothelial cells for culture: the removal of corneal stromal fibroblast contamination using magnetic cell separation.  

PubMed

The culture of human corneal endothelial cells (CECs) is critical for the development of suitable graft alternative on biodegradable material, specifically for endothelial keratoplasty, which can potentially alleviate the global shortage of transplant-grade donor corneas available. However, the propagation of slow proliferative CECs in vitro can be hindered by rapid growing stromal corneal fibroblasts (CSFs) that may be coisolated in some cases. The purpose of this study was to evaluate a strategy using magnetic cell separation (MACS) technique to deplete the contaminating CSFs from CEC cultures using antifibroblast magnetic microbeads. Separated "labeled" and "flow-through" cell fractions were collected separately, cultured, and morphologically assessed. Cells from the "flow-through" fraction displayed compact polygonal morphology and expressed Na(+)/K(+)ATPase indicative of corneal endothelial cells, whilst cells from the "labeled" fraction were mostly elongated and fibroblastic. A separation efficacy of 96.88% was observed. Hence, MACS technique can be useful in the depletion of contaminating CSFs from within a culture of CECs. PMID:22287967

Peh, Gary S L; Lee, Man-Xin; Wu, Fei-Yi; Toh, Kah-Peng; Balehosur, Deepashree; Mehta, Jodhbir S

2012-01-01

200

Near-surface epigenetic magnetic indicators of buried hydrocarbons and separation of spurious signals  

Microsoft Academic Search

Significant geochemical alteration zones occurring over buried hydrocarbon deposits can be recognized and mapped by geophysical methods. The authors believe near-surface secondary magnetic minerals formed as a result of seeping hydrocarbons and associated compounds interacting with constituents of the overlying rocks. A new method is described to identify anomalous magnetic signatures associated with this mineralization, and to differentiate that signal

T. J. Donovan; D. P. OBrien; J. G. Bryan; M. A. Shepherd

1986-01-01

201

High-resolution structure of the Shigella type-III secretion needle by solid-state NMR and cryo-electron microscopy  

NASA Astrophysics Data System (ADS)

We introduce a general hybrid approach for determining the structures of supramolecular assemblies. Cryo-electron microscopy (cryo-EM) data define the overall envelope of the assembly and rigid-body orientation of the subunits while solid-state nuclear magnetic resonance (ssNMR) chemical shifts and distance constraints define the local secondary structure, protein fold and inter-subunit interactions. Finally, Rosetta structure calculations provide a general framework to integrate the different sources of structural information. Combining a 7.7-Å cryo-EM density map and 996 ssNMR distance constraints, the structure of the type-III secretion system needle of Shigella flexneri is determined to a precision of 0.4?Å. The calculated structures are cross-validated using an independent data set of 691 ssNMR constraints and scanning transmission electron microscopy measurements. The hybrid model resolves the conformation of the non-conserved N terminus, which occupies a protrusion in the cryo-EM density, and reveals conserved pore residues forming a continuous pattern of electrostatic interactions, thereby suggesting a mechanism for effector protein translocation.

Demers, Jean-Philippe; Habenstein, Birgit; Loquet, Antoine; Kumar Vasa, Suresh; Giller, Karin; Becker, Stefan; Baker, David; Lange, Adam; Sgourakis, Nikolaos G.

2014-09-01

202

High-resolution structure of the Shigella type-III secretion needle by solid-state NMR and cryo-electron microscopy.  

PubMed

We introduce a general hybrid approach for determining the structures of supramolecular assemblies. Cryo-electron microscopy (cryo-EM) data define the overall envelope of the assembly and rigid-body orientation of the subunits while solid-state nuclear magnetic resonance (ssNMR) chemical shifts and distance constraints define the local secondary structure, protein fold and inter-subunit interactions. Finally, Rosetta structure calculations provide a general framework to integrate the different sources of structural information. Combining a 7.7-Å cryo-EM density map and 996 ssNMR distance constraints, the structure of the type-III secretion system needle of Shigella flexneri is determined to a precision of 0.4?Å. The calculated structures are cross-validated using an independent data set of 691 ssNMR constraints and scanning transmission electron microscopy measurements. The hybrid model resolves the conformation of the non-conserved N terminus, which occupies a protrusion in the cryo-EM density, and reveals conserved pore residues forming a continuous pattern of electrostatic interactions, thereby suggesting a mechanism for effector protein translocation. PMID:25264107

Demers, Jean-Philippe; Habenstein, Birgit; Loquet, Antoine; Kumar Vasa, Suresh; Giller, Karin; Becker, Stefan; Baker, David; Lange, Adam; Sgourakis, Nikolaos G

2014-01-01

203

Vitrification of thick samples for soft X-ray cryo-tomography by high pressure freezing.  

PubMed

Soft X-ray cryo-microscopy (cryo-XT) offers an ideal complement to electron cryo-microscopy (cryo-EM). Cryo-XT is applicable to samples more than an order of magnitude thicker than cryo-EM, albeit at a more modest resolution of tens of nanometers. Furthermore, the natural contrast obtained in the "water-window" by differential absorption by organic matter vs water yields detailed images of organelles, membranes, protein complexes, and other cellular components. Cryo-XT is thus ideally suited for tomography of eukaryotic cells. The increase in sample thickness places more stringent demands on sample preparation, however. The standard method for cryo-EM, i.e., plunging to a cryogenic fluid such as liquid ethane, is no longer ideally suited to obtain vitrification of thick samples for cryo-XT. High pressure freezing is an alternative approach, most closely associated with freeze-substitution and embedding, or with electron cryo-microscopy of vitreous sections (CEMOVIS). We show here that high pressure freezing can be adapted to soft X-ray tomography of whole vitrified samples, yielding a highly reliable method that avoids crystallization artifacts and potentially offers improved imaging conditions in samples not amenable to plunge-freezing. PMID:23079478

Weiner, Allon; Kapishnikov, Sergey; Shimoni, Eyal; Cordes, Sandra; Guttmann, Peter; Schneider, Gerd; Elbaum, Michael

2013-01-01

204

On a plasma sheath separating regions of oppositely directed magnetic field  

Microsoft Academic Search

Summary  An exact solution of the Vlasov equations is found which describes a layer of plasma confined between two regions of oppositely\\u000a directed magnetic field. The electrons and ions have Maxwellian distributions on the plane where the magnetic field vanishes.\\u000a In the coordinate system, in which the electron and ion drift velocities are equal in magnitude but opposite in direction,\\u000a the

E. G. Harris

1962-01-01

205

Cryo-balloon catheter position planning using AFiT  

NASA Astrophysics Data System (ADS)

Atrial fibrillation (AFib) is the most common heart arrhythmia. In certain situations, it can result in life-threatening complications such as stroke and heart failure. For paroxsysmal AFib, pulmonary vein isolation (PVI) by catheter ablation is the recommended choice of treatment if drug therapy fails. During minimally invasive procedures, electrically active tissue around the pulmonary veins is destroyed by either applying heat or cryothermal energy to the tissue. The procedure is usually performed in electrophysiology labs under fluoroscopic guidance. Besides radio-frequency catheter ablation devices, so-called single-shot devices, e.g., the cryothermal balloon catheters, are receiving more and more interest in the electrophysiology (EP) community. Single-shot devices may be advantageous for certain cases, since they can simplify the creation of contiguous (gapless) lesion sets around the pulmonary vein which is needed to achieve PVI. In many cases, a 3-D (CT, MRI, or C-arm CT) image of a patient's left atrium is available. This data can then be used for planning purposes and for supporting catheter navigation during the procedure. Cryo-thermal balloon catheters are commercially available in two different sizes. We propose the Atrial Fibrillation Planning Tool (AFiT), which visualizes the segmented left atrium as well as multiple cryo-balloon catheters within a virtual reality, to find out how well cryo-balloons fit to the anatomy of a patient's left atrium. First evaluations have shown that AFiT helps physicians in two ways. First, they can better assess whether cryoballoon ablation or RF ablation is the treatment of choice at all. Second, they can select the proper-size cryo-balloon catheter with more confidence.

Kleinoeder, Andreas; Brost, Alexander; Bourier, Felix; Koch, Martin; Kurzidim, Klaus; Hornegger, Joachim; Strobel, Norbert

2012-02-01

206

NASA IN-STEP Cryo System Experiment flight test  

Microsoft Academic Search

The Cryo System Experiment (CSE), a NASA In-Space Technology Experiments Program (IN-STEP) flight experiment, was flown on Space Shuttle Discovery (STS 63) in February 1995. The experiment was developed by Hughes Aircraft Company to validate in zero-g space a 65 K cryogenic system for focal planes, optics, instruments or other equipment (gamma-ray spectrometers and infrared and submillimetre imaging instruments) that

S. C. Russo; R. S. Sugimura

1996-01-01

207

Development of a cryopreservation procedure using aluminium cryo-plates.  

PubMed

A cryopreservation procedure using an aluminium cryo-plate was successfully developed using in vitro-grown Dalmatian chrysanthemum (Tanacetum cinerariifolium) shoot tips. Shoot cultures were cold-hardened at 5 degree C on MS medium containing 0.5 M sucrose over a period of 20 to 40 days. Shoot tips with basal plate (1.0-1.5 x 1.0 mm) were dissected from shoot cultures and precultured at 5 degree C for 2 days on MS medium containing 0.5 M sucrose. Precultured shoot tips were placed on aluminium cryo-plates (7 mm x 37 mm x 0.5 mm) with 10 wells (diameter 1.5 mm, depth 0.75 mm) and embedded in alginate gel. Osmoprotection was performed by immersing the cryo-plates for 30 or 60 min in 25 ml pipetting reservoirs filled with loading solution (2 M glycerol + 1.4 M sucrose). For dehydration, the loading solution was replaced with PVS 7M vitrification solution (30 percent glycerol, 19.5 percent ethylene glycol and 0.6 M sucrose in liquid MS basal medium), which was applied for 40 min. After rapid immersion in liquid nitrogen, shoot tips attached to the cryo-plates were rewarmed by immersion in cryotubes containing 2 ml 1 M sucrose solution. Using this procedure, regrowth of cryopreserved shoot tips of line 28v-75 reached 77 degree. This protocol was successfully applied to six additional lines, with high regrowth percentages ranging from 65 to 90 percent. By contrast, the modified vitrification protocol tested as a reference produced only moderate regrowth percentages. This new method displays many advantages and will facilitate large scale cryostorage in genebank. PMID:21766155

Yamamoto, Shin-ichi; Rafique, Tariq; Priyantha, Wickramage Saman; Fukui, Kuniaki; Matsumoto, Toshikazu; Niino, Takao

2011-01-01

208

Cryo Electron Tomography of Herpes Simplex Virus during Axonal Transport and Secondary Envelopment in Primary Neurons  

PubMed Central

During herpes simplex virus 1 (HSV1) egress in neurons, viral particles travel from the neuronal cell body along the axon towards the synapse. Whether HSV1 particles are transported as enveloped virions as proposed by the ‘married’ model or as non-enveloped capsids suggested by the ‘separate’ model is controversial. Specific viral proteins may form a recruitment platform for microtubule motors that catalyze such transport. However, their subviral location has remained elusive. Here we established a system to analyze herpesvirus egress by cryo electron tomography. At 16 h post infection, we observed intra-axonal transport of progeny HSV1 viral particles in dissociated hippocampal neurons by live-cell fluorescence microscopy. Cryo electron tomography of frozen-hydrated neurons revealed that most egressing capsids were transported independently of the viral envelope. Unexpectedly, we found not only DNA-containing capsids (cytosolic C-capsids), but also capsids lacking DNA (cytosolic A-/B-capsids) in mid-axon regions. Subvolume averaging revealed lower amounts of tegument on cytosolic A-/B-capsids than on C-capsids. Nevertheless, all capsid types underwent active axonal transport. Therefore, even few tegument proteins on the capsid vertices seemed to suffice for transport. Secondary envelopment of capsids was observed at axon terminals. On their luminal face, the enveloping vesicles were studded with typical glycoprotein-like spikes. Furthermore, we noted an accretion of tegument density at the concave cytosolic face of the vesicle membrane in close proximity to the capsids. Three-dimensional analysis revealed that these assembly sites lacked cytoskeletal elements, but that filamentous actin surrounded them and formed an assembly compartment. Our data support the ‘separate model’ for HSV1 egress, i.e. progeny herpes viruses being transported along axons as subassemblies and not as complete virions within transport vesicles. PMID:22194682

Ibiricu, Iosune; Huiskonen, Juha T.; Dohner, Katinka; Bradke, Frank; Sodeik, Beate; Grunewald, Kay

2011-01-01

209

Capture and separation of biomolecules using magnetic beads in a simple microfluidic channel without an external flow device.  

PubMed

The use of microfluidic devices and magnetic beads for applications in biotechnology has been extensively explored over the past decade. Many elaborate microfluidic chips have been used in efficient systems for biological assays. However most fail to achieve the ideal point of care (POC) status, as they require larger conventional external devices in conjunction with the microchip. This paper presents a simple technique to capture and separate biomolecules using magnetic bead movement on a microchip without the use of an external flow device. This microchip consisted of two well reservoirs (W1 and W2) connected via a tapered microchannel. Beads were dragged through the microchannel between the two wells at an equivalent speed to a permanent magnet that moved alongside the microchip. More than 95% of beads were transferred from W1 to W2 within 2 min at an average velocity of 0.7 mm s(-1). Enzymatic reactions were employed to test our microchip. Specifically, three assays were performed using the streptavidin coated magnetic beads as a solid support to capture and transfer biomolecules: (1) non-specific adsorption of the substrate, 6-8-difluoro-4-methylumbelliferyl phosphate (DiFMUP), (2) capture of the enzyme, biotinylated alkaline phosphatase (AP), and (3) separation of AP from DiFMUP. Our non-specific adsorption assay indicated that the microchip was capable of transferring the beads with less than 0.002% carryover of DiFMUP. Our capture assay indicated efficient capture and transfer of AP with beads to W2 containing DiFMUP, where the transferred AP converted 100% of DiFMUP to DiFMU within 15 minutes. Our separation assay showed effective separation of AP from DiFMUP and elucidated the binding capacity of the beads for AP. The leftover unbound AP in W1 converted 100% of DiFMUP within 10 minutes and samples with less than the full bead capacity of AP (i.e. all AP was transferred) did not convert any of the DiFMUP. The immobilization of AP on the bead surface resulted in 32% reduced enzymatic speed compared to that of free AP in solution, as a result of altered protein conformation and/or steric hindrance of the catalytic site. Overall, this microfluidic platform was established as a simple, efficient and effective approach for separating biomolecules without any flow apparatus. PMID:24051541

Wang, Jingjing; Morabito, Kenneth; Erkers, Tom; Tripathi, Anubhav

2013-11-01

210

Data quality assessment of CryoSat products  

NASA Astrophysics Data System (ADS)

The main payload of CryoSat is a Ku band pulsewidth limited radar altimeter, called SIRAL (Synthetic interferometric radar altimeter), that transmits pulses at a high pulse repetition frequency thus making the received echoes phase coherent and suitable for azimuth processing. This allows to reach a significantly improved along track resolution with respect to traditional pulse-width limited altimeters. There are three operating modes: low resolution mode (LRM), Synthetic Aperture Radar (SAR) and Synthetic Aperture Radar Interferometric (SARIn). Both the Level 1b and the Level 2 data products are defined depending on the operating mode used by the instrument. However, Level 1b products essentially contain an average echo for each location along the ground track while Level 2 products contains an elevation for each location along the satellite track. In this poster we will detail as first the different data products and then the quality achieved on those products will be described after more than 2 years of operational activity of the CryoSat satellite. In particular, the characteristics of the impulse response function in the two direction, the along track and the across track, will be described in order to verify that the performance are in line with expectation as well as stable over the time. To exploit the stability over the 2 years of mission, the products obtained as outcomes of the reprocessing activity will be exploited, allowing to manage an homogeneous set of data processed with the latest version of the CryoSat IPF.

Scagliola, Michele; Bouzinac, Catherine; Fornari, Marco; Mannan, Rubinder

2013-04-01

211

Hydration-layer models for cryo-EM image simulation  

PubMed Central

To compare cryo-EM images and 3D reconstructions with atomic structures in a quantitative way it is essential to model the electron scattering by solvent (water or ice) that surrounds protein assemblies. The most rigorous method for determing the density of solvating water atoms for this purpose has been to perform molecular-dynamics (MD) simulations of the protein-water system. In this paper we adapt the ideas of bulk-water modeling that are used in the refinement of X-ray crystal structures to the cryo-EM solvent-modeling problem. We present a continuum model for solvent density which matches MD-based results to within sampling errors. However, we also find that the simple binary-mask model of Jiang and Brünger (1994) performs nearly as well as the new model. We conclude that several methods are now available for rapid and accurate modeling of cryo-EM images and maps of solvated proteins. PMID:22609687

Shang, Zhiguo; Sigworth, Fred J.

2013-01-01

212

Cryo-EM modeling by the molecular dynamics flexible fitting method  

PubMed Central

The increasing power and popularity of cryo-electron (cryo-EM) microscopy in structural biology brought about the development of so-called hybrid methods, which permit the interpretation of cryo-EM density maps beyond their nominal resolution in terms of atomic models. The Cryo-EM Modeling Challenge 2010 is the first community effort to bring together developers of hybrid methods as well as cryo-EM experimentalists. Participating in the challenge, the molecular dynamics flexible fitting (MDFF) method was applied to a number of cryo-EM density maps. The results are described here with special emphasis on the use of symmetry-based restraints to improve the quality of atomic models derived from density maps of symmetric complexes; on a comparison of the stereochemical quality of atomic models resulting from different hybrid methods; and on application of MDFF to electron crystallography data. PMID:22696404

Chan, Kwok-Yan; Trabuco, Leonardo G.; Schreiner, Eduard; Schulten, Klaus

2012-01-01

213

Self-assembled monolayers improve protein distribution on holey carbon cryo-EM supports  

PubMed Central

Poor partitioning of macromolecules into the holes of holey carbon support grids frequently limits structural determination by single particle cryo-electron microscopy (cryo-EM). Here, we present a method to deposit, on gold-coated carbon grids, a self-assembled monolayer whose surface properties can be controlled by chemical modification. We demonstrate the utility of this approach to drive partitioning of ionotropic glutamate receptors into the holes, thereby enabling 3D structural analysis using cryo-EM methods. PMID:25403871

Meyerson, Joel R.; Rao, Prashant; Kumar, Janesh; Chittori, Sagar; Banerjee, Soojay; Pierson, Jason; Mayer, Mark L.; Subramaniam, Sriram

2014-01-01

214

Inactivation and magnetic separation of bacteria from liquid suspensions using electrosprayed and nonelectrosprayed nZVI particles: observations and mechanisms.  

PubMed

Here, nonelectrosprayed nanoscale zerovalent iron (NE-nZVI), electrosprayed nZVI (E-nZVI) and preoxidized nZVI (O-nZVI) particles were applied to inactivating Bacillus subtilis, Escherichia coli as well as bacteria in various wastewater samples. In addition, magnetic separation was applied to the mixture of 0.2 mL bacterial sample and 1.8 mL E-nZVI or NE-nZVI suspensions. Bacterial concentrations and optical density of the supernatants were analyzed using culturing, optical adsorption and qPCR tests. In general, for wastewater samples the inactivations were shown to range from 1-log to 3-log. PCR-DGGE analysis indicated that no gene mutation occurred when bacteria were treated with nZVI. Using magnetic separation, significant physical removals, revealed as a function of nZVI type (NE-,E- and O-nZVI) and bacterial concentration, up to 6-log were obtained. E-nZVI and NE-nZVI were shown to react differently with B. subtilis and E. coli, although exhibiting similar inactivation rates. qPCR tests detected higher amount of DNA in the supernatants from mixing E. coli with NE-nZVI, but less for E-nZVI. However, the opposite was observed with B. subtilis. Our data together with optical adsorption analysis suggested that the inactivation and magnetic separation mainly depend on Fe(0)/Fe(3)O(4) shell compositions, the type of bacteria (aerobic and anaerobic) and their concentrations. PMID:22264123

Chen, Qi; Gao, Min; Li, Jing; Shen, Fangxia; Wu, Yan; Xu, Zhenqiang; Yao, Maosheng

2012-02-21

215

Water-compatible magnetic imprinted microspheres for rapid separation and determination of triazine herbicides in environmental water.  

PubMed

A novel kind of water-compatible magnetic imprinted cyromazine microsphere (WCMM) was synthesized by water/oil/water suspension polymerization. The obtained WCMM was homogenously spherical with porous morphology and strong magnetic properties. The microspheres were successfully used as adsorbent in dispersive solid-phase extraction (WCMM-dSPE) to selectively extract cyanazine and atrazine from environmental water. Good linearity of the two analytes was observed in the range from 2.5 to 200.0ngmL(-1). The average recoveries at three spiking levels ranged from 84.8% to 104.3% with relative standard deviations (RSD) less than 6.9%. Compared with magnetic non-imprinted particles (WCMN), the proposed WCMM adsorbent of dSPE efficiently improved the efficiency of extracting cyanazine and atrazine from environmental water samples and eliminated the effect of cyromazine leakage on the quantitative analysis of cyanazine and atrazine. The proposed WCMM-dSPE method combined the advantages of magnetic separation, molecular imprinted microspheres and dSPE. PMID:24657415

Qiao, Fengxia; Row, Kyung Ho; Wang, Mengge

2014-04-15

216

Validation of CryoSat-2 Elevation Measurements along the Greenland Inland Traverse  

NASA Astrophysics Data System (ADS)

The Greenland Ice Sheet's sensitivity to climate change and potential contribution to sea-level rise make its mass balance of critical interest. Altimeter surveys of ice sheet elevation changes are a common method used to estimate changes in ice volume and mass balance. In-situ validation of CryoSat-2's measurements is key to assessing the satellite's performance. The 2011 Greenland Inland Traverse (GrIT) provides a detailed elevation profile across 1120km of the Greenland Ice Sheet. We compare GrIT Kinematic GPS elevations to remotely sensed elevation values from CryoSat-2's synthetic aperture interferometric radar altimeter (SIRAL). We examine CryoSat-2 measurement repeatability by comparing "crossover" points from ascending and descending satellite tracks. Overall CryoSat-2 crossover elevations agree, though some repeat measurements differ due to varying surface slope and facies conditions. Comparison of in-situ GPS data along the traverse with CryoSat-2 measured elevations reveals a small but constant vertical offset between GPS and CryoSat-2 elevation measurements. Comparing the mean GPS elevation within a single footprint reduces the offset. Calibrating CryoSat-2 elevations with GPS elevation measurements improves confidence in CryoSat-2 elevation values. Spatially extensive surface elevation measurements from CryoSat-2, validated with GrIT survey-grade GPS and combined with improved accumulation estimates, will reduce uncertainty in the mass balance of the Greenland Ice Sheet.

Overly, T. B.; Hawley, R. L.; Wong, G. J.; Lutz, E.; Osterberg, E. C.; Courville, Z.

2012-12-01

217

Origin of ferromagnetism and nano-scale phase separations in diluted magnetic semiconductors  

Microsoft Academic Search

This paper reviews various origins of ferromagnetic response that has been detected in diluted magnetic semiconductors (DMS). Particular attention is paid to those ferromagnetic DMS in which no precipitation of other crystallographic phases has been observed. It is argued that these materials can be divided into three categories. The first consists of (Ga,Mn)As and related compounds. In these solid solutions

Tomasz Dietl

2006-01-01

218

Interim cryo-cooler/detector report  

SciTech Connect

This report describes development of an electronic system designed to reduce vibration generated by a cryocooler. The diminished vibration makes it practical to use the active cooler to extract heat from a portable gamma ray detector instrument. The system was developed for a Sunpower cryocooler with an integrated counterbalance mass. The overall momentum cancellation approach is also applicable to other similar cryocoolers. The cancellation system is an assembly of several components tailored to accomplish the required vibration reduction with minimum power consumption and volume. It is designed to be powered by a 18--32 Volt battery. Up to ten harmonics of the 58.65 Hz drive frequency are controlled. In addition to the vibration cancellation, the electronic system produces the drive signal for the cryocooler and regulates the cooler temperature. The system employs a sinusoidal drive to reduce the amount of higher harmonic vibration. A digital signal processor (DSP) is used to perform the high speed vibration control. The Texas Instruments TMS320C31 processor is housed on a third-party board. A second board has analog-to-digital (A/D) and digital-to-analog (D/A) converters. The DSP was programmed in C. The physical system consists of two sets of electronics. The first is housed in a case that is separate from the detector unit.

Neufeld, K.; Ruhter, W. [Lawrence Livermore National Lab., CA (United States); Anderson, E. [CSA Engineering, Inc., Palo Alto, CA (United States)

1995-04-19

219

Multifunctional superparamagnetic nanoshells: combining two-photon luminescence imaging, surface-enhanced Raman scattering and magnetic separation.  

PubMed

With the increasing need for multi-purpose analysis in the biomedical field, traditional single diagnosis methods cannot meet the requirements. Therefore new multifunctional technologies and materials for the integration of sample collection, sensing and imaging are in great demand. Core-shell nanoparticles offer a unique platform to combine multifunctions in a single particle. In this work, we have constructed a novel type of core-shell superparamagnetic nanoshell (Fe3O4@SiO2@Au), composed of a Fe3O4 cluster core, a thin Au shell and a SiO2 layer in between. The obtained multifunctional nanoparticles combine the magnetic properties and plasmonic optical properties effectively, which were well investigated by a number of experimental characterization methods and theoretical simulations. We have demonstrated that Fe3O4@SiO2@Au nanoparticles can be utilized for two-photon luminescence (TPL) imaging, near-infrared surface-enhanced Raman scattering (NIR SERS) and cell collection by magnetic separation. The TPL intensity could be further greatly enhanced through the plasmon coupling effect in the self-assembled nanoparticle chains, which were triggered by an external magnetic field. In addition, Fe3O4@SiO2@Au nanoparticles may have great potential applications such as enhanced magnetic resonance imaging (MRI) and photo-thermotherapy. Successful combination of multifunctions including magnetic response, biosensing and bioimaging in single nanoparticles allows further manipulation, real-time tracking, and intracellular molecule analysis of live cells at a single-cell level. PMID:25329447

Jin, Xiulong; Li, Haiyan; Wang, Shanshan; Kong, Ni; Xu, Hong; Fu, Qihua; Gu, Hongchen; Ye, Jian

2014-11-01

220

Cell labeling and magnetic separation by means of immunoreagents based on polyacrolein microspheres.  

PubMed

Polyacrolein (PA) microspheres were synthesized by means of ionizing radiation and shown to contain aldehyde groups which form covalent bounds with amino compounds and proteins. PA microspheres made fluorescent after reaction with fluorescein-labeled antibodies were found to specifically label sensitized sheep red blood cells (SRBC). PA microspheres could also be grafted onto a variety of polymeric spheres of different sizes and composition by ionizing radiation. These hybrid spheres, i.e., preformed polymeric spheres with PA microspheres grafted on their surfaces could bind antibodies which retained specificity of reaction with cell surface receptors. Purification of sensitized SRBC from a mixture containing chicken red blood cells (CRBC) by means of hybrids magnetic spheres in a magnetic field was demonstrated. PMID:7130709

Rembaum, A; Yen, R C; Kempner, D H; Ugelstad, J

1982-08-13

221

Development of an aptamer-based impedimetric bioassay using microfluidic system and magnetic separation for protein detection.  

PubMed

An aptamer-based impedimetric bioassay using the microfluidic system and magnetic separation was developed for the sensitive and rapid detection of protein. The microfluidic impedance device was fabricated through integrating the gold interdigitated array microelectrode into a flow cell made of polydimethylsiloxane (PDMS). Aptamer modified magnetic beads were used to capture and separate the target protein, and concentrated into a suitable volume. Then the complexes were injected into the microfluidic flow cell for impedance measurement. To demonstrate the high performance of this novel detection system, thrombin was employed as the target protein. The results showed that the impedance signals at the frequency of 90 kHz have a good linearity with the concentrations of thrombin in a range from 0.1 nM to 10nM and the detection limit is 0.01 nM. Compared with the reported impedimetric aptasensors for thrombin detection, this method possesses several advantages, such as the increasing sensitivity, improving reproducibility, reducing sample volume and assay time. All these demonstrate the proposed detection system is an alternative way to enable sensitive, rapid and specific detection of protein. PMID:24709326

Wang, Yixian; Ye, Zunzhong; Ping, Jianfeng; Jing, Shunru; Ying, Yibin

2014-09-15

222

Dual-responsive magnetic core-shell nanoparticles for nonviral gene delivery and cell separation.  

PubMed

We present the synthesis of dual-responsive (pH and temperature) magnetic core-shell nanoparticles utilizing the grafting-from approach. First, oleic acid stabilized superparamagnetic maghemite (?-Fe(2)O(3)) nanoparticles (NPs), prepared by thermal decomposition of iron pentacarbonyl, were surface-functionalized with ATRP initiating sites bearing a dopamine anchor group via ligand exchange. Subsequently, 2-(dimethylamino)ethyl methacrylate (DMAEMA) was polymerized from the surface by ATRP, yielding dual-responsive magnetic core-shell NPs (?-Fe(2)O(3)@PDMAEMA). The attachment of the dopamine anchor group on the nanoparticle's surface is shown to be reversible to a certain extent, resulting in a grafting density of 0.15 chains per nm(2) after purification. Nevertheless, the grafted NPs show excellent long-term stability in water over a wide pH range and exhibit a pH- and temperature-dependent reversible agglomeration, as revealed by turbidimetry. The efficiency of ?-Fe(2)O(3)@PDMAEMA hybrid nanoparticles as a potential transfection agent was explored under standard conditions in CHO-K1 cells. Remarkably, ?-Fe(2)O(3)@PDMAEMA led to a 2-fold increase in the transfection efficiency without increasing the cytotoxicity, as compared to polyethyleneimine (PEI), and yielded on average more than 50% transfected cells. Moreover, after transfection with the hybrid nanoparticles, the cells acquired magnetic properties that could be used for selective isolation of transfected cells. PMID:22296556

Majewski, Alexander P; Schallon, Anja; Jérôme, Valérie; Freitag, Ruth; Müller, Axel H E; Schmalz, Holger

2012-03-12

223

Magnetic bead-based separation of sperm from buccal epithelial cells using a monoclonal antibody against MOSPD3.  

PubMed

Forensic DNA analysis of sexual assault evidence requires unambiguous differentiation of DNA profiles in mixed samples. To investigate the feasibility of magnetic bead-based separation of sperm from cell mixtures using a monoclonal antibody against MOSPD3 (motile sperm domain-containing protein 3), 30 cell samples were prepared by mixing 10(4) female buccal epithelial cells with sperm cells of varying densities (10(3), 10(4), or 10(5) cells/mL). Western blot and immunofluorescence assays showed that MOSPD3 was detectable on the membrane of sperm cells, but not in buccal epithelial cells. After biotinylated MOSPD3 antibody was incubated successively with the prepared cell mixtures and avidin-coated magnetic beads, microscopic observation revealed that each sperm cell was bound by two or more magnetic beads, in the head, neck, mid-piece, or flagellum. A full single-source short tandem repeat profile could be obtained in 80 % of mixed samples containing 10(3) sperm cells/mL and in all samples containing ?10(4) sperm cells/mL. For dried vaginal swab specimens, the rate of successful detection was 100 % in both flocked and cotton swabs preserved for 1 day, 87.5 % in flocked swabs and 40 % in cotton swabs preserved for 3 days, and 40 % in flocked swabs and 16.67 % in cotton swabs preserved for 10 days. Our findings suggest that immunomagnetic bead-based separation is potentially a promising alternative to conventional methods for isolating sperm cells from mixed forensic samples. PMID:24590379

Li, Xue-Bo; Wang, Qing-Shan; Feng, Yu; Ning, Shu-Hua; Miao, Yuan-Ying; Wang, Ye-Quan; Li, Hong-Wei

2014-11-01

224

Greek "red mud" residue: a study of microwave reductive roasting followed by magnetic separation for a metallic iron recovery process.  

PubMed

The present research work is focused on the development of an alternative microwave reductive roasting process of red mud using lignite (30.15 wt.%Cfix), followed by wet magnetic separation, in order to produce a raw material suitable for sponge or cast iron production. The reduction degree of iron was controlled by both the reductive agent content and the microwave heating time. The reduction followed the Fe?O? ? Fe?O? ? FeO ? Fe sequence. The dielectric constants [real (?') and imaginary (??) permittivities] of red mud-lignite mixture were determined at 2.45 GHz, in the temperature range of 25-1100 °C. The effect of parameters such as temperature, intensity of reducing conditions, intensity of magnetic field and dispersing agent addition rate on the result of both processes was investigated. The phase's transformations in reduction process with microwave heating were determined by X-ray diffraction analysis (XRD) in combination with thermogravimetric/differential thermal analysis (TGA/DTA). The microstructural and morphological characterization of the produced calcines was carried out by scanning electron microscopy (SEM). At the optimum conditions a magnetic concentrate with total iron concentration of 35.15 and 69.3 wt.% metallization degree was obtained. PMID:23611801

Samouhos, Michail; Taxiarchou, Maria; Tsakiridis, Petros E; Potiriadis, Konstantinos

2013-06-15

225

Magnetic separation of heavy metal ions and evaluation based on surface-enhanced Raman spectroscopy: copper(II) ions as a case study.  

PubMed

A new approach was developed for the magnetic separation of copper(II) ions with easy operation and high efficiency. p-Mercaptobenzoic acid served as the modified tag of Fe2O3@Au nanoparticles both for the chelation ligand and Raman reporter. Through the chelation between the copper(II) ions and carboxyl groups on the gold shell, the Fe2O3@Au nanoparticles aggregated to form networks that were enriched and separated from the solution by a magnet. A significant decrease in the concentration of copper(II) ions in the supernatant solution was observed. An extremely sensitive method based on surface-enhanced Raman spectroscopy was employed to detect free copper(II) ions that remained after the magnetic separation, and thus to evaluate the separation efficiency. The results indicated the intensities of the surface-enhanced Raman spectroscopy bands from p-mercaptobenzoic acid were dependent on the concentration of copper(II) ions, and the concentration was decreased by several orders of magnitude after the magnetic separation. The present protocol effectively decreased the total amount of heavy metal ions in the solution. This approach opens a potential application in the magnetic separation and highly sensitive detection of heavy metal ions. PMID:24106161

Yan, Xue; Zhang, Xue-Jiao; Yuan, Ya-Xian; Han, San-Yang; Xu, Min-Min; Gu, Ren'ao; Yao, Jian-Lin

2013-11-01

226

Does contamination buildup limit throughput for automated cryoEM?  

PubMed

The development of automated systems for data acquisition in cryo electron microscopy has enabled the possibility of acquiring very large number of images from a single specimen grid. We have demonstrated that over images of 250,000 single particles can be acquired in a 24 h period. This has raised questions as to whether contamination buildup on the specimen limits the quality of the data that can be acquired during these long duration experiments and also whether the data acquisition session could be extended to allow acquisition of more than 1,000,000 particles. We report here a systematic characterization of contamination of specimens maintained for long periods of time at liquid nitrogen temperatures using standard side entry cryo stages. As part of this characterization we developed a more reliable method for accurately estimating specimen ice thickness. Using the method, we were able to calibrate image contrast against ice thickness under a variety of magnifications, objective aperture positions, and defoci, and demonstrated the strong dependence of the calibration curve on these parameters. The results show the anti-contamination aperture is, as expected, critical to the prevention of contamination and that loading film into the microscope dramatically increases the contamination rate, particularly in the first 3 h after the insertion of the film box. In the absence of film, we were able to reproducibly demonstrate that the contamination rate can be limited to a rate of approximately 1 angstrom/h providing reassurance that contamination will not be a major limiting factor for long term cryoEM experiments if a CCD camera is used for the imaging. PMID:16632377

Cheng, Anchi; Fellmann, Denis; Pulokas, James; Potter, Clinton S; Carragher, Bridget

2006-06-01

227

Concentration influences on recovery in a high gradient magnetic separation axial filter  

SciTech Connect

The buildup differential equations for the case of a single wire in high gradient magnetic filtration (HGMF)-axial configuration taking into account the suspension concentration are solved. A new equation for the deposit contour surface at different moments and for different suspension concentrations are obtained. The existence of a particulate suspension concentration, for which the radial extension velocity of deposit is maximum, is evidenced. The recovery for an ordered ferromagnetic matrix is calculated. The influence of the solid particle concentration from suspension on the filtration efficiency is presented.

Murariu, V.; Rezlescu, N.; Rotariu, O.; Badescu, V. [Inst. of Technical Physics, Iasi (Romania)] [Inst. of Technical Physics, Iasi (Romania)

1998-05-01

228

Beam Breakup Studies for New Cryo-Unit  

SciTech Connect

In this paper, we report the numerical simulations of cumulative beam breakup studies for a new cryo-unit for booster design at Jefferson lab. The system consists of two 1-cell and one 7-cell superconducting RF cavities. Combining two 1-cell into a 2-cell together with a 7-cell is also an option. Simulations have been performed using the 2-dimensional time-domain code. The 1-cell+1-cell+7-cell combination confirms beam stability, however, the arrangement 2-cell+7-cell shows instability.

S. Ahmed, I. Shin, R. Kazimi, F. Marhauser ,F. Hannon ,G. Krafft ,B. Yunn ,A. Hofler

2011-03-01

229

Sample preparation induced artifacts in cryo-electron tomographs.  

PubMed

We investigated the effects of sample preparation and of the exposure to an electron beam on particles in cryo-electron tomographs. Various virus particles with icosahedral symmetry were examined, allowing a comparison of symmetrically related components that should be identical in structure but might be affected differently by these imaging artifacts. Comparison of tomographic reconstructions with previously determined structures established by an independent method showed that neither freezing nor electron beam exposure produced a significant amount of shrinkage along the z axis (thickness). However, we observed damage to regions of the particles located close to the surface of the vitreous ice. PMID:23040048

Plevka, Pavel; Battisti, Anthony J; Winkler, Dennis C; Tars, Kaspars; Holdaway, Heather A; Bator, Carol M; Rossmann, Michael G

2012-10-01

230

The long-term storage of cryo-preserved materials  

NASA Astrophysics Data System (ADS)

Were traces of oestrogen present in veal ten years ago, or has it been used for only a short time very recently? There is no scientist who can answer this question, even with the most advanced analytical techniques. This is because unchanged reference specimens from ten years ago are not available. The Cryo-Bank-Krefeld was set up in West Germany at the beginning of 1980, offering facilities for the storage of all types of substances for posterity by preservation with liquid nitrogen.

Thoma, K.

231

Design of Countercurrent Separation of Ginkgo biloba Terpene Lactones by Nuclear Magnetic Resonance  

PubMed Central

Terpene lactones such as bilobalide, ginkgolides A, B, C, and J are major bioactive compounds of Ginkgo biloba L. Purification of these compounds is tedious due to their similar chemical properties. For the purpose of developing an effective and efficient method for both analytical and preparative separation of terpene lactones in G. biloba, an innovative orthogonality-enhanced high-speed countercurrent chromatography (HSCCC) method was established. Taking advantage of quantitative 1H NMR (qHNMR) methodology, partition coefficients (K) of individual terpene lactones were calculated directly from crude G. biloba leaf extract, using their H-12 signals as distinguishing feature. The partitioning experiment assisted the design of a two dimensional (2D) HSCCC procedure using a pair of orthogonal HSCCC solvent systems (SSs), ChMWat +4 and HEMSoWat +3/0.05%. It was surprising that the resolution of ginkgolides A and B was improved by 25% in the HEMWat +3 SS modified with 0.5% DMSO. Consequently, all five terpene lactones could be well separated with qHNMR purity > 95% from G. biloba leaf extract. The separation was further evaluated by offline qHNMR analysis of HSCCC fractions associated with Gaussian curve fitting. The results showed less than 2% error in HSCCC retention predicted from the partitioning experiment. This compelling consistency demonstrates that qHNMR-derived K determination (“K-by-NMR”) can be used to predict CCC fractionation and target purification of analytes from complex mixtures. Furthermore, Gaussian curve fitting enabled an accurate prediction of less than 2% impurity in the CCC fraction, which demonstrates its potential as a powerful tool to study the presence of minor constituents, especially when they are beyond the detection limit of conventional spectroscopic detectors. PMID:22579361

Qiu, Feng; Friesen, Brent J.; McAlpine, James B.; Pauli, Guido F.

2012-01-01

232

High-precision correlative fluorescence and electron cryo microscopy using two independent alignment markers?  

PubMed Central

Correlative light and electron microscopy (CLEM) is an emerging technique which combines functional information provided by fluorescence microscopy (FM) with the high-resolution structural information of electron microscopy (EM). So far, correlative cryo microscopy of frozen-hydrated samples has not reached better than micrometre range accuracy. Here, a method is presented that enables the correlation between fluorescently tagged proteins and electron cryo tomography (cryoET) data with nanometre range precision. Specifically, thin areas of vitrified whole cells are examined by correlative fluorescence cryo microscopy (cryoFM) and cryoET. Novel aspects of the presented cryoCLEM workflow not only include the implementation of two independent electron dense fluorescent markers to improve the precision of the alignment, but also the ability of obtaining an estimate of the correlation accuracy for each individual object of interest. The correlative workflow from plunge-freezing to cryoET is detailed step-by-step for the example of locating fluorescence-labelled adenovirus particles trafficking inside a cell. PMID:24262358

Schellenberger, Pascale; Kaufmann, Rainer; Siebert, C. Alistair; Hagen, Christoph; Wodrich, Harald; Grunewald, Kay

2014-01-01

233

Characterization of model soil colloids by cryo-scanning electron microscopy  

E-print Network

morphology at the observation scale. Cryo-SEM was applied to the study of wet-state model soil colloidsCharacterization of model soil colloids by cryo- scanning electron microscopy M. Nègre a, , P: a soil humic acid, a commercial smectite, a synthetic ferrihydrite and their binary and ternary

Boyer, Edmond

234

Automation for Cryo-TEM: From Specimen Grid to 3D  

E-print Network

Automation for Cryo-TEM: From Specimen Grid to 3D Map B. Carragher, D. Fellmann, N. Kisseberth, R://www.itg.uiuc.edu #12;AUTOMATION FOR CRYO-TEM: FROM SPECIMEN GRID TO 3D MAP B. Carragher, D. Fellmann, N. Kisseberth, R using other methods. The field however suffers from several major disadvantages related to the time

235

Magnetic phase separation in LaMn1-xFexO3+y  

NASA Astrophysics Data System (ADS)

We have investigated the LaMn1-xFexO3+y system in the whole range of 0<=x<=1, for polycrystalline samples prepared by solid state reaction in air. All samples show orthorhombic structure (space group Pnma). For x=0 the oxygen excess, estimated to be y ˜ 0.1, produces vacancies in the La and Mn sites and generates a fraction around 20% of Mn^4+ ions (3t2g) and 80% of the usual Mn^3+ ions (3t2g, 1eg), with possible double exchange interaction between them. The Fe-doping in this system is known to produce only stable Fe^3+ ions (3t2g, 2eg). We find an evolution from a fairly strong ferromagnetic (FM) behavior, with saturation magnetization (T=2K) mS ˜ 4 ?B and Curie temperature Tc ˜ 160 K, for x=0, to an antiferromagnetic (AFM) behavior, with TN=790 K, for x=1. For intermediate Fe contents a mixed phase scenario occurs, with a gradual decrease (increase) of the FM (AFM) phase, accompanied by a systematic transition broadening for 0.2magnetic-ion types, accounts very well for the mS dependence on Fe doping.

de Lima, O. F.; Coaquira, J. A. H.; de Almeida, R. L.; de Carvalho, L. B.; Malik, S. K.

2008-03-01

236

Local CP-violation and electric charge separation by magnetic fields from lattice QCD  

NASA Astrophysics Data System (ADS)

We study local CP-violation on the lattice by measuring the local correlation between the topological charge density and the electric dipole moment of quarks, induced by a constant external magnetic field. This correlator is found to increase linearly with the external field, with the coefficient of proportionality depending only weakly on temperature. Results are obtained on lattices with various spacings, and are extrapolated to the continuum limit after the renormalization of the observables is carried out. This renormalization utilizes the gradient flow for the quark and gluon fields. Our findings suggest that the strength of local CP-violation in QCD with physical quark masses is about an order of magnitude smaller than a model prediction based on nearly massless quarks in domains of constant gluon backgrounds with topological charge. We also show numerical evidence that the observed local CP-violation correlates with spatially extended electric dipole structures in the QCD vacuum.

Bali, G. S.; Bruckmann, F.; Endr?di, G.; Fodor, Z.; Katz, S. D.; Schäfer, A.

2014-04-01

237

EVIDENCE FOR TWO SEPARATE BUT INTERLACED COMPONENTS OF THE CHROMOSPHERIC MAGNETIC FIELD  

SciTech Connect

Chromospheric fibrils are generally thought to trace out low-lying, mainly horizontal magnetic fields that fan out from flux concentrations in the photosphere. A high-resolution ({approx}0.''1 pixel{sup -1}) image, taken in the core of the Ca II 854.2 nm line and covering an unusually large area, shows the dark fibrils within an active region remnant as fine, looplike features that are aligned parallel to each other and have lengths comparable to a supergranular diameter. Comparison with simultaneous line-of-sight magnetograms confirms that the fibrils are centered above intranetwork areas (supergranular cell interiors), with one end rooted just inside the neighboring plage or strong unipolar network but the other endpoint less clearly defined. Focusing on a particular arcade-like structure lying entirely on one side of a filament channel (large-scale polarity inversion), we find that the total amount of positive-polarity flux underlying this 'fibril arcade' is {approx}50 times greater than the total amount of negative-polarity flux. Thus, if the fibrils represent closed loops, they must consist of very weak fields (in terms of total magnetic flux), which are interpenetrated by a more vertical field that contains most of the flux. This surprising result suggests that the fibrils in unipolar regions connect the network to the nearby intranetwork flux, while the bulk of the network flux links to remote regions of the opposite polarity, forming a second, higher canopy above the fibril canopy. The chromospheric field near the edge of the network thus has an interlaced structure resembling that in sunspot penumbrae.

Reardon, K. P. [Osservatorio Astrofisico di Arcetri, 50125 Firenze (Italy); Wang, Y.-M.; Warren, H. P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Muglach, K., E-mail: kreardon@arcetri.astro.it, E-mail: yi.wang@nrl.navy.mil, E-mail: hwarren@nrl.navy.mil, E-mail: karin.muglach@nasa.gov [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2011-12-01

238

Evidence for Two Separate but Interlaced Components of the Chromospheric Magnetic Field  

NASA Technical Reports Server (NTRS)

Chromospheric fibrils are generally thought to trace out low-lying, mainly horizontal magnetic elds that fan out from flux concentrations in the photosphere. A high-resolution (approximately 0.1" per pixel) image, taken in the core of the Ca II 854.2 nm line and covering an unusually large area, shows the dark brils within an active region remnant as fine, looplike features that are aligned parallel to each other and have lengths comparable to a supergranular diameter. Comparison with simultaneous line-of-sight magnetograms confirms that the fibrils are centered above intranetwork areas (supergranular cell interiors), with one end rooted just inside the neighboring plage or strong unipolar network but the other endpoint less clearly defined. Focusing on a particular arcade-like structure lying entirely on one side of a lament channel (large-scale polarity inversion), we find that the total amount of positive-polarity flux underlying this "fibril arcade" is approximately 50 times greater than the total amount of negative-polarity flux. Thus, if the brils represent closed loops, they must consist of very weak fields (in terms of total magnetic flux), which are interpenetrated by a more vertical field that contains most of the flux. This surprising result suggests that the fibrils in unipolar regions connect the network to the nearby intranetwork flux, while the bulk of the network flux links to remote regions of the opposite polarity, forming a second, higher canopy above the fibril canopy. The chromospheric field near the edge of the network thus has an interlaced structure resembling that in sunspot penumbrae.

Reardom, K. P.; Wang, Y.-M.; Muglach, K.; Warren, H. P.

2011-01-01

239

Cryo-fixation by self-pressurized rapid freezing.  

PubMed

High-pressure freeze fixation is the method of choice to arrest instantly all dynamic and physiological processes inside cells, tissues, and small organisms. Embedded in vitreous ice, such samples can be further processed by freeze substitution or directly analyzed in their fully hydrated state by cryo-electron microscopy of vitreous sections (CEMOVIS) to explore cellular ultrastructure as close as possible to the native state. Here, we describe the procedure of self-pressurized rapid freezing as fast, easy-to-use, and low-cost freeze fixation method, avoiding the usage of a high-pressure freezing (HPF) apparatus. Cells or small organisms are placed in capillary metal tubes, which are tightly closed and plunged directly into liquid ethane cooled by liquid nitrogen. In parts of the tube, crystalline ice is formed and builds up pressure sufficient for the liquid-glass transition of the remaining specimen. The quality of samples is equivalent to preparations by conventional HPF apparatus, allowing for high-resolution cryo-EM applications or for freeze substitution and plastic embedding. PMID:24357364

Grabenbauer, Markus; Han, Hong-Mei; Huebinger, Jan

2014-01-01

240

Hybrid magnetic field formulation based on the losses separation method for modified dynamic inverse Jiles-Atherton model  

NASA Astrophysics Data System (ADS)

Dynamic formulation based on the losses separation method in conducting media for the inverse Jiles-Atherton model is proposed. This formulation is based on the concept of the Hybrid Magnetic Field model (HMF). The HMF consists of the modification of the effective field by introducing two counter-fields associated, respectively, with the eddy current and excess losses. Such a formulation is characterized by seven parameters with five parameters issued from the quasi-static Jiles-Atherton model. Thus, two new parameters related to these fields are added to that defined in the quasi-static model. The identification of these new parameters is based on the measurements of the volumetric energy density. To validate this formulation, measurements are carried out on grain non-oriented Fe-Si 3% electrical sheets.

Hamimid, M.; Mimoune, S. M.; Feliachi, M.

2011-07-01

241

From CryoSat-2 to Sentinel-3 and Beyond  

NASA Astrophysics Data System (ADS)

CryoSat-2 carried into Earth orbit the first altimeter using SAR principles, although similar techniques had been used on earlier Venusian missions. Furthermore, it carries a second antenna and receive chain, and has been very carefully calibrated, allowing interferometry between these antennas. The results of the SAR mode and of the interferometer have met all expectations, with handsome margins. Even before the launch of CryoSat-2 the further development of this concept was underway with the radar for the oceanography mission Sentinel-3. While this radar, named SRAL (SAR Radar Altimeter) does not have the interferometer capability of CryoSat-2's SIRAL (SAR Interferometric Radar Altimeter), it does have a second frequency, to enable direct measurement of the delay induced by the ionospheric electron content. Sentinel-3 will have a sun-synchronous orbit, like ERS and EnviSat, and will have a similar latitudinal range: about 82° north and south, compared to CryoSat's 88°. Sentinel-3 will operate its radar altimeter in the high-resolution SAR mode over coastal oceans and inland water, and will revert to the more classical pulse-width limited mode over the open oceans. The SAR mode generates data at a high rate, so the major limiting factor is the amount of on-board storage. The power consumption is also higher, imposing less critical constraints. For sizing purposes the coastal oceans are defined as waters within 300 km of the continental shorelines. Sentinel-3 is expected to be launched in 2013 and be followed 18 months later by a second satellite of the same design. The next step in the development of this family of radar altimeters is Jason-CS, which will provide Continuity of Service to the existing Jason series of operational oceanography missions. Jason-CS has a very strong heritage from CryoSat but will fly the traditional Jason orbit, which covers latitudes up to 66° from a high altitude of 1330 km. The new radar is called Poseidon-4, to emphasise the connection to Jason, but its concept owes more to Sentinel-3's SRAL. It retains SRAL's dual frequencies and its SAR mode, but adds some further refinements. Most notably, an operating mode in which SAR operations and full performance pulse-width limited mode are available simultaneously, is under study. This would enable the benefits of SAR mode to be achieved over all ocean areas if the volume of data generated could be stored and downlinked to the ground. This problem only becomes tractable if an on-board processing system can be introduced to perform the first level of SAR processing, reducing the data volume by several orders of magnitude. This is also under study. The architecture of the radar has a further improvement, in the extension of digital technology further into the domain of analog radio-frequency electronics. While this is essentially invisible to the scientific user, it will yield an instrument with higher quality and markedly superior stability. The Jason-CS missions (at least two satellites are planned) are currently in a study phase with an implementation decision expected at the end of 2012. The planned launch date for the first mission is 2017.

Francis, R.

2011-12-01

242

Separation of Intra- and Extramyocellular Lipid Signals in Proton MR Spectra by Determination of Their Magnetic Field Distribution  

NASA Astrophysics Data System (ADS)

In skeletal musculature intramyocellular (IMCL) and extramyocellular lipids (EMCL) are stored in compartments of different geometry and experience different magnetic field strengths due to geometrical susceptibility effects. The effect is strong enough to—at least partly—separate IMCL and EMCL contributions in 1H MR spectroscopy, despite IMCL and EMCL consisting of the same substances. The assessment of intramyocellular lipid stores in skeletal musculature by 1H MR spectroscopy plays an important role for studying physiological and pathological aspects of lipid metabolism. Therefore, a method using mathematical tools of Fourier analysis is developed to obtain the magnetic field distribution (MFD) from the measured spectra by deconvolution. A reference lipid spectrum is required which was recorded in tibial yellow bone marrow. It is shown that the separation of IMCL contributions can be performed more precisely—compared to other methods—based on the MFD. Examples of deconvolution in model systems elucidate the principle. Applications of the proposed approach on in vivo examinations in m. soleus and m. tibialis anterior are presented. Fitting the IMCL part of the MFD by a Gaussian lineshape with a linewidth kept fixed with respect to the linewidth of creatine and with the assumption of a smooth but not necessarily symmetrical shape for the EMCL part, the only free fit parameter, the amplitude of the IMCL part, is definite and subtraction leads to the EMCL part in the MFD. This procedure is especially justified for the soleus muscle showing a severely asymmetrical distribution which might lead to a marked overestimation of IMCL using common line fitting procedures.

Steidle, G.; Machann, J.; Claussen, C. D.; Schick, F.

2002-02-01

243

Nuclear magnetic resonance studies of domain growth in the late stage of phase separation of a binary liquid mixture  

NASA Astrophysics Data System (ADS)

The domain growth processes occurring during the gravity-dominated regime of the phase separation of a cyclohexane/aniline critical mixture, following a temperature quench in the unstable region below the temperature-composition coexistence curve, were investigated with high-resolution 1H NMR. Diffusive exchange of cyclohexane molecules between a small volume fraction of immiscible droplets and the surrounding fluid with a different cyclohexane concentration leads to a domain-size dependent 1H NMR cyclohexane chemical shift in the continuous phase. In this case, the equations of motion for the transverse magnetization density reduce to a first-order exchange between two immiscible phases with rate coefficients depending on the droplet size and the transport process across the liquid-liquid interface. Application of this model to the data yields a power law for the growing droplets, R(t)=At?, where R is a typical domain size, with the growth exponent ?=0.30±0.01 and the amplitude A?0.9×10-6 ms-?. These values are in close agreement with previous visualization studies on the same binary mixture [F. Cau and S. Lacelle, Phys. Rev. E 47, 1429 (1993)]. The results also confirm the presence of a new domain growth regime involving Brownian coagulation and sedimentation in the very late stage of the phase separation processes of binary liquid mixtures. A strong linear composition dependence of the 1H NMR cyclohexane chemical shift in one-phase cyclohexane/aniline mixtures was interpreted on the basis of solvent shift effects induced by intermolecular interactions and susceptibility effects. In each phase of the two-phase equilibrium mixture, inhomogeneous line broadening, arising from the magnetic susceptibility discontinuity at the interface between phases, is also investigated.

Cau, Franco; Lacelle, Serge

1995-08-01

244

Preparation of chlorogenic acid surface-imprinted magnetic nanoparticles and their usage in separation of traditional Chinese medicine.  

PubMed

The chlorogenic acid (CGA) surface-imprinted magnetic polymer nanoparticles have been prepared via water-in-oil-in-water multiple emulsions suspension polymerization. This kind of molecularly imprinted polymer nanoparticles (MIPs) had the core-shell structure with the size of about 50 nm. Magnetic susceptibility was given by the successful encapsulation of Fe(3)O(4) nanoparticles with a high encapsulation efficiency of 19.3 wt%. MIPs showed an excellent recognition and selection properties for the imprinted molecule CGA. The recognition capacity of MIPs was near three times than that of non-imprinted polymer nanoparticles (NIPs). Compared with the competitive molecule caffeic acid (CFA), the selectivity of MIPs for CGA was 6.06 times as high as that of NIPs. MIPs could be reused and regenerated, and their rebinding amount in the fifth use was up to 78.85% of that in the first use. The MIPs prepared were successfully applied to the separation of CGA from the extract of Traditional Chinese Medicine Honeysuckle. PMID:20708118

Gu, Xiao-hong; Xu, Rong; Yuan, Gao-lin; Lu, Hui; Gu, Bing-ren; Xie, Hong-ping

2010-08-18

245

A rapid method for detection of genetically modified organisms based on magnetic separation and surface-enhanced Raman scattering.  

PubMed

In this study, a new method combining magnetic separation (MS) and surface-enhanced Raman scattering (SERS) was developed to detect genetically modified organisms (GMOs). An oligonucleotide probe which is specific for 35 S DNA target was immobilized onto gold coated magnetic nanospheres to form oligonucleotide-coated nanoparticles. A self assembled monolayer was formed on gold nanorods using 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) and the second probe of the 35 S DNA target was immobilized on the activated nanorod surfaces. Probes on the nanoparticles were hybridized with the target oligonucleotide. Optimization parameters for hybridization were investigated by high performance liquid chromatography. Optimum hybridization parameters were determined as: 4 ?M probe concentration, 20 min immobilization time, 30 min hybridization time, 55 °C hybridization temperature, 750 mM buffer salt concentration and pH: 7.4. Quantification of the target concentration was performed via SERS spectra of DTNB on the nanorods. The correlation between the target concentration and the SERS signal was found to be linear within the range of 25-100 nM. The analyses were performed with only one hybridization step in 40 min. Real sample analysis was conducted using Bt-176 maize sample. The results showed that the developed MS-SERS assay is capable of detecting GMOs in a rapid and selective manner. PMID:22049365

Guven, Burcu; Boyac?, ?smail Hakk?; Tamer, Ugur; Çal?k, P?nar

2012-01-01

246

Separation and purification of Si from solidification of hypereutectic Al-Si melt under rotating magnetic field  

NASA Astrophysics Data System (ADS)

A low-cost and high-efficiency method to purify Si directly from cheap MG-Si at low temperature was proposed and demonstrated in this paper, which used power frequency rotating magnetic field (RMF) to separate the primary Si from a hypereutectic Al-Si alloy and was followed by the acid peeling. The separation mechanism was based on the flow characteristic of melt under RMF and the cooling condition of the liquid metal. A Si-rich layer with Si content of 65-59 wt% was formed in the periphery of alloy, while the inner microstructure of the alloy was mainly the Al-Si eutectic structure. The refined silicon was collected after aqua regia leaching, and had much fewer typical impurities (Fe, Ti, Ca, B, P) than those in MG-Si, and the metallic impurities besides Al had removal fraction higher than 98%, which is mainly ascribed to the segregation effect of Al-30Si alloy during solidification under RMF.

Jie, J. C.; Zou, Q. C.; Wang, H. W.; Sun, J. L.; Lu, Y. P.; Wang, T. M.; Li, T. J.

2014-08-01

247

Evidence for Two Separate but Interlaced Components of the Chromospheric Magnetic Field  

NASA Technical Reports Server (NTRS)

Chromospheric fibrils are generally thought to trace out horizontal magnetic fields that fan out from flux concentrations in the photosphere. A high-resolution (0.2") image taken in the core of the Ca IJ854.2 nm line shows the dark fibrils within an active region remnant as fine, loop-like features that are aligned parallel to each other and have lengths on the order of a supergranular diameter (approx.30 Mm). Comparison with a line-of-sight magnetogram confirms that the fibrils are centered above intranetwork areas, with one end rooted just inside the neighboring plage or strong unipolar network but the other endpoint less clearly defined. Focusing on a particular arcade-like structure lying entirely on one side of a filament channel (large-scale polarity inversion), we find that the total amount of positive-polarity flux underlying this "fibril arcade' is 50 times greater than the total amount of negative-polarity flux. Thus, if the fibrils represent closed loops, they must consist of very weak fields (in terms of flux density), which are interpenetrated by a more vertical field that contains most of the flux. This surprising result suggests that the fibrils in unipolar regions connect the network to the nearby intranetwork flux, while the bulk of the network flux is diverted upward into the corona and connects to remote regions of the opposite polarity. We conclude that the chromospheric field near the edge of the network has an interlaced structure resembling that in sunspot penumbrae, with the fibrils representing the low-lying horizontal flux that remains trapped within the highly nonpotential chromospheric layer.

Muglach, K.; Reardon, K. P.; Wang, Y.-M.; Warren, H. P.

2012-01-01

248

Cryo-soft X-ray tomography: a journey into the world of the native-state cell.  

PubMed

One of the ultimate aims of imaging in biology is to achieve molecular localisation in the context of the structure of cells in their native state. Here, we review the current state of the art in cryo-soft X-ray tomography (cryo-SXT), which is the only imaging modality that can provide nanoscale 3D information from cryo-preserved, unstained, whole cells thicker than 1 ?m. Correlative cryo-fluorescence and cryo-SXT adds functional information to structure, enabling studies of cellular events that cannot be captured using light, electron or X-ray microscopes alone. PMID:24264466

Carzaniga, Raffaella; Domart, Marie-Charlotte; Collinson, Lucy M; Duke, Elizabeth

2014-03-01

249

Cryo-electron microscopy specimen preparation by means of a focused ion beam.  

PubMed

Here we present a protocol used to prepare cryo-TEM samples of Aspergillus niger spores, but which can easily be adapted for any number of microorganisms or solutions. We make use of a custom built cryo-transfer station and a modified cryo-SEM preparation chamber. The spores are taken from a culture, plunge-frozen in a liquid nitrogen slush and observed in the cryo-SEM to select a region of interest. A thin lamella is then extracted using the FIB, attached to a TEM grid and subsequently thinned to electron transparency. The grid is transferred to a cryo-TEM holder and into a TEM for high resolution studies. Thanks to the introduction of a cooled nanomanipulator tip and a cryo-transfer station, this protocol is a straightforward adaptation to cryogenic temperature of the routinely used FIB preparation of TEM samples. As such it has the advantages of requiring a small amount of modifications to existing instruments, setups and procedures; it is easy to implement; it has a broad range of applications, in principle the same as for cryo-TEM sample preparation. One limitation is that it requires skillful handling of the specimens at critical steps to avoid or minimize contaminations. PMID:25146386

Rubino, Stefano; Melin, Petter; Spellward, Paul; Leifer, Klaus

2014-01-01

250

Initial assessment of CryoSat-2 Performance.  

NASA Astrophysics Data System (ADS)

Following the launch of CryoSat-2 in April 2010, we have examined the performance of the CryoSat-2 SAR Interferometer over the continental ice sheets of Antarctica and Greenland, the Artic Ocean, and, for the purposes of calibration, over the oceans. Our aim has been to provide confirmation of the engineering performance of the radar interferometer, and to provide an initial geophysical validation of the resulting elevation measurements. We have confirmed the engineering performance at system level of the interferometer through performing a sequence of satellite rolls over the oceans, which provide a surface of known behavior and surface gradient. The activity has identified some errors in the SARIN L1b data products presently issued by ESA. Once corrected, the ocean calibration has demonstrated that the interferometer measures across-track surface slopes with a precision of 25 micro-radians and an accuracy of 10 micro-radians, which may be compared with a pre-launch estimation of 100 micro-radians; in short, the engineering performance greatly its the specification. The elevation measurement over the ice sheets combines the interferometer measurement of across track slope with the range measurement deduced from the SAR echoes. We have examined the performance of the range estimation, and determined the range precision to be 19 cm RMS at 20 Hz. We have examined the retrieval of the phase information over the ice sheets, and found the phase estimates to be robust and little affected by the uncertain ice sheet topography. Based on the calibration of the interferometer, the contribution of the across track slope error is, at 0.4 mm, negligible. While the quantity of data available to us that contains the corrections identified by the interferometer is limited, we have been able to confirm the range precision values from a limited cross-over analysis. Over marine sea ice, we have verified the discrimination of sea ice and ocean lead returns using contemporaneous SAR imagery from ENVISAT. Using one month's of data, we have determined an initial dynamic topography that agrees with a high resolution region ocean model to 4 cm. We have estimated the precision of individual (20 Hz) measurements to be 2 cm. We have combined estimated the Arctic ice thickness for January and February 2011, and made a preliminary comparison with contemporaneous in-situ and air-borne estimates of thickness which agree to 20 cm. In summary, with the corrected data products, we are able to confirm that the system performance of CryoSat-2 will meet or exceed its specification over the continental and marine ice sheets.

Wingham, D.; Galin, N.; Ridout, A.; Cullen, R.; Giles, K. A.; Laxon, S. W.

2011-12-01

251

Tandem assays of protein and glucose with functionalized core/shell particles based on magnetic separation and surface-enhanced Raman scattering.  

PubMed

Tandem assays of protein and glucose in combination with mannose-functionalized Fe3 O4 @SiO2 and Ag@SiO2 tag particles have promising potential in effective magnetic separation and highly sensitive and selective SERS assays of biomaterials. It is for the first time that tandem assay of glucose is developed using SERS based on the Con A-sandwiched microstructures between the functionalized magnetic and tag particles. PMID:23585333

Kong, Xianming; Yu, Qian; Lv, Zhongpeng; Du, Xuezhong

2013-10-11

252

Microchannel liquid-flow focusing and cryo-polymerization preparation of supermacroporous cryogel beads for bioseparation.  

PubMed

Polymeric cryogels are sponge-like materials with supermacroporous structure, allowing them to be of interest as new chromatographic supports, cell scaffolds and drug carriers in biological and biomedical areas. The matrices of cryogels are always prepared in the form of monoliths by cryo-polymerization under frozen conditions. However, there are limited investigations on the production of cryogels in the form of adsorbent beads suitable for bioseparation. In this work, we provide a new approach by combining the microchannel liquid-flow focusing with cryo-polymerization for the preparation of polyacrylamide-based supermacroporous cryogel beads with a narrow particle size distribution. The present method was achieved by introducing the aqueous phase solution containing monomer, cross-linker and redox initiators, and the water-immiscible organic oil phase containing surfactant simultaneously into a microchannel with a cross-shaped junction, where the aqueous drops with uniform sizes were generated by the liquid shearing and the segmentation due to the steady flow focusing of the immiscible phase streams. These liquid drops were in situ suspended into the freezing bulk oil phase for cryo-polymerization and the cryogel matrix beads were obtained by thawing after the achievement of polymerization. By grafting the polymer chains containing sulfo binding groups onto these matrix beads, the cation-exchange cryogel beads for protein separation were produced. The results showed that at the aqueous phase velocities from 0.5 to 2.0 cm/s and the total velocities of the water-immiscible phase from 2.0 to 6.0 cm/s, the obtained cryogel beads by the present method have narrow size distributions with most of the bead diameters in the range from 800 to 1500 ?m with supermacropores in sizes of about 3-50 ?m. These beads also have high porosities with the averaged maximum porosity of 96.9% and the mean effective porosity of 86.2%, which are close to those of the polyacrylamide-based cryogel monoliths. The packed bed using the cryogel beads with mean diameter of 1248 ?m, as an example, has reasonable and acceptable liquid dispersion, but high water permeability (4.29 × 10?¹? m²) and high bed voidage (90.2%) owing to the supermacropores within the beads, enhanced the rapid binding and separation of protein from the feedstock even at high flow velocities. The purity of the obtained lysozyme from chicken egg white by one-step chromatography using the packed bed was in the range of about 78-92% at the flow velocities of 0.5-15 cm/min, indicating that the present cryogel beads could be an effective chromatographic adsorbent for primary bioseparation. PMID:22695698

Yun, Junxian; Tu, Changming; Lin, Dong-Qiang; Xu, Linhong; Guo, Yantao; Shen, Shaochuan; Zhang, Songhong; Yao, Kejian; Guan, Yi-Xin; Yao, Shan-Jing

2012-07-20

253

Removal of subsurface fluorescence in cryo-imaging using deconvolution  

PubMed Central

We compared image restoration methods [Richardson-Lucy (RL), Wiener, and Next-image] with measured “scatter” point-spread-functions, for removing subsurface fluorescence from section-and-image cryo-image volumes. All methods removed haze, delineated single cells from clusters, and improved visualization, but RL best represented structures. Contrast-to-noise and contrast-to-background improvement from RL and Wiener were comparable and 35% better than Next-image. Concerning detection of labeled cells, ROC analyses showed RL ?Wiener > Next-image >> no processing. Next-image was faster than other methods and less prone to image processing artifacts. RL is recommended for the best restoration of the shape and size of fluorescent structures. PMID:20941133

Krishnamurthi, Ganapathy; Wang, Charlie Y.; Steyer, Grant; Wilson, David L.

2010-01-01

254

Nitride Fuel Development Using Cryo-process Technique  

SciTech Connect

A new cryo-process technique has been developed for the fabrication of advanced fuel for nuclear systems. The process uses a new cryo-processing technique whereby small, porous microspheres (<2000 µm) are formed from sub-micron oxide powder. A simple aqueous particle slurry of oxide powder is pumped through a microsphere generator consisting of a vibrating needle with controlled amplitude and frequency. As the water-based droplets are formed and pass through the microsphere generator they are frozen in a bath of liquid nitrogen and promptly vacuum freeze-dried to remove the water. The resulting porous microspheres consist of half micron sized oxide particles held together by electrostatic forces and mechanical interlocking of the particles. Oxide powder microspheres ranging from 750 µm to 2000 µm are then converted into a nitride form using a high temperature fluidized particle bed. Carbon black can be added to the oxide powder before microsphere formation to augment the carbothermic reaction during conversion to a nitride. Also, the addition of ethyl alcohol to the aqueous slurry reduces the surface tension energy of the droplets resulting in even smaller droplets forming in the microsphere generator. Initial results from this new process indicate a lower impurity contamination in the final nitrides due to the single feed stream of particles, material handling and conversion are greatly simplified, a minimum of waste and personnel exposure are anticipated, and finally the conversion kinetics may be greatly increased because of the small oxide powder size (sub-micron) forming the porous microsphere. Thus far the fabrication process has been successful in demonstrating all of these improvements with surrogate ZrO2 powder. Further tests will be conducted in the future using the technique on UO2 powders.

O'Brien, Brandi M; Windes, William E

2007-06-01

255

Synthesis and characterization of magnetic hexacyanoferrate (II) polymeric nanocomposite for separation of cesium from radioactive waste solutions.  

PubMed

Nanocrystalline potassium zinc hexacyanoferrate loaded on nanoscale magnetite substrate was successfully synthesized for significantly enhanced removal of cesium from low-level radioactive wastes. A description was given for preparation and properties of these precursors. The physicochemical properties of these nanocomposites were determined using different techniques including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Data clarified that supporting potassium zinc hexacyanoferrates on iron ferrite nanoparticles increased their thermal stability. Further, Fourier transform infrared spectra confirmed that the nanocomposites were well coordinated and incorporated in the polymer matrix. The average particle sizes, of these nanoparticles, determined by SEM had a good agreement with XRD results. Based on characterization data, the prepared zinc hexacyanoferrates were proposed to have a zeolitic rhombohedral structure with cavities can host alkali metal ions and water molecules. The magnetic analysis showed a super-paramagnetic behavior. Batch technique was applied to evaluate the influences of initial pH value, contact time, and competing cations on the efficiency of cesium removal. The sorption process was fast initially, and maximum separation was attained within 2h of contact. Cesium exchange was independent from pH value and deviate from ideal exchange phenomena. In neutral solutions, Cs(+) was retained through exchange with K(+); however, in acidic solution, phase transformation was proposed. Sorption capacity of these materials attained values amounted 1965 mg g(-1). The synthesized nanocomposites exhibited different affinities toward Cs(I), Co(II), and Eu(III) elements and showed a good ability to separate them from each other. PMID:23000210

Sheha, Reda R

2012-12-15

256

Ionic pair complexes with well-separated columnar stack structure based on [Pt(mnt)2]- ions showing unusual magnetic transition: syntheses, crystal structures, and magnetic properties.  

PubMed

Three ion pair complexes, [4-R-benzylpyridinium][bis(maleodinitriledithiolato)platinum(III)] (abbreviated as [RBzPy][Pt(mnt)(2)]; R = Cl (1), Br (2), or NO(2) (3)), have been synthesized. The cations and anions stack into well-separated columns in the solid state, and the Pt(III) ions form a 1-D zigzag chain within a [Pt(mnt)(2)](-) column through Pt...S, S...S, and Pt...S...Pt interactions. The chain is uniform in 1 and 2, while it alternates in 3. Unusual magnetic phase transitions from paramagnetism to diamagnetism were observed in these three complexes at approximately 275 K for 1, approximately 269 K for 2, and approximately 184 K for 3. These phase transitions were also found in DSC measurements for 1 and 2. The overall magnetic behaviors for 1-3 indicate the presence of antiferromagnetic exchange interactions in the high-temperature phase and spin-gapped systems in the low-temperature phase. Below 50 K, 2 exhibits weak ferromagnetism. The spontaneous moments are nearly repressed by a field of 1.0 T. The crystal structure of 2 at 173 K reveals that there are two crystallographically independent [Pt(mnt)(2)](-) entries in an asymmetric unit. These two crystallographically independent [Pt(mnt)(2)](-) entries satisfy the spin-canting condition, and the EPR spectra measured at room temperature exhibit anisotropic character. Therefore, the weak ferromagnetic behavior in the low-temperature region for 2 can be attributed to the spin-canting phenomenon. PMID:15074975

Ren, X M; Okudera, H; Kremer, R K; Song, Y; He, C; Meng, Q J; Wu, P H

2004-04-19

257

Design of a core-shell type immuno-magnetic separation system and multiplex PCR for rapid detection of pathogens from food samples.  

PubMed

We report an immuno-magnetic separation system developed by the immobilization of pathogen-specific antibodies on the core-shell magnetic beads. The magnetic beads were grafted with glycidylmethacrylate (GMA) using surface-initiated atom transfer radical polymerization (SI-ATRP). For immuno-magnetic separation (IMS) of target bacterial cells from others, antibodies for Escherichia coli and Salmonella enterica serovar Typhimurium cells were immobilized on the magnetic beads via glutaraldehyde coupling reaction. Our IMS system successfully separated Salmonella cells when the concentrations of target (i.e., Salmonella) and interfering (i.e., E. coli) cells were at the same level. Polymerase chain reaction (PCR) assays amplifying the rfb/rfbE region of the E. coli genome and a 647-bp fragment of the invA region of Salmonella were performed as the specific selection to accurately confirm the presence of E. coli and Salmonella, respectively. IMS and multiplex PCR methods can be used for specific and quantitative detection of pathogens from food samples. Thus, this study developed a reliable and direct system for rapid detection of Salmonella and E. coli in food samples. In addition, IMS method could be easily adapted to detect other pathogens by selecting the pertinent antibody. PMID:24048640

Ozalp, V Cengiz; Bayramoglu, Gulay; Arica, M Yakup; Oktem, H Avni

2013-11-01

258

76 FR 4338 - Research and Development Strategies for Compressed & Cryo-Compressed Hydrogen Storage Workshops  

Federal Register 2010, 2011, 2012, 2013

...performance and safety. Introductory presentations include automotive and manufacturing perspectives, and overviews of carbon fiber development and recent costs analyses. The cryo-compressed hydrogen workshop on Tuesday February 15th will...

2011-01-25

259

Mechanical Property Characterization of Cryo-Rolled Copper by Miniaturized Disk Bend and Nanoindentation Technique  

NASA Astrophysics Data System (ADS)

The present study reports mechanical behavior of severe plastically deformed pure Cu under cryogenic conditions by miniaturized disk bend test (MDBT) and nanoindentation technique. MDBT is a useful technique to determine mechanical property of miniature samples under multiaxial state of stress. The samples were severely deformed by cryo-rolling upto 75% and 95% reduction. Microstructure evolution of cryo-rolled samples has been characterized using optical and EBSD technique. MDBT was performed on cryo-rolled 10-mm disk of ~200-?m thickness. Nanoindentation tests were also performed on the cryo-rolled samples. The hardness values obtained from nanoindentation tests were compared with yield stress obtained from MDBT. The present study established a good quantitative correlation between the two techniques. Mechanical dynamic parameters; strain rate sensitivity (m) and activation volume (V*) determined by MDBT and nanoindentation techniques showed close agreement in the results.

Sharma, Garima; Chatterjee, Arnomitra; Kapoor, Rajeev; Chakravartty, J. K.

2014-09-01

260

Direct observation of liquid crystals using cryo-TEM: Specimen preparation and low-dose imaging.  

PubMed

Liquid crystals (LCs) represent a challenging group of materials for direct transmission electron microscopy (TEM) studies due to the complications in specimen preparation and the severe radiation damage. In this paper, we summarize a series of specimen preparation methods, including thin film and cryo-sectioning approaches, as a comprehensive toolset enabling high-resolution direct cryo-TEM observation of a broad range of LCs. We also present comparative analysis using cryo-TEM and replica freeze-fracture TEM on both thermotropic and lyotropic LCs. In addition to the revisits of previous practices, some new concepts are introduced, e.g., suspended thermotropic LC thin films, combined high-pressure freezing and cryo-sectioning of lyotropic LCs, and the complementary applications of direct TEM and indirect replica TEM techniques. The significance of subnanometer resolution cryo-TEM observation is demonstrated in a few important issues in LC studies, including providing direct evidences for the existence of nanoscale smectic domains in nematic bent-core thermotropic LCs, comprehensive understanding of the twist-bend nematic phase, and probing the packing of columnar aggregates in lyotropic chromonic LCs. Direct TEM observation opens ways to a variety of TEM techniques, suggesting that TEM (replica, cryo, and in situ techniques), in general, may be a promising part of the solution to the lack of effective structural probe at the molecular scale in LC studies. Microsc. Res. Tech. 77:754-772, 2014. © 2014 Wiley Periodicals, Inc. PMID:25045045

Gao, Min; Kim, Young-Ki; Zhang, Cuiyu; Borshch, Volodymyr; Zhou, Shuang; Park, Heung-Shik; Jákli, Antal; Lavrentovich, Oleg D; Tamba, Maria-Gabriela; Kohlmeier, Alexandra; Mehl, Georg H; Weissflog, Wolfgang; Studer, Daniel; Zuber, Benoît; Gnägi, Helmut; Lin, Fang

2014-10-01

261

O-Allylation of phenols with allylic acetates in aqueous media using a magnetically separable catalytic system  

EPA Science Inventory

Allylic ethers were synthesized in water using magnetically recoverable heterogeneous Pd catalyst via O-allylation of phenols with allylic acetates under ambient conditions. Aqueous reaction medium, easy recovery of the catalyst using an external magnet, efficient recycling, and ...

262

CryoSat Products and Data Quality Assessment  

NASA Astrophysics Data System (ADS)

The main payload of CryoSat-2 is a Ku band pulse-width limited radar altimeter, called SIRAL (Synthetic interferometric radar altimeter), that transmits pulses at a high pulse repetition frequency thus making the received echoes phase coherent and suitable for azimuth processing. This allows to reach an along-track resolution of about 250 meters which is a significant improvement over traditional pulse-width limited radar altimeters. There are three operating modes: Low-Resolution mode (LRM), Synthetic Aperture Radar (SAR) and Synthetic Aperture Radar Interferometric (SARIn). Both the Level 1b and the Level 2 data products are defined depending on the operating mode used by the instrument. However, Level 1b products essentially contain an average echo for each location along the ground track while Level 2 products contains an elevation for each location along the satellite track. In this paper we will detail as first the different data products and then the quality achieved on those products will be described after almost two years of operational activity of the Cryosat-2 satellite.

Scagliola, M.; Mannan, R.; Fornari, M.; Bouzinac, C.

2012-12-01

263

A cylindrical specimen holder for electron cryo-tomography  

PubMed Central

The use of slab-like flat specimens for electron cryo-tomography restricts the range of viewing angles that can be used. This leads to the “missing wedge” problem, which causes artefacts and anisotropic resolution in reconstructed tomograms. Cylindrical specimens provide a way to eliminate the problem, since they allow imaging from a full range of viewing angles around the tilt axis. Such specimens have been used before for tomography of radiation-insensitive samples at room temperature, but never for frozen-hydrated specimens. Here, we demonstrate the use of thin-walled carbon tubes as specimen holders, allowing the preparation of cylindrical frozen-hydrated samples of ribosomes, liposomes and whole bacterial cells. Images acquired from these cylinders have equal quality at all viewing angles, and the accessible tilt range is restricted only by the physical limits of the microscope. Tomographic reconstructions of these specimens demonstrate that the effects of the missing wedge are substantially reduced, and could be completely eliminated if a full tilt range was used. The overall quality of these tomograms is still lower than that obtained by existing methods, but improvements are likely in future. PMID:24275523

Palmer, Colin M.; Lowe, Jan

2014-01-01

264

Breaking the Radiation Damage Limit with Cryo-SAXS  

PubMed Central

Small angle x-ray scattering (SAXS) is a versatile and widely used technique for obtaining low-resolution structures of macromolecules and complexes. SAXS experiments measure molecules in solution, without the need for labeling or crystallization. However, radiation damage currently limits the application of SAXS to molecules that can be produced in microgram quantities; for typical proteins, 10–20 ?L of solution at 1 mg/mL is required to accumulate adequate signal before irreversible x-ray damage is observed. Here, we show that cryocooled proteins and nucleic acids can withstand doses at least two orders of magnitude larger than room temperature samples. We demonstrate accurate T = 100 K particle envelope reconstructions from sample volumes as small as 15 nL, a factor of 1000 smaller than in current practice. Cryo-SAXS will thus enable structure determination of difficult-to-express proteins and biologically important, highly radiation-sensitive proteins including light-activated switches and metalloenzymes. PMID:23332075

Meisburger, Steve P.; Warkentin, Matthew; Chen, Huimin; Hopkins, Jesse B.; Gillilan, Richard E.; Pollack, Lois; Thorne, Robert E.

2013-01-01

265

Low-frequency resistance fluctuations in a single nanowire (diameter ? 45 nm) of a complex oxide and its relation to magnetic transitions and phase separation  

NASA Astrophysics Data System (ADS)

We report measurement of low frequency resistance noise spectroscopy in a single strand of a nanowire (NW) (diameter ? 45 nm) of a complex oxide manganite La0.5Sr0.5MnO3, that showed ferromagnetic transition (TC ? 315 K), an antiferromagnetic transition (TN ? 210 K) and a phase-separated region below TN. We demonstrated that noise spectroscopy in a single NW can cleanly detect the magnetic transitions including the phase-coexistence that may not be possible to do by magnetic measurements. The normalized noise in the single NW is an order less than that reported in ultralow-noise Si Junction Field Effect Transistor.

Datta, Subarna; Samanta, Sudeshna; Ghosh, Barnali; Raychaudhuri, A. K.

2014-08-01

266

Phase Separation in Submicron Organic Aerosol  

NASA Astrophysics Data System (ADS)

Aerosol particles affect climate through heterogeneous chemistry, the scattering and absorption of radiation, and through their role as seeds for cloud condensation and ice nuclei. These interactions depend in part on the internal structure of the particles. To investigate the chemical and physical principles that determine the internal structure of organic aerosol, we have characterized the morphology of laboratory-generated, dry, internally mixed particles in the submicron size regime using cryo-transmission electron microscopy (cryo-TEM). We have focused on the well-studied system of dicarboxylic acids mixed with ammonium sulfate. The morphology of dry, organic aerosol particles depends upon the organic solubility, rather than the organic O:C ratio. We observe homogeneous structures for soluble organic compounds and phase separated structures for insoluble organic compounds. The phase-separated structures are partially engulfed rather than core-shell. For organic compounds of intermediate solubility, the aerosol morphology is dependent on the particle size, where the large particles are partially engulfed and the small particles are homogeneous. In addition to our single particle technique, we use cavity ring-down spectroscopy and computation to understand the average particle structure. Our results demonstrate the use of cryo-TEM and cavity ring-down spectroscopy to investigate aerosol structure in the submicron size regime.

Freedman, M. A.; Veghte, D. P.; Altaf, M. B.

2013-12-01

267

Facile preparation of magnetic separable powdered-activated-carbon\\/Ni adsorbent and its application in removal of perfluorooctane sulfonate (PFOS) from aqueous solution  

Microsoft Academic Search

The main aim of this study was to synthesize magnetic separable Nickel\\/powdered activated carbon (Ni\\/PAC) and its application as an adsorbent for removal of PFOS from aqueous solution. In this work, the synthesized adsorbent using simple method was characterized by using X-ray diffractionometer (XRD), surface area and pore size analyzer, vibrating sample magnetometer (VSM), and high resolution transmission electron microscope

Xuanqi Liang; Mohammed A. Gondal; Xiaofeng Chang; Zain H. Yamani; Nianwu Li; Hongling Lu; Guangbin Ji

2011-01-01

268

Electric field within Io s ionosphere caused by charge separation and its role in background magnetic field depression and particle acceleration  

NASA Astrophysics Data System (ADS)

Measurements of Jovian magnetic field near Io by the Galileo spacecraft discover its large depression at the Io's wake. The field decrease is of nearly 40% of the Jovian background field. Recent Galileo's flights near Io's poles show that Io has not internal magnetic field. It means that the field depression is caused by current generated by Io's interaction with its torus. However, modeling of the Io-plasma interaction performed in [1] shows that plasma effects can account for only a part of the observed depression. In this report weconsider the simple case when a 2D slab of weak ionized plasma, modeling the Io's ionosphere, moves across the Jovian magnetic field. We show that there is a possibility for the total Io ionosphere current to flow in direction required by the magnetic observations and to provide the observed magnetic perturbation. The former is due to the electric field created within the ionosphere by the charge separation. We show also that the electric field can accelerate charges moving outwards the Io's ionosphere along the planetary magnetic field. [1] Kivelson, M.C., K.K. Khurana, R.J. Walker et al., Science 274, 396, 1996

Shaposhnikov, V.; Zaitsev, V.; Rucker, H.; Litvinenko, G.

269

The making of frozen-hydrated, vitreous lamellas from cells for cryo-electron microscopy.  

PubMed

There has been a long standing desire to produce thick (up to 500 nm) cryo-sections of fully hydrated cells and tissue for high-resolution analysis in their natural state by cryo-transmission electron microscopy. Here, we present a method that can successfully produce sections (lamellas in FIB-SEM terminology) of fully hydrated, unstained cells from high-pressure frozen samples by focused ion beam (FIB) milling. The samples are therefore placed in thin copper tubes and vitrified by high-pressure freezing. For transfer, handling and subsequent milling, the tubes are placed in a novel connective device (ferrule) that protects the sample from devitrification and contamination and passes through all operation steps. A piezo driven sample positioning stage (cryo-nano-bench, CNB) with three degrees of freedom was additionally developed to enable accurate milling of frozen-hydrated lamellas. With the CNB, high-pressure frozen samples can be milled to produce either thin lamellas (<100 nm), for direct imaging by high-resolution cryo-TEM or thicker lamellas (300-500 nm) for cryo-electron tomography. The sample remains vitreous throughout the process by using the presented tools and methods. The results are an important step towards investigating larger cells and even tissue in there natural state which in the end will enable us to gain better insights into cellular processes. PMID:20638479

Hayles, Michael F; de Winter, D A Matthijs; Schneijdenberg, Chris T W M; Meeldijk, Johannes D; Luecken, Uwe; Persoon, Hans; de Water, Jeroen; de Jong, Frank; Humbel, Bruno M; Verkleij, Arie J

2010-11-01

270

Structural characterization of amphiphilic homopolymer micelles using light scattering, SANS, and cryo-TEM  

PubMed Central

We report the aqueous solution self-assembly of a series of poly(N-isopropylacrylamide) (PNIPAM) polymers end-functionalized with a hydrophobic sulfur-carbon-sulfur (SCS) pincer ligand. Although the hydrophobic ligand accounted for <5 wt% of the overall homopolymer mass, the polymers self-assembled into well-defined spherical micelles in aqueous solution, and these micelles are potential precursors to solution-assembled nanoreactors for small molecule catalysis applications. The micelle structural details were investigated using light scattering, cryogenic transmission electron microscopy (cryo-TEM), and small angle neutron scattering (SANS). Radial density profiles extracted from the cryo-TEM micrographs suggested that the PNIPAM chains formed a diffuse corona with a radially decreasing corona density profile and provided valuable a priori information about the micelle structure for SANS data modeling. SANS analysis indicated a similar profile in which the corona surrounded a small hydrophobic core containing the pincer ligand. The similarity between the SANS and cryo-TEM results demonstrated that detailed information about the micelle density profile can be obtained directly from cryo-TEM and highlighted the complementary use of scattering and cryo-TEM in the structural characterization of solution-assemblies, such as the SCS pincer-functionalized homopolymers described here. PMID:24058209

Patterson, Joseph P.; Kelley, Elizabeth G.; Murphy, Ryan P.; Moughton, Adam O.; Robin, Mathew; Lu, Annhelen; Colombani, Olivier; Chassenieux, Christophe; Cheung, David; Sullivan, Millicent O.

2013-01-01

271

Annealing control of magnetic anisotropy and phase separation in CoFe2O4-BaTiO3 nanocomposite films  

NASA Astrophysics Data System (ADS)

Multiferroic heteroepitaxial nanocomposite films of BaTiO3 and CoFe2O4 (CFO) have been grown by pulsed laser deposition employing alternating ablation of two ceramic targets. Films grown at temperatures between 650 °C and 710 °C contain columnar CFO grains about 10-20 nm in diameter embedded in a BaTiO3 matrix. The very strong vertical compression of these grains causes large perpendicular magnetic anisotropy. Post-growth annealing treatments above the growth temperature gradually release the compression. This allows one to tune the stress-induced magnetic anisotropy. Additionally, annealing leads to substantial enhancement of the saturation magnetization MS. Since MS of a pure CFO film remains unchanged by a similar annealing procedure, MS is proposed to depend on the volume fraction of the obtained CFO phase. We suggest that MS can be utilized to monitor the degree of phase separation in nanocomposite films.

Rafique, Mohsin; Herklotz, A.; Guo, E.-J.; Roth, R.; Schultz, L.; Dörr, K.; Manzoor, Sadia

2013-12-01

272

Novel Phase Separation and Magnetic Volume Tuning in Underdoped NaFe1-xCoxAs (x ˜0.01)  

NASA Astrophysics Data System (ADS)

NaFeAs is a quasi-2D pnictide parent compound with a weak magnetic moment and separate structural and antiferromagnetic transitions. Because Co doping leads to a superconductor with Tc˜20 K at a very low optimal doping of x = 0.02, NaFe1-xCoxAs is uniquely suited to sensitive studies of the cohabitation and competition between magnetism and superconductivity. Using NMR as a local probe of both antiferromagnetic order and superconductivity, we have compared Knight shifts and relaxation rates on the Na, As, and Co nuclei. Above Tc, we find weak doping inhomogeneity, in the form of residual paramagnetic regions with differing TN values, and a strongly field-controlled magnetic volume. Below Tc, we observe a strong competition between antiferromagnetism and superconductivity, in which the temperature is the dominant control parameter, suppressing the magnetic volume fraction very significantly in favor of the superconducting one, while the external field suppresses Tc. Our results suggest both a microscale phase separation in real space and in reciprocal space a competition between two order parameters requiring the same electrons on the quasi-2D Fermi surface.

Ma, Long; Dai, J.; Lu, X. R.; Tan, Guotai; Song, Yu; Dai, Pengcheng; Zhang, C. L.; Normand, B.; Yu, Weiqiang

2013-03-01

273

CRYOGENIC SYSTEM FOR BEPCII SRF CAVITY, IR QUADRUPOLE AND DETECTOR SOLENOID MAGNETS.  

SciTech Connect

Beijing Electron-Positron Collider Upgrade (BEPCII) requires three types of superconducting facilities, including one pair of SRF cavities, one pair of interaction region quadrupole magnets, and one detector solenoid magnet. The cryo-plant for BEPCII has a total cooling capacity of 1kW at 4.5K, which is composed of two separate helium refrigerators of 500W each. Two refrigerators share the same gas storage and recovery system. The engineering design for the cryogenic systems, including power leads, control dewars, subcooler, cryogenic valve boxes, cryogenic transfer-lines and cryogenic controls, is completed. The production of its subsystem is under way. This paper summarizes the progress in cryogenics of the BEPCII project.

JIA,J.X.; WANG.L.

2004-05-11

274

Electron cryo-tomographic structure of cystovirus {phi}12  

SciTech Connect

Bacteriophage {phi}12 is a member of the Cystoviridae virus family and contains a genome consisting of three segments of double-stranded RNA (dsRNA). This virus family contains eight identified members, of which four have been classified in regard to their complete genomic sequence and encoded viral proteins. A phospholipid envelope that contains the integral proteins P6, P9, P10, and P13 surrounds the viral particles. In species {phi}6, host infection requires binding of a multimeric P3 complex to type IV pili. In species {phi}8, {phi}12, and {phi}13, the attachment apparatus is a heteromeric protein assembly that utilizes the rough lipopolysaccharide (rlps) as a receptor. In {phi}8 the protein components are designated P3a and P3b while in species {phi}12 proteins P3a and P3c have been identified in the complex. The phospholipid envelope of the cystoviruses surrounds a nucleocapsid (NC) composed of two shells. The outer shell is composed of protein P8 with a T = 13 icosahedral lattice while the primary component of the inner shell is a dodecahedral frame composed of dimeric protein P1. For the current study, the 3D architecture of the intact {phi}12 virus was obtained by electron cryo-tomography. The nucleocapsid appears to be centered within the membrane envelope and possibly attached to it by bridging structures. Two types of densities were observed protruding from the membrane envelope. The densities of the first type were elongated, running parallel, and closely associated to the envelope outer surface. In contrast, the second density was positioned about 12 nm above the envelope connected to it by a flexible low-density stem. This second structure formed a torroidal structure termed 'the donut' and appears to inhibit BHT-induced viral envelope fusion.

Hu Guobin [Structural Biology Program, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016 (United States); Wei Hui [Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, City College of New York, NY 10031 (United States); Rice, William J. [New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027 (United States); Stokes, David L. [Structural Biology Program, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016 (United States); New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027 (United States); Gottlieb, Paul [Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, City College of New York, NY 10031 (United States); Ph.D. Program in Biology, Graduate School and University Center, City University of New York, NY 10016 (United States)], E-mail: pgottl@med.cuny.edu

2008-03-01

275

Structure, assembly and dynamics of macromolecular complexes by single particle cryo-electron microscopy  

PubMed Central

Background Proteins in their majority act rarely as single entities. Multisubunit macromolecular complexes are the actors in most of the cellular processes. These nanomachines are hold together by weak protein-protein interactions and undergo functionally important conformational changes. TFIID is such a multiprotein complex acting in eukaryotic transcription initiation. This complex is first to be recruited to the promoter of the genes and triggers the formation of the transcription preinitiation complex involving RNA polymerase II which leads to gene transcription. The exact role of TFIID in this process is not yet understood. Methods Last generation electron microscopes, improved data collection and new image analysis tools made it possible to obtain structural information of biological molecules at atomic resolution. Cryo-electron microscopy of vitrified samples visualizes proteins in a fully hydrated, close to native state. Molecular images are recorded at liquid nitrogen temperature in low electron dose conditions to reduce radiation damage. Digital image analysis of these noisy images aims at improving the signal-to-noise ratio, at separating distinct molecular views and at reconstructing a three-dimensional model of the biological particle. Results Using these methods we showed the early events of an activated transcription initiation process. We explored the interaction of the TFIID coactivator with the yeast Rap1 activator, the transcription factor TFIIA and the promoter DNA. We demonstrated that TFIID serves as an assembly platform for transient protein-protein interactions, which are essential for transcription initiation. Conclusions Recent developments in electron microscopy have provided new insights into the structural organization and the dynamic reorganization of large macromolecular complexes. Examples of near-atomic resolutions exist but the molecular flexibility of macromolecular complexes remains the limiting factor in most case. Electron microscopy has the potential to provide both structural and dynamic information of biological assemblies in order to understand the molecular mechanisms of their functions. PMID:24565374

2013-01-01

276

Super-Resolution Microscopy Using Standard Fluorescent Proteins in Intact Cells under Cryo-Conditions  

PubMed Central

We introduce a super-resolution technique for fluorescence cryo-microscopy based on photoswitching of standard genetically encoded fluorescent marker proteins in intact mammalian cells at low temperature (81 K). Given the limit imposed by the lack of cryo-immersion objectives, current applications of fluorescence cryo-microscopy to biological specimens achieve resolutions between 400–500 nm only. We demonstrate that the single molecule characteristics of reversible photobleaching of mEGFP and mVenus at liquid nitrogen temperature are suitable for the basic concept of single molecule localization microscopy. This enabled us to perform super-resolution imaging of vitrified biological samples and to visualize structures in unperturbed fast frozen cells for the first time with a structural resolution of ?125 nm (average single molecule localization accuracy ?40 nm), corresponding to a 3–5 fold resolution improvement. PMID:24884378

2014-01-01

277

Coordinate transformation based cryo-correlative methods for electron tomography and focused ion beam milling.  

PubMed

Correlative microscopy allows imaging of the same feature over multiple length scales, combining light microscopy with high resolution information provided by electron microscopy. We demonstrate two procedures for coordinate transformation based correlative microscopy of vitrified biological samples applicable to different imaging modes. The first procedure aims at navigating cryo-electron tomography to cellular regions identified by fluorescent labels. The second procedure, allowing navigation of focused ion beam milling to fluorescently labeled molecules, is based on the introduction of an intermediate scanning electron microscopy imaging step to overcome the large difference between cryo-light microscopy and focused ion beam imaging modes. These methods make it possible to image fluorescently labeled macromolecular complexes in their natural environments by cryo-electron tomography, while minimizing exposure to the electron beam during the search for features of interest. PMID:24332462

Fukuda, Yoshiyuki; Schrod, Nikolas; Schaffer, Miroslava; Feng, Li Rebekah; Baumeister, Wolfgang; Lucic, Vladan

2014-08-01

278

Phasing of the Triatoma virus diffraction data using a cryo-electron microscopy reconstruction  

SciTech Connect

The blood-sucking reduviid bug Triatoma infestans, one of the most important vector of American human trypanosomiasis (Chagas disease) is infected by the Triatoma virus (TrV). TrV has been classified as a member of the Cripavirus genus (type cricket paralysis virus) in the Dicistroviridae family. This work presents the three-dimensional cryo-electron microscopy (cryo-EM) reconstruction of the TrV capsid at about 25 A resolution and its use as a template for phasing the available crystallographic data by the molecular replacement method. The main structural differences between the cryo-EM reconstruction of TrV and other two viruses, one from the same family, the cricket paralysis virus (CrPV) and the human rhinovirus 16 from the Picornaviridae family are presented and discussed.

Estrozi, L.F.; Neumann, E. [IBS, Institut de Biologie Structurale Jean-Pierre Ebel. CEA, CNRS, Universite Joseph Fourier. 41 rue Jules Horowitz, F-38027 Grenoble (France); Squires, G. [Institut Curie, 26, rue d'Ulm 75248 Paris Cedex 05 (France); Rozas-Dennis, G. [Departamento de Biologia, Bioquimica y Farmacia, U.N.S., San Juan 670, (8000) Bahia Blanca (Argentina); Costabel, M. [Grupo de Biofisica, Departamento de Fisica U.N.S., Av. Alem 1253, (8000) Bahia Blanca (Argentina); Rey, F.A. [Institut Pasteur, 25 rue du Dr. Roux, F-75724 Paris (France); Guerin, D.M.A. [Unidad de Biofisica (UPV/EHU-CSIC), P.O. Box 644, E-48080 Bilbao (Spain)], E-mail: diego.guerin@ehu.es; Navaza, J. [IBS, Institut de Biologie Structurale Jean-Pierre Ebel, CEA, CNRS, Universite Joseph Fourier, 41 rue Jules Horowitz, F-38027 Grenoble (France)], E-mail: jorge.navaza@ibs.fr

2008-05-25

279

Negative staining and Cryo-negative Staining of Macromolecules and Viruses for TEM  

PubMed Central

In this review we cover the technical background to negative staining of biomolecules and viruses, and then expand upon the different possibilities and limitations. Topics range from conventional air-dry negative staining of samples adsorbed to carbon support films, the variant termed the “negative staining-carbon film” technique and negative staining of samples spread across the holes of holey carbon support films, to a consideration of dynamic/time-dependent negative staining. For each of these approaches examples of attainable data are given. The cryo-negative staining technique for the specimen preparation of frozen-hydrated/vitrified samples is also presented. A detailed protocol to successfully achieve cryo-negative staining with ammonium molybdate is given, as well as examples of data, which support the claim that cryo-negative staining provides a useful approach for the high-resolution study of macromolecular and viral structure. PMID:20634082

De Carlo, Sacha; Harris, J. Robin

2010-01-01

280

Fabs enable single particle cryoEM studies of small proteins  

PubMed Central

Summary In spite of its recent achievements, the technique of single particle electron cryomicroscopy (cryoEM) has not been widely used to study proteins smaller than 100kDa, although it is a highly desirable application of this technique. One fundamental limitation is that images of small proteins embedded in vitreous ice do not contain adequate features for accurate image alignment. We describe a general strategy to overcome this limitation by selecting a fragment antigen binding (Fab) to form a stable and rigid complex with a target protein, thus providing a defined feature for accurate image alignment. Using this approach, we determined a three-dimensional structure of a ~65 kDa protein by single particle cryoEM. Because Fabs can be readily generated against a wide range of proteins by phage display, this approach is generally applicable to study many small proteins by single particle cryoEM. PMID:22483106

Wu, Shenping; Avila-Sakar, Agustin; Kim, JungMin; Booth, David S.; Greenberg, Charles H.; Rossi, Andrea; Liao, Maofu; Li, Xueming; Alian, Akram; Griner, Sarah L.; Juge, Narinobu; Yu, Yadong; Mergel, Claudia M.; Chaparro-Riggers, Javier; Strop, Pavel; Tampe, Robert; Edwards, Robert H.; Stroud, Robert M.; Craik, Charles S.; Cheng, Yifan

2012-01-01

281

Reconstructing virus structures from nanometer to near-atomic resolutions with cryo-electron microscopy and tomography  

PubMed Central

The past few decades have seen tremendous advances in single particle electron cryo-microscopy (cryo-EM). The field has matured to the point that near-atomic resolution density maps can be generated for icosahedral viruses without the need for crystallization. In parallel, substantial progress has been made in determining the structures of non-icosahedrally arranged proteins in viruses by employing either single particle cryo-EM or cryo-electron tomography (cryo-ET). Implicit in this course has been the availability of a new generation of electron cryo-microscopes and the development of the computational tools that are essential for generating these maps and models. This methodology has enabled structural biologists to analyze structures in increasing detail for virus particles that are in different morphogenetic and biochemical states. Furthermore, electron imaging of frozen, hydrated cells, in the process of being infected by viruses, has also opened up a new avenue for studying virus structures “in situ”. Here we present the common techniques used to acquire and process cryo-EM and cryo-ET data and discuss their implications for structural virology both now and in the future. PMID:22297510

Chang, Juan; Liu, Xiangan; Rochat, Ryan H.; Baker, Matthew L.; Chiu, Wah

2014-01-01

282

Pulse-to-pulse correlation in CryoSat SAR mode radar altimeter echoes from the sea surface  

NASA Astrophysics Data System (ADS)

Serial correlation among successive radar echoes returned from the ocean surface is an important design constraint in satellite altimetry. Walsh [1974, 1982] established the conventional wisdom. Taking the radar footprint to be a uniformly radiating disk, he derived a theoretically expected echo decorrelation time of about 0.5 milliseconds. Following Walsh, ocean altimeters usually employ a pulse repetition frequency (PRF) around 2 kHz, in order to obtain statistically independent echoes at (so it is thought) the maximum possible rate. CryoSat, designed for ranging to ice surfaces, employs a PRF of 18.2 kHz in its SAR mode. CryoSat SAR echo sequences over ocean surfaces can be used to empirically determine the ocean echo decorrelation, and thus to test Walsh's model. Such a test is presented in this paper. The analysis begins by forming the ensemble average of complex cross products of pairs of echoes separated by a time lag L * PRI, where the pulse repetition interval (PRI) is 55 microseconds and the echo lag L runs from 0 to 32. The L = 0 case yields the conventional pulse-limited waveform, which is used to determine the sea state in each ensemble average. The averages of lagged echo cross products reveal the complex coherency, with sampling in both slow time (lag, L), and fast time (range, sampled in waveform gates). Data from many areas and sea states are analyzed, and the results are explained using a simple theory approximating the complex coherency expected from a Gaussian radar pulse. This theory generalizes the classical Brown [1977] waveform model to lagged echo cross products, and generalizes Walsh's work to the case of footprints with non-uniform illumination and diffuse edges. Phase is due to vertical motion of the antenna. Amplitude variations in fast time are due to horizontal motion of the antenna, and are independent of wave height; their functional form confirms Brown's assumption that scattering is independent of azimuth. In slow time, the amplitude decays with lag at a rate that depends on wave height, and without zero crossings. This is in contrast to Walsh's theory, which established the conventional wisdom based on the first zero crossing of Bessel function J1. These results may be applied to determine the optimally weighted average of SAR echoes that yields the best conventional waveform for inter-calibration of SAR and conventional measurements. This calibration is useful for CryoSat and will be necessary for Sentinel-3 and Jason-CS. The present work finds that a conventional altimeter may obtain useful data at rates as high as 9 kHz. This suggests that the interleaved mode option under consideration for Jason-CS could yield optimal conventional measurements as well as simultaneous SAR. I gratefully acknowledge Ron Abileah, Eric Leuliette, John Lillibridge, Laury Miller, Tom Newman and the CryoSat team for helpful discussions.

Smith, W. H.

2012-12-01

283

Wettability studies at the pore level: A new approach by use of Cryo-SEM  

SciTech Connect

Cryo-scanning electron microscopy (Cryo-SEM) is used to study the wettability of reservoir rocks from fluid distribution at irreducible water saturation, S{sub wi}, and residual oil saturation, S{sub or}. Results on mixed-wettability cores point out the importance of composition, distribution, and accessibility of minerals in determining the macroscopic behavior of the rocks. For the studied samples, wettability of sandstones is related to the presence of kaolinite, while wettability of carbonates seems to be related to pore-size distribution.

Robin, M.; Rosenberg, E. [Inst. Francais du Petrole, Rueil-Malmaison (France); Fassi-Fihri, O.

1995-03-01

284

Retrofit implementation of Zernike phase plate imaging for cryo-TEM  

PubMed Central

In-focus phase-plate imaging is particularly beneficial for cryo-TEM because it offers a substantial overall increase in image contrast, without an electron dose penalty, and it simplifies image interpretation. We show how phase-plate cryo-TEM can be implemented with an appropriate existing TEM, and provide a basic practical introduction to use of thin-film (carbon) phase plates. We point out potential pitfalls of phase-plate operation, and discuss solutions. We provide information on evaluating a particular TEM for its suitability. PMID:21272647

Marko, Michael; Leith, ArDean; Hsieh, Chyongere; Danev, Radostin

2011-01-01

285

Yolk-Shell Nanostructured Fe3O4@NiSiO3 for Selective Affinity and Magnetic Separation of His-Tagged Proteins.  

PubMed

Recent developments of nanotechnology encourage novel materials for facile separations and purifications of recombinant proteins, which are of great importance in disease diagnoses and treatments. We find that Fe3O4@NiSiO3 with yolk-shell nanostructure can be used to specifically purify histidine-tagged (His-tagged) proteins from mixtures of lysed cells with a recyclable process. Each individual nanoparticle composes by a mesoporous nickel silicate shell and a magnetic Fe3O4 core in the hollow inner, which is featured by its great loading efficiency and rapid response toward magnetic fields. The abundant Ni(2+) cations on the shell provide docking sites for selective coordination of histidine and the reversible release is induced by excess imidazole solution. Because of the Fe3O4 cores, the separation, concentration, and recycling of the nanocomposites become feasible under the controls of magnets. These characteristics would be highly beneficial in nanoparticle-based biomedical applications for targeted-drug delivery and biosensors. PMID:25303145

Wang, Yang; Wang, Guangchuan; Xiao, Yun; Yang, Yuling; Tang, Ruikang

2014-11-12

286

A novel magnetically separable TiO{sub 2}/CoFe{sub 2}O{sub 4} nanofiber with high photocatalytic activity under UV-vis light  

SciTech Connect

Graphical abstract: A novel magnetically separable composite photocatalyst TiO{sub 2}/CoFe{sub 2}O{sub 4} nanofiber was prepared by sol-gel method and electrospinning technique, which can be reclaimed with a magnet, and the decolorizing efficiency of MB solution reached 95.87%. Highlights: Black-Right-Pointing-Pointer The composite TiO{sub 2}/CoFe{sub 2}O{sub 4} nanofibers with diameter of 110 {+-} 28 nm have been successfully synthesized by the combination of sol-gel method and electrospinning technique. Black-Right-Pointing-Pointer The presence of Co{sup 2+} or/and Fe{sup 3+} ions may occupy some of the lattice sites of TiO{sub 2} to form an iron-titanium solid solution and narrow the band gap, which broadens the response region of visible light. Black-Right-Pointing-Pointer The resultant nanofibers not only have high decomposition efficiency with methylene blue (MB) under the UV irradiation, which is close to that of Degussa P25, but also can be separated with a magnet and avoid the secondary pollution of the treated water. -- Abstract: A novel magnetically separable heterogeneous photocatalyst TiO{sub 2}/CoFe{sub 2}O{sub 4} nanofiber was prepared by sol-gel method and electrospinning technology, followed by heat treatment at 550 Degree-Sign C for 2 h. The phase structure, morphology and magnetic property of the composite nanofibers were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope and vibrating sample magnetometer analysis. The photocatalytic studies of TiO{sub 2}/CoFe{sub 2}O{sub 4} fibers suggested that the presence of CoFe{sub 2}O{sub 4} not only enhanced the absorbance of UV light, but also broadened the response region to visible light. The decolorizing efficiency of methylene blue (MB) solution reaches 95.87% over TiO{sub 2}/CoFe{sub 2}O{sub 4} nanofibers under 300 W Hg lamp after 5 h, which is close to that of Degussa P25. Furthermore, these fibers can be collected with a magnet for reuse and effectively avoid the secondary pollution of the treated water.

Li, Cong-Ju, E-mail: congjuli@gmail.com [Beijing Key Laboratory of Clothing Materials R and D and Assessment, Beijing Institute of Fashion Technology, Beijing 100029 (China)] [Beijing Key Laboratory of Clothing Materials R and D and Assessment, Beijing Institute of Fashion Technology, Beijing 100029 (China); Wang, Jiao-Na; Wang, Bin [Beijing Key Laboratory of Clothing Materials R and D and Assessment, Beijing Institute of Fashion Technology, Beijing 100029 (China)] [Beijing Key Laboratory of Clothing Materials R and D and Assessment, Beijing Institute of Fashion Technology, Beijing 100029 (China); Gong, Jian Ru, E-mail: gongjr@nanoctr.cn [National Center for Nanoscience and Technology, China, 11 Zhongguancun Beiyitiao, Beijing 100190 (China); Lin, Zhang [Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian 350002 (China)] [Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian 350002 (China)

2012-02-15

287

Magnetically separable ternary hybrid of ZnFe2O4-Fe2O3-Bi2WO6 hollow nanospheres with enhanced visible photocatalytic property  

NASA Astrophysics Data System (ADS)

Magnetically separable ternary hybrid ZnFe2O4-Fe2O3-Bi2WO6 hollow nanospheres were designed and synthesized by an effective three-step approach. Specifically, using phenolic formaldehyde microspheres (PFS) as template direct the sequential coating of ?-Fe2O3/ZnFe2O4 layer and subsequent Bi2WO6 layer via impregnating-calcination process. The photocatalytic activity under visible light irradiation is in the order of ZnFe2O4-Fe2O3-Bi2WO6 > ZnFe2O4-Bi2WO6 > Bi2WO6 > ZnFe2O4-Fe2O3 > ZnFe2O4. The enhanced activity could be attributed to the cascade electron transfer from ZnFe2O4 to ?-Fe2O3 then to Bi2WO6 through the interfacial potential gradient in the ternary hybrid conduction bands, which facilitate the charge separation and retard the charge pair recombination. Furthermore, the ternary hybrid ZnFe2O4-Fe2O3-Bi2WO6 hollow nanospheres could be conveniently separated by using an external magnetic field, and be chemically and optically stable after several repetitive tests. The study also provides a general and effective method in the composite hollow nanomaterials with sound heterojunctions that may show a variety of applications.

Li, Junqi; Liu, Zhenxing; Zhu, Zhenfeng

2014-11-01

288

Magnetically separable core-shell structural ?-Fe2O3@Cu/Al-MCM-41 nanocomposite and its performance in heterogeneous Fenton catalysis.  

PubMed

To target the low catalytic activity and the inconvenient separation of copper loading nanocatalysts in heterogeneous Fenton-like reaction, a core-shell structural magnetically separable catalyst, with ?-Fe2O3 nanoparticles as the core layer and the copper and aluminum containing MCM-41 as the shell layer, has been fabricated. The role of aluminum has been discussed by comparing the copper containing mesoporous silica with various Cu contents. Their physiochemical properties have been characterized by XRD, UV-vis, FT-IR, TEM, nitrogen physisorption and magnetite susceptibility measurements. Double content Cu incorporation results in an improved catalytic activity for phenol degradation at the given condition (40°C, initial pH=4), but leads to a declined BET surface area and less ordered mesophase structure. Aluminum incorporation helps to retain the high BET surface area (785.2m(2)/g) and the regular hexagonal mesoporous structure of MCM-41, which make the catalyst possess a lower copper content and even a higher catalytic activity than that with the double copper content in the absence of aluminum. The catalysts can be facilely separated by an external magnetic field for recycle usage. PMID:24295771

Ling, Yuhan; Long, Mingce; Hu, Peidong; Chen, Ya; Huang, Juwei

2014-01-15

289

Popcorn-shaped magnetic core-plasmonic shell multifunctional nanoparticles for the targeted magnetic separation and enrichment, label-free SERS imaging, and photothermal destruction of multidrug-resistant bacteria.  

PubMed

Over the last few years, one of the most important and complex problems facing our society is treating infectious diseases caused by multidrug-resistant bacteria (MDRB), by using current market-existing antibiotics. Driven by this need, we report for the first time the development of the multifunctional popcorn-shaped iron magnetic core-gold plasmonic shell nanotechnology-driven approach for targeted magnetic separation and enrichment, label-free surface-enhanced Raman spectroscopy (SERS) detection, and the selective photothermal destruction of MDR Salmonella DT104. Due to the presence of the "lightning-rod effect", the core-shell popcorn-shaped gold-nanoparticle tips provided a huge field of SERS enhancement. The experimental data show that the M3038 antibody-conjugated nanoparticles can be used for targeted separation and SERS imaging of MDR Salmonella DT104. A targeted photothermal-lysis experiment, by using 670 nm light at 1.5 W cm(-2) for 10 min, results in selective and irreparable cellular-damage to MDR Salmonella. We discuss the possible mechanism and operating principle for the targeted separation, label-free SERS imaging, and photothermal destruction of MDRB by using the popcorn-shaped magnetic/plasmonic nanotechnology. PMID:23296491

Fan, Zhen; Senapati, Dulal; Khan, Sadia Afrin; Singh, Anant Kumar; Hamme, Ashton; Yust, Brian; Sardar, Dhiraj; Ray, Paresh Chandra

2013-02-18

290

Theory of high gradient attractive magnetic separation of superconducting materials and its experimental verification by YBa2Cu3Ox particles  

NASA Astrophysics Data System (ADS)

The calculation of trajectories for sedimenting diamagnetic particles shows that superconducting matter in the Meissner or vortex state can be captured sidewise to a ferromagnetic wire magnetized perpendicular to its length. Capture is possible for externally applied fields lower than typical critical fields Hc1(c), Hc1(a,b) of cuprates. For single crystalline particles in the vortex state, the magnetic anisotropy may reduce the capture force because of alignment. Theoretical predictions were confirmed experimentally for suspensions of polycrystalline and single crystalline particles of YBa2Cu3Ox (size range: 2-125 µm) in liquid nitrogen. As a general conclusion we find that for the extraction of superconducting particles out of combinatorial ceramic reaction mixtures, separation in the Meissner state might be most effective because of the presence of an excess of normal state matter featuring a much lower diamagnetic susceptibility.

Dessauges, L.; Willems, J. B.; Favre, D.; Bohrer, C.; Helbling, F.; Hulliger, J.

2006-08-01

291

Whole Cell Cryo-Electron Tomography Reveals Distinct Disassembly Intermediates of Vaccinia Virus  

PubMed Central

At each round of infection, viruses fall apart to release their genome for replication, and then reassemble into stable particles within the same host cell. For most viruses, the structural details that underlie these disassembly and assembly reactions are poorly understood. Cryo-electron tomography (cryo-ET), a unique method to investigate large and asymmetric structures at the near molecular resolution, was previously used to study the complex structure of vaccinia virus (VV). Here we study the disassembly of VV by cryo-ET on intact, rapidly frozen, mammalian cells, infected for up to 60 minutes. Binding to the cell surface induced distinct structural rearrangements of the core, such as a shape change, the rearrangement of its surface spikes and de-condensation of the viral DNA. We propose that the cell surface induced changes, in particular the decondensation of the viral genome, are a prerequisite for the subsequent release of the vaccinia DNA into the cytoplasm, which is followed by its cytoplasmic replication. Generally, this is the first study that employs whole cell cryo-ET to address structural details of pathogen-host cell interaction. PMID:17487274

Cyrklaff, Marek; Linaroudis, Alexandros; Boicu, Marius; Chlanda, Petr; Baumeister, Wolfgang; Griffiths, Gareth; Krijnse-Locker, Jacomine

2007-01-01

292

Helium Cryo Testing of a SLMS(TM) (Silicon Lightweight Mirrors) Athermal Optical Assembly  

NASA Technical Reports Server (NTRS)

SLMS (TM) a thermal technology has been demonstrated in the small 4-foot helium cryogenic test chamber located at the NASA/MSFC X-Ray Calibration Facility (XRCF). A SLMS (TM) Ultraviolet Demonstrator Mirror (UVDM) produced by Schafer under a NASA/MSFC Phase I SBIR was helium cryo tested both free standing and bonded to a Schafer designed prototype carbon fiber reinforced silicon carbide (Cesic) mount. Surface figure data was obtained with a test measurement system that featured an Instantaneous Phase Interferometer (IPI) by ADE Phase Shift. The test measurement system s minimum resolvable differential figure deformation and possible contributions from test chamber ambient to cryo window deformation are under investigation. The free standing results showed differential figure deformation of 10.4 nm rms from 295K to 27K and 3.9 nm rms after one cryo cycle. The surface figure of the UVDM degraded by lambda/70 rms HeNe once it was bonded to the prototype Cesic mount. The change was due to a small astigmatic aberration in the rototype Cesic mount due to lack of finish machining and not the bonding technique. This effect was seen in SLMST (TM) optical assembly results, which showed differential figure deformation of 46.5 nm rms from 294K to 27K, 42.9 nm rms from 294K to 77K, 28.0 nm rms from 294K to 193K and 6.2 nm rms after one cryo cycle.

Jacoby, Marc T.; Goodman, William A.; Stahl, H. Philip; Keys, Andrew S.; Reily, Jack C.; Eng, Ron; Hadaway, James B.; Hogue, William D.; Kegley, Jeffrey R.; Siler, Richard

2003-01-01

293

Direct electron detection yields cryo-EM reconstructions at resolutions beyond 3/4 Nyquist frequency  

PubMed Central

One limitation in electron cryo-microscopy (cryo-EM) is the inability to recover high-resolution signal from the image-recording media at the full-resolution limit of the transmission electron microscope. Direct electron detection using CMOS-based sensors for digitally recording images has the potential to alleviate this shortcoming. Here, we report a practical performance evaluation of a Direct Detection Device (DDD) for biological cryo-EM at two different microscope voltages: 200 and 300 kV. Our DDD images of amorphous and graphitized carbon show strong per-pixel contrast with image resolution near the theoretical sampling limit of the data. Single-particle reconstructions of two frozen-hydrated bacteriophages, P22 and ?15, establish that the DDD is capable of recording usable signal for 3-D reconstructions at about 4/5 of the Nyquist frequency, which is a vast improvement over the performance of conventional imaging media. We anticipate the unparalleled performance of this digital recording device will dramatically benefit cryo-EM for routine tomographic and single-particle structural determination of biological specimens. PMID:22285189

Bammes, Benjamin E.; Rochat, Ryan H.; Jakana, Joanita; Chen, Dong-Hua; Chiu, Wah

2012-01-01

294

Reaching the information limit in cryo-EM of biological macromolecules: experimental aspects.  

PubMed

Although cryo-electron microscopy (cryo-EM) of biological macromolecules has made important advances in the past few years, the level of current technical performance is still well below what the physics of electron scattering would allow. It should be possible, for example, to use cryo-EM to solve protein structures at atomic resolution for particle sizes well below 80 kDa, but currently this has been achieved only for particles at least 10 times larger than that. In this review, we first examine some of the reasons for this large gap in performance. We then give an overview of work that is currently in progress to 1), improve the signal/noise ratio for area detectors; 2), improve the signal transfer between the scattered electrons and the corresponding images; and 3), reduce the extent to which beam-induced movement causes a steep fall-off of signal at high resolution. In each case, there is substantial reason to think that cryo-EM can indeed be made to approach the estimated physical limits. PMID:21575566

Glaeser, Robert M; Hall, Richard J

2011-05-18

295

Characterization of emulsions and suspensions in the petroleum industry using cryo-SEM and CLSM  

Microsoft Academic Search

Confocal laser scanning and cryogenic scanning electron microscopy techniques for imaging colloidal systems are discussed. The advantages of each technique are shown along with examples of emulsions and suspensions from the petroleum industry. Given the sample preparation and manipulation that is sometimes required for cryo-SEM observation, the degree to which the images actually represent the sample morphology can be in

R. J Mikula; V. A Munoz

2000-01-01

296

Cryo-SEM specimen preparation under controlled temperature and concentration conditions.  

PubMed

Cryogenic temperature scanning electron microscopy (cryo-SEM) is an excellent technique for imaging liquid and semi-liquid materials of high vapour pressure, which are highly viscous or contain large (>0.5 ?m) aggregates, in which nanometric details are to be studied. However, so far there have been no adequate tools for controlled cryo-specimen preparation. The specimen preparation stage is critical, because most of those samples are very sensitive to concentration and temperature changes, leading to nanostructural artefacts in the specimens. We designed and built a system for easy and reliable cryo-SEM specimen preparation under controlled conditions of fixed temperature and humidity. We describe this new methodology, and demonstrate its applicability, by showing imaging data of three liquid material systems. We have studied carbon nanotubes (CNTs) dispersions in superacid. We also characterized a number of systems made of water/isooctane/nonionic and cationic surfactant that showed different microemulsion phases as function of the system composition and temperature. In all of the examples given, we demonstrate artefact- and contamination-free specimens, which have preserved their native nanostructure. Our new system paves the way for a new methodology for the newly emerging field of cryo-SEM. PMID:22268668

Issman, L; Talmon, Y

2012-04-01

297

Special features of phosphatidylcholine vesicles as seen in cryo-transmission electron microscopy  

Microsoft Academic Search

Vesicles of egg yolk phosphatidylcholine (EYPC) were studied by cryo-transmission electron microscopy. The electron micrographs indicate that, despite the rapidity of cooling, membrane undulations are flattened and some vesicles change their shapes before the samples freeze. These artefacts are attributed to the action of the lateral tension that results from the membrane area contraction associated with the temperature drop. Other

Beate Klösgen; Wolfgang Helfrich

1993-01-01

298

Ribosome structures to near-atomic resolution from thirty thousand cryo-EM particles  

PubMed Central

Although electron cryo-microscopy (cryo-EM) single-particle analysis has become an important tool for structural biology of large and flexible macro-molecular assemblies, the technique has not yet reached its full potential. Besides fundamental limits imposed by radiation damage, poor detectors and beam-induced sample movement have been shown to degrade attainable resolutions. A new generation of direct electron detectors may ameliorate both effects. Apart from exhibiting improved signal-to-noise performance, these cameras are also fast enough to follow particle movements during electron irradiation. Here, we assess the potentials of this technology for cryo-EM structure determination. Using a newly developed statistical movie processing approach to compensate for beam-induced movement, we show that ribosome reconstructions with unprecedented resolutions may be calculated from almost two orders of magnitude fewer particles than used previously. Therefore, this methodology may expand the scope of high-resolution cryo-EM to a broad range of biological specimens. DOI: http://dx.doi.org/10.7554/eLife.00461.001 PMID:23427024

Bai, Xiao-chen; Fernandez, Israel S; McMullan, Greg; Scheres, Sjors HW

2013-01-01

299

3D cryo-section\\/imaging of blood vessel lesions for validation of MRI data  

Microsoft Academic Search

Vascular disease is a leading cause of death and disability in the western world. Diagnosis and staging of atherosclerosis is a challenge, especially with regards to the identification of plaque vulnerability. We are developing imaging methods based upon MRI and intravascular microcoils. In order to rigorously validate our MRI imaging methods and algorithms, we have developed a new cryo-imaging system

Olivier Salvado; Debashish Roy; Meredith Heinzel; Eliot McKinley; David Wilson

2006-01-01

300

COMPOSITE TECHNOLOGY DEVELOPMENT INC. CryoCoatTM UltraLightTM  

E-print Network

: Adhesives Thermal Insulation Protective Coatings Each layer can be optimized gives best system performance Change to LHe Stop LHe Flow Insulation Thickness Approx. 1 1/2" LN2 Pre-Cool Thermal Time HistoryCOMPOSITE TECHNOLOGY DEVELOPMENT INC. CTD CryoCoatTM UltraLightTM Insulation presented by: Michael

McDonald, Kirk

301

Cryomesh(TM): A new substrate for cryo-electron microscopy  

PubMed Central

Here we evaluate a new grid substrate developed by ProtoChips Inc. for cryo-transmission electron microscopy. The new grids are fabricated from doped silicon carbide using processes adapted from the semi-conductor industry. A major motivating purpose in the development of these grids was to increase the low-temperature conductivity of the substrate, a characteristic that is thought to affect the appearance of beam-induced movement (BIM) in TEM images of biological specimens. BIM degrades the quality of data, and is especially severe when frozen biological specimens are tilted in the microscope. Our results show that this new substrate does indeed have a significant impact on reducing the appearance and severity of beam-induced movement in TEM images of tilted cryo-preserved samples. Furthermore, while we have not been able to ascertain the exact causes underlying the BIM phenomenon, we have evidence that the rigidity and flatness of these grids may play a major role in its reduction. This improvement in the reliability of imaging at tilt has a significant impact on using data collection methods such as random conical tilt or orthogonal tilt reconstruction with cryo-preserved samples. Reduction in BIM also has the potential for improving the resolution of 3D cryo-reconstructions in general. PMID:20082728

Yoshioka, Craig; Carragher, Bridget; Potter, Clint

2010-01-01

302

Structure of intact Thermus thermophilus V-ATPase by cryo-EM reveals organization of the membrane-bound VO motor  

PubMed Central

The eubacterium Thermus thermophilus uses a macromolecular assembly closely related to eukaryotic V-ATPase to produce its supply of ATP. This simplified V-ATPase offers several advantages over eukaryotic V-ATPases for structural analysis and investigation of the mechanism of the enzyme. Here we report the structure of the complex at ?16 ? resolution as determined by single particle electron cryomicroscopy (cryo-EM). The resolution of the map and our use of cryo-EM, rather than negative stain EM, reveals detailed information about the internal organization of the assembly. We could separate the map into segments corresponding to subunits A and B, the threefold pseudosymmetric C-subunit, a central rotor consisting of subunits D and F, the L-ring, the stator subcomplex consisting of subunits I, E, and G, and a micelle of bound detergent. The architecture of the VO region shows a remarkably small area of contact between the I-subunit and the ring of L-subunits and is consistent with a two half-channel model for proton translocation. The arrangement of structural elements in VO gives insight into the mechanism of torque generation from proton translocation. PMID:20080582

Lau, Wilson C. Y.; Rubinstein, John L.

2010-01-01

303

Separation of the contributions to the magnetization of Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions in steady and pulsed magnetic fields  

SciTech Connect

The magnetization of substitutional Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions is studied in the composition range 0 < x {<=} 0.81. The measurements are performed at low temperatures (1.9-300 K) in steady (up to 11 T) and pulsed (up to 50 T, pulse duration of 20-100 ms) magnetic fields. An analysis of the experimental data allowed the contributions to the magnetization of the paramagnetic phase of the Tm{sub 1-x}Yb{sub x}B{sub 12} compounds to be separated. These contributions include a Pauli component, which corresponds to the response of the heavy-fermion manybody states that appears in the energy gap in the vicinity of the Fermi level (density of states (3-4) Multiplication-Sign 10{sup 21} cm{sup -3} meV{sup -1}), and a contribution with saturation in high magnetic fields attributed to the localized magnetic moments ((0.8-3.7){mu}{sub B} per unit cell) of the nanoclusters formed by rare-earth ions with an antiferromagnetic interaction.

Bogach, A. V., E-mail: alex@lt.gpi.ru; Sluchanko, N. E.; Glushkov, V. V.; Demishev, S. V.; Azarevich, A. N.; Filippov, V. B. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Shitsevalova, N. Yu.; Levchenko, A. V. [National Academy of Sciences of Ukraine, Institute of Problems of Materials Science (Ukraine); Vanacken, J.; Moshchalkov, V. V. [Katholieke Universiteit Leuven, Institute of Nanoscale Physics and Chemistry (Belgium); Gabani, S.; Flachbart, K. [Slovak Academy of Sciences, Institute of Experimental Physics (Slovakia)

2013-05-15

304

Time series over the Brahmaputra River from CryoSat-2/SIRAL altimetry  

NASA Astrophysics Data System (ADS)

CryoSat-2 was launched in 2010 with the purpose of monitoring polar ice caps, but the satellite has also proven to be useful for studies at lower latitudes. CryoSat-2 carries a new type of instrument, the SIRAL altimeter, which implements SAR and SARIn mode in addition to the standard LRM. In these modes the along-track resolution is 300m, giving rise to new opportunities for inland water altimetry, which requires a high along-track resolution in order to accurately capture the return signals from the water bodies. Here, we have investigated the possibilities for monitoring river water levels with CryoSat-2 as a part of the EU FP7 LOTUS (Preparing Land and Ocean Take Up from Sentinel-3). The LOTUS project will develop new methodologies, data processing chains, and applications of the SAR mode data for the inland water levels in rivers and lakes. Time series analysis for CryoSat-2 altimetry is not straightforward due to the satellite's very long repeat period of 369 days. It is therefore necessary to take new methods into use. Using slope correction, i.e. taking advantage of the drifting orbit, we have derived time series from retracked heights in all three modes of the CryoSat-2 altimeter over the Brahmaputra River. From the time series we can estimate the amplitude and the seasonal signal of the flow in the river. Presented here is a comparison of the results between modes and with Envisat time series.

Villadsen, Heidi; Baltazar Andersen, Ole; Knudsen, Per; Nielsen, Karina; Stenseng, Lars

2014-05-01

305

Limiting factors in atomic resolution cryo electron microscopy: no simple tricks.  

PubMed

To bring cryo electron microscopy (cryoEM) of large biological complexes to atomic resolution, several factors--in both cryoEM image acquisition and 3D reconstruction--that may be neglected at low resolution become significantly limiting. Here we present thorough analyses of four limiting factors: (a) electron-beam tilt, (b) inaccurate determination of defocus values, (c) focus gradient through particles, and (d) particularly for large particles, dynamic (multiple) scattering of electrons. We also propose strategies to cope with these factors: (a) the divergence and direction tilt components of electron-beam tilt could be reduced by maintaining parallel illumination and by using a coma-free alignment procedure, respectively. Moreover, the effect of all beam tilt components, including spiral tilt, could be eliminated by use of a spherical aberration corrector. (b) More accurate measurement of defocus value could be obtained by imaging areas adjacent to the target area at high electron dose and by measuring the image shift induced by tilting the electron beam. (c) Each known Fourier coefficient in the Fourier transform of a cryoEM image is the sum of two Fourier coefficients of the 3D structure, one on each of two curved 'characteristic surfaces' in 3D Fourier space. We describe a simple model-based iterative method that could recover these two Fourier coefficients on the two characteristic surfaces. (d) The effect of dynamic scattering could be corrected by deconvolution of a transfer function. These analyses and our proposed strategies offer useful guidance for future experimental designs targeting atomic resolution cryoEM reconstruction. PMID:21627992

Zhang, Xing; Zhou, Z Hong

2011-09-01

306

Imaging system for creating 3D block-face cryo-images of whole mice  

NASA Astrophysics Data System (ADS)

We developed a cryomicrotome/imaging system that provides high resolution, high sensitivity block-face images of whole mice or excised organs, and applied it to a variety of biological applications. With this cryo-imaging system, we sectioned cryo-preserved tissues at 2-40 ?m thickness and acquired high resolution brightfield and fluorescence images with microscopic in-plane resolution (as good as 1.2 ?m). Brightfield images of normal and pathological anatomy show exquisite detail, especially in the abdominal cavity. Multi-planar reformatting and 3D renderings allow one to interrogate 3D structures. In this report, we present brightfield images of mouse anatomy, as well as 3D renderings of organs. For BPK mice model of polycystic kidney disease, we compared brightfield cryo-images and kidney volumes to MRI. The color images provided greater contrast and resolution of cysts as compared to in vivo MRI. We note that color cryo-images are closer to what a researcher sees in dissection, making it easier for them to interpret image data. The combination of field of view, depth of field, ultra high resolution and color/fluorescence contrast enables cryo-image volumes to provide details that cannot be found through in vivo imaging or other ex vivo optical imaging approaches. We believe that this novel imaging system will have applications that include identification of mouse phenotypes, characterization of diseases like blood vessel disease, kidney disease, and cancer, assessment of drug and gene therapy delivery and efficacy and validation of other imaging modalities.

Roy, Debashish; Breen, Michael; Salvado, Olivier; Heinzel, Meredith; McKinley, Eliot; Wilson, David

2006-03-01

307

3D Cryo-Imaging: A Very High-Resolution View of the Whole Mouse  

PubMed Central

We developed the Case Cryo-imaging system that provides information rich, very high-resolution, color brightfield, and molecular fluorescence images of a whole mouse using a section-and-image block-face imaging technology. The system consists of a mouse-sized, motorized cryo-microtome with special features for imaging, a modified, brightfield/ fluorescence microscope, and a robotic xyz imaging system positioner, all of which is fully automated by a control system. Using the robotic system, we acquired microscopic tiled images at a pixel size of 15.6 µm over the block face of a whole mouse sectioned at 40 µm, with a total data volume of 55 GB. Viewing 2D images at multiple resolutions, we identified small structures such as cardiac vessels, muscle layers, villi of the small intestine, the optic nerve, and layers of the eye. Cryo-imaging was also suitable for imaging embryo mutants in 3D. A mouse, in which enhanced green fluorescent protein was expressed under gamma actin promoter in smooth muscle cells, gave clear 3D views of smooth muscle in the urogenital and gastrointestinal tracts. With cryo-imaging, we could obtain 3D vasculature down to 10 µm, over very large regions of mouse brain. Software is fully automated with fully programmable imaging/sectioning protocols, email notifications, and automatic volume visualization. With a unique combination of field-of-view, depth of field, contrast, and resolution, the Case Cryo-imaging system fills the gap between whole animal in vivo imaging and histology. PMID:19248166

Roy, Debashish; Steyer, Grant J.; Gargesha, Madhusudhana; Stone, Meredith E.; Wilson, David L.

2009-01-01

308

High-speed cryo-focusing injection for gas chromatography: reduction of injection band broadening with concentration enrichment.  

PubMed

In order to maximize peak capacity and detection sensitivity of fast gas chromatography (GC) separations, it is necessary to minimize band broadening, and in particular due to injection since this is often a major contributor. A high-speed cryo-focusing injection (HSCFI) system was constructed to first cryogenically focus analyte compounds in a 6 cm long section of metal MXT column, and second, reinject the focused analytes by rapidly resistively heating the metal column via an in-house built electronic circuit. Since the cryogenically cooled section of column is small (?750 nl) and the direct resistive heating is fast (?6000 °C/s), HSCFI is demonstrated to produce an analyte peak with a 6.3 ms width at half height, w(1/2). This was achieved using a 1m long column with a 180 ?m inner diameter (i.d.) operated at an absolute head pressure of 55 psi and an oven temperature of 60 °C, with a 10 V pulse applied to the metal column for 50 ms. HSCFI was also used to demonstrate the head space sampling and fast GC analysis of an aqueous solution containing six test analytes (acetone, methanol, ethanol, toluene, chlorobenzene, pentanol). Using Henry's law constants for each of the analytes, injected mass limits of detection (LODs) were typically in the low pg levels (e.g., 1.2 pg for acetone) for the high speed separation. Finally, to demonstrate the use of HSCFI with a complex sample, a gasoline was separated using a 20 m × 100 ?m i.d. column and the stock GC oven for temperature programming, which provided a separation time of 200 s and an average peak width at the base of 440 ms resulting in a total peak capacity of 460 peaks (at unit resolution). PMID:22841041

Wilson, Ryan B; Fitz, Brian D; Mannion, Brandyn C; Lai, Tina; Olund, Roy K; Hoggard, Jamin C; Synovec, Robert E

2012-08-15

309

Enantiomeric separation by microchip electrophoresis using bovine serum albumin conjugated magnetic core-shell Fe3 O4 @Au nanocomposites as stationary phase.  

PubMed

In this work, a novel enantioselective MCE was developed employing BSA-conjugated Fe3 O4 @Au nanoparticles (Fe3 O4 @Au NPs) as stationary phase. Fe3 O4 @Au NPs with high magnetic responsively, excellent solubility, and high dispersibility in water were prepared through a sonochemical synthesis strategy. BSA was then immobilized onto the Fe3 O4 @Au NPs surfaces through the well-developed interaction between Au NPs and amine groups of BSA to form Fe3 O4 @Au NPs-BSA conjugates, which were then locally packed into PDMS microchannels with the help of magnets. The resultant Fe3 O4 @Au NPs-BSA conjugates not only have the magnetism of Fe3 O4 NPs that make them easily manipulated by an external magnetic field, but also have the larger surface and excellent biocompatibility of Au shell, which can incorporate much more biomolecules and well maintain their biological activity. In addition, the successful BSA decorations endowed Fe3 O4 @Au NPs-BSA conjugates with pH-tunable water solubility related to the pI of BSA (pI 4.7) and led to enhanced stability against high ionic strength. Compared with the native PDMS microchannel, the modified surfaces exhibited more stable and suppressed electroosmotic mobility, and less nonspecific adsorption toward analytes. Successful separation of chiral amino acids (tryptophan and threonine) and ofloxacin enantiomers demonstrate that the constructed MCE columns own ideal enantioselectivity. The results are expected to open up a new possibility for high-throughput screening of enantiomers with protein targets as well as a new application of magnetic NPs. PMID:25042461

Liang, Ru-Ping; Wang, Xiao-Ni; Wang, Li; Qiu, Jian-Ding

2014-10-01

310

Magnetically-Separable and Highly-Stable Enzyme System Based on Crosslinked Enzyme Aggregates Shipped in Magnetite-Coated Mesoporous Silica  

SciTech Connect

Magnetically-separable and highly-stable enzyme system was developed by adsorption of enzymes in superparamagnetic hierarchically ordered mesocellular mesoporous silica (M-HMMS) and subsequent enzyme crosslinking. Superparamagnetic nanoparticles were homogeneously incorporated into hierarchically-ordered mesocellular mesoporous silica (HMMS) by the decomposition of preformed iron propionate complex. The size of incorporated superparamagnetic 15 nanoparticles was around 5 nm, generating a magnetically separable host with high pore volumes and large pores (M-HMMS). ?-chymotrypsin (CT) was adsorbed into M-HMMS with high loading (~30 wt%) in less than 30 minutes. Glutaraldehyde (GA) treatment of adsorbed CT resulted in nanometer scale crosslinked enzyme aggregates in M-HMMS (CLEA-M). The activity of these CT aggregates in M-HMMS (CLEA-M-CT) was 34 times than that of simply adsorbed CT in M20 HMMS, due to an effective prevention of enzyme leaching during washing via a ship-in-a-bottle approach. CLEA-M-CT maintained the intial activity not only under shaking (250 rpm) for 30 days, but also under recycled uses of 35 times. The same approach was employed for the synthesis of CLEA-M of lipase (CLEA-M-LP), and proven to be effective in improving the loading, activity, and stability of enzyme when compared to those of adsorbed LP in M-HMMS.

Lee, Jinwoo; Na, Hyon Bin; Kim, Byoung Chan; Lee, Jin Hyung; Lee, Byoungsoo; Kwak, Ja Hun; Hwang, Yosun; Park, Je-Geun; Gu, Man Bock; Kim, Jaeyun; Joo, Jin; Shin, Chae-Ho; Grate, Jay W.; Hyeon, Taeghwan; Kim, Jungbae

2009-10-15

311

Phase separation in Fe-Si and Co-Si sputtered ferromagnetic alloys and the origin of their magnetic anisotropy  

SciTech Connect

Fe-Si and Co-Si thin films were studied with different Si concentrations by x-ray absorption spectroscopy (XAFS), and the analysis was confronted to their magnetic properties of coercivity and anisotropy. The analysis of the XAFS spectra showed a higher disorder in the amorphous Fe-Si films than in the Co-Si films and a larger degree of clustering of Co atoms, consistent with the higher heat of alloying of Fe-Si with respect to Co-Si alloys. Both kinds of amorphous films contained a strongly disordered silicide phase that was hardly detected by extended XAFS spectroscopy (EXAFS). EXAFS spectra were dominated by the nonmagnetic (Fe,Co)Si{sub 2} environments. The orientation of the magnetic easy axis of the films was correlated with the expected anisotropic spatial distribution of Si concentration, which was defined by the oblique angle of incidence of Si atoms during film deposition. This indicates that such a detected nonmagnetic Si rich environments were anisotropically distributed and possibly segregated, influencing in a significant way the magnetic anisotropy of these films.

Diaz, J.; Morales, R.; Valvidares, S.M.; Alameda, J.M. [Departamento de Fisica, Universidad de Oviedo, Avenida de Calvo Sotelo s/n, Oviedo-33007 (Spain)

2005-10-01

312

Magnetic affinity microspheres with meso-/macroporous shells for selective enrichment and fast separation of phosphorylated biomolecules.  

PubMed

The flowerlike multifunctional affinity microspheres prepared by a facile solvothermal synthesis and subsequent calcination process consist of magnetic cores and hierarchical meso-/macroporous TiO2 shells. The hierarchical porous structure of the flowerlike affinity microspheres is constructed by the macroporous shell from the stacked mesoporous nanopetals which are assembled by small crystallites. The affinity microspheres have a relatively large specific surface area of 50.45 m(2) g(-1) and superparamagnetism with a saturation magnetization (Ms) value of 30.1 emu g(-1). We further demonstrate that they can be applied for rapid and effective purification of phosphoproteins, in virtue of their selective affinity, porous structure, and strong magnetism. In addition, the affinity microspheres can also be used for enrichment of phosphopeptides, and the selectivity is greatly improved due to the increase of mass transport and prevention of the possible "shadow effect" resulting from the smaller and deeper pores by taking advantage of the unique porous structure. Overall, this work will be highly beneficial for future applications in the isolation and identification of phosphorylated biomolecules. PMID:23514605

Cheng, Gong; Wang, Zhi-Gang; Liu, Yan-Lin; Zhang, Ji-Lin; Sun, De-Hui; Ni, Jia-Zuan

2013-04-24

313

The high Beta cryo-modules and the associated cryogenic system for the HIE-ISOLDE upgrade at CERN  

NASA Astrophysics Data System (ADS)

The major upgrade of the energy and intensity of the existing ISOLDE and REX-ISOLDE radioactive ion beam facilities at CERN requires the replacement of most of the existing ISOLDE post-acceleration equipment by a superconducting linac based on quarter-wave resonators housed together with superconducting solenoids in a series of four high-? and two low-? cryo-modules. As well as providing optimum conditions for physics, the cryo-modules need to function under stringent vacuum and cryogenic conditions. We present the detail design and expected cryogenic performance of the high- ? cryo-module together with the cryogenic supply and distribution system destined to service the complete superconducting linac.

Delruelle, N.; Leclercq, Y.; Pirotte, O.; Ramos, D.; Tibaron, P.; Vandoni, G.; Williams, L.

2014-01-01

314

Solid-solid grinding/templating route to magnetically separable nitrogen-doped mesoporous carbon for the removal of Cu(2+) ions.  

PubMed

N-doped ordered mesoporous carbon materials (NOMC) with 2D hexagonal symmetry structure were synthesized via a facile solid-solid grinding/templating route, in which the ionic liquids (ILs) of 1-cyanoethyl-3-methylimidazolium chloride and SBA-15 were employed as the precursor and hard template, respectively. The as-synthesized NOMC features with a uniform mesoporous size (3.5nm), ropes-like morphology (0.4-1?m in length) and high surface area (803m(2)/g). The quantitative analysis revealed the nitrogen content on the surface of NOMC is 5.5at%. Magnetic iron nanoparticles were successfully embedded into the carbon matrix by introducing iron chloride to the mixture of SBA-15 and ILs during the synthesis process. The NOMC-Fe composite possessed superior adsorption capacity of Cu(2+) ions (23.6mg/g). Kinetic and isothermal analysis demonstrated the strong interactions between Cu(2+) ion and the adsorbent. Furthermore, the composite was magnetically separable from solution under an external magnetic field and thus displayed a superior reusability in the recycling test. PMID:25072134

Chen, Aibing; Yu, Yifeng; Zhang, Yue; Xing, Tingting; Wang, Yanyan; Zhang, Yexin; Zhang, Jian

2014-08-30

315

Separation and characterization of modified pregabalins in terms of cyclodextrin complexation, using capillary electrophoresis and nuclear magnetic resonance.  

PubMed

The (S)-(+)-isomer of 3-isobutyl-GABA (pregabalin), the blockbuster drug in the treatment of neuropathic pain has been separated from its R isomer by cyclodextrin modified capillary zone electrophoresis (CZE) using uncoated fused-silica capillary. Derivatization of the single isomer and the racemate with tosyl- and dansyl-chloride was carried out to introduce strong UV chromophores of different size. CE-pH titrations were performed to determine the dissociation constants for both derivatives. 30 cyclodextrin (CD) derivatives as chiral agents were used at four different pH values to study the enantioseparation of the differently protonated guest molecules. The separation was optimized as a function of CD concentration, buffer type and concentration, pH and applied voltage. For the tosylated derivate the best resolution (R(s)=2.76) was found with 6-monodeoxy-6-mono-(3-hydroxy)-propylamino-beta-cyclodextrin hydrochloride (PA-beta-CD) at pH 6.8, while with the same selector at pH 7.2 enantioseparation with an R(s) value of 4.32 could be achieved for the dansylated pregabalin. At pH 2.5 for the dansylated derivative trimethylated alpha- and beta-CD systems resulted the most significant separation (R(s)=7.38 and R(s)=7.74, respectively). Experiments with dual CD systems were carried out as well. The stoichiometry of the complexes was determined using the Job plot method and resulted in a 1:1 complex in both cases. The structures of the inclusion complexes were elucidated using 2D ROESY NMR experiments. PMID:19914021

Béni, Szabolcs; Sohajda, Tamás; Neumajer, Gábor; Iványi, Róbert; Szente, Lajos; Noszál, Béla

2010-03-11

316

Selective adsorption and separation of chromium (VI) on the magnetic iron-nickel oxide from waste nickel liquid.  

PubMed

The selective adsorption of Cr (VI) from the wastewater of Cr (VI)-Ni (II) by magnetically iron-nickel oxide was investigated in this study. Synthetic iron-nickel oxide magnetic particles in the co-sedimentation method were used as adsorbent to remove hexavalent chromium ions. The characteristic of adsorption was evaluated by Langmuir, Freundlich isotherm and Dubinin-Kaganer-Radushkevich (DKR) equations in the simulation wastewater of Cr (VI)-Ni (II) bi-system. The energy spectra and FT-IR analysis were used to test adsorbent before and after adsorption. The obtained results suggest that the uptake of chromium (VI) effect is obvious from phosphate anions and that from others is unobvious. The maximum adsorption capacity of hexavalent chromium is about 30 mg/g at pH 5.00+/-0.02, and it was reduced by increasing the total dissolved substance (TDS) of system. Adsorption energies E are about 10.310-21.321 kJ/mol which were obtained from DKR equation in difference TDS conditions. The regeneration shows that the iron-nickel oxide has good reuse performance and the hexavalent chromium was recycled. The major adsorption mechanism proposed was the ions exchange; however the surface coordination was a main role in the condition of TDS less than 200mg/L. PMID:18954940

Wei, Linsen; Yang, Gang; Wang, Ren; Ma, Wei

2009-05-30

317

Separation of lanthanides and actinides using magnetic silica particles bearing covalently attached tetra-CMPO-calix[4]arenes.  

PubMed

Calix[4]arene tetraethers in the cone conformation bearing four -NH-CO-CH2-P(O)Ph2 (= CMPO) residues on their wide rim and one, two or four omega-amino alkyl residues of various lengths at the narrow rim were synthesized. Reaction with dichlorotriazinyl (DCT) functionalized magnetic particles led to complete coverage of the available surface by covalently linked CMPO-calix[4]arenes in all cases. Magnetically assisted removal of Eu(iii) and Am(iii) from acidic solutions was distinctly more efficient with these particles in comparison to analogous particles bearing the same amount of analogous single-chain CMPO-functions. The best result, an increase of the extraction efficiency by a factor of 140-160, was obtained for attachment via two propyl spacers. The selectivity Am/Eu was in the range of 1.9-2.8. No decrease of the extraction ability was observed, when the particles were repeatedly used, after simple back extraction with water. PMID:15305214

Böhmer, Volker; Dozol, Jean-François; Grüttner, Cordula; Liger, Karine; Matthews, Susan E; Rudershausen, Sandra; Saadioui, Mohamed; Wang, Pingshan

2004-08-21

318

Along-track Resolution of CryoSat Data for Marine Gravity Recovery  

NASA Astrophysics Data System (ADS)

The CryoSat mission's primary goal is to monitor elevation changes of ice-covered areas, but its excellent altimeter range precision and dense spatial coverage are providing major improvements to the accuracy of the marine gravity field. Development of optimal methods for combining CryoSat measurements with older altimetry data sets first requires an assessment of this new altimeter's spatial resolution capabilities. This is accomplished by performing a cross-spectral analysis of tracks that repeat to within about 1 kilometer apart. The spectral coherence is a measure of the ratio of the common geoid signal to the time varying oceanographic noise, as a function of spatial wavelength. The value of coherence is close to 1 at longer wavelengths where the signal dominates, and is small (< 0.2) where the noise dominates. A conservative estimate of the effective resolution is given by the wavelength at which the coherence level is 0.5. We conducted our analysis on CryoSat data acquired in two of its operating modes: the conventional pulse-limited mode (LRM), and also the novel beam-forming synthetic aperture mode (SAR). The waveform records were retracked using methods optimized for gravity recovery. The 369-day repeat tracks come from adjacent regions in the North Atlantic Ocean. To obtain statistically significant coherence estimates we used the Welch's modified periodogram method on multiple passes. The data were pre-whitened by taking the along-track derivative, resulting in along-track slope. We found that LRM slope acquisitions have a resolution limit of 28 kilometers, while for SAR, this was at 29 kilometers. In comparison, previously published values using a similar analysis in another area of the Atlantic quote a 33-kilometer resolution for Geosat, and 38-kilometer resolution for ERS-1 (Yale et al, 1995). These preliminary results suggest that the spatial resolution of CryoSat-derived gravity will be at least 1.2 times better than previous models. Additional improvements in resolution will come from averaging all available altimetry data, as well as additional repeat measurements by CryoSat. We note that the geoid signal and oceanographic noise are expected to vary throughout the global ocean. At the meeting, we will present a global investigation of the resolution of CryoSat data, and also a comparison of coherence levels with those from Envisat and Jason-1.

Garcia, E. M.; Sandwell, D. T.

2012-12-01

319

The performance of CryoSat-2 as an ocean altimeter  

NASA Astrophysics Data System (ADS)

Two years after the launch of CryoSat-2, oceanographic uses of the CryoSat-2 data have well taken off, after several institutes, NOAA included, have spent a dedicated effort to upgrade the official CryoSat-2 data products to a level that is suitable for monitoring of mesoscale phenomena, as well as wind speed and wave height. But in the coastal areas, this is much less the case. This is mostly the result of the fact that CryoSat-2 is running in SAR or InSAR mode in many of the focus areas, like the Mediterranean Sea. We have shown, however, that the CryoSat data is intrinsically of high quality and for over a year now have been producing "IGDR" type data through FTP and through RADS. These steps include: ? Combine final (LRM) and fast-delivery (FDM) products and split the segmented files into pass files. ? Divide the 369-day repeat cycle into subcycles of 29 or 27 days. ? Retrack the conventional low-rate data to determine range, significant wave height, backscatter (and off-nadir angle). ? Add or replace the usual corrections for ionospheric and atmospheric delays, tides, dynamic atmospheric correction, sea state bias, mean sea surface. ? Update orbits and corrections whenever they become available. This way NOAA produces an "IGDR" product from the fast-delivery FDM and the CNES MOE orbit in about 2 days after real time, and a "GDR" product from the final LRM data and the CNES POE orbit with a delay of about 1 month. In order to extend the data products to the coastal regime, we have developed a process in which the SAR data are first combined to "Pseudo-LRM" or "reduced SAR" wave forms, that are similar to the conventional low-rate wave forms. After this the reduced SAR data are retracked and combined with the conventional data to form a harmonised product. Although this sounds relatively straightforward, many steps were needed to get this done: ? Combine the SAR wave forms to conventional wave forms, without loss of information. ? Reconstruct backscatter and significant wave height in a meaningful way, consistent with low-rate data. ? Cross-calibrate the conventional and SAR mode data. ? Validate the data quality of conventional and SAR mode data through crossovers and collinear track analyses. In this presentation we will demonstrate how the CryoSat-2 data quality compares to other altimeters (Envisat, Jason-1 and Jason-2) by means of data distribution maps, histograms and crossover comparisons.

Scharroo, R.; Smith, W. H.; Leuliette, E. W.; Lillibridge, J. L.

2012-12-01

320

Magnetism  

NSDL National Science Digital Library

This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

Team, University C.

2007-12-12

321

Crystal and cryoEM structural studies of a cell wall degrading enzyme in the bacteriophage [psi]29 tail  

SciTech Connect

The small bacteriophage {phi}29 must penetrate the {approx}250-{angstrom} thick external peptidoglycan cell wall and cell membrane of the Gram-positive Bacillus subtilis, before ejecting its dsDNA genome through its tail into the bacterial cytoplasm. The tail of bacteriophage {phi}29 is noncontractile and {approx}380 {angstrom} long. A 1.8-{angstrom} resolution crystal structure of gene product 13 (gp13) shows that this tail protein has spatially well separated N- and C-terminal domains, whose structures resemble lysozyme-like enzymes and metallo-endopeptidases, respectively. CryoEM reconstructions of the WT bacteriophage and mutant bacteriophages missing some or most of gp13 shows that this enzyme is located at the distal end of the {phi}29 tail knob. This finding suggests that gp13 functions as a tail-associated, peptidoglycan-degrading enzyme able to cleave both the polysaccharide backbone and peptide cross-links of the peptidoglycan cell wall. Comparisons of the gp13{sup -} mutants with the {phi}29 mature and emptied phage structures suggest the sequence of events that occur during the penetration of the tail through the peptidoglycan layer.

Xiang, Ye; Morais, Marc C.; Cohen, Daniel N.; Bowman, Valorie D.; Anderson, Dwight L.; Rossmann, Michael G. (Purdue); (UMM)

2009-08-28

322

Drive tube 60009 - A chemical study of magnetic separates of size fractions from five strata. [lunar soil analysis  

NASA Technical Reports Server (NTRS)

Each bulk soil and both the magnetic and nonmagnetic components of the 90-150 micron and below 20 micron fractions of five soils from drive tube 60009 were analyzed. Samples were analyzed for FeO, Na2O, Sc, Cr, Co, Ni, Hf, Ta, Th, La, Ce, Sm, Eu, Tb, Yb, and Lu by neutron activation analysis. Several samples were fused and analyzed for major elements by electron microprobe analysis. Compositional variations are not systematically related to depth. The compositions of the five soils studied are well explained by a two-component mixing model whose end members are a submature Apollo 16-type soil and an extremely immature anorthositic material similar to 60025. There is evidence that the anorthositic component had received a small amount of exposure before these soils were mixed. After mixing, the soils received little exposure suggesting mixing and deposition on a rapid time scale.

Blanchard, D. P.; Jacobs, J. W.; Brannon, J. C.; Brown, R. W.

1976-01-01

323

An automated system to mount cryo-cooled protein crystals on a synchrotron beam line, using compact sample cassettes and a small-scale robot  

PubMed Central

An automated system for mounting and dismounting pre-frozen crystals has been implemented at the Stanford Synchrotron Radiation Laboratory (SSRL). It is based on a small industrial robot and compact cylindrical cassettes, each holding up to 96 crystals mounted on Hampton Research sample pins. For easy shipping and storage, the cassette fits inside several popular dry-shippers and long-term storage Dewars. A dispensing Dewar holds up to three cassettes in liquid nitrogen adjacent to the beam line goniometer. The robot uses a permanent magnet tool to extract samples from, and insert samples into a cassette, and a cryo-tong tool to transfer them to and from the beam line goniometer. The system is simple, with few moving parts, reliable in operation and convenient to use. PMID:24899734

Cohen, Aina E.; Ellis, Paul J.; Miller, Mitchell D.; Deacon, Ashley M.; Phizackerley, R. Paul

2014-01-01

324

Ionic liquids as floatation media for cryo-ultramicrotomy of soft polymeric materials.  

PubMed

Ionic liquids (ILs) and their mixtures with low molecular solvents present ideal properties for use as flotation liquids in cryo-ultramicrotomy. With control of T g and ? by co-solvent addition, flat, ultra-thin sections are reliably floated onto transmission electron microscopy grids even at temperatures as low as -100°C. Even more, the liquids and their mixtures are stable in the microtome trough for several hours because of low vapor pressure and low solidification temperature. Compared to established flotation media for soft polymer systems, the time and skill needed for cryo-ultramicrotomy are significantly reduced. Although just a handful of ILs are discussed and a good general choice identified, if different liquid characteristics are needed for a particular sample, thousands of additional ILs will perform similarly, giving this new approach enormous flexibility. PMID:24124997

Kim, Paul; David, Emeric; Raboin, Louis; Ribbe, Alexander E; Russell, Thomas P; Hoagland, David A

2013-12-01

325

Opening windows into the cell: focused-ion-beam milling for cryo-electron tomography.  

PubMed

Cryo-electron tomography (CET) is ideally suited for bridging the resolution gap between molecular and cellular structural studies. However, CET is limited to a sample thickness under 500nm, which is thinner than most cells. Here, we review a method for preparing cells for CET using focused-ion-beam milling, a technique commonly used in materials science. Adapted to cryogenic conditions, FIB milling can be applied to various cell types to produce samples thin enough for CET that do not present the artefacts typical to other preparation techniques, for example, cryo-ultramicrotomy, effectively opening windows into intact cells. Samples can be produced routinely and reproducibly. The data obtained from CET can be used for structural studies in situ, or to do quantitative cell biology studies, in which cells can be observed at the molecular level under different physiological conditions. PMID:24090931

Villa, Elizabeth; Schaffer, Miroslava; Plitzko, Jürgen M; Baumeister, Wolfgang

2013-10-01

326

Cryo-electron tomography and 3-D analysis of the intact flagellum in Trypanosoma brucei  

PubMed Central

Trypanosoma brucei is a uni-cellular protist that causes African sleeping sickness. These parasites have a flagellum that is attached to the cell body and is indispensible for its motility. The flagellum consists of a canonical 9 + 2 axoneme and a paraflagellar rod (PFR), an intricate tripartite, fibrous structure that is connected to the axoneme. In this paper we describe results from cryo-electron tomography of unperturbed flagella. This method revealed novel structures that are likely involved in attaching the flagellum to the cell. We also show the first cryo-electron tomographic images of a basal body in situ, revealing electron dense structures inside its triplet microtubules. Sub-tomogram averaging of the PFR revealed that its distal region is organized as an orthorhombic crystal. PMID:22285651

Hoog, Johanna L.; Bouchet-Marquis, Cedric; McIntosh, J. Richard; Hoenger, Andreas; Gull, Keith

2012-01-01

327

Cross-linking cellulose nanofibrils for potential elastic cryo-structured gels  

NASA Astrophysics Data System (ADS)

Cellulose nanofibrils were produced from P. radiata kraft pulp fibers. The nanofibrillation was facilitated by applying 2,2,6,6-tetramethylpiperidinyl-1-oxyl-mediated oxidation as pretreatment. The oxidized nanofibrils were cross-linked with polyethyleneimine and poly N-isopropylacrylamide- co-allylamine- co-methylenebisacrylamide particles and were frozen to form cryo-structured gels. Samples of the gels were critical-point dried, and the corresponding structures were assessed with scanning electron microscopy. It appears that the aldehyde groups in the oxidized nanofibrils are suitable reaction sites for cross-linking. The cryo-structured materials were spongy, elastic, and thus capable of regaining their shape after a given pressure was released, indicating a successful cross-linking. These novel types of gels are considered potential candidates in biomedical and biotechnological applications.

Syverud, Kristin; Kirsebom, Harald; Hajizadeh, Solmaz; Chinga-Carrasco, Gary

2011-12-01

328

Noise models and cryo-EM drift correction with a direct-electron camera  

PubMed Central

Blurring due to specimen-holder drift is a common occurrence in cryo-EM images. Cameras employing active-pixel sensors are capable of high frame rates such that a single low-dose exposure can be acquired as a series of frames. In this paper we consider the possibility of tracking and compensating for overall drift in typical single-particle specimens through the analysis of frame sequences. A problem that arises in tracking through cross-correlation of frames obtained with the DE-12 camera from Direct Electron LLC is the presence of “hot-pixel noise”. This random pattern of bright pixels is highly correlated among frames. We show how a model of this noise can be employed to greatly reduce its effects. A filter function is derived that optimizes the tracking of image shifts by cross-correlation, and we demonstrate the tracking of specimen drift in typical cryo-EM specimens. PMID:23748163

Shigematsu, H.; Sigworth, F. J.

2013-01-01

329

CryoSat Level1b SAR/SARin: quality improvements towards BaselineC  

NASA Astrophysics Data System (ADS)

CryoSat was launched on the 8th April 2010 and it is the first European ice mission dedicated to monitoring precise changes in the thickness of polar ice sheets and floating sea ice over a 3-year period. Cryosat carries an innovative radar altimeter called the Synthetic Aperture Interferometric Altimeter (SIRAL), that transmits pulses at a high pulse repetition frequency thus making the received echoes phase coherent and suitable for azimuth processing. This allows to reach a significantly improved along track resolution with respect to traditional pulse-width limited altimeters. CryoSat is the first altimetry mission operating in SAR mode and continuous improvement in the Level1 Instrument Processing Facility (IPF1) are being identified, tested and validated in order to improve the quality of the Level1b products. Towards the release of the BaselineC of the CryoSat Level1b SAR/SARin products, that is expected during 2014, several improvements have been identified: • a datation bias of about -0.5195 ms will be corrected • a range bias of about -0.6730 m will be corrected • the waveform length in the Level1b product will be doubled with respect to BaselineB • improved processing for 1Hz echoes to have sharper waveforms • surface sample stack weighting to filter out the single look echoes acquired at highest look angle, that results in a sharpening of the 20Hz waveforms This poster details the main improvements that are foreseen to be included in the CryoSat Level1b SAR/SARin products in BaselineC.

Scagliola, Michele; Fornari, Marco; Bouzinac, Catherine; Tagliani, Nicolas; Parrinello, Tommaso

2014-05-01

330

Cryo-EM Model of the Bullet-Shaped Vesicular Stomatitis Virus  

Microsoft Academic Search

Vesicular stomatitis virus (VSV) is a bullet-shaped rhabdovirus and a model system of negative-strand RNA viruses. Through direct visualization by means of cryo-electron microscopy, we show that each virion contains two nested, left-handed helices: an outer helix of matrix protein M and an inner helix of nucleoprotein N and RNA. M has a hub domain with four contact sites that

Peng Ge; Jun Tsao; Stan Schein; Todd J. Green; Ming Luo; Z. Hong Zhou

2010-01-01

331

Identifying the assembly pathway of cyanophage inside the marine bacterium using electron cryo-tomography  

PubMed Central

Advances in electron cryo-tomography open up a new avenue to visualize the 3-D internal structure of a single bacterium before and after its infection by bacteriophages in its native environment, without using chemical fixatives, fluorescent dyes or negative stains. Such direct observation reveals the presence of assembly intermediates of the bacteriophage and thus allows us to map out the maturation pathway of the bacteriophage inside its host.

Dai, Wei; Schmid, Michael F.; King, Jonathan A.; Chiu, Wah

2014-01-01

332

Correlative VIS-fluorescence and soft X-ray cryo-microscopy/tomography of adherent cells  

PubMed Central

Soft X-ray cryo-microscopy/tomography of vitreous samples is becoming a valuable tool in structural cell biology. Within the ‘water-window’ wavelength region (2.34–4.37 nm), it provides absorption contrast images with high signal to noise ratio and resolution of a few tens of nanometer. Soft X-rays with wavelengths close to the K-absorption edge of oxygen penetrate biological samples with thicknesses in the micrometer range. Here, we report on the application of a recently established extension of the transmission soft X-ray cryo-microscope (HZB TXM) at the beamline U41-XM of the BESSY II electron storage ring by an in-column epi-fluorescence and reflected light cryo-microscope. We demonstrate the new capability for correlative fluorescence and soft X-ray cryo-microscopy/tomography of this instrument along a typical life science experimental approach – the correlation of a fluorophore-tagged protein (pUL34-GFP of pseudorabies virus, PrV, the nuclear membrane-anchored component of the nuclear egress complex of the Herpesviridae which interacts with viral pUL31) in PrV pUL34-GFP/pUL31 coexpressing mammalian cells, with virus-induced vesicular structures in the nucleus, expanding the nucleoplasmic reticulum. Taken together, our results demonstrate new possibilities to study the role of specific proteins in substructures of adherent cells, especially of the nucleus in toto, accessible to electron microscopy in thinned samples only. PMID:22210307

Hagen, Christoph; Guttmann, Peter; Klupp, Barbara; Werner, Stephan; Rehbein, Stefan; Mettenleiter, Thomas C.; Schneider, Gerd; Grunewald, Kay

2012-01-01

333

Magnetism  

NSDL National Science Digital Library

This radio broadcast discusses the history of magnetism from the time of its discovery by an apocryphal Greek sheperd until the late 16th century and the work of William Gilbert. There is also discussion of who pioneered the study of magnetism, what theories they constructed from its curious abilities, and how the power of the magnet was brought out of the realm of magic and into the service of science. The broadcast concludes with a discussion of why magnetism is still mysterious and how the modern search for the single magnetic pole, or magnetic monopole, could provide a fundamental unit of magnetism, essential for ultimate explanation. The broadcast is 41 minutes and 45 seconds in length.

2010-10-27

334

Characterization of Antibiotic Peptide Pores Using Cryo-EM and Comparison to Neutron Scattering  

PubMed Central

Abstract Magainin, a 23-residue antibiotic peptide, interacts directly with the lipid bilayer leading to cell lysis in a strongly concentration-dependent fashion. Utilizing cryo-electron microscopy, we have directly observed magainin interacting with synthetic DMPC/DMPG membranes. Visual examination shows that visibly unperturbed vesicles are often found adjacent to vesicles that are lysed or porous, demonstrating that magainin disruption is a highly stochastic process. Quantitatively, power spectra of large numbers of porous vesicles can be averaged together to produce the equivalent of an electron scattering curve, which can be related to theory, simulation, and published neutron scattering experiments. We demonstrate that magainin-induced pores in lipid vesicles have a mean diameter of ?80 Å, compatible with earlier reported results in multilayer stacks. In addition to establishing a connection between experiments in multilayer stacks and vesicles, this also demonstrates that computed power spectra from windowed-out regions of cryo-EM images can be compared to neutron scattering data in a meaningful way, even though the pores of interest cannot yet be individually identified in images. Cryo-EM offers direct imaging of systems in configurations closely related to in vivo conditions, whereas neutron scattering has a greater variety of mechanisms for specific contrast variation via D2O and deuterated lipids. Combined, the two mechanisms support each other, and provide a clearer picture of such ‘soft’ systems than either could provide alone. PMID:19580754

Han, Mikyung; Mei, Yuan; Khant, Htet; Ludtke, Steven J.

2009-01-01

335

Microstructure development in latex coatings: High-resolution cryo-scanning electron microscopy  

NASA Astrophysics Data System (ADS)

High-resolution cryogenic scanning electron microscopy (Cryo-SEM) was used to investigate microstructure development in drying latex coatings: from a colloidal stable suspension into a coherent strong film by drying. Useful sample preparation artifacts during the freeze-fracture, i.e., pullouts were documented and analyzed. Pullouts indicate both physical properties of latex particles and the drying stages in latex coatings. The mechanism of pullout formation was studied both theoretically and experimentally. Latex coatings must possess satisfactory freeze-thaw stability to avoid problems during transportation and storage in cold winter. The behavior of latex particles during freeze-thaw cycles was visualized by Cryo-SEM. The images indicated that high concentration of polymerizable surfactant in a latex suspension improved its freeze-thaw stability. In film formation, skinning was captured from edge in and top down in coatings of 80nm diameter styrene-butadiene latex particles with exceptional low Tg (-65°C). Effects on skinning of drying conditions and the way the latex was initially stabilized against flocculation were investigated. A skinned pocket was unexpectedly found in the coating. The cause of such a skin around the air bubble was explained by both simple models calculating the dissolution time and force analysis on the particles. The film formation processes in conventional and low volatile organic compound (VOC) latex coatings were compared by time-sectioning Cryo-SEM. Some low-VOC latex coatings were found to dry as fast as conventional ones without deteriorating final good film properties.

Ge, Haiyan

336

Beam-induced motion correction for sub-megadalton cryo-EM particles  

PubMed Central

In electron cryo-microscopy (cryo-EM), the electron beam that is used for imaging also causes the sample to move. This motion blurs the images and limits the resolution attainable by single-particle analysis. In a previous Research article (Bai et al., 2013) we showed that correcting for this motion by processing movies from fast direct-electron detectors allowed structure determination to near-atomic resolution from 35,000 ribosome particles. In this Research advance article, we show that an improved movie processing algorithm is applicable to a much wider range of specimens. The new algorithm estimates straight movement tracks by considering multiple particles that are close to each other in the field of view, and models the fall-off of high-resolution information content by radiation damage in a dose-dependent manner. Application of the new algorithm to four data sets illustrates its potential for significantly improving cryo-EM structures, even for particles that are smaller than 200 kDa. DOI: http://dx.doi.org/10.7554/eLife.03665.001 PMID:25122622

Scheres, Sjors HW

2014-01-01

337

Cryo-EM visualization of an exposed RGD epitope on adenovirus that escapes antibody neutralization.  

PubMed Central

Interaction of the adenovirus penton base protein with alpha v integrins promotes virus entry into host cells. The location of the integrin binding sequence Arg-Gly-Asp (RGD) on human type 2 adenovirus (Ad2) was visualized by cryo-electron microscopy (cryo-EM) and image reconstruction using a mAb (DAV-1) which recognizes a linear epitope, IRGDTFATR. The sites for DAV-1 binding corresponded to the weak density above each of the five 22 A protrusions on the adenovirus penton base protein. Modeling of a Fab fragment crystal structure into the adenovirus-Fab cryo-EM density indicated a large amplitude of motion for the Fab and the RGD epitope. An unexpected finding was that Fab fragments, but not IgG antibody molecules, inhibited adenovirus infection. Steric hindrance from the adenovirus fiber and a few bound IgG molecules, as well as epitope mobility, most likely prevent binding of IgG antibodies to all five RGD sites on the penton base protein within the intact virus. These studies indicate that the structure of the adenovirus particle facilitates interaction with cell integrins, whilst restricting binding of potentially neutralizing antibodies. PMID:9135136

Stewart, P L; Chiu, C Y; Huang, S; Muir, T; Zhao, Y; Chait, B; Mathias, P; Nemerow, G R

1997-01-01

338

Effect of cryo-induced microcracks on microindentation of hydrated cortical bone tissue  

SciTech Connect

Microcracks accumulate in cortical bone tissue as a consequence of everyday cyclic loading. However, it remains unclear to what extent microdamage accumulation contributes to an increase in fracture risk. A cryo-preparation technique was applied to induce microcracks in cortical bone tissue. Microcracks with lengths up to approximately 20 {mu}m, which were initiated mainly on the boundaries of haversian canals, were observed with cryo-scanning electron microscopy. A microindentation technique was applied to study the mechanical loading effect on the microcracked hydrated bone tissue. The microindentation patterns were section-scanned using confocal laser scanning microscopy to understand the deformation and bone damage mechanisms made by mechanical loading. The results show that there was no significant difference with respect to microhardness between the original and microcracked hydrated cortical bone tissues (ANOVA, p > 0.05). The cryo-induced microcracks in the bone tissue were not propagated further under the mechanical loads applied. The deformation mechanism of the microcracked cortical bone tissue was plastic deformation, not brittle fracture.

Yin Ling, E-mail: ling.yin@jcu.edu.au [School of Engineering, James Cook University, Townsville, QLD 4811 (Australia); Venkatesan, Sudharshan [Department of Engineering, Australian National University, Canberra, ACT 0200 Australia (Australia); Webb, Daryl [Electron Microscopy Unit, Australian National University, Canberra, ACT 0200 (Australia); Kalyanasundaram, Shankar; Qin Qinghua [Department of Engineering, Australian National University, Canberra, ACT 0200 Australia (Australia)

2009-08-15

339

Cryo ultra-low-angle microtomy for XPS-depth profiling of organic coatings.  

PubMed

In X-ray photoelectron spectroscopy (XPS) Ar(+) ion sputtering is usually used for depth profiling. However, for such samples as organic coatings, this is not feasible because of degradation. Also, measurement of a depth profile on a conventionally prepared cross-section is not possible if, for example, sample thickness is below the smallest available measurement spot size of the XPS system. In our approach we used a rotary microtome to cut samples under a shallow tilting angle of 0.5° to obtain an extended cross-section suitable for XPS investigations. We also used liquid nitrogen cooling to ensure an exposed area of higher quality: topography measurements with a novel optical 3D microscope and by atomic force microscopy revealed the linearity of the inclined sections. With our cryo ultra-low-angle microtomy (cryo-ULAM) preparation technique we were able to determine, by XPS, elemental and chemical gradients within a 25 ?m thick polyester-based organic coating deposited on steel. The gradients were related to, for example, depletion of the crosslinking agent in the sub-surface region. Complementary reflection electron energy-loss spectroscopy measurements performed on the cryo-ULAM sections also support the findings obtained from the XPS depth profiles. PMID:23529414

Greunz, T; Strauß, B; Schausberger, S E; Heise, B; Jachs, B; Stifter, D

2013-09-01

340

Near-Atomic Resolution Cryo-Electron Microscopic Structure of Dengue Serotype 4 Virus  

PubMed Central

Dengue virus (DENV), a mosquito-borne virus, is responsible for millions of cases of infections worldwide. There are four DENV serotypes (DENV1 to -4). After a primary DENV infection, the antibodies elicited confer lifetime protection against that DENV serotype. However, in a secondary infection with another serotype, the preexisting antibodies may cause antibody-dependent enhancement (ADE) of infection of macrophage cells, leading to the development of the more severe form of disease, dengue hemorrhagic fever. Thus, a safe vaccine should stimulate protection against all dengue serotypes simultaneously. To facilitate the development of a vaccine, good knowledge of different DENV serotype structures is crucial. Structures of DENV1 and DENV2 had been solved previously. Here we present a near-atomic resolution cryo-electron microscopy (cryo-EM) structure of mature DENV4. Comparison of the DENV4 structure with similar-resolution cryo-EM structures of DENV1 and DENV2 showed differences in surface charge distribution, which may explain their differences in binding to cellular receptors, such as heparin. Also, observed variations in amino acid residues involved in interactions between envelope and membrane proteins on the virus surface correlate with their ability to undergo structural changes at higher temperatures. PMID:24155405

Kostyuchenko, Victor A.; Chew, Pau Ling; Ng, Thiam-Seng

2014-01-01

341

Joint interpretation of gravity and magnetic data in the Kolárovo anomaly region by separation of sources and the inversion method of local corrections  

NASA Astrophysics Data System (ADS)

We present a new interpretation of the Kolárovo gravity and magnetic anomalies in the Danube Basin based on an inversion methodology that comprises the following numerical procedures: removal of regional trend, depth-wise separation of signal of sources, approximation of multiple sources by 3D line segments, non-linear inversion based on local corrections resulting in found sources specified as 3D star-convex homogenous bodies and/or 3D contrasting structural contact surfaces. This inversion methodology produces several admissible solutions from the viewpoint of potential field data. These solutions are then studied in terms of their feasibility taking into consideration all available tectono-geological information. By this inversion methodology we interpret here the Kolárovo gravity and magnetic anomalies jointly. Our inversion generates several admissible solutions in terms of the shape, size and location of a basic intrusion into the upper crust, or the shape and depth of the upper/lower crust interface, or an intrusion into the crystalline crust above a rise of the mafic lower crust. Our intrusive bodies lie at depths between 5 and 12 km. Our lower crust elevation rises to 12 km with and 8 km without the accompanying intrusion into the upper crust, respectively. Our solutions are in reasonable agreement with various previous interpretations of the Kolárovo anomaly, but yield a better and more realistic geometrical resolution for the source bodies. These admissible solutions are next discussed in the context of geological and tectonic considerations, mainly in relation to the fault systems.

Prutkin, Ilya; Vajda, Peter; Bielik, Miroslav; Bezák, Vladimír; Tenzer, Robert

2014-04-01

342

Rapid ionic liquid-based ultrasound assisted dual magnetic microextraction to preconcentrate and separate cadmium-4-(2-thiazolylazo)-resorcinol complex from environmental and biological samples.  

PubMed

A rapid and innovative microextraction technique named as, ionic liquid-based ultrasound-assisted dual magnetic microextraction (IL-UA-DMME) was developed for the preconcentration and extraction of trace cadmium from environmental and biological samples, prior to analyzed by flame atomic absorption spectrometry (FAAS). The proposed method has many obvious advantages, including evading the use of organic solvents and achieved high extraction yields by the combination of dispersive liquid-liquid microextraction (DLLME) and magnetic mediated-solid phase extraction (MM-SPE). In this approach ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6] play an important role to extract the cadmium-4-(2-thiazolylazo)-resorcinol (Cd-TAR) complex from acid digested sample solutions and ultrasonic irradiation was applied to assist emulsification. After then, dispersed small amount of Fe3O4 magnetic nanoparticles (MNPs) in sample solutions to salvaged the IL and complete phase separation was attained. Some analytical parameters that influencing the efficiency of proposed (IL-UA-DMME) method, such as pH, volume of IL, ligand concentration, ultra-sonication time, amount of Fe3O4 MNPs, sample volume and matrix effect were optimized. Limit of detection (LOD) and enrichment factor (EF) of the method under optimal experimental conditions were found to be 0.40?gL(-1) and 100, respectively. The relative standard deviation (RSD) of 50?gL(-1) Cd was 4.29%. The validity and accuracy of proposed method, was assessed to analyzed certified reference materials of fortified lake water TMDA-54.4, SPS-WW2 waste water, spinach leaves 1570a and also checked by standard addition method. The obtained values showed good agreement with the certified values and sufficiently high recovery were found in the range of 98.1-101% for Cd. The proposed method was facile, rapid and successfully applied for the determination of Cd in environmental and different biological samples. PMID:24398463

Khan, Sumaira; Kazi, Tasneem Gul; Soylak, Mustafa

2014-04-01

343

Coupling of magnetic field and lattice strain and its impact on electronic phase separation in La0.335Pr0.335Ca0.33MnO3/ferroelectric crystal heterostructures  

NASA Astrophysics Data System (ADS)

Phase-separated La0.335Pr0.335Ca0.33MnO3 films were epitaxially grown on (001)- and (111)-oriented ferroelectric single-crystal substrates. Upon poling along the [001] or [111] direction, dramatic decrease in resistance, up to 99.98%, and complete melting of the charge-ordered phase were observed, caused by poling-induced strain rather than accumulation of electrostatic charge at interface. Such poling-induced strain effects can be effectively tuned by a magnetic field and mediated by electronic phase separation. In particular, our findings show that the evolution of the strength of electronic phase separation against temperature and magnetic field can be determined by measuring the strain-tunability of resistance [(?R/R)strain] under magnetic fields.

Zheng, M.; Li, X. Y.; Yang, M. M.; Zhu, Q. X.; Wang, Y.; Li, X. M.; Shi, X.; Chan, H. L. W.; Li, X. G.; Luo, H. S.; Zheng, R. K.

2013-12-01

344

Distinct constrictive processes, separated in time and space,divide Caulobacter inner and outer membranes  

SciTech Connect

Cryo-electron microscope tomography (cryoEM) and a fluorescence loss in photobleaching (FLIP) assay were used to characterize progression of the terminal stages of Caulobacter crescentus cell division. Tomographic cryoEM images of the cell division site show separate constrictive processes closing first the inner, and then the outer, membrane in a manner distinctly different from septum-forming bacteria. The smallest observed pre-fission constrictions were 60 nm for both the inner and outer membrane. FLIP experiments had previously shown cytoplasmic compartmentalization, when cytoplasmic proteins can no longer diffuse between the two nascent progeny cell compartments, occurring 18 min before daughter cell separation in a 135 min cell cycle. Here, we used FLIP experiments with membrane-bound and periplasmic fluorescent proteins to show that (1) periplasmic compartmentalization occurs after cytoplasmic compartmentalization, consistent with the cryoEM observations, and (2) inner membrane and periplasmic proteins can diffuse past the FtsZ constriction site, indicating that the cell division machinery does not block membrane diffusion.

Judd, Ellen M.; Comolli, Luis R.; Chen, Joseph C.; Downing,Kenneth H.; Moerner, W.E.; McAdams, Harley H.

2005-05-01

345

ESA-NASA collaboration in support of CryoSat-2  

NASA Astrophysics Data System (ADS)

In the framework of its Earth Observation Programmes the European Space Agency (ESA) carries out groundbased and airborne campaigns to support geophysical algorithm development, calibration/validation, simulation of future spaceborne earth observation missions, and applications development related to land, oceans and atmosphere. ESA has been conducting airborne and ground measurements campaigns since 1981 by deploying a broad range of active and passive instrumentation in both the optical and microwave regions of the electromagnetic spectrum such as lidars, limb/nadir sounding interferometers/spectrometers, high-resolution spectral imagers, advanced synthetic aperture radars, altimeters and radiometers. These campaigns take place inside and outside Europe in collaboration with national research organisations in the ESA member states as well as with international organisations harmonising European campaign activities. For the different activities a rich variety of datasets has been recorded, are archived and users can access campaign data through the EOPI web portal [http://eopi.esa.int]. CryoSat-2, ESA's third Earth Explorer, is Europe's first mission dedicated to monitoring Earth's ice fields. The satellite carries a sophisticated radar altimeter that can measure the thickness of sea ice down to centimetres and also monitor changes in ice sheets, particularly around the edges where icebergs are calved from the vast ice sheets that cover Greenland and Antarctica. On order to gather data to help ensure the accuracy of ESA's ice mission, in yet another remarkable collaborative effort, ESA and NASA met up over the Arctic Ocean in April 2012 to perform some carefully coordinated flights directly under CryoSat orbiting above. The aim of this large-scale campaign was to record sea-ice thickness and conditions of the ice exactly along the line traced by ESA's CryoSat satellite orbiting high above. A range of sensors installed on the different aircraft was used to gather complementary information. These airborne instruments included simple cameras to get a visual record of the sea ice, laser scanners to clearly map the height of the ice, an ice-thickness sensor (EM-Bird), ESA's radar altimeter (ASIRAS) and NASA's snow and Ku-band radars, which mimic CryoSat's measurements but at a higher resolution. Preliminary results, obtained from the pooled flight time among teams of scientists from Europe, US and Canada, already show the capability to determine the amount of snow on the ice. Even more interestingly, from 700 km away, CryoSat is able to detect centimeter differences between sea-ice and thin ice/water, which in turn allow for the estimation of actual sea ice thickness at the time of the measurement.

Casal, T. G.; Davidson, M.; Schuettemeyer, D.; Perrera, A.; Armitage, T.; Bianchi, R.; Parrinello, T.; Fornari, M.; Skourup, H.

2012-12-01

346

Cryo-EM Imaging of DNA-PK DNA Damage Repair Complexes  

SciTech Connect

Exposure to low levels of ionizing radiation causes DNA double-strand breaks (DSBs) that must be repaired for cell survival. Higher eukaryotes respond to DSBs by arresting the cell cycle, presumably to repair the DNA lesions before cell division. In mammalian cells, the nonhomologous end-joining DSB repair pathway is mediated by the 470 kDa DNA-dependent protein kinase catalytic subunit (DNA-PKcs) together with the DNA-binding factors Ku70 and Ku80. Mouse knock-out models of these three proteins are all exquisitely sensitive to low doses of ionizing radiation. In the presence of DNA ends, Ku binds to the DNA and then recruits DNA-PKcs. After formation of the complex, the kinase activity associated with DNA-PKcs becomes activated. This kinase activity has been shown to be essential for repairing DNA DSBs in vivo since expression of a kinase-dead form of DNA-PKcs in a mammalian cell line that lacks DNA-PKcs fails to complement the radiosensitive phenotype. The immense size of DNA-PKcs suggests that it may also serve as a docking site for other DNA repair proteins. Since the assembly of the DNA-PK complex onto DNA is a prerequisite for DSB repair, it is critical to obtain structural information on the complex. Cryo-electron microscopy (cryo-EM) and single particle reconstruction methods provide a powerful way to image large macromolecular assemblies at near atomic (10-15 ?) resolution. We have already used cryo-EM methods to examine the structure of the isolated DNA-PKcs protein. This structure reveals numerous cavities throughout the protein that may allow passage of single or double-stranded DNA. Pseudo two-fold symmetry was found for the monomeric protein, suggesting that DNA-PKcs may interact with two DNA ends or two Ku heterodimers simultaneously. Here we propose to study the structure of the cross-linked DNA-PKcs/Ku/DNA complex. Difference imaging with our published DNA-PKcs structure will enable us to elucidate the architecture of the complex. A second objective is to locate the kinase domain of DNA-PKcs by determining the structure of a kinase deletion mutant both as an isolated protein and as part of a DNA-PKcs/Ku/DNA complex. A third objective is to pursue higher resolution studies of DNA-PKcs and the DNA-PKcs/Ku/DNA complex. If the crystal structure determination of DNA-PKcs is completed during the project period, the atomic coordinates of DNA-PKcs will be modeled within the cryo-EM structure of the complex. In order to achieve these goals, a collaborative effort is proposed between Dr. Phoebe Stewart at UCLA, whose laboratory has expertise in cryo-EM reconstruction methods, and Dr. David Chen at the Lawrence Berkeley National Laboratory, who has a long-standing interest in DNA repair. Advantages of the cryo-EM structural method include the fact that the sample is imaged in a frozen-hydrated and unstained state, avoiding artifacts associated with drying and staining in other EM approaches. Also crystals of the sample are not needed for the single particle reconstruction method and only microgram quantities of sample are required. Cryo-EM structural information of macromolecular assemblies is complementary to both atomic structures of individual component molecules, as well as low resolution information obtained from x-ray and neutron scattering. Knowledge of the geometrical arrangement of the complex, and the position of the essential DNA-PKcs kinase domain, should lead to a greater understanding of the molecular events in DNA double-strand break repair following exposure to low doses of radiation.

Phoebe L. Stewart

2005-06-27

347

Nitrogen Separation and Liquefaction Apparatus for Medical Applications and Its Thermodynamic Optimization  

NASA Astrophysics Data System (ADS)

Low temperature medicine is becoming a widely appreciated method in surgery, dermatology, gynecology and rheumatology. The cryomedical equipment is usually supplied with liquid nitrogen LN2 stored in a dewar and transferred to a tip, where it is evaporated providing a cooling power. LN2 in quantities sufficient for cryo-surgical and cryo-therapeutical applications can be first separated from air and then liquefied using a system combining polymer membrane gas separation technology and a Joule-Thomson closed-cycle refrigerator filled with a nitrogen-hydrocarbons gas mixture. Nitrogen is separated from the compressed air, then liquefied and throttled to atmospheric pressure. The paper analyzes the demanded cooling capacity of the system resulting from cryomedical treatment requirements. Thermal design and flow scheme of the apparatus are given. The system is thermodynamically optimized.

Chorowski, M.; Piotrowska, A.; Polinski, J.

2006-04-01

348

Size-regulated group separation of CoFe2O4 nanoparticles using centrifuge and their magnetic resonance contrast properties  

PubMed Central

Magnetic nanoparticle (MNP)-based magnetic resonance imaging (MRI) contrast agents (CAs) have been the subject of extensive research over recent decades. The particle size of MNPs varies widely and is known to influence their physicochemical and pharmacokinetic properties. There are two commonly used methods for synthesizing MNPs, organometallic and aqueous solution coprecipitation. The former has the advantage of being able to control the particle size more effectively; however, the resulting particles require a hydrophilic coating in order to be rendered water soluble. The MNPs produced using the latter method are intrinsically water soluble, but they have a relatively wide particle size distribution. Size-controlled water-soluble MNPs have great potential as MRI CAs and in cell sorting and labeling applications. In the present study, we synthesized CoFe2O4 MNPs using an aqueous solution coprecipitation method. The MNPs were subsequently separated into four groups depending on size, by the use of centrifugation at different speeds. The crystal shapes and size distributions of the particles in the four groups were measured and confirmed by transmission electron microscopy and dynamic light scattering. Using X-ray diffraction analysis, the MNPs were found to have an inverse spinel structure. Four MNP groups with well-selected semi-Gaussian-like diameter distributions were obtained, with measured T2 relaxivities (r2) at 4.7 T and room temperature in the range of 60 to 300 mM?1s?1, depending on the particle size. This size regulation method has great promise for applications that require homogeneous-sized MNPs made by an aqueous solution coprecipitation method. Any group of the CoFe2O4 MNPs could be used as initial base cores of MRI T2 CAs, with almost unique T2 relaxivity owing to size regulation. The methodology reported here opens up many possibilities for biosensing applications and disease diagnosis. PACS 75.75.Fk, 78.67.Bf, 61.46.Df PMID:24004536

2013-01-01

349

Development in processing of MgB2 cryo-magnet superconductors  

NASA Astrophysics Data System (ADS)

Spark Plasma Sintering is a promising rapid consolidation technique that allows a better understanding and manipulating of sintering kinetics and therefore makes it possible to obtain MgB2-based ceramics with tailored microstructures. Commercial MgB2 powders were spark plasma sintered with an applied mechanical pressure, leading to MgB2 pellets with 99% relative density. The obtained samples show a sharp superconducting transition with an onset at 38.5 K. The critical current density was measured equal to 5.6 × 104 A/cm2 at 20 K under 1 T applied field. Otherwise, the trapped field was also investigated. A 5 mm thick pellet with a 20 mm diameter prepared with optimized processing temperature demonstrated a trapped field of 1.2 T at 15 K and up to 2.5 T at 10 K.

Noudem, J. G.; Aburras, M.; Bernstein, P.; Chaud, X.; Muralidhar, M.; Murakami, M.

2014-10-01

350

CryoSat-2 science algorithm status, expected future improvements and impacts concerning Sentinel-3 and Jason-CS missions  

NASA Astrophysics Data System (ADS)

With CryoSat-2 soon to enter its second year of post commissioning operations there is now sufficient experience and evidence showing improvements of the SIRAL's (Synthetic interferometric radar altimeter) SAR and SARIn modes over conventional pulse-width limited altimeters for both the targeted marine/land ice fields but also for non mission relevant surfaces such as the ocean, for example. In the process of understanding the CryoSat data some side effects of the end-to-end platform measurement and ground retrieval system have been identified and whilst those key to mission success are understood and are being handled others, remain open and pave the way to longer term fine-tuning. Of interest to the session will be a summary of the manditory changes made during 2011 to all the modes of CryoSat-2 science processing with a view to longer term algorithm improvements that could benefit the planned mid-to-late nominal operations re-processing. Since some of the science processor improvements have direct implication to the SAR mode processing of Sentinel-3 and Jason-CS science then these will also be highlighted. Finally a summary of the CryoSat-2 in-orbit platform and payload performances and their stability will also be provided. Expectations of the longer term uses of CryoSat's primary sensor (SIRAL) and its successors will be discussed.

Cullen, R.; Wingham, D.; Francis, R.; Parrinello, T.

2011-12-01

351

Molecular Dynamics Flexible Fitting: A practical guide to combine cryo-electron microscopy and X-ray crystallography  

PubMed Central

Hybrid computational methods for combining structural data from different sources and resolutions are becoming an essential part of structural biology, especially as the field moves toward the study of large macromolecular assemblies. We have developed the molecular dynamics flexible fitting (MDFF) method for combining high-resolution atomic structures with cryo-electron microscopy (cryo-EM) maps, that results in atomic models representing the conformational state captured by cryo-EM. The method has been applied successfully to the ribosome, a ribonucleoprotein complex responsible for protein synthesis. MDFF involves a molecular dynamics simulation in which a guiding potential, based on the cryo-EM map, is added to the standard force field. Forces proportional to the gradient of the density map guide an atomic structure, available from X-ray crystallography, into high-density regions of a cryo-EM map. In this paper we describe the necessary steps to set up, run, and analyze MDFF simulations and the software packages that implement the corresponding functionalities. PMID:19398010

Trabuco, Leonardo G.; Villa, Elizabeth; Schreiner, Eduard; Harrison, Christopher B.; Schulten, Klaus

2009-01-01

352

Closer to the native state. Critical evaluation of cryo-techniques for Transmission Electron Microscopy: preparation of biological samples.  

PubMed

Over the years Transmission Electron Microscopy (TEM) has evolved into a powerful technique for the structural analysis of cells and tissues at various levels of resolution. However, optimal sample preservation is required to achieve results consistent with reality. During the last few decades, conventional preparation methods have provided most of the knowledge about the ultrastructure of organelles, cells and tissues. Nevertheless, some artefacts can be introduced at all stagesofstandard electron microscopy preparation technique. Instead, rapid freezing techniques preserve biological specimens as close as possible to the native state. Our review focuses on different cryo-preparation approaches, starting from vitrification methods dependent on sample size. Afterwards, we discuss Cryo-Electron Microscopy Of VItreous Sections (CEMOVIS) and the main difficulties associated with this technique. Cryo-Focused Ion Beam (cryo-FIB) is described as a potential alternative for CEMOVIS. Another post-processing route for vitrified samples is freeze substitution and embedding in resin for structural analysis or immunolocalization analysis. Cryo-sectioning according to Tokuyasu is a technique dedicated to high efficiency immunogold labelling. Finally, we introduce hybrid techniques, which combine advantages of primary techniques originally dedicated to different approaches. Hybrid approaches permit to perform the study of difficult-to-fix samples and antigens or help optimize the sample preparation protocol for the integrated Laser and Electron Microscopy (iLEM) technique. PMID:24802956

Mielanczyk, Lukasz; Matysiak, Natalia; Michalski, Marek; Buldak, Rafal; Wojnicz, Romuald

2014-01-01

353

Magnetism  

NSDL National Science Digital Library

This overview of magnetism provides a brief history prior to 1600 and continues with the work of William Gilbert, Hans Christian Oersted, and Andre-Marie Ampere in describing and exploring the magnetosphere and learning the role that electric current plays in producing magnetism. Magnetic field lines are then discussed, citing the work of Michael Faraday. The work of James Clerk Maxwell and Heinrich Hertz is mentioned in a discussion of the relationship of light waves and radio waves as part of the electromagnetic spectrum.

Stern, David

354

Spotiton: A prototype for an integrated inkjet dispense and vitrification system for cryo-TEM  

PubMed Central

Over the last three decades, Cryo-TEM has developed into a powerful technique for high-resolution imaging of biological macromolecules in their native vitrified state. However, the technique for vitrifying specimens onto EM grids is essentially unchanged – application of ~ 3 µL sample to a grid, followed by blotting and rapid plunge freezing into liquid ethane. Several trials are often required to obtain suitable thin (few hundred nanometers or less) vitrified layers amenable for cryo-TEM imaging, which results in waste of precious sample and resources. While commercially available instruments provide some level of automation to control the vitrification process in an effort to increase quality and reproducibility, obtaining satisfactory vitrified specimens remains a bottleneck in the Cryo-TEM pipeline. We describe here a completely novel method for EM specimen preparation based on small volume (picoliter to nanoliter) dispensing using inkjet technology. A first prototype system (Spotiton v0.5) demonstrates feasibility of this new approach for specimen vitrification. A piezo-electric inkjet dispenser is integrated with optical real-time cameras (100 Hz frame rate) to analyze picoliter to nanoliter droplet profiles in-flight and spreading dynamics on the grid, and thus provides a method to optimize timing of the process. Using TEM imaging and biochemical assays we demonstrate that the piezo-electric inkjet mechanism does not disrupt the structural or functional integrity of macromolecules. These preliminary studies provide insight into the factors and components that will need further development to enable a robust and repeatable technique for specimen vitrification using this novel approach. PMID:22569522

Jain, Tilak; Sheehan, Patrick; Crum, John; Carragher, Bridget; Potter, Clinton S.

2012-01-01

355

Improving the Arctic Mean Sea Surface with CryoSat-2 Data  

NASA Astrophysics Data System (ADS)

A fundamental basis for estimating short and long-term changes in the sea surface is a reliable mean sea surface (MSS). Existing MSS models, derived from satellite radar altimetry, generally lack observations above 82 degrees latitude making high Arctic sea surface change estimates unreliable. Most current MSS models use ICESat data, geoid models, ocean circulation models, or a combination of these to extrapolate the MSS above 82 degrees latitude. This approach makes the MSS models unsuited for deriving sea surface anomalies from short-term observations like airborne campaigns (e.g. operation IceBridge). The new state of the art DTU13MSS is a global high-resolution MSS that includes retracked CryoSat-2 data and thereby extends the polar data coverage up to 88 degrees latitude. Furthermore, in the sea-ice covered areas, the SAR and SARin feature of the altimeter on-board CryoSat-2 increases the amount of useable observations dramatically compared to conventional altimeters like ENVISAT and ERS-1/2. Finally the continuous time-series, below 82 degrees latitude, has been extended to cover more than 20 years compared to the 17 years use for the DTU10MSS model. A comparison between DTU13MSS and DTU10MSS show an improvement of more than 20 cm between 82 and 88 degrees latitude. For the first time the three years of retracked CryoSat-2 data will, in combination with DTU13MSS, allow reliable estimation of the trend and annual variations in the high Arctic Ocean sea surface height.

Stenseng, L.; Andersen, O. B.

2013-12-01

356

Cryo FIB-SEM: volume imaging of cellular ultrastructure in native frozen specimens.  

PubMed

Volume microscopy at high resolution is increasingly required to better understand cellular functions in the context of three-dimensional assemblies. Focused ion beam (FIB) milling for serial block face imaging in the scanning electron microscope (SEM) is an efficient and fast method to generate such volume data for 3D analysis. Here, we apply this technique at cryo-conditions to image fully hydrated frozen specimen of mouse optic nerves and Bacillus subtilis spores obtained by high-pressure freezing (HPF). We established imaging conditions to directly visualize the ultrastructure in the block face at -150 °C by using an in-lens secondary electron (SE) detector. By serial sectioning with a focused ion beam and block face imaging of the optic nerve we obtained a volume as large as X=7.72 ?m, Y=5.79 ?m and Z=3.81 ?m with a lateral pixel size of 7.5 nm and a slice thickness of 30 nm in Z. The intrinsic contrast of membranes was sufficient to distinguish structures like Golgi cisternae, vesicles, endoplasmic reticulum and cristae within mitochondria and allowed for a three-dimensional reconstruction of different types of mitochondria within an oligodendrocyte and an astrocytic process. Applying this technique to dormant B. subtilis spores we obtained volumes containing numerous spores and discovered a bright signal in the core, which cannot be related to any known structure so far. In summary, we describe the use of cryo FIB-SEM as a tool for direct and fast 3D cryo-imaging of large native frozen samples including tissues. PMID:24121039

Schertel, Andreas; Snaidero, Nicolas; Han, Hong-Mei; Ruhwedel, Torben; Laue, Michael; Grabenbauer, Markus; Möbius, Wiebke

2013-11-01

357

Cryo X-ray microscope with flat sample geometry for correlative fluorescence and nanoscale tomographic imaging.  

PubMed

X-ray imaging offers a new 3-D view into cells. With its ability to penetrate whole hydrated cells it is ideally suited for pairing fluorescence light microscopy and nanoscale X-ray tomography. In this paper, we describe the X-ray optical set-up and the design of the cryo full-field transmission X-ray microscope (TXM) at the electron storage ring BESSY II. Compared to previous TXM set-ups with zone plate condenser monochromator, the new X-ray optical layout employs an undulator source, a spherical grating monochromator and an elliptically shaped glass capillary mirror as condenser. This set-up improves the spectral resolution by an order of magnitude. Furthermore, the partially coherent object illumination improves the contrast transfer of the microscope compared to incoherent conditions. With the new TXM, cells grown on flat support grids can be tilted perpendicular to the optical axis without any geometrical restrictions by the previously required pinhole for the zone plate monochromator close to the sample plane. We also developed an incorporated fluorescence light microscope which permits to record fluorescence, bright field and DIC images of cryogenic cells inside the TXM. For TXM tomography, imaging with multi-keV X-rays is a straightforward approach to increase the depth of focus. Under these conditions phase contrast imaging is necessary. For soft X-rays with shrinking depth of focus towards 10nm spatial resolution, thin optical sections through a thick specimen might be obtained by deconvolution X-ray microscopy. As alternative 3-D X-ray imaging techniques, the confocal cryo-STXM and the dual beam cryo-FIB/STXM with photoelectron detection are proposed. PMID:22273540

Schneider, Gerd; Guttmann, Peter; Rehbein, Stefan; Werner, Stephan; Follath, Rolf

2012-02-01

358

Gas-assisted annular microsprayer for sample preparation for time-resolved cryo-electron microscopy  

NASA Astrophysics Data System (ADS)

Time-resolved cryo-electron microscopy (TRCEM) has emerged as a powerful technique for transient structural characterization of isolated biomacromolecular complexes in their native state within the time scale of seconds to milliseconds. For TRCEM sample preparation, a microfluidic device has been demonstrated to be a promising approach to facilitate TRCEM biological sample preparation. It is capable of achieving rapidly aqueous sample mixing, controlled reaction incubation, and sample deposition on electron microscopy (EM) grids for rapid freezing. One of the critical challenges is to transfer samples to cryo-EM grids from the microfluidic device. By using a microspraying method, the generated droplet size needs to be controlled to facilitate thin ice film formation on the grid surface for efficient data collection, whilst not being so thin that it dries out before freezing, i.e. an optimized mean droplet size needs to be achieved. In this work, we developed a novel monolithic three dimensional (3D) annular gas-assisted microfluidic sprayer using 3D MEMS (MicroElectroMechanical System) fabrication techniques. The microsprayer demonstrated dense and consistent microsprays with average droplet size between 6 and 9??m, which fulfilled the droplet size requirement for TRCEM sample preparation. With droplet density of around 12–18 per grid window (window size 58? × ?58??m), and a data collectible thin ice region of >50% total wetted area, we collected ~800–1000 high quality CCD micrographs in a 6–8?h period of continuous effort. This level of output is comparable to what were routinely achieving using cryo-grids prepared by conventional blotting and manual data collection. In this case, weeks of data collection with the previous device has been shortened to a day or two. And hundreds of microliters of valuable sample consumption can be reduced to only a small fraction.

Lu, Zonghuan; Barnard, David; Shaikh, Tanvir R.; Meng, Xing; Mannella, Carmen A.; Yassin, Aymen S.; Agrawal, Rajendra K.; Wagenknecht, Terence; Lu, Toh-Ming

2014-11-01

359

Monolithic Microfluidic Mixing-Spraying Devices for Time-Resolved Cryo-Electron Microscopy  

PubMed Central

The goal of time-resolved cryo-electron microscopy is to determine structural models for transient functional states of large macromolecular complexes such as ribosomes and viruses. The challenge of time-resolved cryo-electron microscopy is to rapidly mix reactants, and then, following a defined time interval, to rapidly deposit them as a thin film and freeze the sample to the vitreous state. Here we describe a methodology in which reaction components are mixed and allowed to react, and are then sprayed onto an EM grid as it is being plunged into cryogen. All steps are accomplished by a monolithic, microfabricated silicon device that incorporates a mixer, reaction channel, and pneumatic sprayer in a single chip. We have found that microdroplets produced by air atomization spread to sufficiently thin films on a millisecond time scale provided that the carbon supporting film is made suitably hydrophilic. The device incorporates two T-mixers flowing into a single channel of four butterfly-shaped mixing elements that ensure effective mixing, followed by a microfluidic reaction channel whose length can be varied to achieve the desired reaction time. The reaction channel is flanked by two ports connected to compressed humidified nitrogen gas (at 50 psi) to generate the spray. The monolithic mixer-sprayer is incorporated into a computer-controlled plunging apparatus. To test the mixing performance and the suitability of the device for preparation of biological macromolecules for cryo-EM, ribosomes and ferritin were mixed in the device and sprayed onto grids. Three-dimensional reconstructions of the ribosomes demonstrated retention of native structure, and 30S and 50S subunits were shown to be capable of reassociation into ribosomes after passage through the device. PMID:19683579

Lu, Zonghuan; Shaikh, Tanvir R.; Barnard, David; Meng, Xing; Mohamed, Hisham; Yassin, Aymen; Mannella, Carmen A.; Agrawal, Rajendra K.; Lu, Toh-Ming

2009-01-01

360

Atomic Model of Rabbit Hemorrhagic Disease Virus by Cryo-Electron Microscopy and Crystallography  

PubMed Central

Rabbit hemorrhagic disease, first described in China in 1984, causes hemorrhagic necrosis of the liver. Its etiological agent, rabbit hemorrhagic disease virus (RHDV), belongs to the Lagovirus genus in the family Caliciviridae. The detailed molecular structure of any lagovirus capsid has yet to be determined. Here, we report a cryo-electron microscopic (cryoEM) reconstruction of wild-type RHDV at 6.5 Å resolution and the crystal structures of the shell (S) and protruding (P) domains of its major capsid protein, VP60, each at 2.0 Å resolution. From these data we built a complete atomic model of the RHDV capsid. VP60 has a conserved S domain and a specific P2 sub-domain that differs from those found in other caliciviruses. As seen in the shell portion of the RHDV cryoEM map, which was resolved to ?5.5 Å, the N-terminal arm domain of VP60 folds back onto its cognate S domain. Sequence alignments of VP60 from six groups of RHDV isolates revealed seven regions of high variation that could be mapped onto the surface of the P2 sub-domain and suggested three putative pockets might be responsible for binding to histo-blood group antigens. A flexible loop in one of these regions was shown to interact with rabbit tissue cells and contains an important epitope for anti-RHDV antibody production. Our study provides a reliable, pseudo-atomic model of a Lagovirus and suggests a new candidate for an efficient vaccine that can be used to protect rabbits from RHDV infection. PMID:23341770

Gao, Bingquan; Liu, Yanxin; Zhai, Yujia; Ma, Jun; Zhang, Kai; Baker, Timothy S.; Schulten, Klaus; Zheng, Dong; Pang, Hai; Sun, Fei

2013-01-01

361

Three-Dimensional cryoEM Reconstruction of Native LDL Particles to 16? Resolution at Physiological Body Temperature  

PubMed Central

Background Low-density lipoprotein (LDL) particles, the major carriers of cholesterol in the human circulation, have a key role in cholesterol physiology and in the development of atherosclerosis. The most prominent structural components in LDL are the core-forming cholesteryl esters (CE) and the particle-encircling single copy of a huge, non-exchangeable protein, the apolipoprotein B-100 (apoB-100). The shape of native LDL particles and the conformation of native apoB-100 on the particles remain incompletely characterized at the physiological human body temperature (37°C). Methodology/Principal Findings To study native LDL particles, we applied cryo-electron microscopy to calculate 3D reconstructions of LDL particles in their hydrated state. Images of the particles vitrified at 6°C and 37°C resulted in reconstructions at ?16 Å resolution at both temperatures. 3D variance map analysis revealed rigid and flexible domains of lipids and apoB-100 at both temperatures. The reconstructions showed less variability at 6°C than at 37°C, which reflected increased order of the core CE molecules, rather than decreased mobility of the apoB-100. Compact molecular packing of the core and order in a lipid-binding domain of apoB-100 were observed at 6°C, but not at 37°C. At 37°C we were able to highlight features in the LDL particles that are not clearly separable in 3D maps at 6°C. Segmentation of apoB-100 density, fitting of lipovitellin X-ray structure, and antibody mapping, jointly revealed the approximate locations of the individual domains of apoB-100 on the surface of native LDL particles. Conclusions/Significance Our study provides molecular background for further understanding of the link between structure and function of native LDL particles at physiological body temperature. PMID:21573056

Kumar, Vibhor; Butcher, Sarah J.; Oorni, Katariina; Engelhardt, Peter; Heikkonen, Jukka; Kaski, Kimmo; Ala-Korpela, Mika; Kovanen, Petri T.

2011-01-01

362

NiO nanosteps on Ni: wide band gap p-type nanostructure for efficient cold cathode and magnetically separable photocatalyst  

NASA Astrophysics Data System (ADS)

Pure nickel micro particles were chemically treated with various concentrations of NaOH and were subsequently annealed in 800 °C. The dimensions of the resulting nanosteps were tuned by simply varying the annealing time durations. Formation of Ni-NiO composite phase was confirmed by x-ray diffraction studies. The morphology of the as-prepared samples was investigated by field emission scanning electron microscope whereas the transmission electron microscope revealed the Ni core NiO shell structure of the samples. The NiO nanosteps showed much improved field emission properties compared to pure Ni micro particles and pure NiO powder synthesized by simply annealing the Ni particles. Finite element based simulation studies revealed strong enhancement of the electric field in the NiO nanostep samples and the simulated results were compared with the experimental outcome. The photocatalytic activities of the as-prepared samples were also investigated, which showed that Ni-NiO nanosteps is a magnetically separable photocatalyst.

Das, N. S.; Santra, S.; Banerjee, D.; Das, G. C.; Chattopadhyay, K. K.

2014-04-01

363

Radiation damage in single-particle cryo-electron microscopy: effects of dose and dose rate  

PubMed Central

Radiation damage is an important resolution limiting factor both in macromolecular X-ray crystallography and cryo-electron microscopy. Systematic studies in macromolecular X-ray crystallography greatly benefited from the use of dose, expressed as energy deposited per mass unit, which is derived from parameters including incident flux, beam energy, beam size, sample composition and sample size. In here, the use of dose is reintroduced for electron microscopy, accounting for the electron energy, incident flux and measured sample thickness and composition. Knowledge of the amount of energy deposited allowed us to compare doses with experimental limits in macromolecular X-ray crystallography, to obtain an upper estimate of radical concentrations that build up in the vitreous sample, and to translate heat-transfer simulations carried out for macromolecular X-ray crystallography to cryo-electron microscopy. Stroboscopic exposure series of 50–250 images were collected for different incident flux densities and integration times from Lumbricus terrestris extracellular hemoglobin. The images within each series were computationally aligned and analyzed with similarity metrics such as Fourier ring correlation, Fourier ring phase residual and figure of merit. Prior to gas bubble formation, the images become linearly brighter with dose, at a rate of approximately 0.1% per 10?MGy. The gradual decomposition of a vitrified hemoglobin sample could be visualized at a series of doses up to 5500?MGy, by which dose the sample was sublimed. Comparison of equal-dose series collected with different incident flux densities showed a dose-rate effect favoring lower flux densities. Heat simulations predict that sample heating will only become an issue for very large dose rates (50?e?Å?2?s?1 or higher) combined with poor thermal contact between the grid and cryo-holder. Secondary radiolytic effects are likely to play a role in dose-rate effects. Stroboscopic data collection combined with an improved understanding of the effects of dose and dose rate will aid single-particle cryo-electron microscopists to have better control of the outcome of their experiments. PMID:21525648

Karuppasamy, Manikandan; Karimi Nejadasl, Fatemeh; Vulovic, Milos; Koster, Abraham J.; Ravelli, Raimond B. G.

2011-01-01

364

CryoSat-2: Measuring fluctuations of land and marine ice fields from space  

NASA Astrophysics Data System (ADS)

1. INTRODUCTION CryoSat was chosen as the first of ESA's Earth Explorer Opportunity missions in late 1999, following a competitive selection process [1]. Unfortunately, the CryoSat satellite was lost as the result of a launch failure on 8 October 2005. The decision was made to rebuild the satellite in order to complete the mission, and as a result of this the new satellite, CryoSat-2, will be launched on 25 February 2010. 2. MISSION OBJECTIVES The mission goal of CryoSat is the measurement of secular change in the cryosphere, particularly in the elevation of the ice caps and the thickness of sea ice [2]. The required accuracy corresponds to about half of the variation expected due to natural variability, over reasonable scales for the surfaces concerned. The selected technique is radar altimetry, although the instrument has been modified to provide the enhanced capabilities needed to significantly extend the spatial coverage of previous altimetry missions, particularly ERS and EnviSat. Thus the radar includes a synthetic aperture mode which enables the along- track resolution to be improved to about 250 m. This will enable detection of leads in sea-ice which are narrower than those detected hitherto, so that operation deeper into pack-ice can be achieved with a consequent reduction in errors due to omission. Altimetry over the steep edges of ice caps is hampered by the irregular topography which, since the radar ranging is performed to the closest reflector rather than the point directly below, introduces uncertainty into the exactitude of repeat measurements. CryoSat's radar includes a second antenna and receiver chain so that interferometry may be used to determine the arrival angle of the echo and so improve localisation of the reflection. The satellite payload, which includes a DORIS receiver for precise orbit determination and a set of star trackers to measure the orientation of the interferometer, is quite complex and demanding. 3. CRYOSAT-1 LAUNCH FAILURE AND THE MISSION RECOVERY WITH CRYOSAT-2 CryoSat was launched on 8 October 2005, just less than 6 years after the start of the programme. Unfortunately the launch vehicle, a Rockot launcher derived from the Russian SS-19 ICBM, suffered an anomaly at the end of its second-stage flight, with the result that the satellite was lost, the debris falling close to the North pole. Determination to rebuild the satellite and carry out the mission was extremely widespread: within 5 months all of the necessary funding issues, legal procedures, industrial commitments and resource demands had been solved and the programme restarted. The new satellite, inevitably called CryoSat-2, includes a large number of improvements compared to its predecessor, although many are internal changes to improve the reliability and ease of operations. More significantly, the expected lifetime has been increased. The satellite measurements will be supported by a comprehensive set of validation data, collected on the surface and from airborne platforms. These validation data, designed to specifically address the uncertainties in the interpretation of the radar echoes, have been collected during a series of carefully co-ordinated measurement campaigns over several years. Additionally, techniques to enable the collocation of surface and satellite measurements over the moving sea-ice have been developed and rehearsed, ready to support the dedicated validation campaigns during the mission. CryoSat-2 will be launched from Baikonur, Kazakhstan on 25 February 2010. Launch was originally planned for March 2009, again with a Rockot. But lack of availability of this vehicle (more specifically, the versatile third stage added to the ICBM) has induced a change to the Dnepr launcher, also an ICBM: the SS-18. So finally, about 11 years after it was first selected, the CryoSat mission will start collecting data. 4. REFERENCES [1] http://www.esa.int/livingplanet/cryosat [2] Wingham, D. J., Francis, C. R., Baker, S., Bouzinac, C., Cullen, R., de Chateau-Thierry, P., Laxon, S. W., Mallow, U., Mavrocordatos, C., Phalip

Francis, Richard; Wingham, Duncan; Cullen, Robert

2010-05-01

365

Tomographic imaging of biological specimens with the cryo transmission X-ray microscope  

NASA Astrophysics Data System (ADS)

Using the photoelectric absorption contrast between water and protein at 2.4 nm wavelength, cryo X-ray microscopy has visualized protein structures down to 30 nm size in unstained, unsectioned biological specimens. Due to the large depth of focus of the Fresnel zone plate objectives, computed tomography based on a tilt series of X-ray microscopic images can be used to reconstruct the three-dimensional specimen structure. This method has been applied to the green alga Chlamydomonas reinhardtii, and to cell nuclei of male Drosophila melanogaster fruit fly cells.

Weiß, D.; Schneider, G.; Vogt, S.; Guttmann, P.; Niemann, B.; Rudolph, D.; Schmahl, G.

2001-07-01

366

In-plane magnetic anisotropy and domain transition in phase separated (La0.4Pr0.6)0.67Ca0.33MnO3 thin films on orthorhombic NdGaO3 substrates  

NASA Astrophysics Data System (ADS)

Phase separated manganites are a model system to study the interplay among crystal structure, transport and magnetism of materials, since it is believed that the free energies of the insulating and metallic phases are similar, but their crystal structures, magnetic and electronic properties are quite different. Thus, strain effects may play a critical role in determining the magnetic properties in manganite thin films. However, it is still unclear how the ferromagnetic metallic phase evolves in the temperature region where the insulator to metal transition occurs. We will present extensive studies of magnetic properties of phase separated (La0.4Pr0.6)0.67Ca0.33MnO3 (LPCMO) thin films. Atomically smooth LPCMO thin films were grown on NdGaO3 substrates by pulsed laser deposition technique. The observed change in coercive field as a function of temperature is similar to that of the coercivity as a function of grain size observed in fine ferromagnetic particles. Also, an in-plane magnetic anisotropy is observed from the magnetization hysteresis loops at different angles and temperatures.

Jeen Jeen, Hyoung; Biswas, Amlan

2010-03-01

367

Water activity and mobility in solutions of glycerol and small molecular weight sugars: Implication for cryo- and lyopreservation  

NASA Astrophysics Data System (ADS)

In this study, the free volume models, originally developed for large molecular weight polymer-solvent systems, were used to study the water activity and mobility in solutions of four small molecular weight cryo-/lyoprotectants, viz., glycerol, a monosaccharide (fructose), and two disaccharides (sucrose and trehalose). The free volume model parameters were determined by fitting the models to available experimental data using a nonlinear optimization procedure. It was found that free volume models could accurately predict the available experimental data, which suggests that the free volume models might be generally applicable to aqueous solutions of small molecular weight cryo-/lyoprotectants. Furthermore, several models for estimating the mutual diffusion coefficient were tested using available experimental data for aqueous solutions of glycerol and a better method to estimate the mutual diffusion coefficient was proposed. Free volume models were used to predict and analyze the water activity and mobility in solutions of four cryo-/lyoprotectants under conditions frequently encountered in cryo-/lyopreservation applications. It was found that the water mobility in the glassy state of the above four solutions is essentially negligible in the case of cryopreservation with storage temperature lower than -110°C. However, the water mobility in a glass at higher temperature (>-80°C) may be significant. As a result, a subcooling of up to 50°C may be necessary for the long-term cryo-/lyopreservation of biomaterials depending on the water content and the type of cryo-/lyoprotectants. It was further shown that trehalose might be the best of the four protectants studied for lyopreservation (water mass fraction ?0.1) when the storage temperature is above the room temperature. The results from this study might be useful for the development of more effective protocols for both cryopreservation and lyopreservation of living cells and other biomaterials.

He, Xiaoming; Fowler, Alex; Toner, Mehmet

2006-10-01

368

Three-dimensional mapping by CryoSat-2 of subglacial lake volume changes  

NASA Astrophysics Data System (ADS)

analyze data acquired by the CryoSat-2 interferometric radar altimeter and demonstrate its novel capability to track topographic features on the Antarctic Ice Sheet. We map the perimeter and depth of a 260 km2 surface depression above an Antarctic subglacial lake (SGL) and, in combination with Ice, Cloud and land Elevation Satellite laser altimetry, chart decadal changes in SGL volume. During 2007-2008, between 4.9 and 6.4 km3 of water drained from the SGL, and peak discharge exceeded 160 m3 s-1. The flood was twice as large as any previously recorded and equivalent to ~ 10% of the meltwater generated annually beneath the ice sheet. The ice surface has since uplifted at a rate of 5.6 ± 2.8 m yr-1. Our study demonstrates the ability of CryoSat-2 to provide detailed maps of ice sheet topography, its potential to accurately measure SGL drainage events, and the contribution it can make to understanding water flow beneath Antarctica.

McMillan, Malcolm; Corr, Hugh; Shepherd, Andrew; Ridout, Andrew; Laxon, Seymour; Cullen, Robert

2013-08-01

369

Estimating loop length from CryoEM images at medium resolutions  

PubMed Central

Background De novo protein modeling approaches utilize 3-dimensional (3D) images derived from electron cryomicroscopy (CryoEM) experiments. The skeleton connecting two secondary structures such as ?-helices represent the loop in the 3D image. The accuracy of the skeleton and of the detected secondary structures are critical in De novo modeling. It is important to measure the length along the skeleton accurately since the length can be used as a constraint in modeling the protein. Results We have developed a novel computational geometric approach to derive a simplified curve in order to estimate the loop length along the skeleton. The method was tested using fifty simulated density images of helix-loop-helix segments of atomic structures and eighteen experimentally derived density data from Electron Microscopy Data Bank (EMDB). The test using simulated density maps shows that it is possible to estimate within 0.5Å of the expected length for 48 of the 50 cases. The experiments, involving eighteen experimentally derived CryoEM images, show that twelve cases have error within 2Å. Conclusions The tests using both simulated and experimentally derived images show that it is possible for our proposed method to estimate the loop length along the skeleton if the secondary structure elements, such as ?-helices, can be detected accurately, and there is a continuous skeleton linking the ?-helices. PMID:24565041

2013-01-01

370

Cryo X-ray nano-tomography of vaccinia virus infected cells.  

PubMed

We have performed full-field cryo X-ray microscopy in the water window photon energy range on vaccinia virus (VACV) infected cells to produce tomographic reconstructions. PtK2 cells were infected with a GFP-expressing VACV strain and frozen by plunge fast freezing. The infected cells were selected by light fluorescence microscopy of the GFP marker and subsequently imaged in the X-ray microscope under cryogenic conditions. Tomographic tilt series of X-ray images were used to yield three-dimensional reconstructions showing different cell organelles (nuclei, mitochondria, filaments), together with other structures derived from the virus infection. Among them, it was possible to detect viral factories and two types of viral particles related to different maturation steps of VACV (immature and mature particles), which were compared to images obtained by standard electron microscopy of the same type of cells. In addition, the effect of radiation damage during X-ray tomographic acquisition was analyzed. Thin sections studied by electron microscopy revealed that the morphological features of the cells do not present noticeable changes after irradiation. Our findings show that cryo X-ray nano-tomography is a powerful tool for collecting three-dimensional structural information from frozen, unfixed, unstained whole cells with sufficient resolution to detect different virus particles exhibiting distinct maturation levels. PMID:22178221

Chichón, Francisco Javier; Rodríguez, Maria Josefa; Pereiro, Eva; Chiappi, Michele; Perdiguero, Beatriz; Guttmann, Peter; Werner, Stephan; Rehbein, Stefan; Schneider, Gerd; Esteban, Mariano; Carrascosa, José L

2012-02-01

371

Visualization of ATP Synthase Dimers in Mitochondria by Electron Cryo-tomography.  

PubMed

Electron cryo-tomography is a powerful tool in structural biology, capable of visualizing the three-dimensional structure of biological samples, such as cells, organelles, membrane vesicles, or viruses at molecular detail. To achieve this, the aqueous sample is rapidly vitrified in liquid ethane, which preserves it in a close-to-native, frozen-hydrated state. In the electron microscope, tilt series are recorded at liquid nitrogen temperature, from which 3D tomograms are reconstructed. The signal-to-noise ratio of the tomographic volume is inherently low. Recognizable, recurring features are enhanced by subtomogram averaging, by which individual subvolumes are cut out, aligned and averaged to reduce noise. In this way, 3D maps with a resolution of 2 nm or better can be obtained. A fit of available high-resolution structures to the 3D volume then produces atomic models of protein complexes in their native environment. Here we show how we use electron cryo-tomography to study the in situ organization of large membrane protein complexes in mitochondria. We find that ATP synthases are organized in rows of dimers along highly curved apices of the inner membrane cristae, whereas complex I is randomly distributed in the membrane regions on either side of the rows. By subtomogram averaging we obtained a structure of the mitochondrial ATP synthase dimer within the cristae membrane. PMID:25285856

Davies, Karen M; Daum, Bertram; Gold, Vicki A M; Mühleip, Alexander W; Brandt, Tobias; Blum, Thorsten B; Mills, Deryck J; Kühlbrandt, Werner

2014-01-01

372

Cryo-transmission electron tomography of native casein micelles from bovine milk  

PubMed Central

Caseins are the principal protein components in milk and an important ingredient in the food industry. In liquid milk, caseins are found as micelles of casein proteins and colloidal calcium nanoclusters. Casein micelles were isolated from raw skim milk by size exclusion chromatography and suspended in milk protein-free serum produced by ultrafiltration (molecular weight cut-off of 3 kDa) of raw skim milk. The micelles were imaged by cryo-electron microscopy and subjected to tomographic reconstruction methods to visualize the 3-dimensional and internal organization of native casein micelles. This provided new insights into the internal architecture of the casein micelle that had not been apparent from prior cryo-transmission electron microscopy studies. This analysis demonstrated the presence of water-filled cavities (~20 to 30 nm in diameter), channels (diameter greater than ~5 nm), and several hundred high-density nanoclusters (6 to 12 nm in diameter) within the interior of the micelles. No spherical protein submicellar structures were observed. PMID:22118067

Trejo, R.; Dokland, T.; Jurat-Fuentes, J.; Harte, F.

2013-01-01

373

An approach to automated acquisition of cryoEM images from lacey carbon grids  

PubMed Central

An approach to automated acquisition of cryoEM image data from lacey carbon grids using the Leginon program is described. Automated liquid nitrogen top up of the specimen holder dewar was used as a step towards full automation, without operator intervention during the course of data collection. During cryoEM studies of actin labelled with myosin V, we have found it necessary to work with lacey grids rather than Quantifoil or C-flat grids due to interaction of myosin V with the support film. Lacey grids have irregular holes of variable shape and size, in contrast to Quantifoil or C-flat grids which have a regular array of similar circular holes on each grid square. Other laboratories also prefer to work with grids with irregular holes for a variety of reasons. Therefore, it was necessary to develop a different strategy from normal Leginon usage for working with lacey grids for targetting holes for image acquisition and suitable areas for focussing prior to image acquisition. This approach was implemented by using the extensible framework provided by Leginon and by developing a new MSI application within that framework which includes a new Leginon node (for a novel method for finding focus targets). PMID:20817100

Nicholson, William V.; White, Howard; Trinick, John

2010-01-01

374

Ice sheet elevation change in West Antarctica from CryoSat interferometric altimetry  

NASA Astrophysics Data System (ADS)

Two decades of radar altimetry have shown accelerating mass losses from the Amundsen Sea Sector of West Antarctica. The mass imbalance of this region, which dominates that of all Antarctica, manifests as sustained ice thinning focussed upon fast-flowing ice streams and their tributaries. Ongoing observations are required to determine whether rates of mass loss continue to increase and, more widely, to monitor the stability of this sector of the ice sheet. With the retirement of the ERS-2 satellite in 2011 and the loss of Envisat in 2012, CryoSat-2 offers the unique potential to extend the current altimetry record. In coastal regions of Antarctica the satellite operates in a novel Synthetic Aperture Radar interferometric (SARin) mode, which enables improved resolution and echo location. Here, we apply a repeat track algorithm to SARin mode data to derive ice sheet elevation, volume and mass changes during the period 2010-2013, focussing upon the Amundsen Sea Sector of West Antarctica. Binning elevation change measurements at 5 km resolution gives on average 40 observations per grid cell, illustrating the high sampling density offered by CryoSat-2. We find that, since the cessation of ERS and Envisat measurements, thinning continues to be most pronounced along the fast-flowing ice streams and tributaries, with rates of 4-8 m/yr near the grounding lines of the Pine Island, Thwaites and Smith Glaciers. We compare these new observations to previous measurements made by the ERS and Envisat satellites.

McMillan, M.; Shepherd, A.; Ridout, A.; Sundal, A.

2013-12-01

375

Cryo-EM Structure of Isomeric Molluscan Hemocyanin Triggered by Viral Infection  

PubMed Central

Hemocyanins (Hcs) of arthropods and mollusks function not only as oxygen transporters, but also as phenoloxidases (POs). In invertebrates, PO is an important component in the innate immune cascade, where it functions as the initiator of melanin synthesis, a pigment involved in encapsulating and killing of pathogenic microbes. Although structures of Hc from several species of invertebrates have been reported, the structural basis for how PO activity is triggered by structural changes of Hc in vivo remains poorly understood. Here, we report a 6.8 Å cryo-electron microscopy (cryo-EM) structure of the isomeric form of hemocyanin, which was isolated from Abalone Shriveling syndrome-associated Virus (AbSV) infected abalone (Halitotis diversicolor), and build a pseudoatomic model of isomeric H. diversicolor hemocyanin 1 (HdH1). Our results show that, compared with native form of HdH1, the architecture of isomeric HdH1 turns into a more relaxed form. The interactions between certain functional units (FUs) present in the native form of Hc either decreased or were totally abolished in the isomeric form of Hc. As a result of that, native state Hc switches to its isomeric form, enabling it to play its role in innate immune responses against invading pathogens. PMID:24887432

Feng, Hongli; Liang, Rongfeng; Wang, Jiangyong; Xie, Lianhui; Zhu, Ping

2014-01-01

376

D0 Silicon Upgrade: D0 Cryo to D0 Physics DAQ Communications Link  

SciTech Connect

This engineering note documents a communication link between the D0 cryo/gas control system and the D0 physics data acquisition computer system. This note is being written well after the work has been completed, in order to document this communications link, and to satisfy needs of planned upgrades. These upgrades are the D0 Super Conducting Solenoid, VLPC system, and Silicon Detector System. The D0 cryo/gas control system is a Programmable Logic Controller based process control system. It is responsible for controlling many of the physical parameters of the D0 experiment, such as Calorimeter cooling, vacuum, Instrument air, TRD gas pressures and flows, W AMUS pressures and flows, SAMUS pressure and flows, etc. It works independent of the Physics DAQ system. There is a need for the Physics DAQ system to record some of these process values with the D0 physics data. This process data will later be used to calibrate certain features of the Physics data during reconstruction. The process data is also used to interlock (via the Physics DAQ system) some of the other D0 systems such as the TRD high voltage system. Some of the Process data values will be continuously monitored and will stop the Physics data taking of the experiment if it is out of tolerance.

Markley, Dan; /Fermilab

1995-03-07

377

High-resolution cryo-electron microscopy on macromolecular complexes and cell organelles.  

PubMed

Cryo-electron microscopy techniques and computational 3-D reconstruction of macromolecular assemblies are tightly linked tools in modern structural biology. This symbiosis has produced vast amounts of detailed information on the structure and function of biological macromolecules. Typically, one of two fundamentally different strategies is used depending on the specimens and their environment. A: 3-D reconstruction based on repetitive and structurally identical unit cells that allow for averaging, and B: tomographic 3-D reconstructions where tilt-series between approximately ± 60 and ± 70° at small angular increments are collected from highly complex and flexible structures that are beyond averaging procedures, at least during the first round of 3-D reconstruction. Strategies of group A are averaging-based procedures and collect large number of 2-D projections at different angles that are computationally aligned, averaged together, and back-projected in 3-D space to reach a most complete 3-D dataset with high resolution, today often down to atomic detail. Evidently, success relies on structurally repetitive particles and an aligning procedure that unambiguously determines the angular relationship of all 2-D projections with respect to each other. The alignment procedure of small particles may rely on their packing into a regular array such as a 2-D crystal, an icosahedral (viral) particle, or a helical assembly. Critically important for cryo-methods, each particle will only be exposed once to the electron beam, making these procedures optimal for highest-resolution studies where beam-induced damage is a significant concern. In contrast, tomographic 3-D reconstruction procedures (group B) do not rely on averaging, but collect an entire dataset from the very same structure of interest. Data acquisition requires collecting a large series of tilted projections at angular increments of 1-2° or less and a tilt range of ± 60° or more. Accordingly, tomographic data collection exposes its specimens to a large electron dose, which is particularly problematic for frozen-hydrated samples. Currently, cryo-electron tomography is a rapidly emerging technology, on one end driven by the newest developments of hardware such as super-stabile microscopy stages as well as the latest generation of direct electron detectors and cameras. On the other end, success also strongly depends on new software developments on all kinds of fronts such as tilt-series alignment and back-projection procedures that are all adapted to the very low-dose and therefore very noisy primary data. Here, we will review the status quo of cryo-electron microscopy and discuss the future of cellular cryo-electron tomography from data collection to data analysis, CTF-correction of tilt-series, post-tomographic sub-volume averaging, and 3-D particle classification. We will also discuss the pros and cons of plunge freezing of cellular specimens to vitrified sectioning procedures and their suitability for post-tomographic volume averaging despite multiple artifacts that may distort specimens to some degree. PMID:24390311

Hoenger, Andreas

2014-03-01

378

Molecular Expressions: Color Separation  

NSDL National Science Digital Library

This item is an interactive Java simulation for introductory physics students on the topic of color. It explores how individual subtractive primary colors can be separated from a full-color photograph and then be reassembled to create the original scene. The mouse cursor may be used to superimpose color separations over one another. As additional separations are added, the resulting image exhibits the realism of a color photograph. This item is part of a larger collection of materials on optics and microscopy developed by the National High Magnetic Field Laboratory and Florida State University.

Davidson, Michael; Parry-Hill, Matthew J.; Sutter, Robert

2008-08-21

379

Battery separators  

Microsoft Academic Search

A novel, improved battery separator and process for making the separator. Essentially, the separator carries a plurality of polymeric ribs bonded to at least one surface and the ribs have alternating elevated segments of uniform maxiumum heights and depressed segments along the length of the ribs.

R. Le Bayon; R. Faucon; J. Legrix

1984-01-01

380

Battery separator  

Microsoft Academic Search

A battery separator is described that is embossed with a configuration that is neither vertical corrugation or vertical rib and yet in which all of the surface areas of the two separator faces open or slant upwardly except the portions actually directly engaged against a battery plate. Thus all intended recesses in the faces of the battery separator are open

N. J. Lin; D. D. ORell

1980-01-01

381

Battery separator  

Microsoft Academic Search

The instant invention is directed to a sheet product capable of forming an improved battery separator. The present sheet product is formed from a thin, acid-stable, porous material and has a first and a second major face with a plurality of separate, continuous, open channels on each face such that each channel on each major face defines a separation between

N. J. Lin; D. D. Orell

1983-01-01

382

Soft X-ray microscopy with a cryo scanning transmission X-ray microscope: I. Instrumentation, imaging and spectroscopy  

Microsoft Academic Search

Summary We have developed a cryo scanning transmission X-ray microscope which uses soft X-rays from the National Synchrotron Light Source. The system is capable of imaging frozen hydrated specimens with a thickness of up to 10 mm at temperatures of around 100 K. We show images and spectra from frozen hydrated eukaryotic cells, and a demonstration that biological specimens do

Maser; Osanna; Kirz; Winn; Tennant

2000-01-01

383

Fabrication of carbon films with ? 500nm holes for cryo-EM with a direct detector device.  

PubMed

Single particle electron cryomicroscopy (cryo-EM) is often performed using EM grids coated with a perforated or holey layer of amorphous carbon. Regular arrays of holes enable efficient cryo-EM data collection and several methods for the production of micropatterned holey-carbon film coated grids have been described. However, a new generation of direct detector device (DDD) electron microscope cameras can benefit from hole diameters that are smaller than currently available. Here we extend a previously proposed method involving soft lithography with a poly(dimethylsiloxane) (PDMS) stamp for the production of holey-carbon film coated EM grids. By incorporating electron-beam (e-beam) lithography and modifying the procedure, we are able to produce low-cost high-quality holey-carbon film coated EM grids with ?500nm holes spaced 4?m apart centre-to-centre. We demonstrate that these grids can be used for cryo-EM. Furthermore, we show that by applying image shifts to obtain movies of the carbon regions beside the holes after imaging the holes, the contrast transfer function (CTF) parameters needed for calculation of high-resolution cryo-EM maps with a DDD can be obtained efficiently. PMID:24269484

Marr, Chelsea R; Benlekbir, Samir; Rubinstein, John L

2014-01-01

384

Cryo-Scanning Electron Microscopy Observations of Vessel Content during Transpiration in Walnut Petioles. Facts or Artifacts?  

PubMed Central

The current controversy about the “cohesion-tension” of water ascent in plants arises from the recent cryo-scanning electron microscopy (cryo-SEM) observations of xylem vessels content by Canny and coworkers (1995). On the basis of these observations it has been claimed that vessels were emptying and refilling during active transpiration in direct contradiction to the previous theory. In this study we compared the cryo-SEM data with the standard hydraulic approach on walnut (Juglans regia) petioles. The results of the two techniques were in clear conflict and could not both be right. Cryo-SEM observations of walnut petioles frozen intact on the tree in a bath of liquid nitrogen (LN2) suggested that vessel cavitation was occurring and reversing itself on a diurnal basis. Up to 30% of the vessels were embolized at midday. In contrast, the percentage of loss of hydraulic conductance (PLC) of excised petiole segments remained close to 0% throughout the day. To find out which technique was erroneous we first analyzed the possibility that PLC values were rapidly returned to zero when the xylem pressures were released. We used the centrifugal force to measure the xylem conductance of petiole segments exposed to very negative pressures and established the relevance of this technique. We then analyzed the possibility that vessels were becoming partially air-filled when exposed to LN2. Cryo-SEM observations of petiole segments frozen shortly after their xylem pressure was returned to atmospheric values agreed entirely with the PLC values. We confirmed, with water-filled capillary tubes exposed to a large centrifugal force, that it was not possible to freeze intact their content with LN2. We concluded that partially air-filled conduits were artifacts of the cryo-SEM technique in our study. We believe that the cryo-SEM observations published recently should probably be reconsidered in the light of our results before they may be used as arguments against the cohesion-tension theory. PMID:11080296

Cochard, Herve; Bodet, Christian; Ameglio, Thierry; Cruiziat, Pierre

2000-01-01

385

Comparative study on histological structures of the vitelline membrane of hen and duck egg observed by cryo-scanning electron microscopy.  

PubMed

The histological structures of the vitelline membranes (VM) of hen and duck eggs were observed by cryo-scanning electron microscopy (cryo-SEM), and the chemical characteristics were also compared. The outer layer surface (OLS) of duck egg VM showed networks constructed by fibrils and sheets (0.1-5.2 microm in width), and that of hen egg presented networks formed only by sheets (2-6 microm in width). Thicker fibrils (0.5-1.5 microm in width) with different arrangement were observed on the inner layer surface (ILS) of duck egg VM as compared to those (0.3-0.7 microm in width) of hen egg VM. Upon separation, the outer surface of the outer layer (OSOL) and the inner surface of the inner layer (ISIL) of hen and duck egg VMs were quite similar to fresh VM except that the OSOL of duck egg VM showed networks constructed only by sheets. Thin fibrils interlaced above a bumpy or flat structure were observed at the exposed surface of the outer layer (ESOL) of hen and duck egg VMs. The exposed surfaces of inner layers (ESIL) of hen and duck egg VMs showed similar structures of fibrils, which joined, branched, and ran in straight lines for long distances up to 30 microm; however, the widths of the fibrils shown in ESOL and ESIL of duck egg VM were 0.1 and 0.7-1.4 microm, respectively, and were greater than those (<0.1 and 0.5-0.8 microm) of hen egg VM. The continuous membranes of both hen and duck egg VMs were still attached to the outer layers when separated. The content of protein, the major component of VM, was higher in duck egg VM (88.6%) than in hen egg VM (81.6%). Four and six major SDS-soluble protein patterns with distinct localization were observed in hen and duck egg VMs, respectively. Overall, the different histological structures of hen and duck egg VMs were suggested to be majorly attributable to the diverse protein components. PMID:20055415

Chung, Wen-Hsin; Lai, Kung-Ming; Hsu, Kuo-chiang

2010-02-10

386

First results of CryoSat-2 observations of Pine Island Glacier  

NASA Astrophysics Data System (ADS)

Antarctica's ice sheets contain enough water to raise global sea levels by some 60 m, were they to be rapidly discharged. Satellite radar altimeters have monitored changes in the surface elevation of the Antarctic continent since 1992 and up to the present day. These data have permitted us to estimate that, overall, Antarctica is losing about 25 GT of ice per year, potentially contributing some 0.07 mm per year to the present rate of 3.0 mm per year global sea level rise. The greatest thinning has been observed to occur at the margins of the ice sheet, through accelerated drainage of glaciers into the ocean. Yet, due to the roughness and steepness of these fast-changing surfaces, these fast-changing areas have proven difficult to survey with conventional pulse-limited satellite radar altimetry. A striking example of rapid retreat and ice sheet thinning is the Pine Island Glacier, the central trunk of which has been observed to be losing volume at an accelerating rate, increasing from 2.6 ± 0.3 cubic kilometres per y