11 May 2017

Best Research of 2016

35 highlights out of 474 reports representing the best of life sciences, chemistry, magnet science and technology, and condensed matter physics.

Best Research of 2016

 
 

In 2016, a record number of researchers — nearly 1,780 — performed experiments across our lab’s seven user facilities. Their work is summarized in more than 470 research reports across 17 categories. From those hundreds of reports, the MagLab’s Science Council and Director Greg Boebinger selected the year’s best, presented below.

These 35 exceptional experiments are the cream of the crop, representing dynamic discoveries across condensed matter sciences, chemistry, life sciences and magnet technology. The Best Research of 2016 showcases the important role magnets play in detecting new phases of matter, defining the properties of unique materials, understanding dissolved organic materials in our water, exploring the chemistry of a battery life cycle and helping fight disease. There are also advances in magnet-making and technique development included in the list, work that is critical in the quest for ever-stronger tools to facilitate the discoveries of the future.

Select a specific category to view below, or simply scroll down to read these highlights and follow links for more details.

 

Condensed Matter | Chemistry | Life Sciences | Magnets & Magnetic Materials

 
 

2D Materials

Report Number: 146

Magnetic Exciton Superfluidity in Bilayer Graphene Double-Layer

Liu, X.; Watanabe, K.; Taniguchi, T.; Halperin, B.I. and Kim, P.
Submitted to Nature Phys.; arXiv:1608.03726.

The Bose-Einstein condensation of excitons, or strongly bound pairs of electrons and holes, in conventional semiconductor structures has been known as a possible pathway towards building devices with low dissipation. The quest for exciton condensates that remain stable up to relatively high temperatures has been renewed by the availability of atomically thin materials, such as graphene. Here two groups report the observation of exciton condensates in the quantum Hall effect regime of double bilayer graphene devices. By measuring the Coulomb drag, they find signatures of the superfluid condensate phase to temperatures in excess of 4 K (Li et al.), i.e. up to record high 8 K (Liu et al.). These findings open up new opportunities to study the phase diagram of the exciton Bose-Einstein condensate and engineer novel devices based on dissipationless transport. Read report ....

 

Report Number: 252

Excitonic Superfluid Phase in Double Bilayer Graphene

Li, J.I.A.; Hone, J. and Dean, C.
Submitted to Nature Phys.; arXiv:1608.05846.

The Bose-Einstein condensation of excitons, or strongly bound pairs of electrons and holes, in conventional semiconductor structures has been known as a possible pathway towards building devices with low dissipation. The quest for exciton condensates that remain stable up to relatively high temperatures has been renewed by the availability of atomically thin materials, such as graphene. Here two groups report the observation of exciton condensates in the quantum Hall effect regime of double bilayer graphene devices. By measuring the Coulomb drag, they find signatures of the superfluid condensate phase to temperatures in excess of 4 K (Li et al.), i.e. up to record high 8 K (Liu et al.). These findings open up new opportunities to study the phase diagram of the exciton Bose-Einstein condensate and engineer novel devices based on dissipationless transport. Read report ....

 

Report Number: 69

Novel Quantum Phases in Multi-Subband Two-Dimensional Hole Systems

Liu, Y.; Mueed, M.A.; Winkler, R.; Pfeiffer, L.N.; West, K.W.; Baldwin, K.W. and Shayegan, M.
Published in Phys. Rev. Lett. 117, 106802 (2016).

Very clean two-dimensional (2D) electron systems in semiconductor quantum wells, subjected to high perpendicular magnetic fields, exhibit a plethora of collective quantum phases. Electron nematic or stripe phases that occur in high Landau levels have been widely studied, but the microscopic details remain elusive. Liu et al. report the discovery of a new correlated phase that shows anisotropic insulating behavior, in contrast to nematic phases, which are not insulating. The novel phase is manifested only in a range of low fillings near ν=½ in a 2D hole system with a bilayer charge distribution, and near the crossing of the lowest two Landau levels caused by tilting the sample in a magnetic field. The results suggest that the new insulating phase is an anisotropic (striped), two-component, pinned Wigner crystal. Read report ....

 

Report Number: 96

Orientation of Quantum Hall Stripes Under In-Plane Magnetic Fields

Shi, Q.; Zudov, M.A.; Watson, J.; Gardner, G.; Qian, Q. and Manfra, M.
Published in Phys. Rev. B 93, 121404(R) (2016); Phys. Rev. B 93, 121411(R) (2016).

Very clean two-dimensional (2D) electron systems in semiconductor quantum wells, subjected to high perpendicular magnetic fields, exhibit a plethora of collective quantum phases. Electron nematic or stripe phases that occur in high Landau levels have been widely studied, but the microscopic details remain elusive. In higher Landau levels, Shi et al. demonstrate that the orientation of stripes depends on the subtle interplay of several factors, including the carrier density, filling factor ν, and magnitude of the in-plane field. Read report ....

 

Report Number: 259

Tunable Symmetries of Integer and Fractional Quantum Hall Phases in Multi-Dirac-Band Heterostructure

Stepanov, P.; Barlas, Y.; Espiritu, T.; Che, S.; Lau, C.N.; Watanabe, K.; Taniguchi, T. and Smirnov D.
Published in Phys. Rev. Lett. 117, 076807 (2016)

The study of electrically gated multilayer graphene in high magnetic fields provides a rich playground to tune spin, valley, orbital and parity polarizations of resulting Landau level spectrum. For both these studies the Riverside Group employs dual-gated devices to enable both the carrier density and out of plane displacement electric field to be independently controlled, providing in-situ tuning of the Landau-level symmetries. Stepanov et al employ magnetotransport up to 45T to focusing upon the behavior at fractional 2/3 and 11/3 landau level filling in trilayer graphene — in this case the perpendicular electric field breaks the mirror symmetry tuning the hybridization between mass-less and massive fermions due to their opposite parities. Read report ....

 

Report Number: 279

Probing the Influence of Dielectric Environment on Excitons in Monolayer WSe2: Insight from High Magnetic Fields

Stier, A.V.; Crooker, S.A.; Wilson, N.P.; Clark, G. and Xu, X.
Published in Nano Letters 16, 7054 (2016).

Exfoliated monolayers of the new two-dimensional semiconductor WSe2 were encapsulated in different materials to tune their local dielectric environment. Using single-mode optical fibers, polarized, low-temperature magneto-absorption studies were carried out in pulsed magnetic fields of up to 65 T. The diamagnetic shifts of the excitons were used as a gauge of their radii, allowing a quantitative determination of the effect of dielectric screening to be made; data are being compared with current theoretical models. Such exciton parameters are of great interest in the new monolayer semiconductors, and understanding and controlling them will be of critical importance for future two-dimensional optoelectronic devices. Read report ....

 

Kondo/Heavy Fermions Systems

Report Number: 66

Phase Diagram of URu2-xFexSi2 in High Magnetic Fields

Ran, S.; Jeon, I.; Kanchanavatee, N.; Huang, K.; Maple, M.B.; Gallagher, A.; Chen, K.; Graf, D.; Baumbach, R.E. and Singleton, J.
Manuscript in Preparation

The behavior of the compound URu2Si2 poses a longstanding challenge in condensed matter physics because it hosts an unidentified low-temperature ordered state (“hidden order”), in addition to unconventional superconductivity. This study employs both chemical substitution and large applied magnetic fields to explore the electronic landscape of the URu2-xFexSi2 alloy. New ordered phases are uncovered at high fields, providing important insights into correlated electronic states that are closely related to the hidden order. Read report ....

 

Report Number: 326

Unusual Phase Diagram of CeOs4Sb12

Ho, P.-C.; Goddard, P.A.; Maple, M. B. (UCSD, Physics) and Singleton, J.
Published in Phys. Rev. B 94, 205140.

The authors study the geometry of the Fermi surface and the phase of CeOs4Sb12 and NdOs4Sb12 in pulsed magnetic fields. The latter compound is proposed to undergo a phase transition from a semi-metallic state to state characterized by nearly isotropic Fermi surfaces. The authors argue that this transition is akin to the α- γ valence or Kondo collapse like transition observed in elemental Ce. Read report ....

 

Report Number: 357

Electronic In-plane Symmetry Breaking at Field-tuned Quantum Criticality in CeRhIn5

Ronning, F.; Helm, T.; Bachmann, M.; Moll, P.J.W.; Balicas, L.; Chan, M.; Ramshaw, B.; McDonald, R.; Balakirev, F. and Bauer, E.D.
Submitted to Science

The authors report evidence for field-induced electronic in-plane symmetry breaking in the tetragonal heavy fermion superconductor CeRhIn5 through measurements of the in-plane magnetoresistivity anisotropy in microstructured single-crystals. This “nematic” phase-transition appears to occur within a two-dimensional electronic sub-system that dominates the in-plane transport but contributes quite negligibly to the out-of-plane transport. The appearance of nematic like behavior in a heavy fermion superconductor suggests a relation between nematicity and unconventional superconductivity as observed in other families of compounds. Read report ....

 

Condensed Matter Technique Development

Report Number: 140

Quantum Oscillations in the High Pressure Metallised Mott Insulator NiS2

Grosche, F.M.; Chang, H.; Baglo, J.; Semeniuk, K.; Friedemann, S.; Grockowiack, A.; Coniglio, W. and Tozer, S.
Manuscript in preparation

The metallization of Mott insulators under pressure provides an opportunity to understand the nature of the electronic interactions leading to the formation of the Mott insulating phase. In this report, Grosche and coworkers metallize NiS2. They succeed at not only measuring the quantum oscillation evidence for a Fermi surface, but performing a rotation study which enables the topology of the Fermi surface to be mapped out. Read report ....

 

Report Number: 492

Enhanced MRI Relaxivity in Anchor-free PEGylated Iron Oxides: Towards High Performance Targeted Cancer Imaging

Beltran-Huarac, J.; Thapa, B. and Diaz-Diestra, D.
Submitted to Nanoscale Research Letters

MRI contrast agents based on nanoparticles of Fe3O4 need to be suspended in blood for extended time periods, while maintaining a high contrast ratio. For this, the nanoparticles are coated in PEG. For the PEG coating to adhere, an anchor is usually used. However, the anchor molecule may interfere with the biological function of the nanoparticles. Here, anchor free PEG coated nanoparticles with a high contrast ratio is developed and tested. The contrast enhancement is correlated to the increased effective radius due to nanoparticle clustering and the local field inhomogeneity of the magnetic core. Read report ....

 

Superconductivity – Basic

Report Number: 5

Pressure and high-Tc Superconductivity in Sulfur Hydrides

Gor’kov, L.P. and Kresin, V.Z.
Published in Nature Scientific Reports 6:256086.

The authors argue that the rapid increase in the superconducting transition temperature Tc of H3S around 120 GPa ought to result from a structural phase-transition. The authors argue that the complex phonon spectrum in H3S require a new approach provided here to calculate Tc. The authors claim to achieve a good correlation between their calculations and the experiments. Read report ....

 

Report Number: 25

Two-Dimensional Superconductivity in a Bulk Single-Crystal

Zhang, Q.R.; Rhodes, D.; Zeng, B.; Johannes, M.D. and Balicas, L.
Published in Phys. Rev. B 94/094511.

The authors report magnetic field as a function of the temperature superconducting phase-diagram of Pd based chalcogenide superconductors. They find that Ta4Pd3Te16 displays anomalous upper critical fields, that is that depending linearly on temperature even for fields above the weakly coupling Pauli limiting field. While Nb3PdxSe7 displays a T1/2 dependence, as observed in mono- and few- layered NbSe2, indicating that its superconducting planes are decoupled and thus behaving as a two-dimensional superconductor. Read report ....

 

Report Number: 164

Evolution of the Fermi Surface of the Nematic Superconductors FeSe1-xSx

Coldea, A.I.; Reiss, P.; Blake, S.F.; Graf. D. and Choi, E.S.
Submitted to Phys. Rev. Lett.

The authors observe Fermi surfaces of FeSe to increase monotonically with S doping, and as the in-plane anisotropy observed in the transport is suppressed. The authors claim to detect signatures of orbital-dependent quasiparticle mass renomalization which is suppressed for those orbits with dominant dxz/dyz character, but unusually enhanced for those orbits with dominant dxy character. The fact that superconductivity is continuously suppressed by chemical pressure (S doping) might imply that nematic fluctuations are not the main factor for the superconducting pairing of FeSe1−xSx. Read report ....

 

Condensed Matter Other (Topological Matter)

Report Number: 157

Landau Level Spectroscopy of Massive Dirac Fermions in ZrTe5

Jiang, Y.; Jiang, Z.; Dun, Z.; Zhou, H.D.; Chen, K.-W.; Moon, S.; Besara, T.; Siegrist, T.M.; Baumbach, R.E. and Smirnov, D.

Exfoliated films of ZrTe5 were examined in magnetotransmission using two sources, a tunable quantum-cascade laser (QCL) and a Fourier transform IR spectrometer, at magnetic fields of up to 17.5 T. The circularly-polarized QCL measurements are particularly interesting, because they allow cyclotron resonances due to electrons and holes to be distinguished easily. These measurements illustrate the diagnostic power of cyclotron resonance, and will form a valuable “smoking gun” test of the various conflicting models of the bandstructure of ZrTe5, identified as a candidate quantum spin Hall insulator. Read report ....

 

Report Number: 412

Field-Induced Phase Transition in the Weyl Semimetal TaAs

Ramshaw, B.J.; Modic, K.A.; Moll, P.J.W.; N.J. Ghimire; Bauer, E.D.; Ronning, F.; McDonald, R.D.
Manuscript in preparation

In Dirac metals there is considerable interest in the ability to tune the strength of interactions so as to control the massive term leading to the opening of a gap. Here the authors succeed to do this in the Weyl semimetal TaAsm using the strongest available magnetic fields. The find evidence for a magnetic field-induced insulating phase at magnetic fields above ~ 65 T, which could be a form of chiral symmetry breaking. Read report ....

 

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Chemistry – Environmental

Report Number: 131

Biodegradability and Molecular Composition of Dissolved Organic Nitrogen in Urban Stormwater Runoff and Outflow Water from a Stormwater Retention Pond

Lusk, M.G. and Toor, G.S.
Published in Environmental Science and Technology 50, 3391-3398 (2016).

Dissolved organic nitrogen (DON) is a potential source of reactive N in aquatic ecosystems and can be a key player in supporting the phytoplankton and bacteria that cause water quality degradation. The bulk DON in a water body may include thousands of molecules ranging from simple compounds (e.g., sugars and amino acids) readily used by plants and microbes to more complex molecules (e.g., tannins) that are not as easily metabolized. The biodegradability of the DON increased from 10% in the stormwater runoff to 40% in the pond outflow water. DON was less aromatic and had lower overall molecular weight in the pond outflow water than in the stormwater runoff. We attribute higher biodegradability in the pond outflow water to its lower aromaticity and lower molecular weight, indicating an in-pond process of labile DON generation. Read report ....

 

Report Number: 240

Coherent Spectroscopy at 25 Tesla in a Photosynthetic Protein Complex

Maiuri, M. (Princeton U., Chemistry); Oviedo, M.B. (Princeton U., Chemistry); Dean J.C.; Bishop, M.; Toa, Z.S.D.; McGill, S. and Scholes, G.D.
Submitted to Nature Chem

In photosynthesis specialized pigments such as chlorophylls bounded to a protein, absorb sunlight and transfer energy to reaction centers that act as solar cells. Recent theoretical studies predict that vibrations at the pigment sites delocalize and transfer the harvested energy, an effect that depends on their coupling with the electrons. Through a pump-probe experiment in the Split Florida Helix magnet they demonstrate that they can detune this vibronic coupling in a particular light harvesting complex by modifying the electronic levels of the molecules in the proteins, while not perturbing their vibrational structure. Therefore the authors claim that magnetic field allows one to reveal and detune the vibronic coupling in a photosynthetic complex. Read report ....

 

Chemistry - General (Chemical Materials)

Report Number: 370

Reversible Solvatomagnetic Switching in a Single-Ion Magnet from an Entatic State

Vallejo, J.; Pardo, E.; Viciano-Chumillas, M.; Castro, I.; Amorós, P.; Julve, M.; Lloret, F.; Cano, J.; Krzystek, J. and Ruiz-Pérez, C.
Published in Chemical Science 2017, DOI: 10.1039/C6SC05188J.

This project is a novel multi-disciplinary study on properties of coordination complexes of cobalt(II). Depending on subtle change of geometry, triggered by external factors such as temperature and moisture, these complexes simultaneously change their magnetic properties (in the tetrahedral coordination they are so-called single-ion magnets, in octahedral geometry they are not) and optical characteristics (change of colors). Read report ....

 

Report Number: 390

An Integrated Magnetic Resonance Study of a V–Fe Complex with Metal–Metal Multiple Bonds

Thomas, C.M.; Gramigna, K.; Greer, S.M.; Stoian, S.A; McKay, J.E. and Hill, S.
Manuscript in preparation

This report describes an investigation of multiple metal-metal bonds in a heterobimetallic (vanadium-iron) complex. It combines an impressive variety of techniques: EPR, ELDOR-NMR, Mössbauer for this purpose. The use of the newest instrument in the EMR program, the so-called HiPER, is worth emphasizing. Read report ....

 

Report Number: 302

Characterization of Surface Accessible Catalytic 27Al, 119Sn, and 17O Species by DNP-Enhanced NMR Using Targeted Nitroxide Spin Probes as Reactant Models

Schurko, R.W., Hirsh, D.A., Veinberg, S.L., Jaroszewicz, M.J., Sandre, A.R., Namespetra, A.M.; Frydman, L.; Hung, I. and Gan, Z.
Published in Cryst Eng Comm 16, 31, 7334-7356 (2014)

Dynamic Nuclear Polarization can dramatically enhance not only the overall NMR sensitivity but also selectively the surface species closer to radical agent. Wi et al used this selectivity property of DNP and other NMR pulse techniques to probe surface 27Al sites of aluminum containing catalytic sample system Al-SBA15. They have found that 27Al T1 relaxations are drastically different between surface and bulk aluminum sites. Read report ....

 

Report Number: 67

Solid-State NMR Studies of Composite Electrolytes: Li7La3Zr2O12-PEO (LiClO4)

Schurko, R.W., Hirsh, D.A., Veinberg, S.L., Jaroszewicz, M.J., Sandre, A.R., Namespetra, A.M.; Frydman, L.; Hung, I. and Gan, Z.
Published in Cryst Eng Comm 16, 31, 7334-7356 (2014)

Solid-state composite electrolytes such as Li7La3Zr2O12 (LLZO) with PEO have many advantages over traditional liquid electrolytes in terms of safety, performances and stability of rechargeable batteries. Zheng et al used high-resolution solid-state Li NMR to identify different chemical environments of LLZO-PEO (LiClO4) and track the pathway of Li ions during charge-discharge process. They found that Li ions prefer to maximize the fraction of LLZO ceramic phase and minimize that of the interface or PEO polymer phase on their diffusion pathway. This study have been published in Angewandte Chemie as a "Hot Paper". Read report ....

 

Chemistry – Petroleum

Report Number: 14

Photochemical Changes in Water Accommodated Fractions of MC252 and Surrogate Oil Created During Solar Exposure as Determined by FT-ICR MS

Vaughan, P.; Wilson, T.; Kamerman, R.; Hagy, M.E.; McKenna, A.; Chen, H. and Jeffrey, W.
Published in Marine Pollution Bulletin 104(1-2), 262-268 (2016).

To determine effects of photochemical weathering of petroleum, surrogate and Macondo (MC252) crude oils were exposed to solar radiation during the formation of Water Accommodated Fractions (WAF) in sterile seawater. Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) analyses of water soluble species formed during exposure to sunlight were compared for the different treatments. Photochemical alterations resulted in differences in compound class distributions. In general, surrogate oil was photo-oxidized across a wider carbon number range compared to MC252. Importantly, Surrogate Oil has been provided to researcher worldwide in lieu of limited MC252 for research purpose, but this is the first molecular characterization of the two oils that shows difference in physical and chemical properties. Read report ....

 

Report Number: 57

4 Years after the Deepwater Horizon Spill: Molecular Transformation of Macondo Well Oil in Louisiana Salt Marsh Sediments Revealed by FT-ICR Mass Spectrometry

Chen, H.; Hou, A.; Corilo, Y.E.; Lin, Q.; Lu, J.; Mendelssohn, I.A. ; Zhang, R.; Rodgers, R.P. and McKenna, A.M.
Published in Environmental Science and Technology 50 (17), 9061-9069 (2016).

This study represents the first temporal characterization of MWO transformation products at the molecular level. Here, we identify persistent MWO transformation products and catalogue compositional changes that occur to parent MWO in Barataria Bay saltmarsh sediments up to 4 years after the Deepwater Horizon oil spill. The increased abundance of highly polar compounds of low volatility is ideally suited for FT-ICR MS can address the complexity of these highly polar, multifunctional oxidized transformation products at the molecular level. Oil weathering pattern revealed by FT-ICR MS indicate both photo-oxidation and biodegradation contribute to the molecular modification of weathered oil in surface layers of saltmarsh sediments. Read report ....

 

FT-ICR Mass Spectrometry Technique & Instrumentation Development

Report Number: 271

Analysis of Human Cell Lysate by Qualitative Top-Down Proteomics at 21 T

DeHart, C.J.; Anderson, L.C.; Kaiser, N.K. ; Fellers, R.T. Smith, D.F.; Greer, J.B.; LeDuc, R.D.; Blakney, G.T.; Thomas, P.M.; Kelleher, N.L. and Hendrickson, C.L.
Published in Journal of Proteome Research 26, 1626-1632 (2015)doi: 10.1021/acs.jproteome.6b00696.

The primary goal was to establish and optimize a workflow for qualitative high-throughput top-down proteomics on the 21T FT-ICR mass spectrometer. We selected a well-characterized human colorectal cancer cell line and performed a series of prototypical LC-MS/MS experiments with the aim of identifying the maximum number of proteins and proteoforms (MW ≤ 50 kDa) within the minimum possible time. The 21T FT-ICR mass spectrometer at NHMFL is the new state-of-the-art in qualitative top-down proteomics and stands poised to accelerate top-down proteomics research for future users. Read report ....

 

Magnetic Resonance Technique & Development

Report Number: 354

Development of Pulsed Dynamic Nuclear Polarization at High Magnetic Fields

Can, T.V.; Griffin, R.G.; McKay, J.E.; Dubroca, T; van Tol, J. and Hill, S.

Pulsed rotating frame DNP can transfer electron polarization rapidly to nuclear spins. It requires strong microwave B1 field matching the nuclear Larmor frequency and has been implemented only at x-band frequency and 0.35T low field. The MIT group achieved rotating frame DNP for the first time at 3.32T field using the 1kW HiPER 94GHz source at the NHMFL. They introduced CHIRP pulse for rotating frame DNP such that the enhancement can occurs with microwave B1 field lower than the nuclear Larmor frequency. These progress represent a major step closer making the efficient rotating frame DNP a reality for high-field NMR applications. Read report ....

 

Report Number: 449

Expeditious Dissolution Dynamic Nuclear Polarization without Glassing Agents

Lama, B.; Downes, D.; Collins, J. and Long, J.
Published in NMR Biomedicine 11, 6892-6905

The authors have developed a sample preparation approach for dynamic nuclear polarization (DNP) which is broadly applicable for the rapid polarization of aqueous small-molecule substrate solutions and obviates the need for glassing agents. The polarization behavior of substrates prepared using rapid freezing without glassing agents enabled a 1.5–3-fold time savings in polarization buildup without the need for the standard toxic glassing agents used for dissolution DNP. This preparation technique allows for the rapid and non-toxic preparation of polarized substrates and it is anticipated to increase the throughput and biological application of DNP. Read report ....

 

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Biochemistry

Report Number: 285

Tablet Composition for Anti-tuberculosis Antibiotics

Manning, T.J.; Plummer, S.E.; Baker, T.
Published in Bioorg. Med. Chem. Lett., 26, 10, 2489-2497 (2016)

We demonstrated that certain copper complexes of existing antibiotics can be made to work again against Mycobacterium tuberculosis. In particular, it worked against resistant strains of the disease. Both U.S. and International patent applications have been published on-line for this work. Read report ....

 

Report Number: 361

Binding Sites for DNA on a DNA-Unwinding Protein, Probed by Hydrogen/ Deuterium Exchange Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Graham, B.W.; Tao, Y.; Dodge, K.L.; Thaxton, C.T.; Olaso, D.; Young, N.L.; Marshall, A.G. and Trakselis, M.A.
Published in Journal of Biological Chemistry 291, 12467-12480 (2016).

The archaebacterial MCM A “helicase” protein from Sulfolobus solfactaricus is a model for understanding DNA unwinding. Although interactions of the DNA double-strand portion within the central channel are known, interactions with the excluded unwound single-strand on the exterior surface of the helicase have mostly been ignored. By “spray-painting” the DNA:protein complex (by exposing it to D2O), we can map the DNA:protein contact regions as those that are protected against H/D exchange relative to the free protein. That instrument readily resolves and identifies dozens of segments, to provide a detailed map of the contact surface. Read report ....

 

Biology

Report Number: 101

Protein Conformation Determined in Native Cellular Environments

Costello, W.N. and Frederick, K.K.

Costello and Frederick are developing the methodology to study protein structures in their native environment: the cell. To achieve this, they are combining new sample preparation methods with dynamically nuclear polarized solid-state nuclear magnetic resonance (DNP-ssNMR). Using a self-polymerizing yeast prion protein, which was the segmentally isotopically labeled, they obtained NMR spectra selective for adjacent 13C and 15N sites in 256 scans. These results indicate that the sensitivity enhancement using DNP-ssNMR enables detection of a small number of sites within a protein in its native cellular environment not possible with traditional methods. Read report ....

 

Report Number: 482

MR Microscopy of Single Mammalian Muscle Fibers and Nuclei Detection

Lee, C.H.; Bengtsson, N.; Chrzanowski, S.M.; Flint, J.J. ; Walter, G.A. and Blackband, S.J.
Published in Scientific Reports 7:39496 , DOI: 10.1038/srep39496, 2017

In this report, the Blackband lab has combined high magnetic fields with miniature RF coils to image isolated, single mouse muscle fibers or cells. A single muscle cell can be up to a cm in length, typically ranges in diameter between 30-100 microns, and is surrounded by a membrane which contains thousands of myonuclei. In this case, the muscle fibers were isolated from mice which express a MRI reporter gene only within their myonuclei. Using MR microscopy (MRM), not only could the investigators image single fibers at a resolution of six microns but they could also visualize myonuclei following contrast enhancement using the reporter gene. The use of the reporter gene and MRM, could be used for future studies when verifying MR contrast within specific areas of targeted gene expression and cellular imaging. Read report ....

 

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Magnet Materials & Magnet Technology

Report Number: 143

Magnetic Properties of Doped Mn-Ga Alloys

Han, K.; Brown D.R.; Siegrist, T.; Besara, T. and Niu, R.M.
Published in AIP Conf. Proc 6 (2016).

High energy product magnetic materials not containing rare earth elements are important for wide applications of permanent magnets devices such as magnetic bearings, electric generators and motors. In the Mn-Ga-X ternary system, with X = Bi, a high coercive field of 16.6kOe and remanent magnetization of 7.4emu/g was obtained. Further optimization with substitution of Fe for Mn, and addition of boron, a coercive field of 15.3kOe and remanent magnetization of 9.9 emu/g was achieved, demonstrating that high energy product, rare earth free, permanent magnets are possible. Read report ....

 

Report Number: 196

Generation of 40 T with a 9 T No-Insulation REBCO Insert Operated in a 31 T Resistive Background Magnet

Hahn, S.; Kim, S.; Kim, K.; Dixon, I.; Trociewitz, U.; Jaroszynski, J.; Abraimov, D.; Miller, G.; Noyes, P.; Marshall, W.S. and Larbalestier, D.C.

REBCO coated conductors are a second commercial HTS candidate conductor, particularly for very high-field, high-stress applications. Although magnetic field quality challenges remain with No-Insulation coils, the demonstrated winding current density here is more than triple compared to any insulated HTS coil, and represents a promise of dramatically more compact and less expensive high field magnets. Read report ....

 

Superconductivity – Applied

Report Number: 170

A New Heat Treatment for High Critical Current Nb3Sn Wires

Sanabria, C.; Lee, P.J.; Larbalestier, D.C., Field, M; Miao, H. and Parrell, J.

This work rethinks the first part of the heat treatment of high current density (Jc) Nb3Sn conductors used for the Series Connected Hybrid and other recent CICC magnets made at the lab, as well as the even higher Jc conductors needed for the High Luminosity upgrade of the LHC. The novel insight here is that formation of a Sn-Nb-Cu membrane at about 350-390 C enables diode-like counterflow of Cu and Sn and much higher Jc at smaller filament diameters than hitherto. Read report ....

 

Report Number: 226

Electrically Insulating Bi-2212 Round Wires Using a Combination of TiO2 Coating and Alumino-silicate Braid

Trociewitz, U.P.; Hilton, D.K.; Kim, Y.; Bosque, E.; Chen, P.; Davis, D.; Jiang, J.; Hellstrom, E.E.; Lu, J.; Levitan, J.; English, C.L.; Miller, G.E. and Larbalestier, D.C.

Bi-2212 round wires are one of three commercial HTS candidate conductors for very high field magnets, particularly for NMR above 25 or even 30 T. Insulation problems have plagued the application of Wind&React Bi-2212 since the early 1990-ies and have proven difficult to solve. This work not only presents a proven solution to the insulation problem, it also adds useful reinforcement and facilitates epoxy impregnation, and thereby represents a major step forward and vital to Bi-2212 coil technology. Read report ....

 

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