I05-ARPES
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H. F.
Yang
,
L. X.
Yang
,
Z. K.
Liu
,
Y.
Sun
,
C.
Chen
,
H.
Peng
,
M.
Schmidt
,
D.
Prabhakaran
,
B. A.
Bernevig
,
C.
Felser
,
B. H.
Yan
,
Y. L.
Chen
Diamond Proposal Number(s):
[19310, 18005]
Open Access
Abstract: Surface Fermi arcs (SFAs), the unique open Fermi-surfaces (FSs) discovered recently in topological Weyl semimetals (TWSs), are unlike closed FSs in conventional materials and can give rise to many exotic phenomena, such as anomalous SFA-mediated quantum oscillations, chiral magnetic effects, three-dimensional quantum Hall effect, non-local voltage generation and anomalous electromagnetic wave transmission. Here, by using in-situ surface decoration, we demonstrate successful manipulation of the shape, size and even the connections of SFAs in a model TWS, NbAs, and observe their evolution that leads to an unusual topological Lifshitz transition not caused by the change of the carrier concentration. The phase transition teleports the SFAs between different parts of the surface Brillouin zone. Despite the dramatic surface evolution, the existence of SFAs is robust and each SFA remains tied to a pair of Weyl points of opposite chirality, as dictated by the bulk topology.
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Aug 2019
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[15848]
Open Access
Abstract: Molecular crystals can be bent elastically by expansion or plastically by delamination into slabs that glide along slip planes. Here we report that upon bending, terephthalic acid crystals can undergo a mechanically induced phase transition without delamination and their overall crystal integrity is retained. Such plastically bent crystals act as bimorphs and their phase uniformity can be recovered thermally by taking the crystal over the phase transition temperature. This recovers the original straight shape and the crystal can be bent by a reverse thermal treatment, resulting in shape memory effects akin of those observed with some metal alloys and polymers. We anticipate that similar memory and restorative effects are common for other molecular crystals having metastable polymorphs. The results demonstrate the advantage of using intermolecular interactions to accomplish mechanically adaptive properties with organic solids that bridge the gap between mesophasic and inorganic materials in the materials property space.
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Aug 2019
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I03-Macromolecular Crystallography
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Daniel
Merk
,
Sridhar
Sreeramulu
,
Denis
Kudlinzki
,
Krishna
Saxena
,
Verena
Linhard
,
Santosh L.
Gande
,
Fabian
Hiller
,
Christina
Lamers
,
Ewa
Nilsson
,
Anna
Aagaard
,
Lisa
Wissler
,
Niek
Dekker
,
Krister
Bamberg
,
Manfred
Schubert-zsilavecz
,
Harald
Schwalbe
Open Access
Abstract: The bile acid-sensing transcription factor farnesoid X receptor (FXR) regulates multiple metabolic processes. Modulation of FXR is desired to overcome several metabolic pathologies but pharmacological administration of full FXR agonists has been plagued by mechanism-based side effects. We have developed a modulator that partially activates FXR in vitro and in mice. Here we report the elucidation of the molecular mechanism that drives partial FXR activation by crystallography- and NMR-based structural biology. Natural and synthetic FXR agonists stabilize formation of an extended helix α11 and the α11-α12 loop upon binding. This strengthens a network of hydrogen bonds, repositions helix α12 and enables co-activator recruitment. Partial agonism in contrast is conferred by a kink in helix α11 that destabilizes the α11-α12 loop, a critical determinant for helix α12 orientation. Thereby, the synthetic partial agonist induces conformational states, capable of recruiting both co-repressors and co-activators leading to an equilibrium of co-activator and co-repressor binding.
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Jul 2019
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I13-2-Diamond Manchester Imaging
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Tamara L.
Akentjew
,
Claudia
Terraza
,
Cristian
Suazo
,
Jekaterina
Maksimuck
,
Camila A.
Wilkens
,
Francisco
Vargas
,
Gabriela
Zavala
,
Macarena
Ocaña
,
Javier
Enrione
,
Claudio M.
García-herrera
,
Loreto M.
Valenzuela
,
Jonny J.
Blaker
,
Maroun
Khoury
,
Juan Pablo
Acevedo
Diamond Proposal Number(s):
[15507]
Open Access
Abstract: Design strategies for small diameter vascular grafts are converging toward native-inspired tissue engineered grafts. A new automated technology is presented that combines a dip-spinning methodology for depositioning concentric cell-laden hydrogel layers, with an adapted solution blow spinning (SBS) device for intercalated placement of aligned reinforcement nanofibres. This additive manufacture approach allows the assembly of bio-inspired structural configurations of concentric cell patterns with fibres at specific angles and wavy arrangements. The middle and outer layers were tuned to structurally mimic the media and adventitia layers of native arteries, enabling the fabrication of small bore grafts that exhibit the J-shape mechanical response and compliance of human coronary arteries. This scalable automated system can fabricate cellularized multilayer grafts within 30 min. Grafts were evaluated by hemocompatibility studies and a preliminary in vivo carotid rabbit model. The dip-spinning-SBS technology generates constructs with native mechanical properties and cell-derived biological activities, critical for clinical bypass applications.
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Jul 2019
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I11-High Resolution Powder Diffraction
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Dirk
Lenzen
,
Jingjing
Zhao
,
Sebastian-johannes
Ernst
,
Mohammad
Wahiduzzaman
,
A.
Ken Inge
,
Dominik
Fröhlich
,
Hongyi
Xu
,
Hans-jörg
Bart
,
Christoph
Janiak
,
Stefan
Henninger
,
Guillaume
Maurin
,
Xiaodong
Zou
,
Norbert
Stock
Diamond Proposal Number(s):
[16502]
Open Access
Abstract: Efficient use of energy for cooling applications is a very important and challenging field in science. Ultra-low temperature actuated (Tdriving < 80 °C) adsorption-driven chillers (ADCs) with water as the cooling agent are one environmentally benign option. The nanoscale metal-organic framework [Al(OH)(C6H2O4S)] denoted CAU-23 was discovered that possess favorable properties, including water adsorption capacity of 0.37 gH2O/gsorbent around p/p0 = 0.3 and cycling stability of at least 5000 cycles. Most importantly the material has a driving temperature down to 60 °C, which allows for the exploitation of yet mostly unused temperature sources and a more efficient use of energy. These exceptional properties are due to its unique crystal structure, which was unequivocally elucidated by single crystal electron diffraction. Monte Carlo simulations were performed to reveal the water adsorption mechanism at the atomic level. With its green synthesis, CAU-23 is an ideal material to realize ultra-low temperature driven ADC devices.
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Jul 2019
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[6603]
Open Access
Abstract: Mammalian fertilisation begins when sperm interacts with the egg zona pellucida (ZP), whose ZP1 subunit is important for fertility by covalently cross-linking ZP filaments into a three-dimensional matrix. Like ZP4, a structurally-related component absent in the mouse, ZP1 is predicted to contain an N-terminal ZP-N domain of unknown function. Here we report a characterisation of ZP1 proteins carrying mutations from infertile patients, which suggests that, in human, filament cross-linking by ZP1 is crucial to form a stable ZP. We map the function of ZP1 to its ZP-N1 domain and determine crystal structures of ZP-N1 homodimers from a chicken homolog of ZP1. These reveal that ZP filament cross-linking is highly plastic and can be modulated by ZP1 fucosylation and, potentially, zinc sparks. Moreover, we show that ZP4 ZP-N1 forms non-covalent homodimers in chicken but not in human. Together, these data identify human ZP1 cross-links as a promising target for non-hormonal contraception.
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Jul 2019
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I05-ARPES
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Soeren
Ulstrup
,
Cristina E.
Giusca
,
Jill A.
Miwa
,
Charlotte
Sanders
,
Alex
Browning
,
Pavel
Dudin
,
Cephise
Cacho
,
Olga
Kazakova
,
D. Kurt
Gaskill
,
Rachael L.
Myers-ward
,
Tianyi
Zhang
,
Mauricio
Terrones
,
Philip
Hofmann
Diamond Proposal Number(s):
[19260]
Open Access
Abstract: Control of atomic-scale interfaces between materials with distinct electronic structures is crucial for the design and fabrication of most electronic devices. In the case of two-dimensional materials, disparate electronic structures can be realized even within a single uniform sheet, merely by locally applying different vertical gate voltages. Here, we utilize the inherently nano-structured single layer and bilayer graphene on silicon carbide to investigate lateral electronic structure variations in an adjacent single layer of tungsten disulfide (WS2). The electronic band alignments are mapped in energy and momentum space using angle-resolved photoemission with a spatial resolution on the order of 500 nm (nanoARPES). We find that the WS2 band offsets track the work function of the underlying single layer and bilayer graphene, and we relate such changes to observed lateral patterns of exciton and trion luminescence from WS2.
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Jul 2019
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I05-ARPES
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Sergey
Borisenko
,
Daniil
Evtushinsky
,
Quinn
Gibson
,
Alexander
Yaresko
,
Klaus
Koepernik
,
Timur
Kim
,
Mazhar
Ali
,
Jeroen
Van Den Brink
,
Moritz
Hoesch
,
Alexander
Fedorov
,
Erik
Haubold
,
Yevhen
Kushnirenko
,
Ivan
Soldatov
,
Rudolf
Schäfer
,
Robert J.
Cava
Diamond Proposal Number(s):
[11643]
Open Access
Abstract: Spectroscopic detection of Dirac and Weyl fermions in real materials is vital for both, promising applications and fundamental bridge between high-energy and condensed-matter physics. While the presence of Dirac and noncentrosymmetric Weyl fermions is well established in many materials, the magnetic Weyl semimetals still escape direct experimental detection. In order to find a time-reversal symmetry breaking Weyl state we design two materials and present here experimental and theoretical evidence of realization of such a state in one of them, YbMnBi2. We model the time-reversal symmetry breaking observed by magnetization and magneto-optical microscopy measurements by canted antiferromagnetism and find a number of Weyl points. Using angle-resolved photoemission, we directly observe two pairs of Weyl points connected by the Fermi arcs. Our results not only provide a fundamental link between the two areas of physics, but also demonstrate the practical way to design novel materials with exotic properties.
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Jul 2019
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I02-Macromolecular Crystallography
I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
|
Diamond Proposal Number(s):
[8987, 12788, 17773]
Open Access
Abstract: The alpha helical CytolysinA family of pore forming toxins (α-PFT) contains single, two, and three component members. Structures of the single component Eschericia coli ClyA and the two component Yersinia enterolytica YaxAB show both undergo conformational changes from soluble to pore forms, and oligomerization to produce the active pore. Here we identify tripartite α-PFTs in pathogenic Gram negative bacteria, including Aeromonas hydrophila (AhlABC). We show that the AhlABC toxin requires all three components for maximal cell lysis. We present structures of pore components which describe a bi-fold hinge mechanism for soluble to pore transition in AhlB and a contrasting tetrameric assembly employed by soluble AhlC to hide their hydrophobic membrane associated residues. We propose a model of pore assembly where the AhlC tetramer dissociates, binds a single membrane leaflet, recruits AhlB promoting soluble to pore transition, prior to AhlA binding to form the active hydrophilic lined pore.
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Jul 2019
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E02-JEM ARM 300CF
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Diamond Proposal Number(s):
[19793]
Abstract: Materials with highly crystalline lattice structures and low defect concentrations have classically been considered essential for high-performance optoelectronic devices. However, the emergence of high-efficiency devices based on halide perovskites is provoking researchers to rethink this traditional picture, as the heterogeneity in several properties within these materials occurs on a series of length scales. Perovskites are typically fabricated crudely through simple processing techniques, which leads to large local fluctuations in defect density, lattice structure, chemistry and bandgap that appear on short length scales (<100 nm) and across long ranges (>10 μm). Despite these variable and complex non-uniformities, perovskites maintain exceptional device efficiencies and are, as of 2018, the best-performing polycrystalline thin-film solar cell material. In this Review, we highlight the multiple layers of heterogeneity ascertained using high-spatial-resolution methods that provide access to the relevant length scales. We discuss the impact that the optoelectronic variations have on halide perovskite devices, including the prospect that it is this very disorder that leads to their remarkable power-conversion efficiencies.
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Jul 2019
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