| 1. |
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| 2. |
- Björling, Fiona, et al.
(author)
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Introduction
- 2005
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In: Words, Deeds and Values. The Intelligentsia in Russia and Poland during the Nineteenth and Twentieth Centuries. - 9197020192
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Book chapter (other academic/artistic)
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| 3. |
- Hammarberg, Susanna, et al.
(author)
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High resolution strain mapping of a single axially heterostructured nanowire using scanning X-ray diffraction
- 2020
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In: Nano Research. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 13:9, s. 2460-2468
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Journal article (peer-reviewed)abstract
- Axially heterostructured nanowires are a promising platform for next generation electronic and optoelectronic devices. Reports based on theoretical modeling have predicted more complex strain distributions and increased critical layer thicknesses than in thin films, due to lateral strain relaxation at the surface, but the understanding of the growth and strain distributions in these complex structures is hampered by the lack of high-resolution characterization techniques. Here, we demonstrate strain mapping of an axially segmented GaInP-InP 190 nm diameter nanowire heterostructure using scanning X-ray diffraction. We systematically investigate the strain distribution and lattice tilt in three different segment lengths from 45 to 170 nm, obtaining strain maps with about 10−4 relative strain sensitivity. The experiments were performed using the 90 nm diameter nanofocus at the NanoMAX beamline, taking advantage of the high coherent flux from the first diffraction limited storage ring MAX IV. The experimental results are in good agreement with a full simulation of the experiment based on a three-dimensional (3D) finite element model. The largest segments show a complex profile, where the lateral strain relaxation at the surface leads to a dome-shaped strain distribution from the mismatched interfaces, and a change from tensile to compressive strain within a single segment. The lattice tilt maps show a cross-shaped profile with excellent qualitative and quantitative agreement with the simulations. In contrast, the shortest measured InP segment is almost fully adapted to the surrounding GaInP segments. [Figure not available: see fulltext.].
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| 4. |
- Ji, Cheng, et al.
(author)
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Crystallography of low Z material at ultrahigh pressure : Case study on solid hydrogen
- 2020
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In: Matter and Radiation at Extremes. - : American Institute of Physics (AIP). - 2468-2047 .- 2468-080X. ; 5:3
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Journal article (peer-reviewed)abstract
- Diamond anvil cell techniques have been improved to allow access to the multimegabar ultrahigh-pressure region for exploring novel phenomena in condensed matter. However, the only way to determine crystal structures of materials above 100 GPa, namely, X-ray diffraction (XRD), especially for low Z materials, remains nontrivial in the ultrahigh-pressure region, even with the availability of brilliant synchrotron X-ray sources. In this work, we perform a systematic study, choosing hydrogen (the lowest X-ray scatterer) as the subject, to understand how to better perform XRD measurements of low Z materials at multimegabar pressures. The techniques that we have developed have been proved to be effective in measuring the crystal structure of solid hydrogen up to 254 GPa at room temperature [C. Ji et al., Nature 573, 558–562 (2019)]. We present our discoveries and experiences with regard to several aspects of this work, namely, diamond anvil selection, sample configuration for ultrahigh-pressure XRD studies, XRD diagnostics for low Z materials, and related issues in data interpretation and pressure calibration. We believe that these methods can be readily extended to other low Z materials and can pave the way for studying the crystal structure of hydrogen at higher pressures, eventually testing structural models of metallic hydrogen.
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| 5. |
- Berkowicz, Sharon, et al.
(author)
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Nanofocused x-ray photon correlation spectroscopy
- 2022
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In: Physical Review Research. - 2643-1564. ; 4:3
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Journal article (peer-reviewed)abstract
- Here, we demonstrate an experimental proof of concept for nanofocused x-ray photon correlation spectroscopy, a technique sensitive to nanoscale fluctuations present in a broad range of systems. The experiment, performed at the NanoMAX beamline at MAX IV, uses a novel event-based x-ray detector to capture nanoparticle structural dynamics with microsecond resolution. By varying the nanobeam size from σ=88 nm to σ=2.5μm, we quantify the effect of the nanofocus on the small-angle scattering lineshape and on the diffusion coefficients obtained from nano-XPCS. We observe that the use of nanobeams leads to a multifold increase in speckle contrast, which greatly improves the experimental signal-to-noise ratio, quantified from the two-time intensity correlation functions. We conclude that it is possible to account for influence of the high beam divergence on the lineshape and measured dynamics by including a convolution with the nanobeam profile in the model.
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| 6. |
- Berntsson, Oskar, 1989, et al.
(author)
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Sequential conformational transitions and alpha-helical supercoiling regulate a sensor histidine kinase
- 2017
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8
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Journal article (peer-reviewed)abstract
- Sensor histidine kinases are central to sensing in bacteria and in plants. They usually contain sensor, linker, and kinase modules and the structure of many of these components is known. However, it is unclear how the kinase module is structurally regulated. Here, we use nano- to millisecond time-resolved X-ray scattering to visualize the solution structural changes that occur when the light-sensitive model histidine kinase YF1 is activated by blue light. We find that the coiled coil linker and the attached histidine kinase domains undergo a left handed rotation within microseconds. In a much slower second step, the kinase domains rearrange internally. This structural mechanism presents a template for signal transduction in sensor histidine kinases.
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| 7. |
- Berntsson, Oskar, 1989, et al.
(author)
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Time-Resolved X-Ray Solution Scattering Reveals the Structural Photoactivation of a Light-Oxygen-Voltage Photoreceptor
- 2017
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In: Structure. - : Elsevier BV. - 0969-2126. ; 25:6
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Journal article (peer-reviewed)abstract
- Light-oxygen-voltage (LOV) receptors are sensory proteins controlling a wide range of organismal adaptations in multiple kingdoms of life. Because of their modular nature, LOV domains are also attractive for use as optogenetic actuators. A flavin chromophore absorbs blue light, forms a bond with a proximal cysteine residue, and induces changes in the surroundings. There is a gap of knowledge on how this initial signal is relayed further through the sensor to the effector module. To characterize these conformational changes, we apply time-resolved X-ray scattering to the homodimeric LOV domain from Bacillus subtilis YtvA. We observe a global structural change in the LOV dimer synchronous with the formation of the chromophore photoproduct state. Using molecular modeling, this change is identified as splaying apart and relative rotation of the two monomers, which leads to an increased separation at the anchoring site of the effector modules.
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| 8. |
- Björling, Alexander, et al.
(author)
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Chemical Limits on X-ray Nanobeam Studies in Water
- 2023
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In: Journal of Physical Chemistry C. - 1932-7447. ; 127:28, s. 13877-13885
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Journal article (peer-reviewed)abstract
- Operando X-ray studies of chemical reactions have gained increasing interest lately, fueled by the emergence of a new generation of powerful focused X-ray sources. Although it is well known that ionizing radiation causes damage to samples via radical chemistry, this effect is often overlooked in studies of working devices or catalysts where intense focused beams are used as nanoscale probes. Here, we show how an X-ray nanobeam directly causes a phase transition in shape-controlled Pd nanoparticles and that a large oxidative potential must be applied to counteract the effect. In addition, we present a chemical reaction-diffusion model that offers a plausible qualitative explanation of the observations, and which also suggests that prohibitive concentrations of reactive species will arise under any focused X-ray probe, calling into question the validity of these methods as applied to aqueous chemical and catalytic systems.
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| 9. |
- Björling, Alexander, et al.
(author)
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Coherent Bragg imaging of 60 nm Au nanoparticles under electrochemical control at the NanoMAX beamline
- 2019
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In: Journal of Synchrotron Radiation. - 0909-0495. ; 26, s. 1830-1834
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Journal article (peer-reviewed)abstract
- Nanoparticles are essential electrocatalysts in chemical production, water treatment and energy conversion, but engineering efficient and specific catalysts requires understanding complex structure-reactivity relations. Recent experiments have shown that Bragg coherent diffraction imaging might be a powerful tool in this regard. The technique provides three-dimensional lattice strain fields from which surface reactivity maps can be inferred. However, all experiments published so far have investigated particles an order of magnitude larger than those used in practical applications. Studying smaller particles quickly becomes demanding as the diffracted intensity falls. Here, in situ nanodiffraction data from 60 nm Au nanoparticles under electrochemical control collected at the hard X-ray nanoprobe beamline of MAX IV, NanoMAX, are presented. Two-dimensional image reconstructions of these particles are produced, and it is estimated that NanoMAX, which is now open for general users, has the requisites for three-dimensional imaging of particles of a size relevant for catalytic applications. This represents the first demonstration of coherent X-ray diffraction experiments performed at a diffraction-limited storage ring, and illustrates the importance of these new sources for experiments where coherence properties become crucial.
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| 10. |
- Björling, Alexander, et al.
(author)
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Contrast - a lightweight Python framework for beamline orchestration and data acquisition
- 2021
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In: Journal of Synchrotron Radiation. - 1600-5775. ; 28:4, s. 1253-1260
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Journal article (peer-reviewed)abstract
- The emergence of fourth-generation synchrotrons is prompting the development of new systems for experimental control and data acquisition. However, as general control systems are designed to cover a wide set of instruments and techniques, they tend to become large and complicated, at the cost of experimental flexibility. Here we present Contrast, a simple Python framework for interacting with beamline components, orchestrating experiments and managing data acquisition. The system is presented and demonstrated via its application at the NanoMAX beamline of the MAX IV Laboratory.
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