55 research outputs found
Ultrafast element-resolved magneto-optics using a fiber-laser-driven extreme ultraviolet light source
We present a novel setup to measure the transverse magneto-optical Kerr
effect in the extreme ultraviolet spectral range at exceptionally high
repetition rates based on a fiber laser amplifier system. This affords a very
high and stable flux of extreme ultraviolet light, which we use to measure
element-resolved demagnetization dynamics with unprecedented depth of
information. Furthermore, the setup is equipped with a strong electromagnet and
a cryostat, allowing measurements between 10 and 420 K using magnetic fields up
to 0.86 T. The performance of our setup is demonstrated by a set of
temperature- and time-dependent magnetization measurements showing distinct
element-dependent behavior
Probing correlations in the exciton landscape of a moir\'e heterostructure
Excitons are two-particle correlated bound states that are formed due to
Coulomb interaction between single-particle holes and electrons. In the
solid-state, cooperative interactions with surrounding quasiparticles can
strongly tailor the exciton properties and potentially even create new
correlated states of matter. It is thus highly desirable to access such
cooperative and correlated exciton behavior on a fundamental level. Here, we
find that the ultrafast transfer of an exciton's hole across a type-II
band-aligned moir\'e heterostructure leads to a surprising sub-200-fs upshift
of the single-particle energy of the electron being photoemitted from the
two-particle exciton state. While energy relaxation usually leads to an
energetic downshift of the spectroscopic signature, we show that this unusual
upshift is a clear fingerprint of the correlated interactions of the electron
and hole parts of the exciton quasiparticle. In this way, time-resolved
photoelectron spectroscopy is straightforwardly established as a powerful
method to access exciton correlations and cooperative behavior in
two-dimensional quantum materials. Our work highlights this new capability and
motivates the future study of optically inaccessible correlated excitonic and
electronic states in moir\'e heterostructures.Comment: 32 pages, 4 main figures, 5 supplemental figure
Ultrafast dynamics of bright and dark excitons in monolayer WSe and heterobilayer WSe/MoS
The energy landscape of optical excitations in mono- and few-layer transition
metal dichalcogenides (TMDs) is dominated by optically bright and dark
excitons. These excitons can be fully localized within a single TMD layer, or
the electron- and the hole-component of the exciton can be charge-separated
over multiple TMD layers. Such intra- or interlayer excitons have been
characterized in detail using all-optical spectroscopies, and, more recently,
photoemission spectroscopy. In addition, there are so-called hybrid excitons
whose electron- and/or hole-component are delocalized over two or more TMD
layers, and therefore provide a promising pathway to mediate charge-transfer
processes across the TMD interface. Hence, an in-situ characterization of their
energy landscape and dynamics is of vital interest. In this work, using
femtosecond momentum microscopy combined with many-particle modeling, we
quantitatively compare the dynamics of momentum-indirect intralayer excitons in
monolayer WSe with the dynamics of momentum-indirect hybrid excitons in
heterobilayer WSe/MoS, and draw three key conclusions: First, we find
that the energy of hybrid excitons is reduced when compared to excitons with
pure intralayer character. Second, we show that the momentum-indirect
intralayer and hybrid excitons are formed via exciton-phonon scattering from
optically excited bright excitons. And third, we demonstrate that the
efficiency for phonon absorption and emission processes in the mono- and the
heterobilayer is strongly dependent on the energy alignment of the intralayer
and hybrid excitons with respect to the optically excited bright exciton.
Overall, our work provides microscopic insights into exciton dynamics in TMD
mono- and bilayers.Comment: 27 pages, 5 figure
Ultrafast nano-imaging of dark excitons
The role and impact of spatial heterogeneity in two-dimensional quantum
materials represents one of the major research quests regarding the future
application of these materials in optoelectronics and quantum information
science. In the case of transition-metal dichalcogenide heterostructures, in
particular, direct access to heterogeneities in the dark-exciton landscape with
nanometer spatial and ultrafast time resolution is highly desired, but remains
largely elusive. Here, we introduce ultrafast dark field momentum microscopy to
spatio-temporally resolve dark exciton formation dynamics in a twisted
WSe/MoS heterostructure with 55 femtosecond time- and 500~nm spatial
resolution. This allows us to directly map spatial heterogeneity in the
electronic and excitonic structure, and to correlate these with the dark
exciton formation and relaxation dynamics. The benefits of simultaneous
ultrafast nanoscale dark-field momentum microscopy and spectroscopy is
groundbreaking for the present study, and opens the door to new types of
experiments with unprecedented spectroscopic and spatiotemporal capabilities.Comment: 39 pages, 4 main figures, 8 supplemental figure
Occupational exposure to gases/fumes and mineral dust affect DNA methylation levels of genes regulating expression
Many workers are daily exposed to occupational agents like gases/fumes, mineral dust or biological dust, which could induce adverse health effects. Epigenetic mechanisms, such as DNA methylation, have been suggested to play a role. We therefore aimed to identify differentially methylated regions (DMRs) upon occupational exposures in never-smokers and investigated if these DMRs associated with gene expression levels. To determine the effects of occupational exposures independent of smoking, 903 never-smokers of the LifeLines cohort study were included. We performed three genome-wide methylation analyses (Illumina 450 K), one per occupational exposure being gases/fumes, mineral dust and biological dust, using robust linear regression adjusted for appropriate confounders. DMRs were identified using comb-p in Python. Results were validated in the Rotterdam Study (233 never-smokers) and methylation-expression associations were assessed using Biobank-based Integrative Omics Study data (n = 2802). Of the total 21 significant DMRs, 14 DMRs were associated with gases/fumes and 7 with mineral dust. Three of these DMRs were associated with both exposures (RPLP1 and LINC02169 (2x)) and 11 DMRs were located within transcript start sites of gene expression regulating genes. We replicated two DMRs with gases/fumes (VTRNA2-1 and GNAS) and one with mineral dust (CCDC144NL). In addition, nine gases/fumes DMRs and six mineral dust DMRs significantly associated with gene expression levels. Our data suggest that occupational exposures may induce differential methylation of gene expression regulating genes and thereby may induce adverse health effects. Given the millions of workers that are exposed daily to occupational exposures, further studies on this epigenetic mechanism and health outcomes are warranted
Resolving sepsis-induced immunoparalysis via trained immunity by targeting interleukin-4 to myeloid cells.
Immunoparalysis is a compensatory and persistent anti-inflammatory response to trauma, sepsis or another serious insult, which increases the risk of opportunistic infections, morbidity and mortality. Here, we show that in cultured primary human monocytes, interleukin-4 (IL4) inhibits acute inflammation, while simultaneously inducing a long-lasting innate immune memory named trained immunity. To take advantage of this paradoxical IL4 feature in vivo, we developed a fusion protein of apolipoprotein A1 (apoA1) and IL4, which integrates into a lipid nanoparticle. In mice and non-human primates, an intravenously injected apoA1-IL4-embedding nanoparticle targets myeloid-cell-rich haematopoietic organs, in particular, the spleen and bone marrow. We subsequently demonstrate that IL4 nanotherapy resolved immunoparalysis in mice with lipopolysaccharide-induced hyperinflammation, as well as in ex vivo human sepsis models and in experimental endotoxemia. Our findings support the translational development of nanoparticle formulations of apoA1-IL4 for the treatment of patients with sepsis at risk of immunoparalysis-induced complications.We thank M. Jaeger (Radboudumc) for kindly providing flourescein
isothiocyanate-labelled Candida albicans. D. Williams (East
Tennessee State University) provided the β-glucan we used in our
initial experiments. H. Lemmers (Radboudumc) kindly prepared the
purified lipopolysaccharide used for stimulation of primary human
monocytes and macrophages. Part of the figures were prepared
using (among other software) Biorender.com. B.N. is supported
by a National Health and Medical Research Council (Australia)
Investigator Grant (APP1173314). This work was supported by
National Institutes of Health grants R01 HL144072, R01 CA220234
and P01 HL131478, as well as a Vici grant from the Dutch Research
Council NWO and an ERC Advanced Grant (all to W.J.M.M.). M.G.N.
was supported by a Spinoza grant from Dutch Research Council
NWO and an ERC Advanced Grant (#833247).S
Implementation and benchmarking of a novel analytical framework to clinically evaluate tumor-specific fluorescent tracers
During the last decade, the emerging field of molecular fluorescence imaging has led to the development of tumor-specific fluorescent tracers and an increase in early-phase clinical trials without having consensus on a standard methodology for evaluating an optical tracer. By combining multiple complementary state-of-the-art clinical optical imaging techniques, we propose a novel analytical framework for the clinical translation and evaluation of tumor-targeted fluorescent tracers for molecular fluorescence imaging which can be used for a range of tumor types and with different optical tracers. Here we report the implementation of this analytical framework and demonstrate the tumor-specific targeting of escalating doses of the near-infrared fluorescent tracer bevacizumab-800CW on a macroscopic and microscopic level. We subsequently demonstrate an 88% increase in the intraoperative detection rate of tumor-involved margins in primary breast cancer patients, indicating the clinical feasibility and support of future studies to evaluate the definitive clinical impact of fluorescence-guided surgery
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