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A prerequisite for advancing hybrid solar light harvesting systems is a comprehensive understanding of the spatiotemporal dynamics of photoinduced interfacial charge separation. Here, we demonstrate access to this transient charge redistribution for a model hybrid system of nanoporous zinc oxide (ZnO) and ruthenium bipyridyl chromophores. The site-selective probing of the molecular electron donor and semiconductor acceptor by time-resolved X-ray photoemission provides direct insight into the depth distribution of the photoinjected electrons and their interaction with the local band structure on a nanometer length scale. Our results show that these electrons remain localized within less than 6 nm from the interface, due to enhanced downward band bending by the photoinjected charge carriers. This spatial confinement suggests that light-induced charge generation and transport in nanoscale ZnO photocatalytic devices proceeds predominantly within the defect-rich surface region, which may lead to enhanced surface recombination and explain their lower performance compared to titanium dioxide (TiO2)-based systems.

Warm dense matter (WDM) is a ubiquitous state of matter encountered in various high energy density environments, at the frontier between a plasma and a condensed phase. It is key to astrophysics, planetary science and inertial confinement fusion research, but its electronic and ionic structure and dynamics remain poorly understood. Here, an intense and ultrafast X-ray free electron laser (XFEL) pulse is used to simultaneously create and characterize warm dense copper via L-edge X-ray absorption spectroscopy. The rich electron dynamics occurring within the 15-femtosecond pulse duration are revealed over a large irradiation intensity range. Below 1015 W cm-2, an absorption peak below the L-edge appears, originating from the depletion of the 3d band, and shows a distinct energy redshift with increasing intensity. This shift is a possible signature of ionization potential depression and electronic bond hardening. At higher intensities, massive ionization and collisions lead to the transition from reverse saturable absorption (opening absorption channels) to saturable absorption (material bleaching) of the XFEL pulse, an effect that holds promise for X-ray pulse shaping. The presented method is applicable to a wide range of materials and constitutes a robust benchmark for non-equilibrium models of electron dynamics in WDM.

Introduction: Data on the effects of phytoestrogens soy exposure on pubertal timing have been equivocal. We reported a case of a girl who had eaten only soy and derivatives for her first 9 years of life and presented clinical manifestation of precocious pubertal development. Case presentation: A caucasian female infant, after 40 days of exclusive breastfeeding, was introduced to soy formula due to suspected milk protein allergy. Since then, the patient ate soy beverage and soy-based foods exclusively. At the age of 7 years and 9 months, the girl showed premature thelarche and pubarche. Advanced skeletal age was detected. Peak of LH after GnRH stimulation test was

A real-time and accurate characterization of the X-ray beam size is essential to enable a large variety of different experiments at free-electron laser facilities. Typically, ablative imprints are employed to determine shape and size of µm-focused X-ray beams. The high accuracy of this state-of-the-art method comes at the expense of the time required to perform an ex-situ image analysis. In contrast, diffraction at a curved grating with suitably varying period and orientation forms a magnified image of the X-ray beam, which can be recorded by a 2D pixelated detector providing beam size and pointing jitter in real time. In this manuscript, we compare results obtained with both techniques, address their advantages and limitations, and demonstrate their excellent agreement. We present an extensive characterization of the FEL beam focused to ≈1 µm by two Kirkpatrick-Baez (KB) mirrors, along with optical metrology slope profiles demonstrating their exceptionally high quality. This work provides a systematic and comprehensive study of the accuracy provided by curved gratings in real-time imaging of X-ray beams at a free-electron laser facility. It is applied here to soft X-rays and can be extended to the hard X-ray range. Furthermore, curved gratings, in combination with a suitable detector, can provide spatial properties of µm-focused X-ray beams at MHz repetition rate.

Symmetry is a powerful concept in physics, but its applicability to far-from-equilibrium states is still being understood. Recent attention has focused on how far-from-equilibrium states lead to spontaneous symmetry breaking. Conversely, ultrafast optical pumping can be used to drastically change the energy landscape and quench the magnetic order parameter in magnetic systems. Here, we find a distinct symmetry-dependent ultrafast behaviour by use of ultrafast x-ray scattering from magnetic patterns with varying degrees of isotropic and anisotropic symmetry. After pumping with an optical laser, the scattered intensity reveals a radial shift exclusive to the isotropic component and exhibits a faster recovery time from quenching for the anisotropic component. These features arise even when both symmetry components are concurrently measured, suggesting a correspondence between the excitation and the magnetic order symmetry. Our results underline the importance of symmetry as a critical variable to manipulate the magnetic order in the ultrafast regime.

A classical ghost imaging experiment performed at the free-electron laser FLASH is presented. The possibility of image formation, a double bar in our case, in the beam that has never interacted with the sample is demonstrated.

The intensity correlations in incoherently scattered X-rays from a free-electron laser can be exploited to image 2D objects with a resolution close to or below the diffraction limit. The advent of accelerator-driven free-electron lasers (FEL) has opened new avenues for high-resolution structure determination via diffraction methods that go far beyond conventional X-ray crystallography methods1,2,3,4,5,6,7,8,9,10. These techniques rely on coherent scattering processes that require the maintenance of first-order coherence of the radiation field throughout the imaging procedure. Here we show that higher-order degrees of coherence, displayed in the intensity correlations of incoherently scattered X-rays from an FEL, can be used to image two-dimensional objects with a spatial resolution close to or even below the Abbe limit. This constitutes a new approach towards structure determination based on incoherent processes11,12, including fluorescence emission or wavefront distortions, generally considered detrimental for imaging applications. Our method is an extension of the landmark intensity correlation measurements of Hanbury Brown and Twiss13 to higher than second order, paving the way towards determination of structure and dynamics of matter in regimes where coherent imaging methods have intrinsic limitations14.

Physical review / A covering atomic, molecular, and optical physics and quantum information 101(1), 013820 (2020). doi:10.1103/PhysRevA.101.013820, Here we present the results of a classical ghost imaging experiment accomplished at an XUV free-electronlaser (FEL). To perform such experiment at an FEL source each x-ray pulse was transmitted through a movingdiffuser, which created a noncorrelated speckled beam. This beam was then split in two identical branches byintroducing a beam splitter in the form of a transmission grating. In one of these branches the sample waspositioned. We demonstrate the possibility of image formation, a double bar in our case, in the beam that hasnever interacted with the sample. With this experiment we extend the quantum optics methodology to the FELcommunity., Published by Inst., Woodbury, NY

New journal of physics 21(3), 033031 (2019). doi:10.1088/1367-2630/aafa47, We demonstrate the structural sensitivity and accuracy of the x-ray standing wave technique at a high repetition rate free-electron laser, FLASH at DESY in Hamburg, by measuring the photoelectron yield from the surface SiO$_2$ of Mo/Si multilayers. These experiments open up the possibility to obtain unprecedented structural information of adsorbate and surface atoms with picometer spatial and femtosecond temporal resolution. This technique will substantially contribute to a fundamental understanding of chemical reactions at catalytic surfaces and the structural dynamics of superconductors., Published by IOP, [London]

Catching CO oxidation Details of the transition state that forms as carbon monoxide (CO) adsorbed on a ruthenium surface is oxidized to CO 2 have been revealed by ultrafast excitation and probe methods. Öström et al. initiated the reaction between CO and adsorbed oxygen atoms with laser pulses that rapidly heated the surface and then probed the changes in electronic structure with oxygen x-ray absorption spectroscopy. They observed transition-state configurations that are consistent with density functional theory and a quantum oscillator model. Science , this issue p. 978

Introduction: Diamine oxidase (DAO) catabolizes and inactivates histamine, a key player in a wide range of invalidating conditions, such as migraine and chronic spontaneous urticaria (CSU). The highest expression of DAO occurs in the gastrointestinal tract, possibly to control the burden of histamine intake from food. Methods: Here, we tested the hypothesis that a 30-day oral supplementation with DAO (1 capsule b.i.d., 15 min before a meal) could reduce the severity of CSU as estimated by the 7-Day Urticaria Activity Score (UAS-7). The study was designed as a double-blind, placebo-controlled, crossover investigation of 22 patients with CSU incompletely controlled by first-line antihistamine therapy. Results: Twenty patients completed the study. Supplemental therapy with DAO caused a 3.8 ± 1.2 point mean ± SEM UAS-7 score reduction in patients with low serum DAO levels at time 0 (p = 0.041 compared to placebo). The degree of UAS-7 improvement was inversely correlated with the levels of basal DAO (p = 0.019). Patients receiving DAO supplementation were able to slightly reduce their daily antihistamine dose (p = 0.049). Conclusion: These data suggest that DAO may be involved in the pathogenic cascade of CSU and that DAO supplementation could be effective for symptom relief in patients with low DAO levels in serum.

The journal of physical chemistry letters 8(16), 3820 - 3825(2017). doi:10.1021/acs.jpclett.7b01549, The direct elucidation of the reaction pathways in heterogeneous catalysis has been challenging due to the short-lived nature of reaction intermediates. Here, we directly measured on ultrafast time scales the initial hydrogenation steps of adsorbed CO on a Ru catalyst surface, which is known as the bottleneck reaction in syngas and CO$_2$ reforming processes. We initiated the hydrogenation of CO with an ultrafast laser temperature jump and probed transient changes in the electronic structure using real-time X-ray spectroscopy. In combination with theoretical simulations, we verified the formation of CHO during CO hydrogenation., Published by ACS, Washington, DC

The journal of physical chemistry letters 7(18), 3647 - 3651(2016). doi:10.1021/acs.jpclett.6b01543, The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free-electron laser to directly observe the decreased bonding–antibonding splitting following bond-activation using an ultrashort optical laser pulse., Published by ACS, Washington, DC

Over the last few years, there has been an increased interest in exploiting allelopathy in organic agriculture. The aim of this investigation was to examine the effects of essential oil mixtures in order to establish their allelopathic use in agriculture. Two mixtures of essential oils consisting respectively of tea tree oil (TTO) and clove plus rosemary (C + R) oils were tested. Phytotoxicity and genotoxicity tests on the root meristems of Vicia faba minor were performed. A phytotoxic influence was particularly relevant for C + R mixture, while genotoxicity tests revealed significant results with both C + R oil mixture and TTO. Phenotypic analysis on Vicia faba minor primary roots following C + R oil mixture treatment resulted in callose production, an early symptom attributed to lipid peroxidation. The approach described in this study, based on genotoxicity bioassays, might identify specific DNA damage induced by essential oil treatments. These tests may represent a powerful method to evaluate potential adverse effects of different mixtures of essential oils that might be useful in alternative agriculture. Future studies are focusing on the positive synergism of more complex mixtures of essential oils in order to reduce concentrations of potentially toxic components while at the same time maintaining efficacy in antimicrobial and antifungal management.

Physical review / A 95(2), 023843(2017). doi:10.1103/PhysRevA.95.023843, We present a comprehensive experimental analysis of statistical properties of the self-amplified spontaneous emission free-electron laser (FEL) FLASH by means of Hanbury Brown and Twiss interferometry. The experiments were performed at FEL wavelengths of 5.5, 13.4, and 20.8 nm. We determined the second-order intensity correlation function for all wavelengths and different operation conditions of FLASH. In all experiments a high degree of spatial coherence (above 50%) was obtained. Our analysis performed in spatial and spectral domains provided us with the independent measurements of an average pulse duration of the FEL that were below 60 fs. To explain the complicated behavior of the second-order intensity correlation function we developed an advanced theoretical model that includes the presence of multiple beams and external positional jitter of the FEL pulses. By this analysis we determined that in one of the experiments external positional jitter was about 25% of the beam size. We envision that methods developed in our study will be used widely for analysis and diagnostics of FEL radiation., Published by APS, Woodbury, NY

We show that coadsorbed oxygen atoms have a dramatic influence on the CO desorption dynamics from Ru(0001). In contrast to the precursor-mediated desorption mechanism on Ru(0001), the presence of surface oxygen modifies the electronic structure of Ru atoms such that CO desorption occurs predominantly via the direct pathway. This phenomenon is directly observed in an ultrafast pump-probe experiment using a soft x-ray free-electron laser to monitor the dynamic evolution of the valence electronic structure of the surface species. This is supported with the potential of mean force along the CO desorption path obtained from density-functional theory calculations. Charge density distribution and frozen-orbital analysis suggest that the oxygen-induced reduction of the Pauli repulsion, and consequent increase of the dative interaction between the CO 5 sigma and the charged Ru atom, is the electronic origin of the distinct desorption dynamics. Ab initio molecular dynamics simulations of CO desorption from Ru(0001) and oxygen-coadsorbed Ru(0001) provide further insights into the surface bond-breaking process., US Department of Energy, Basic Energy Science; Swedish Research Council (VR); Department of Energy, Laboratory Directed Research and Development; VolkswagenStiftung; LCLS, Stanford University; Lawrence Berkeley National Laboratory (LBNL); University of Hamburg; Center for Free Electron Laser Science (CFEL)

The adsorption structure of the molecular switch azobenzene on Ag(111) is investigated by a combination of normal incidence x-ray standing waves and dispersion-corrected density functional theory. The inclusion of nonlocal collective substrate response (screening) in the dispersion correction improves the description of dense monolayers of azobenzene, which exhibit a substantial torsion of the molecule. Nevertheless, for a quantitative agreement with experiment explicit consideration of the effect of vibrational mode anharmonicity on the adsorption geometry is crucial. © 2013 American Physical Society.

The normal incidence x-ray standing wave (NIXSW) technique is used to determine the adsorption geometry of submonolayer 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) adsorbed on the Ag(110) surface. An accurate analysis of both C1$s$ and O1$s$ photoemission (PE) spectra allows the respective adsorption heights of carbon and oxygen atoms in different chemical environments within PTCDA to be distinguished. Due to the intricacy of the PE fitting models, a systematic error analysis of NIXSW structural parameters was developed and employed. Based on the adsorption geometry of PTCDA on Ag(110) a bonding mechanism is discussed.

The trends in the bonding mechanism of 3,4,9,10-perylenetetracarboxylic acid dianhydride (PTCDA) to the Ag(111), Ag(100), and Ag(110) surfaces were analyzed on the basis of data obtained from x-ray standing waves and dispersion-corrected density functional theory. Of importance are the attractive local O-Ag bonds on the anhydride groups. They are the shorter, the more open the surface is, and lead even to partly repulsive interactions between the perylene core and the surface. In parallel, there is an increasing charge donation from the Ag surface into the \ensuremath{\pi} system of the PTCDA. This synergism explains the out-of-plane distortion of the adsorbed PTCDA and the surface buckling.

We present a comprehensive study of structural and electronic properties of the adsorbate system H${}_{2}$-phthalocyanine (H${}_{2}$Pc) on Ag(111). A comparison with copper-phthalocyanine (CuPc) on Ag(111) allows us to elucidate the impact of the central metal atom in the molecule on the adsorbate-substrate interaction. This metal atom is one fundamental parameter which can be changed in order to modify the properties of phthalocyanine molecules, and therefore its influence on the adsorption behavior is highly relevant. From high-resolution electron diffraction, we obtained a phase diagram for submonolayer coverages which turns out to be similar to that of CuPc/Ag(111). The most striking difference is a higher stability of a commensurate phase, indicating a stronger and more adsorption site-specific bonding of the H${}_{2}$Pc molecules. Furthermore, ultraviolet photoelectron spectroscopy and x-ray standing waves prove chemisorptive interaction between molecules and substrate and a significant bending of the molecules with the nitrogen atoms approaching the surface. We conclude that the attractive interaction of metal-phthalocyanine molecules with Ag(111) is mainly mediated by the aromatic body of the molecule (the tetraazaporphyrin ring in particular) rather than by the central metallic atom which (in the case of CuPc) already shows Pauli repulsion.

We employ normal-incidence x-ray standing wave and temperature programed desorption spectroscopy to derive the adsorption geometry and energetics of the prototypical molecular switch azobenzene at Ag(111). This allows us to assess the accuracy of semiempirical correction schemes as a computationally efficient means to overcome the deficiency of semilocal density-functional theory with respect to long-range van der Waals (vdW) interactions. The obtained agreement underscores the significant improvement provided by the account of vdW interactions, with remaining differences mainly attributed to the neglect of electronic screening at the metallic surface.

In the present report we describe the case of a repeat blood donor infected with HIV-1. In January 2000 the donor was found to be repeatedly reactive to HIV1/2 antibodies and HIV-1 RNA screening tests. The donation was confirmed to be HIV-1 positive by Western blot. During the post-test counselling session, the donor reported a risk sexual behaviour denied during the pre-donation interview, and he recalled that in May 1998 he had undergone a check-up including the test for the detection of HIV1/2 antibodies, which was negative. This check-up was dated four months the next to the donor's previous donation in January 1998, which had been found HIV1/2 antibody negative, too. Serum and plasma specimens, properly stored at -80 degrees C, were available at the hospital where the donor had undergone the HIV antibody test in May 1998. Thus, the specimens dated May 1998 and the specimen of the last donation in January 2000 were investigated again by using the most sensitive tests currently available in the setting of donation screening. On the whole, the results suggest that in May 1998 the donor was in the pre-seroconversion period for HIV-1 infection. The case reported here stresses that a residual risk for HIV transmission through blood products still relies on the possibility that an individual may be accepted as blood donor during the asymptomatic pre-seroconversion window period of HIV-1 infection. Actually, this phase of the infection cannot be detected by the routine antibody/antigen-based HIV1/2 screening tests but only by using more sensitive techniques such as genomic screening.