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Interactions among and between electrons and phonons steer the energy flow in photo-excited materials and govern the emergence of correlated phases. The strength of electron-phonon interactions, decay channels of strongly coupled modes and the evolution of three-dimensional order are revealed by electron or X-ray pulses tracking non-equilibrium structural dynamics. Despite such capabilities, the growing relevance of inherently anisotropic two-dimensional materials and functional heterostructures still calls for techniques with monolayer sensitivity and, specifically, access to out-of-plane phonon polarizations. Here, we resolve non-equilibrium phonon dynamics and quantify the excitonic contribution to the structural order parameter in 1T-TiSe 2 . To this end, we introduce ultrafast low-energy electron diffuse scattering and trace strongly momentum- and fluence-dependent phonon populations. Mediated by phonon-phonon scattering, a few-picosecond build-up near the zone boundary precedes a far slower generation of zone-centre acoustic modes. These weakly coupled phonons are shown to substantially delay overall equilibration in layered materials. Moreover, we record the surface structural response to a quench of the material's widely investigated exciton condensate, identifying an approximate 30:70 ratio of excitonic versus Peierls contributions to the total lattice distortion in the charge density wave phase. The surface-sensitive approach complements the ultrafast structural toolbox and may further elucidate the impact of phonon scattering in numerous other phenomena within two-dimensional materials, such as the formation of interlayer excitons in twisted bilayers., (© 2024. The Author(s).)

Exploiting vibrational excitation for the dynamic control of material properties is an attractive goal with wide-ranging technological potential. Most metal-to-insulator transitions are mediated by few structural modes and are, thus, ideal candidates for selective driving toward a desired electronic phase. Such targeted navigation within a generally multi-dimensional potential energy landscape requires microscopic insight into the non-equilibrium pathway. However, the exact role of coherent inertial motion across the transition state has remained elusive. Here, we demonstrate mode-selective control over the metal-to-insulator phase transition of atomic indium wires on the Si(111) surface, monitored by ultrafast low-energy electron diffraction. We use tailored pulse sequences to individually enhance or suppress key phonon modes and thereby steer the collective atomic motion within the potential energy surface underlying the structural transformation. Ab initio molecular dynamics simulations demonstrate the ballistic character of the structural transition along the deformation vectors of the Peierls amplitude modes. Our work illustrates that coherent excitation of collective modes via exciton-phonon interactions evades entropic barriers and enables the dynamic control of materials functionality., (© 2022 Author(s).)

Active optical control over matter is desirable in many scientific disciplines, with prominent examples in all-optical magnetic switching 1,2 , light-induced metastable or exotic phases of solids 3-8 and the coherent control of chemical reactions 9,10 . Typically, these approaches dynamically steer a system towards states or reaction products far from equilibrium. In solids, metal-to-insulator transitions are an important target for optical manipulation, offering ultrafast changes of the electronic 4 and lattice 11-16 properties. The impact of coherences on the efficiencies and thresholds of such transitions, however, remains a largely open subject. Here, we demonstrate coherent control over a metal-insulator structural phase transition in a quasi-one-dimensional solid-state surface system. A femtosecond double-pulse excitation scheme 17-20 is used to switch the system from the insulating to a metastable metallic state, and the corresponding structural changes are monitored by ultrafast low-energy electron diffraction 21,22 . To govern the transition, we harness vibrational coherence in key structural modes connecting both phases, and observe delay-dependent oscillations in the double-pulse switching efficiency. Mode-selective coherent control of solids and surfaces could open new routes to switching chemical and physical functionalities, enabled by metastable and non-equilibrium states.

Near-field manipulation in plasmonic nanocavities can provide various applications in nanoscale science and technology. In particular, a gap plasmon in a scanning tunneling microscope (STM) junction is of key interest to nanoscale imaging and spectroscopy. Here we show that spectral features of a plasmonic STM junction can be manipulated by nanofabrication of Au tips using focused ion beam. An exemplary Fabry-Pérot type resonator of surface plasmons is demonstrated by producing the tip with a single groove on its shaft. Scanning tunneling luminescence spectra of the Fabry-Pérot tips exhibit spectral modulation resulting from interference between localized and propagating surface plasmon modes. In addition, the quality factor of the plasmonic Fabry-Pérot interference can be improved by optimizing the overall tip shape. Our approach paves the way for near-field imaging and spectroscopy with a high degree of accuracy.

The near-field spectral response of metallic nanocavities is a key characteristic in plasmon-assisted photophysical and photochemical processes. Here, we show that the near-field spectral response of an optically excited plasmonic scanning tunneling microscope (STM) junction can be probed by single-molecule reactions that serve as a nanoscale sensor detecting the local field intensity. Near-field action spectroscopy for the cis ↔ cis tautomerization of porphycene on a Cu(110) surface reveals that the field enhancement in the STM junction largely depends on microscopic structures not only on the tip apex, but also on its shaft. Using nanofabrication of Au tips with focused ion beam, we show that the spectral response is strongly modulated through the interference between the localized surface plasmon in the junction and propagating surface plasmon polariton generated on the shaft. Furthermore, it is demonstrated that the near-field spectral response can be manipulated by precisely shaping the tip shaft.

Based on clinical and experimental data, oropharyngeal squamous cell carcinomas (OPSCC) associated with human papillomavirus (HPV) have been recognized as a distinct entity of head and neck cancers. However, outside of clinical trials, HPV status currently has no impact on treatment. The natural replication cycle of HPV takes place in epithelial cells, and is thus spatially separated from cytotoxic immune cells in the epidermis. Dendritic cells (Langerhans cells, LC), however, are frequent in this upper dermal layer. The ability of LC to process antigens, migrate, and, ultimately activate T cells is inhibited by the activity of the viral oncoproteins (E5-E7). Downregulation of functional human leukocyte antigen I (HLA-I) epithelial cell surface expression contributes to LC inhibition. However, due to their absence in upper skin layers, corresponding activation of natural killer (NK) cells via missing-self recognition is not relevant. Genome-wide analyses have revealed specific expression signatures for HPV-associated OPSCC that are distinct from HPV-negative cancers. Interestingly, aberrations in HLA-I genes were common in HPV-associated OPSCC. Our own findings indicate more frequent infiltration of HPV-associated OPSCC by CD56-positive (CD56 + ) NK cells, which might be related to HLA-I downregulation during HPV-associated carcinogenesis. In patients with OPSCC, CD56 positivity correlates with improved prognosis after conventional therapy. This could be evidence for HPV-associated OPSCC being especially eligible for novel immune-based therapies and an indication that immunological data should be included in the design of clinical trials.

Optical near-field excitation of metallic nanostructures can be used to enhance photochemical reactions. The enhancement under visible light illumination is of particular interest because it can facilitate the use of sunlight to promote photocatalytic chemical and energy conversion. However, few studies have yet addressed optical near-field induced chemistry, in particular at the single-molecule level. In this Letter, we report the near-field enhanced tautomerization of porphycene on a Cu(111) surface in a scanning tunneling microscope (STM) junction. The light-induced tautomerization is mediated by photogenerated carriers in the Cu substrate. It is revealed that the reaction cross section is significantly enhanced in the presence of a Au tip compared to the far-field induced process. The strong enhancement occurs in the red and near-infrared spectral range for Au tips, whereas a W tip shows a much weaker enhancement, suggesting that excitation of the localized plasmon resonance contributes to the process. Additionally, using the precise tip-surface distance control of the STM, the near-field enhanced tautomerization is examined in and out of the tunneling regime. Our results suggest that the enhancement is attributed to the increased carrier generation rate via decay of the excited near-field in the STM junction. Additionally, optically excited tunneling electrons also contribute to the process in the tunneling regime.

Graphene is a promising two-dimensional platform for widespread nanophotonic applications. Recent theories have predicted that graphene can also enhance evanescent fields for subdiffraction-limited imaging. Here, for the first time we experimentally demonstrate that monolayer graphene offers a 7-fold enhancement of evanescent information, improving conventional infrared near-field microscopy to resolve buried structures at a 500 nm depth with λ/11-resolution.

In Germany, use and contents of EPRs are largely unknown and expected to be highly variable, due to missing standards. We conducted a telephone survey to describe and compare computer documentation habits in general practices. Specifically, we were interested in: (1) the type of medical data recorded; and (2) which factors influence the extent to which doctors used the EPR while seeing their patients. The sampling frame consisted of family physicians participating in a general practice research project: 32% (145/452) of family physicians in the district of Göttingen, Lower Saxony, and 63% (52/83) of physicians from a quality assurance network of family practices in the district of Freiburg, Baden-Württemberg. With the exception of two practices in Göttingen, all practices (n = 165 of 167) took part in this survey. Diagnoses, digital codes for service fees, and prescriptions were computerized in nearly all practices, although doctors were significantly more involved in Freiburg than in Göttingen. Clinical symptoms and findings were recorded in 80% of Freiburg and 52% of Göttingen practices (p = 0.008). Overall, in 74% of Freiburg and 51% of Göttingen practices, the physicians opened the EPR while seeing patients (p = 0.022). Nearly half of the Göttingen practices (49%) and 24% of the Freiburg practices (p < 0.05) entered digital codes for service fees and diagnoses on paper before entering them electronically. In multivariate models adjusting for sex, target group and training specialty, internet access in the office was independently predictive of 'EPR-activity' (OR: 2.23; 95%-confidence interval: 1.12-4.43). There seems to be room for improvement in terms of degree and intensity of recording of clinically-relevant data. Technical interest, i.e., internet access in the office, seems to enhance electronic documentation activities.

Various authors have demonstrated that estrogens stimulate both protein and DNA synthesis, as well as cell proliferation. This study was therefore undertaken to investigate the correlation between these physiological effects of estrogens and the total prostatic catecholestrogens. Either 17 beta-estradiol (5 ng), 2-hydroxyestradiol (40 ng), 4-hydroxyestradiol (17 ng), propane-1,2-diol or a saline solution was injected intraperitoneally to 22-day-old Sprague-Dawley rats daily. Regardless of the treatment, the prostate mass, the rate of DNA or protein synthesis correlates positively with the total prostatic catecholestrogen concentration. We therefore conclude that the effect of each estrogen per se should be regarded in terms of the total prostatic catecholestrogen concentration.

The follow-up of Graves' ophthalmopathy was analysed regarding to clinical and chemical data on the one hand and to dependence on different therapeutic alternatives on the other. 297 patients (44 +/- 14 years, 249 female, 48 men) were observed with inclusion of data from the history and clinical data as well (computer tomography and orbital sonography). At the onset of therapy 253 patients were hyperthyroid, 36 euthyroid and eight showed hypothyroidism. The staging was: I 13, II 54, III 113, IV 95, V five, VI eight patients. The HLA-typing in 89 patients showed the following results: B8 in 32%, DR3 in 42%, B8 as well as DR3 in 24% of the patients. In about 50% of the cases there were raised microsomal and in about 18% there were raised thyroglobuline antibodies. 63% of the patients received immunosuppressive medication: corticosteroids in 100% (more than one time in 43%), cyclosporine A in 11%, ciamexone in 10%, other non-steroid immunosuppressants in 5% of the cases. The retrobulbar irradiation was performed in 9%, and total thyroidectomy in 7%. During therapy the inflammatory process was clearly ameliorated, however exophthalmos and diplopia were more resistant to treatment. In the group of patients with combined cyclosporine and prednisone therapy and in the group of patients with total thyroidectomy and partly retrobulbar radiotherapy, significant differences were observed regarding to visual acuity and Hertel values. None of the therapies applied constitutes an optimal treatment with the regard to the long-term course. Under therapy an improvement can be reached, but no complete healing.