Far-field probing of leaky topological states in all-dielectric metasurfaces

© 2018 The Author(s). Topological phase transitions in condensed matter systems give rise to exotic states of matter such as topological insulators, superconductors, and superfluids. Photonic topological systems open a whole new realm of research and technological opportunities, exhibiting a number of important distinctions from their condensed matter counterparts. Photonic modes can leak into free space, which makes it possible to probe topological photonic phases by spectroscopic means via Fano resonances. Based on this idea, we develop a technique to retrieve the topological properties of all-dielectric metasurfaces from the measured far-field scattering characteristics. Collected angle-resolved spectra provide the momentum-dependent frequencies and lifetimes of the photonic modes that enable the retrieval of the effective Hamiltonian and extraction of the topological invariant. Our results demonstrate how the topological states of open non-Hermitian systems can be explored via far-field measurements, thus paving a way to the design of metasurfaces with unique scattering characteristics controlled via topological effects

Enhanced light–matter interactions in dielectric nanostructures via machine-learning approach

A key concept underlying the specific functionalities of metasurfaces is the use of constituent components to shape the wavefront of the light on demand. Metasurfaces are versatile, novel platforms for manipulating the scattering, color, phase, or intensity of light. Currently, one of the typical approaches for designing a metasurface is to optimize one or two variables among a vast number of fixed parameters, such as various materials’ properties and coupling effects, as well as the geometrical parameters. Ideally, this would require multidimensional space optimization through direct numerical simulations. Recently, an alternative, popular approach allows for reducing the computational cost significantly based on a deep-learning-assisted method. We utilize a deep-learning approach for obtaining high-quality factor (high-Q) resonances with desired characteristics, such as linewidth, amplitude, and spectral position. We exploit such high-Q resonances for enhanced light–matter interaction in nonlinear optical metasurfaces and optomechanical vibrations, simultaneously. We demonstrate that optimized metasurfaces achieve up to 400-fold enhancement of the third-harmonic generation; at the same time, they also contribute to 100-fold enhancement of the amplitude of optomechanical vibrations. This approach can be further used to realize structures with unconventional scattering responses

Comparative Efficacy Analysis of Mobilization and Collection of Autologous Hematopoietic Stem Cells in Patients with Lymphoproliferative Disorders and Multiple Sclerosis

Aim. Comparative efficacy analysis of autologous hematopoietic stem cells (HSC) prior to auto-HSCT in patients with lymphoproliferative disorders (LPDs) and multiple sclerosis (MS). Materials & Methods. The trial included 237 patients: 103 LPD and 134 MS patients. In 225 patients HSC mobilization involved only colony-stimulating factors (CSFs), in 12 patients chemotherapy (cyclophosphamide, etoposide) was combined with CSFs. On the intended date of cytapheresis all the patients were tested for CD34+ marker expression. Сytapheresis followed in the patients with CD34+ count more than 0.01 × 106/mL. Results. In 23 (22 %) LPD patients CD34+ count was too low for auto-HSCT (‘collection failure group’). Within this group 19 patients received CSF mobilization, and 4 patients received chemotherapy + CSF. Plerixafor was administered in 5 patients, in 4 of them a repeated mobilization also failed to collect enough cells. In 80 LPD patients the number of mobilized and collected CD34+ cells was sufficient for auto-HSCT (‘collection success group’). Within this group 77 patients received auto-HSCT, 74 patients were treated with CSF mobilization, 6 patients received chemotherapy + CSF, and in 11 patients plerixafor was administered. Median total number of CD34+ cells in the ‘collection success group’ was 2.7 × 106/kg. All 134 MS patients had enough CD34+ cells for auto-HSCT. All of them received CSF mobilization. Median total number of CD34+ cells in the MS group was 2.34 × 106/kg. Potential risk factors for HSC mobilization failure in LPDs were evaluated. They included age, gender, prior radiotherapy, number of antitumor treatment lines prior to auto-HSCT, clinical response prior to auto-HSCT (complete/partial remission or stabilization), and HSC mobilization regimen. These factors with the exception of gender were not associated with mobilization failure parameters. The worst mobilization outcomes were reported in male patients. Conclusion. In 22 % of LPD patients the planned high-dose chemotherapy and auto-HSCT failed due to insufficient counts of autologous CD34+ cells in apheresis product. Male gender can be considered to be a prognostic factor of mobilization failure in LPDs

Outcome of Classical Hodgkin’s Lymphoma Treatment Based on High-Dose Chemotherapy and Autologous Hematopoietic Stem Cell Transplantation: The Experience in the NI Pirogov Russian National Medical Center of Surgery

Aim. To estimate the long-term outcome of the programmed treatment of classical Hodgkin’s lymphoma (cHL) including high-dose chemotherapy (HDCT) and autologous hematopoietic stem cell transplantation (auto-HSCT) as well as the effect of various factors on the achieved results in a single-center study. Materials & Methods. In the A.A. Maksimov Clinical Center of Hematology and Cellular Therapy of the NI Pirogov Russian National Medical Center of Surgery 260 cHL patients received HDCT combined with auto-HSCT within the period from December 2006 to March 2017. The median age was 29 years (range 17–62). The study included 40 % men (n = 104), and 60 % women (n = 156). The median pretransplantation chemotherapy line was 3 (range 2–9). At this stage, prior to auto-HSCT, complete remission (CR) rate was 26.5 %, partial remission (PR) rate was 52.3 %, disease stabilisation rate was 13.5 %. HDCT with auto-HSCT was applied beyond progression as a salvage therapy in 7.7 % of patients. In 79.6 % of patients the standard BEAM and CBV conditioning regimens were used. Results. After HDCT combined with auto-HSCT overall 5-year survival (OS) of 260 cHL patients was 74 %, and 5-year progression-free survival (PFS) was 48 %, which corresponds to the results of some international studies. 5-year OS rates were significantly higher after HDCT and auto-HSCT performed during the first CR or PR (85 %) vs the second and subsequent CR and PR (71 %). Neither gender (p = 0.4) nor ECOG status (p = 0.2) effects on OS and PFS were revealed. 5-year OS rates were significantly higher after HDCT and auto-HSCT performed during CR or PR (82 %) vs disease stabilisation and progression (54 %) as well as upon achieving CR (93 %) vs PR (77 %). Conclusion. In cHL tumor sensitivity to chemotherapy is the essential indication for HDCT combined with auto-HSCT. The optimal time for HDCT and auto-HSCT in cHL is the first CR/PR, and the best treatment outcome is achieved in patients with complete response prior to HDCT and auto-HSCT

Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance

This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions, for the e+e- -> ffbar process for centre-of-mass energies above the Z resonance, from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study a variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering and several models which include physics beyond the Standard Model: the exchange of Z' bosons, contact interactions between fermions, the exchange of gravitons in large extra dimensions and the exchange of sneutrino in R-parity violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.

A Determination of the Centre-of-Mass Energy at LEP2 using Radiative 2-fermion Events

Using e+e- -> mu+mu-(gamma) and e+e- -> qqbar(gamma) events radiative to the Z pole, DELPHI has determined the centre-of-mass energy, sqrt{s}, using energy and momentum constraint methods. The results are expressed as deviations from the nominal LEP centre-of-mass energy, measured using other techniques. The results are found to be compatible with the LEP Energy Working Group estimates for a combination of the 1997 to 2000 data sets.Comment: 20 pages, 6 figures, Accepted by Eur. Phys. J.

Study of Tau-pair Production in Photon-Photon Collisions at LEP and Limits on the Anomalous Electromagnetic Moments of the Tau Lepton

Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb^{-1}. The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.Comment: 20 pages, 9 figures, Accepted by Eur. Phys. J.

Evidence for an Excess of Soft Photons in Hadronic Decays of Z^0

Soft photons inside hadronic jets converted in front of the DELPHI main tracker (TPC) in events of qqbar disintegrations of the Z^0 were studied in the kinematic range 0.2 < E_gamma < 1 GeV and transverse momentum with respect to the closest jet direction p_T < 80 MeV/c. A clear excess of photons in the experimental data as compared to the Monte Carlo predictions is observed. This excess (uncorrected for the photon detection efficiency) is (1.17 +/- 0.06 +/- 0.27) x 10^{-3} gamma/jet in the specified kinematic region, while the expected level of the inner hadronic bremsstrahlung (which is not included in the Monte Carlo) is (0.340 +/- 0.001 +/- 0.038) x 10^{-3} gamma/jet. The ratio of the excess to the predicted bremsstrahlung rate is then (3.4 +/- 0.2 +/- 0.8), which is similar in strength to the anomalous soft photon signal observed in fixed target experiments with hadronic beams.Comment: 37 pages, 9 figures, Accepted by Eur. Phys. J.

A Measurement of the Tau Hadronic Branching Ratios

The exclusive and semi-exclusive branching ratios of the tau lepton hadronic decay modes (h- v_t, h- pi0 v_t, h- pi0 pi0 v_t, h- \geq 2pi0 v_t, h- \geq 3pi0 v_t, 2h- h+ v_t, 2h- h+ pi0 v_t, 2h- h+ \geq 2pi0 v_t, 3h- 2h+ v_t and 3h- 2h+ \geq 1pi0 v_t) were measured with data from the DELPHI detector at LEP.Comment: 53 pages, 18 figures, Accepted by Eur. Phys. J.

Study of Inclusive J/psi Production in Two-Photon Collisions at LEP II with the DELPHI Detector

Inclusive J/psi production in photon-photon collisions has been observed at LEP II beam energies. A clear signal from the reaction gamma gamma -> J/psi+X is seen. The number of observed N(J/psi -> mu+mu-) events is 36 +/- 7 for an integrated luminosity of 617 pb^{-1}, yielding a cross-section of sigma(J/psi+X) = 45 +/- 9 (stat) +/- 17 (syst) pb. Based on a study of the event shapes of different types of gamma gamma processes in the PYTHIA program, we conclude that (74 +/- 22)% of the observed J/psi events are due to `resolved' photons, the dominant contribution of which is most probably due to the gluon content of the photon.Comment: 13 pages, 8 figures, Accepted by Phys. Lett.