Enhanced light-matter interaction in an atomically thin semiconductor coupled with dielectric nano-antennas.

Unique structural and optical properties of atomically thin two-dimensional semiconducting transition metal dichalcogenides enable in principle their efficient coupling to photonic cavities having the optical mode volume close to or below the diffraction limit. Recently, it has become possible to make all-dielectric nano-cavities with reduced mode volumes and negligible non-radiative losses. Here, we realise low-loss high-refractive-index dielectric gallium phosphide (GaP) nano-antennas with small mode volumes coupled to atomic mono- and bilayers of WSe[Formula: see text]. We observe a photoluminescence enhancement exceeding 10[Formula: see text] compared with WSe[Formula: see text] placed on planar GaP, and trace its origin to a combination of enhancement of the spontaneous emission rate, favourable modification of the photoluminescence directionality and enhanced optical excitation efficiency. A further effect of the coupling is observed in the photoluminescence polarisation dependence and in the Raman scattering signal enhancement exceeding 10[Formula: see text]. Our findings reveal dielectric nano-antennas as a promising platform for engineering light-matter coupling in two-dimensional semiconductors.

Tracking Dark Excitons with Exciton Polaritons in Semiconductor Microcavities.

Dark excitons are of fundamental importance for a wide variety of processes in semiconductors but are difficult to investigate using optical techniques due to their weak interaction with light fields. We reveal and characterize dark excitons nonresonantly injected into a semiconductor microcavity structure containing InGaAs/GaAs quantum wells by a gated train of eight 100 fs pulses separated by 13 ns by monitoring their interactions with the bright lower polariton mode. We find a surprisingly long dark exciton lifetime of more than 20 ns, which is longer than the time delay between two consecutive pulses. This creates a memory effect that we clearly observe through the variation of the time-resolved transmission signal. We propose a rate equation model that provides a quantitative agreement with the experimental data.

Rydberg Excitons in the Presence of an Ultralow-Density Electron-Hole Plasma.

We study the Rydberg exciton absorption of Cu_{2}O in the presence of free carriers injected by above-band-gap illumination. Already at plasma densities ρ_{EH} below one hundredth electron-hole pair per µm^{3}, exciton lines are bleached, starting from the highest observed principal quantum number, while their energies remain constant. Simultaneously, the band gap decreases by correlation effects with the plasma. An exciton line loses oscillator strength when the band gap approaches its energy, vanishing completely at the crossing point. Adapting a plasma-physics description, we describe the observations by an effective Bohr radius that increases with rising plasma density, reflecting the Coulomb interaction screening by the plasma.

Signatures of Quantum Coherences in Rydberg Excitons.

Coherent optical control of individual particles has been demonstrated both for atoms and semiconductor quantum dots. Here we demonstrate the emergence of quantum coherent effects in semiconductor Rydberg excitons in bulk Cu_{2}O. Because of the spectral proximity between two adjacent Rydberg exciton states, a single-frequency laser may pump both resonances with little dissipation from the detuning. As a consequence, additional resonances appear in the absorption spectrum that correspond to dressed states consisting of two Rydberg exciton levels coupled to the excitonic vacuum, forming a V-type three-level system, but driven only by one laser light source. We show that the level of pure dephasing in this system is extremely low. These observations are a crucial step towards coherently controlled quantum technologies in a bulk semiconductor.

Photon-Statistics Excitation Spectroscopy of a Quantum-Dot Micropillar Laser.

We introduce photon-statistics excitation spectroscopy and exemplarily apply it to a quantum-dot micropillar laser. Both the intensity and the photon number statistics of the emission from the micropillar show a strong dependence on the photon statistics of the light used for excitation of the sample. The results under coherent and pseudothermal excitation reveal that a description of the laser properties in terms of mean input photon numbers is not sufficient. It is demonstrated that the micropillar acts as a superthermal light source when operated close to its threshold. Possible applications for important spectroscopic techniques are discussed.

Observation of High Angular Momentum Excitons in Cuprous Oxide.

The recent observation of dipole-allowed P excitons up to principal quantum numbers of n=25 in cuprous oxide has given insight into exciton states with unprecedented spectral resolution. While so far the exciton description as a hydrogenlike complex has been fully adequate for cubic crystals, we demonstrate here distinct deviations: The breaking of rotational symmetry leads to mixing of high angular momentum F and H excitons with the P excitons so that they can be observed in absorption. The F excitons show a threefold splitting that depends systematically on n, in agreement with theoretical considerations. From detailed comparison of experiment and theory we determine the cubic anisotropy parameter of the Cu(2)O valence band.

Quantum-memory effects in the emission of quantum-dot microcavities.

The experimentally measured input-output characteristics of optically pumped semiconductor microcavities exhibits unexpected oscillations modifying the fundamentally linear slope in the excitation power regime below lasing. A systematic microscopic analysis reproduces these oscillations, identifying them as a genuine quantum-memory effect, i.e., a photon-density correlation accumulated during the excitation. With the use of projected quantum measurements, it is shown that the input-output oscillations can be controlled and enhanced by an order of magnitude when the quantum fluctuations of the pump are adjusted.

Direct observation of correlations between individual photon emission events of a microcavity laser.

Lasers are recognized for coherent light emission, the onset of which is reflected in a change in the photon statistics. For many years, attempts have been made to directly measure correlations in the individual photon emission events of semiconductor lasers. Previously, the temporal decay of these correlations below or at the lasing threshold was considerably faster than could be measured with the time resolution provided by the Hanbury Brown/Twiss measurement set-up used. Here we demonstrate a measurement technique using a streak camera that overcomes this limitation and provides a record of the arrival times of individual photons. This allows us to investigate the dynamical evolution of correlations between the individual photon emission events. We apply our studies to micropillar lasers with semiconductor quantum dots as the active material, operating in the regime of cavity quantum electrodynamics. For laser resonators with a low cavity quality factor, Q, a smooth transition from photon bunching to uncorrelated emission with increasing pumping is observed; for high-Q resonators, we see a non-monotonic dependence around the threshold where quantum light emission can occur. We identify regimes of dynamical anti-bunching of photons in agreement with the predictions of a microscopic theory that includes semiconductor-specific effects.

Higher-order photon bunching in a semiconductor microcavity.

Quantum mechanically indistinguishable particles such as photons may show collective behavior. Therefore, an appropriate description of a light field must consider the properties of an assembly of photons instead of independent particles. We have studied multiphoton correlations up to fourth order in the single-mode emission of a semiconductor microcavity in the weak and strong coupling regimes. The counting statistics of single photons were recorded with picosecond time resolution, allowing quantitative measurement of the few-photon bunching inside light pulses. Our results show bunching behavior in the strong coupling case, which vanishes in the weak coupling regime as the cavity starts lasing. In particular, we verify the n factorial prediction for the zero-delay correlation function of n thermal light photons.

A multicentre phase II study of docetaxel plus cisplatin for the treatment of advanced gastric cancer.

BACKGROUND: The optimum regimen for advanced gastric cancer requires definition. This multicentre phase II study evaluated docetaxel-cisplatin combination in advanced gastric cancer. METHODS: Chemotherapy-naive patients with locally advanced or metastatic disease received docetaxel plus cisplatin (75/75 mg/m(2)) every 21 days for up to 9 cycles. Endpoints included tumour response, time to progression, overall survival and toxicity. RESULTS: Of 113 patients recruited, 88 were completely evaluable. The median age was 58 years, and most patients had metastatic disease. The overall response rate was 29.6%. Five patients (5.7%) achieved a complete response and 21 patients (23.9%) had a partial response. Tumour control, including stable disease, was achieved in 57 patients (64.8%). The median time to progression and median overall survival time was 4.8 and 8.7 months, respectively. The major toxicity was haematological: 37.5% of patients experienced grade 3-4 neutropenia, whereas febrile neutropenia was observed in only 2% of patients. CONCLUSION: Docetaxel-cisplatin was active with a predictable and manageable toxicity profile.

Treatment of bendamustine and prednisone in patients with newly diagnosed multiple myeloma results in superior complete response rate, prolonged time to treatment failure and improved quality of life compared to treatment with melphalan and prednisone--a randomized phase III study of the East German Study Group of Hematology and Oncology (OSHO).

PURPOSE: This randomized phase III study compared bendamustine and prednisone (BP) to standard melphalan and prednisone (MP) treatment in previously untreated patients with multiple Myeloma (MM). PATIENTS AND METHODS: To be included, patients had to have histologically and cytologically proven stage II with progressive diseases or stage III MM. They were randomly assigned to receive BP (n=68) or MP (n=63). The primary endpoint was the time to treatment failure (TTF). Secondary endpoints included survival, remission rate, toxicity and quality of life. RESULTS: The overall response rate was 75% in the BP and 70% in the MP group. A significantly higher number of patients treated with BP achieved a complete remission than did patients receiving MP (32 vs. 13%; P=0.007), and the maximum response was achieved more rapidly in patients treated with BP compared to those receiving MP (6.8 vs. 8.7 cycles; P<0.02). TTF and remission duration were significantly longer in the BP group. Patients receiving BP had higher QoL scores and reported pain less frequently than patients receiving MP. CONCLUSION: BP is superior to MP with respect to complete remission rate, TTF, cycles needed to achieve maximum remission and quality of life and should be considered the new standard in first-line treatment of MM patients not eligible for transplantation.

New antifeedant bromopyrrole alkaloid from the Caribbean sponge Stylissa caribica.

In this first report on the chemistry of the sponge Stylissa caribica, two known bromopyrrole metabolites and a new compound, N-methyldibromoisophakellin (1), were isolated and identified. The structure of 1 was determined using spectroscopic methods and the computer program COCON. N-Methyldibromoisophakellin (1) was shown to be the only secondary metabolite in Stylissa caribica that, at its natural concentration, is active as a feeding deterrent against a common omnivorous reef fish.

Sventrin, a new bromopyrrole alkaloid from the Caribbean sponge Agelas sventres.

A detailed analysis of the secondary metabolites of a specimen of Agelas sventres was carried out here for the first time. The chemistry of Agelas sponges is dominated by bromopyrrole derivatives. Besides three known bromopyrrole metabolites, a new compound, sventrin (1), was isolated and its structure identified using spectroscopic methods. Sventrin (1) was shown to be a feeding deterrent compound against a common omnivorous reef fish.

Synthesis of the marine natural product nalpha-(4-bromopyrrolyl-2-carbonyl)-L-homoarginine, a putative biogenetic precursor of the pyrrole-imidazole alkaloids.

Lysine is proposed as an alternative biosynthetic precursor of the pyrrole-imidazole alkaloids frequently found in marine sponges. As a putative key intermediate, the natural product Nalpha-(4-bromopyrrolyl-2-carbonyl)-L-homoarginine (1) from the sponge Agelas wiedenmayeri was synthesized in the solid phase starting from Fmoc/Pmc-protected L-homoarginine and in solution starting from readily available L-lysine methyl ester.

Shift of aberrant antigen expression at relapse or at treatment failure in acute leukemia.

The flow cytometric detection of aberrant antigen expression is one method proposed for the quantification of minimal residual disease (MRD) in acute leukemias. The present study was designed to investigate the stability of the aberrant antigen expression at relapse or at treatment failure of initial chemotherapy. For this purpose, multiparameter immunophenotyping with a panel of 15 monoclonal antibodies was used at diagnosis as well as at relapse (43 patients with overall 65 aberrations) and at treatment failure (35 patients with overall 66 aberrations). There was a significant decrease in the percentage of the initially described aberrant antigen expression on leukemia blasts at relapse (P = 0.001; n = 65) as well as at treatment failure (P = 0.0001; n = 66) considering all aberrations in the whole leukemia population. Concerning only patients with acute myelogenous leukemia (AML), significant decreases in the aberrant expression could be detected at relapse (P = 0.031; n = 42) and at treatment failure (P = 0.0001; n = 52). The changes in patients with acute lymphoblastic leukemia (ALL) were significant only at relapse (P = 0.006; n = 23). Initially, the most informative aberration was not detectable in four patients at relapse and in seven patients at treatment failure. A decrease of under 50% of the initial value was observed in another 8 patients at relapse and in 10 patients at treatment failure. In further studies assessing the detection of aberrant antigen expression for MRD, quantification of the relapses should be explicitly analyzed regarding the persistence of the initially described aberrant antigen expression.

The role of cytochrome P450 2E1 in the species-dependent biotransformation of 1,2-dichloro-1,1,2-trifluoroethane in rats and mice.

1,2-Dichloro-1,1,2-trifluoroethane (HCFC-123a) is a potential alternative to replace ozone-depleting chlorofluorocarbons. The metabolism of HCFC-123a was studied in microsomes of rats, mice, and humans as well as in rats and mice in vivo. Rat, mouse, and human liver microsomes metabolized HCFC-123a to inorganic fluoride and chlorodifluoroacetic acid. Fluoride formation was dependent on time and NADPH, HCFC-123a, and protein concentration. Microsomes from untreated rats oxidized HCFC-123a at low rates (0.49 nmol fluoride/20 min x mg protein). Pretreatment of rats with pyridine and ethanol, inducers of P450 2E1, increased the rates of fluoride release. In mouse liver microsomes, the rates of HCFC-123a oxidation to release fluoride were significantly higher (1.68 nmol fluoride/20 min x mg) than in rat liver microsomes. Incubation of HCFC-123a with microsomes and diethyldithiocarbamate (100 microM), an inhibitor of P450 2E1, reduced fluoride formation by more than 60%. In different samples of human liver microsomes, rates of fluoride formation were between two- and fourfold higher than those observed in liver microsomes from untreated rats. In rats and mice exposed to concentrations of HCFC-123a up to 5000 ppm in a closed recirculating exposure system, chlorodifluoroacetic acid, and inorganic fluoride were identified as urinary metabolites. The biotransformation of HCFC-123a in rats was saturated after exposure to more than 2000 ppm HCFC-123a for 6 hr, whereas no saturation was evident in mice exposed to concentrations of up to 5000 ppm. The obtained results suggest a major role of P450 2E1 in the oxidation of HCFC-123a and in the different capacities for oxidative biotransformation of HCFC-123a in rodents. Mice may thus be more sensitive to toxic effects of HCFC-123a depending on biotransformation after administration of high doses.

Epidemiologic investigation by macrorestriction analysis and by using monoclonal antibodies of nosocomial pneumonia caused by Legionella pneumophila serogroup 10.

A 67-year-old woman was hospitalized with an acute pneumonia of the left lower lobe. Legionella pneumophila serogroup 10 was cultured from two sputum specimens taken on days 18 and 20 and was also detected by direct immunofluorescence assay by using a commercially available species-specific monoclonal antibody as well as serogroup 10-specific monoclonal antibodies. Antigenuria was detected in enzyme-linked immunosorbent assays by using serogroup 10-specific polyclonal and monoclonal antibodies. In the indirect immunofluorescence test rising antibody titers against serogroups 1, 4, 5, 8, 9, 10, 14, and 15 were found in serum, with the highest titers found against serogroups 8, 9, and 10. L. pneumophila serogroups 10 and 6 and a strain that reacted with serogroup 4 and 14 antisera were cultured from both central and peripheral hot water systems of the hospital. Macrorestriction analyses of the genomic DNAs by pulsed-field gel electrophoresis showed that the isolate from the patient was identical to the serogroup 10 strains from the hospital hot water system. In contrast, the genomic DNAs of 16 unrelated L. pneumophila serogroup 10 strains showed 12 different restriction patterns. Monoclonal antibody subtyping revealed only minor differences in L. pneumophila serogroup 10 strains isolated from different sources. In conclusion, macrorestriction analysis is a valuable tool for studying the molecular epidemiology of L. pneumophila serogroup 10.