Interaction-Induced ac Stark Shift of Exciton-Polaron Resonances.

Laser-induced shift of atomic states due to the ac Stark effect has played a central role in cold-atom physics and facilitated their emergence as analog quantum simulators. Here, we explore this phenomenon in an atomically thin layer of semiconductor MoSe_{2}, which we embedded in a heterostructure enabling charge tunability. Shining an intense pump laser with a small detuning from the material resonances, we generate a large population of virtual collective excitations and achieve a regime where interactions with this background population are the leading contribution to the ac Stark shift. Using this technique we study how itinerant charges modify-and dramatically enhance-the interactions between optical excitations. In particular, our experiments show that the interaction between attractive polarons could be more than an order of magnitude stronger than those between bare excitons.

Kinetic magnetism in triangular moiré materials.

Magnetic properties of materials ranging from conventional ferromagnetic metals to strongly correlated materials such as cuprates originate from Coulomb exchange interactions. The existence of alternate mechanisms for magnetism that could naturally facilitate electrical control has been discussed theoretically1-7, but an experimental demonstration8 in an extended system has been missing. Here we investigate MoSe2/WS2 van der Waals heterostructures in the vicinity of Mott insulator states of electrons forming a frustrated triangular lattice and observe direct evidence of magnetic correlations originating from a kinetic mechanism. By directly measuring electronic magnetization through the strength of the polarization-selective attractive polaron resonance9,10, we find that when the Mott state is electron-doped, the system exhibits ferromagnetic correlations in agreement with the Nagaoka mechanism.

Spin-Valley Relaxation and Exciton-Induced Depolarization Dynamics of Landau-Quantized Electrons in MoSe_{2} Monolayer.

Nonequilibrium dynamics of strongly correlated systems constitutes a fascinating problem of condensed matter physics with many open questions. Here, we investigate the relaxation dynamics of Landau-quantized electron system into spin-valley polarized ground state in a gate-tunable MoSe_{2} monolayer subjected to a strong magnetic field. The system is driven out of equilibrium with optically injected excitons that depolarize the electron spins and the subsequent electron spin-valley relaxation is probed in time-resolved experiments. We demonstrate that both the relaxation and light-induced depolarization rates at millikelvin temperatures sensitively depend on the Landau level filling factor: the relaxation is enhanced whenever the electrons form an integer quantum Hall liquid and slows down appreciably at noninteger fillings, while the depolarization rate exhibits an opposite behavior. Our findings suggest that spin-valley dynamics may be used as a tool to investigate the interplay between the effects of disorder and strong interactions in the electronic ground state.

Interaction-Induced Shubnikov-de Haas Oscillations in Optical Conductivity of Monolayer MoSe_{2}.

We report polarization-resolved resonant reflection spectroscopy of a charge-tunable atomically thin valley semiconductor hosting tightly bound excitons coupled to a dilute system of fully spin- and valley-polarized holes in the presence of a strong magnetic field. We find that exciton-hole interactions manifest themselves in hole-density dependent, Shubnikov-de Haas-like oscillations in the energy and line broadening of the excitonic resonances. These oscillations are evidenced to be precisely correlated with the occupation of Landau levels, thus demonstrating that strong interactions between the excitons and Landau-quantized itinerant carriers enable optical investigation of quantum-Hall physics in transition metal dichalcogenides.

Lipocalin-2 contributes to experimental atherosclerosis in a stage-dependent manner.

BACKGROUND AND AIMS: Lipocalin-2 (Lcn2) is a glycoprotein which can be secreted by immune cells. Several studies in humans have suggested Lcn2 can be used as a biomarker for the detection of unstable atherosclerotic lesions, partly as it is known to interact with MMP-9. METHODS: In this study, we generated Ldlr-/-Lcn2-/- mice to assess the functional role of Lcn2 in different stages of atherosclerosis. Atherosclerotic lesions were characterized through histological analysis and myeloid cell populations were examined using flow cytometry. RESULTS: We show that Ldlr-/-Lcn2-/- mice developed larger atherosclerotic lesions during earlier stages of atherosclerosis and had increased circulating Ly6Chi inflammatory monocytes compared to Ldlr-/- mice. Advanced atherosclerotic lesions from Ldlr-/-Lcn2-/- mice had decreased necrotic core area, suggesting Lcn2 deficiency may affect lesion stability. Furthermore, MMP-9 activity was diminished in plaques from Ldlr-/-Lcn2-/- mice. CONCLUSIONS: Altogether, these findings suggest that Lcn2 deficiency promotes lesion growth in earlier stages of the disease while it decreases MMP-9 activity and necrotic core size in advanced atherosclerosis.

Dynamic nuclear spin polarization in the resonant laser excitation of an InGaAs quantum dot.

Resonant optical excitation of lowest-energy excitonic transitions in self-assembled quantum dots leads to nuclear spin polarization that is qualitatively different from the well-known optical orientation phenomena. By carrying out a comprehensive set of experiments, we demonstrate that nuclear spin polarization manifests itself in quantum dots subjected to finite external magnetic field as locking of the higher energy Zeeman transition to the driving laser field, as well as the avoidance of the resonance condition for the lower energy Zeeman branch. We interpret our findings on the basis of dynamic nuclear spin polarization originating from noncollinear hyperfine interaction and find excellent agreement between experiment and theory. Our results provide evidence for the significance of noncollinear hyperfine processes not only for nuclear spin diffusion and decay, but also for buildup dynamics of nuclear spin polarization in a coupled electron-nuclear spin system.

Optically induced hybridization of a quantum dot state with a filled continuum.

We present an optical signature of a hybridization between a localized quantum dot state and a filled continuum. Radiative recombination of the negatively charged trion in a single quantum dot leaves behind a single electron. We show that in two regions of vertical electric field, the electron hybridizes with a continuum through a tunneling interaction. The hybridization manifests itself through an unusual voltage dependence of the emission energy and a non-Lorentzian line shape, features which we reproduce with a theory based on the Anderson Hamiltonian.

The nonlinear Fano effect.

The Fano effect is ubiquitous in the spectroscopy of, for instance, atoms, bulk solids and semiconductor heterostructures. It arises when quantum interference takes place between two competing optical pathways, one connecting the energy ground state and an excited discrete state, the other connecting the ground state with a continuum of energy states. The nature of the interference changes rapidly as a function of energy, giving rise to characteristically asymmetric lineshapes. The Fano effect is particularly important in the interpretation of electronic transport and optical spectra in semiconductors. Whereas Fano's original theory applies to the linear regime at low power, at higher power a laser field strongly admixes the states and the physics becomes rich, leading, for example, to a remarkable interplay of coherent nonlinear transitions. Despite the general importance of Fano physics, this nonlinear regime has received very little attention experimentally, presumably because the classic autoionization processes, the original test-bed of Fano's ideas, occur in an inconvenient spectral region, the deep ultraviolet. Here we report experiments that access the nonlinear Fano regime by using semiconductor quantum dots, which allow both the continuum states to be engineered and the energies to be rescaled to the near infrared. We measure the absorption cross-section of a single quantum dot and discover clear Fano resonances that we can tune with the device design or even in situ with a voltage bias. In parallel, we develop a nonlinear theory applicable to solid-state systems with fast relaxation of carriers. In the nonlinear regime, the visibility of the Fano quantum interferences increases dramatically, affording a sensitive probe of continuum coupling. This could be a unique method to detect weak couplings of a two-level quantum system (qubits), which should ideally be decoupled from all other states.

Synthesis and cytostatic activities of didemnin derivatives.

The highly cytostatic didemnins contain a 23-membered cyclopeptolide with a side chain attached to the backbone through the amine group of threonine. Thirty-six derivatives varying the side chain were prepared, but only compounds with D-MeLeu attached to threonine show remarkable biological activities. To protect the macrocycle from degradation by lipases the two ester bonds were replaced successively by amide bonds. Although these variations have a major effect on the conformation and rigidity of the ring, the compound which contains exclusively amide bonds is highly active, equivalent to acetyl-didemnin A.

Disease-adapted relapse therapy for ovarian cancer: results of a prospective study.

Primary therapy of advanced ovarian cancer is standardized, the therapy in relapsed ovarian cancer however is still controversial. In a prospective study the benefit of secondary surgery and/or second-line chemotherapy were evaluated. 139 patients with relapsed ovarian cancer were stratified according to a treatment plan: patients with early relapse (recurrence-free interval 12 months) or primary progression during chemotherapy (n=43) were treated chemotherapeutically with etoposide (p.o. vs. i.v.). Patients with late relapse (recurrence-free interval >12 months, n=96) were referred, if possible, to a secondary debulking operation, followed by a platinum-based chemotherapy. Remission-rate, toxicity and survival time were analyzed. Median survival time in the group was 15 months compared to 30 months in patients with late relapse (p=0.0004). Within the group patients with secondary debulking and chemotherapy (n=59) had a statistically significant survival advantage compared to patients who had only chemotherapy (n=37) (38 vs. 12 months, p<0.0001). The unfavorable group of patients with early relapse should be treated chemotherapeutically, whereas in patients with late relapse a secondary debulking seems to improve prognosis.

[Status of ultrasound diagnosis in differential cholestasis diagnosis]. / Stellenwert der Ultraschalldiagnostik in der Differentialdiagnostik der Cholestase.

Differentiating between the hepatocellular "internal" and the "surgical" or "endoscopic" cholestasis syndrome has become a domain of sonography. There is a 92 to 99% success rate, due to the possibility of diagnosing by means of sonography dilations of the gall bladder, the extrahepatic biliary tract and the intrahepatic bile ducts, as well as numerous diseases of the hepatobiliary system and of the pancreas. Congested intra- and extrahepatic bile ducts indicate the presence of a deep-seated distal obstruction, such s a prepapillary concrement, an inflammatory or malignant papillary stenosis or of a process in the area of the head of the pancreas. If the intrahepatic bile ducts alone are dilated the obstructive process has to be assumed near the portal fissure of the liver. Frequent causes are directly demonstrable tumors or metastases on the hilum or high-lying concrements. By using sonography, the level of obstruction can be determined correctly in about 90% of cases, while the cause of obstruction can be diagnosed in about 60 to 70%. In most cases intrahepatic cholestase can only be demonstrated indirectly through the absence of a bile duct dilation. Characteristic diffuse changes in the liver (e.g. fatty liver, cirrhosis, cardiac liver) or intrahepatic space claims-may be in combination with an ultrasound-directed puncture-may support or confirm the diagnosis.

[Full inpatient versus partial inpatient psychiatric after-care--a comparative retrospective study]. / Vollstationäre versus halbstationäre psychiatrische Anschlussbehandlung--Eine vergleichende retrospektive Studie.

In a retrospective study 80 inpatients (Sociotherapy, Therapeutic Community) were compared to 160 outpatients (80 patient Day Clinic, 80 patients Night Clinic). With a mean treatment duration of 4-5 1/2 month a significant decrease was found for each group in the frequency and duration of further hospital admissions after end of therapy. Day and Night Clinic patients tending to a better outcome than the inpatients. Advantages of the Day and Night Clinic are seen e.g. in a higher degree of acceptance by patients and family doctors, disadvantages in the increased rate of suicide found in our sample.

Living arrangement options for young people preparing for independent living.

Innovative living arrangement options are being developed around the country to provide both preparation and practical experience in independent living for older youths unable to return home. This article describes in detail the full continuum of existing options and their general characteristics.

[Priming and medical abortion induction by PGF2 alpha]. / Priming und medizinische Abortinduktion durch PGF2 alpha.

In the Dept. of Obstetrics of the Gera district hospital prostaglandin F2 alpha has been applied for priming and therapeutic abortion since 1979. A total of 600 women, among them 482 primigravidae, 47 with missed abortion and 71 having been admitted on behalf of the abortion panel's decision, underwent therapeutic abortion. Age distribution, clinical course, unwanted side effects and early complications after intracervical-extraamnial instillation of 5 mg prostaglandin F2 alpha have been investigated. Application of prostaglandin F2 alpha can be considered the method of choice in particular when therapeutic abortion is indicated in younger women or in patients showing suspect findings in cervical smear cytology.