Emergence of Interlayer Coherence in Twist-Controlled Graphene Double Layers.

We report enhanced interlayer tunneling with reduced linewidth at zero interlayer bias in a twist-controlled double monolayer graphene heterostructure in the quantum Hall regime, when the top (ν_{T}) and bottom (ν_{B}) layer filling factors are near ν_{T}=±1/2,±3/2 and ν_{B}=±1/2,±3/2, and the total filling factor ν=±1 or ±3. The zero-bias interlayer conductance peaks are stable against variations of layer filling factor, and signal the emergence of interlayer phase coherence. Our results highlight twist control as a key attribute in revealing interlayer coherence using tunneling.

Emergence of correlations in alternating twist quadrilayer graphene.

Alternating twist multilayer graphene (ATMG) has recently emerged as a family of moiré systems that share several fundamental properties with twisted bilayer graphene, and are expected to host similarly strong electron-electron interactions near the magic angle. Here, we study alternating twist quadrilayer graphene (ATQG) samples with twist angles of 1.96° and 1.52°, which are slightly removed from the magic angle of 1.68°. At the larger angle, we find signatures of correlated insulators only when the ATQG is hole doped, and no signatures of superconductivity, and for the smaller angle we find evidence of superconductivity, while signs of the correlated insulators weaken. Our results provide insight into the twist angle dependence of correlated phases in ATMG and shed light on the nature of correlations in the intermediate coupling regime at the edge of the magic angle range where dispersion and interaction are of the same order.

Quantum Lifetime Spectroscopy and Magnetotunneling in Double Bilayer Graphene Heterostructures.

We describe a tunneling spectroscopy technique in a double bilayer graphene heterostructure where momentum-conserving tunneling between different energy bands serves as an energy filter for the tunneling carriers, and allows a measurement of the quasiparticle state broadening at well-defined energies. The broadening increases linearly with the excited state energy with respect to the Fermi level and is weakly dependent on temperature. In-plane magnetotunneling reveals a high degree of rotational alignment between the graphene bilayers, and an absence of momentum randomizing processes.

Interlayer exciton laser of extended spatial coherence in atomically thin heterostructures.

Two-dimensional semiconductors have emerged as a new class of materials for nanophotonics owing to their strong exciton-photon interaction1,2 and their ability to be engineered and integrated into devices3. Here we take advantage of these properties to engineer an efficient lasing medium based on direct-bandgap interlayer excitons in rotationally aligned atomically thin heterostructures4. Lasing is measured from a transition-metal dichalcogenide heterobilayer (WSe2-MoSe2) integrated in a silicon nitride grating resonator. An abrupt increase in the spatial coherence of the emission is observed across the lasing threshold. The work establishes interlayer excitons in two-dimensional heterostructures as a gain medium with spatially coherent lasing emission and potential for heterogeneous integration. With electrically tunable exciton-photon interaction strengths5 and long-range dipolar interactions, these interlayer excitons are promising for application as low-power, ultrafast lasers and modulators and for the study of many-body quantum phenomena6.

Correlated Insulating States in Twisted Double Bilayer Graphene.

We present a combined experimental and theoretical study of twisted double bilayer graphene with twist angles between 1° and 1.35°. Consistent with moiré band structure calculations, we observe insulators at integer moiré band fillings one and three, but not two. An applied transverse electric field separates the first moiré conduction band from neighboring bands, and favors the appearance of correlated insulators at 1/4, 1/2, and 3/4 band filling. Insulating states at 1/4 and 3/4 band filling emerge only in a parallel magnetic field (B_{||}), whereas the resistivity at half band filling is weakly dependent on B_{||}. Our findings suggest that correlated insulators are favored when a moiré flat band is spectrally isolated, and are consistent with a mean-field picture in which insulating states are established by breaking both spin and valley symmetries at 1/4 and 3/4 band filling and valley polarization alone at 1/2 band filling.

Spin-Conserving Resonant Tunneling in Twist-Controlled WSe2-hBN-WSe2 Heterostructures.

We investigate interlayer tunneling in heterostructures consisting of two tungsten diselenide (WSe2) monolayers with controlled rotational alignment, and separated by hexagonal boron nitride. In samples where the two WSe2 monolayers are rotationally aligned we observe resonant tunneling, manifested by a large conductance and negative differential resistance in the vicinity of zero interlayer bias, which stem from energy- and momentum-conserving tunneling. Because the spin-orbit coupling leads to coupled spin-valley degrees of freedom, the twist between the two WSe2 monolayers allows us to probe the conservation of spin-valley degree of freedom in tunneling. In heterostructures where the two WSe2 monolayers have a 180° relative twist, such that the Brillouin zone of one layer is aligned with the time-reversed Brillouin zone of the opposite layer, the resonant tunneling between the layers is suppressed. These findings provide evidence that, in addition to momentum, the spin-valley degree of freedom is also conserved in vertical transport.

Strongly Enhanced Tunneling at Total Charge Neutrality in Double-Bilayer Graphene-WSe_{2} Heterostructures.

We report the experimental observation of strongly enhanced tunneling between graphene bilayers through a WSe_{2} barrier when the graphene bilayers are populated with carriers of opposite polarity and equal density. The enhanced tunneling increases sharply in strength with decreasing temperature, and the tunneling current exhibits a vertical onset as a function of interlayer voltage at a temperature of 1.5 K. The strongly enhanced tunneling at overall neutrality departs markedly from single-particle model calculations that otherwise match the measured tunneling current-voltage characteristics well, and suggests the emergence of a many-body state with condensed interbilayer excitons when electrons and holes of equal densities populate the two layers.

Coherent Interlayer Tunneling and Negative Differential Resistance with High Current Density in Double Bilayer Graphene-WSe2 Heterostructures.

We demonstrate gate-tunable resonant tunneling and negative differential resistance between two rotationally aligned bilayer graphene sheets separated by bilayer WSe2. We observe large interlayer current densities of 2 and 2.5 µA/µm2 and peak-to-valley ratios approaching 4 and 6 at room temperature and 1.5 K, respectively, values that are comparable to epitaxially grown resonant tunneling heterostructures. An excellent agreement between theoretical calculations using a Lorentzian spectral function for the two-dimensional (2D) quasiparticle states, and the experimental data indicates that the interlayer current stems primarily from energy and in-plane momentum conserving 2D-2D tunneling, with minimal contributions from inelastic or non-momentum-conserving tunneling. We demonstrate narrow tunneling resonances with intrinsic half-widths of 4 and 6 meV at 1.5 and 300 K, respectively.

History of sexually transmitted infections (STI).

Sexually transmitted diseases (STD) are as old as mankind and epidemics are mentioned already in the Old Testament. However, the perception of the conditions has changed over the centuries. In ancient times they were taken for an individual punishment for a blasphemic conduct of life or as a consequence of low sanitation and hygiene. In the medieval ages, the relation to sexual activities was recognized, but the diversity of clinical symptoms was seen as variations of one disease, depending on the stage of the disease and the general health condition of the diseased person. In the late 15th and 16th century a presumably "new plague" had been imported to Europe and was rapidly spread by soldiers. Misinterpretations of wrong experiments on the suspected identity of syphilis and gonorrhoea led to nosologic misconceptions in the 17th and early 19th century. The late 19th and beginning of 20st century due to the many achievements in microbiology and chemistry finally took the frightening threat from the STDs, which have terrorized millions of "normal" and "famous" people of all social classes over centuries and has been linked to many scandals. Moreover, the perception of STDs has turned from a "personal stroke of fate" into a collectively important issue of public health.

[The age of Gutenberg is over: a consideration of medical education--past, present and future]. / Gutenberg war gestern: Ein Beitrag zur Ausbildung in der Medizin gestern, heute und morgen.

Education is the basis for reliable medical care and medical progress. Our medical knowledge has increased more in the past 50 years than in the 500 years before. The spatial and human resource capacity of our universities cannot cope with the existing academic structures and needs. Part of the problem can be solved by "blended learning", that is a combination of traditional teaching methods (frontal lectures, courses, bedside teaching) with supplementary web-based e-learning. In addition to conveying a sound basic knowledge, the ability to cope with modern media and prepare for lifelong learning must also be taught. Out of the large number of e-learning platforms for undergraduate students offered in the internet, we present the program DOIT (Dermatology Online with Interactive Technology; http://www.swisdom.org) and the program Dermokrates (http://www.Dermokrates.com) of the German, Austrian and Swiss Dermatological Societies for postgraduate Continuing Medical Education (CME). The biggest obstacle in the implementation of new developments is the stubborn adherence to traditional structures.

Combination of 308-nm xenon chloride excimer laser and topical calcipotriol in vitiligo.

BACKGROUND: A large variety of therapeutic agents are being used for the treatment of vitiligo, but treatment remains a challenge. Recently, monochromatic phototherapies such as 311-nm narrowband ultraviolet B therapy and 308-nm xenon chloride excimer laser have been reported to be an effective and safe therapeutic option in children and adult patients with vitiligo. Single reports stipulate that the addition of topically applied calcipotriol to phototherapy increases its effectiveness. OBJECTIVE: The purpose of the present pilot study was to determine if the addition of topical calcipotriol increases the efficacy of the 308-nm xenon chloride excimer in the treatment of vitiligo. METHODS: Ten patients with vitiligo with essentially bilateral symmetrical lesions were enrolled in this prospective right/left comparative, single-blinded trial conducted over a 15-month period. All patients received 308-nm XeCl excimer laser therapy three times weekly. Calcipotriol ointment (Daivonex) was applied to lesions on one side of the body twice daily. RESULTS: After 24 treatments (8 weeks), nine patients were evaluated. Eight patients showed evidence of repigmentation on both body sides, with no significant difference between the body side treated with calcipotriol and excimer laser and the side treated with excimer laser alone. The mean repigmentation rate was 22.4% (1-37%). CONCLUSION: The addition of calcipotriol ointment to 308-nm xenon chloride excimer laser phototherapy does not significantly enhance its efficacy. Small additive effects must be investigated in a larger trial.

Dacarbazine (DTIC) versus vaccination with autologous peptide-pulsed dendritic cells (DC) in first-line treatment of patients with metastatic melanoma: a randomized phase III trial of the DC study group of the DeCOG.

BACKGROUND: This randomized phase III trial was designed to demonstrate the superiority of autologous peptide-loaded dendritic cell (DC) vaccination over standard dacarbazine (DTIC) chemotherapy in stage IV melanoma patients. PATIENTS AND METHODS: DTIC 850 mg/m2 intravenously was applied in 4-week intervals. DC vaccines loaded with MHC class I and II-restricted peptides were applied subcutaneously at 2-week intervals for the first five vaccinations and every 4 weeks thereafter. The primary study end point was objective response (OR); secondary end points were toxicity, overall (OS) and progression-free survival (PFS). RESULTS: At the time of the first interim analysis 55 patients had been enrolled into the DTIC and 53 into the DC-arm (ITT). OR was low (DTIC: 5.5%, DC: 3.8%), but not significantly different in the two arms. The Data Safety & Monitoring Board recommended closure of the study. Unscheduled subset analyses revealed that patients with normal serum LDH and/or stage M1a/b survived longer in both arms than those with elevated serum LDH and/or stage M1c. Only in the DC-arm did those patients with (i) an initial unimpaired general health status (Karnofsky = 100) or (ii) an HLA-A2+/HLA-B44- haplotype survive significantly longer than patients with a Karnofsky index <100 (P = 0.007 versus P = 0.057 in the DTIC-arm) or other HLA haplotypes (P = 0.04 versus P = 0.57 in DTIC-treated patients). CONCLUSIONS: DC vaccination could not be demonstrated to be more effective than DTIC chemotherapy in stage IV melanoma patients. The observed association of overall performance status and HLA haplotype with overall survival for patients treated by DC vaccination should be tested in future trials employing DC vaccines.

HLA-G expression in basal cell carcinomas of the skin recurring after radiotherapy.

Basal cell carcinoma (BCC) of the skin represents the most common malignancy in the fair-skinned population worldwide. HLA-G is one of the molecules implicated in immunotolerance. To investigate the role of HLA-G in recurring BCCs, we constructed a tissue microarray containing 38 primary BCCs that underwent radiotherapy and 14 secondary BCCs recurring on the primary site after radiotherapy, and evaluated the HLA-G protein expression by immunohistochemistry. The HLA-G protein was most frequently expressed in aggressive sclerosing BCCs. Nodular BCC demonstrated the strongest HLA-G expression. Interestingly, tumor infiltrating mononuclear cells (TIMC) expressed the HLA-G molecule in BCCs that showed no recurrence. After comparing primary BCCs and BCCs relapsed after radiotherapy, we observed decreased HLA-G expression on tumor cells and the loss of HLA-G expression on TIMC in relapsed BCCs. After radiotherapy, immunobiology of BCC may change resulting in the down-regulation of HLA-G expression on tumor and on tumor-infiltrating cells.

Paraneoplastic pityriasis lichenoides in cutaneous lymphoma: case report and review of the literature on paraneoplastic reactions of the skin in lymphoma and leukaemia.

Paraneoplastic dermatoses are non-neoplastic skin disorders which occur in the context of an underlying malignant neoplasm. The classic paraneoplastic dermatoses are mostly associated with solid internal malignancies. They only rarely occur in the context of nodal or primary cutaneous lymphomas. Apart from these classic paraneoplastic dermatoses, there are additional skin disorders reported to occur in close association with haematological and lymphoproliferative disorders which can thus be regarded as paraneoplastic manifestations. We report for the first time two patients with pityriasis lichenoides et varioliformis acuta in association with mycosis fungoides. In addition, we review the literature on paraneoplastic dermatoses of the skin which have been described in patients with leukaemias and primary cutaneous lymphomas.