Control of structure and spin texture in the van der Waals layered magnet CrSBr.

Controlling magnetism at nanometer length scales is essential for realizing high-performance spintronic, magneto-electric and topological devices and creating on-demand spin Hamiltonians probing fundamental concepts in physics. Van der Waals (vdW)-bonded layered magnets offer exceptional opportunities for such spin texture engineering. Here, we demonstrate nanoscale structural control in the layered magnet CrSBr with the potential to create spin patterns without the environmental sensitivity that has hindered such manipulations in other vdW magnets. We drive a local phase transformation using an electron beam that moves atoms and exchanges bond directions, effectively creating regions that have vertical vdW layers embedded within the initial horizontally vdW bonded exfoliated flakes. We calculate that the newly formed two-dimensional structure is ferromagnetically ordered in-plane with an energy gap in the visible spectrum, and weak antiferromagnetism between the planes, suggesting possibilities for creating spin textures and quantum magnetic phases.

Prospects and Limitations of Transition Metal Dichalcogenide Laser Gain Materials.

Nanolasers operate with a minimal amount of active material and low losses. In this regime, single layers of transition-metal dichalcogenides (TMDs) are being investigated as next generation gain materials due to their high quantum efficiency. We provide results from microscopic gain calculations of highly excited TMD monolayers and specify requirements to achieve lasing with four commonly used TMD semiconductors. Our approach includes band-structure renormalizations due to excited carriers that trigger a direct-to-indirect band gap transition. As a consequence, we predict a rollover for the gain that limits the excitation regime where laser operation is possible. A parametrization of the peak gain is provided that is used in combination with a rate-equation theory to discuss consequences for experimentally accessible laser characteristics.

Exciton fission in monolayer transition metal dichalcogenide semiconductors.

When electron-hole pairs are excited in a semiconductor, it is a priori not clear if they form a plasma of unbound fermionic particles or a gas of composite bosons called excitons. Usually, the exciton phase is associated with low temperatures. In atomically thin transition metal dichalcogenide semiconductors, excitons are particularly important even at room temperature due to strong Coulomb interaction and a large exciton density of states. Using state-of-the-art many-body theory, we show that the thermodynamic fission-fusion balance of excitons and electron-hole plasma can be efficiently tuned via the dielectric environment as well as charge carrier doping. We propose the observation of these effects by studying exciton satellites in photoemission and tunneling spectroscopy, which present direct solid-state counterparts of high-energy collider experiments on the induced fission of composite particles.

Observation of Exciton Redshift-Blueshift Crossover in Monolayer WS2.

We report a rare atom-like interaction between excitons in monolayer WS2, measured using ultrafast absorption spectroscopy. At increasing excitation density, the exciton resonance energy exhibits a pronounced redshift followed by an anomalous blueshift. Using both material-realistic computation and phenomenological modeling, we attribute this observation to plasma effects and an attraction-repulsion crossover of the exciton-exciton interaction that mimics the Lennard-Jones potential between atoms. Our experiment demonstrates a strong analogy between excitons and atoms with respect to interparticle interaction, which holds promise to pursue the predicted liquid and crystalline phases of excitons in two-dimensional materials.

Electric-Field Switchable Second-Harmonic Generation in Bilayer MoS2 by Inversion Symmetry Breaking.

We demonstrate pronounced electric-field-induced second-harmonic generation in naturally inversion symmetric 2H stacked bilayer MoS2 embedded into microcapacitor devices. By applying strong external electric field perturbations (|F| = ±2.6 MV cm-1) perpendicular to the basal plane of the crystal, we control the inversion symmetry breaking and, hereby, tune the nonlinear conversion efficiency. Strong tunability of the nonlinear response is observed throughout the energy range (Eω ∼ 1.25-1.47 eV) probed by measuring the second-harmonic response at E2ω, spectrally detuned from both the A- and B-exciton resonances. A 60-fold enhancement of the second-order nonlinear signal is obtained for emission at E2ω = 2.49 eV, energetically detuned by ΔE = E2ω - EC = -0.26 eV from the C-resonance (EC = 2.75 eV). The pronounced spectral dependence of the electric-field-induced second-harmonic generation signal reflects the bandstructure and wave function admixture and exhibits particularly strong tunability below the C-resonance, in good agreement with density functional theory calculations. Moreover, we show that the field-induced second-harmonic generation relies on the interlayer coupling in the bilayer. Our findings strongly suggest that the strong tunability of the electric-field-induced second-harmonic generation signal in bilayer transition metal dichalcogenides may find applications in miniaturized electrically switchable nonlinear devices.

Efficient Excitonic Photoluminescence in Direct and Indirect Band Gap Monolayer MoS2.

We discuss the photoluminescence (PL) of semiconducting transition metal dichalcogenides on the basis of experiments and a microscopic theory. The latter connects ab initio calculations of the single-particle states and Coulomb matrix elements with a many-body description of optical emission spectra. For monolayer MoS2, we study the PL efficiency at the excitonic A and B transitions in terms of carrier populations in the band structure and provide a quantitative comparison to an (In)GaAs quantum well-structure. Suppression and enhancement of PL under biaxial strain is quantified in terms of changes in the local extrema of the conduction and valence bands. The large exciton binding energy in MoS2 enables two distinctly different excitation methods: above-band gap excitation and quasi-resonant excitation of excitonic resonances below the single-particle band gap. The latter case creates a nonequilibrium distribution of carriers predominantly in the K-valleys, which leads to strong emission from the A-exciton transition and a visible B-peak even if the band gap is indirect. For above-band gap excitation, we predict a strongly reduced emission intensity at comparable carrier densities and the absence of B-exciton emission. The results agree well with PL measurements performed on monolayer MoS2 at excitation wavelengths of 405 nm (above) and 532 nm (below the band gap).

Influence of excited carriers on the optical and electronic properties of MoS2.

We study the ground-state and finite-density optical response of molybdenum disulfide by solving the semiconductor Bloch equations, using ab initio band structures and Coulomb interaction matrix elements. Spectra for excited carrier densities up to 10(13) cm(-2) reveal a redshift of the excitonic ground-state absorption, whereas higher excitonic lines are found to disappear successively due to Coulomb-induced band gap shrinkage of more than 500 meV and binding-energy reduction. Strain-induced band variations lead to a redshift of the lowest exciton line by ∼110 meV/% and change the direct transition to indirect while maintaining the magnitude of the optical response.

Indirect RT-PCR in-situ hybridization: a novel non-radioactive method for detecting glucose-dependent insulinotropic peptide.

To establish indirect in-situ PCR for the detection of intestinal peptide hormones, rat intestine and a murine intestinal tumor cell line, STC 1, were used. The results exhibited intensive staining of GIP-producing K-cells. Paraformaldehyde-fixed cryostat sections yielded the best results in signal to background ratio with RT-PCR in-situ hybridization. Moreover, it was possible to elevate the positive staining signal and to reduce background staining. Digoxigenin-labeled in-situ hybridization served as a control for specificity and sensitivity of GIP (glucose-dependent insulinotropic peptide) mRNA expression on cryostat as well as paraffin sections. In conclusion, this RT-PCR in-situ hybridization protocol proves to be a specific, sensitive and reliable non-radioactive technique for the detection of intestinal peptide hormone mRNA, especially in tissues or tumor cells where the application of ISH is limited.

Evidence for a role of macrophage migration inhibitory factor in psoriatic skin disease.

Macrophage migration inhibitory factor (MIF) was originally described as a T-cell-derived lymphokine with the potential to inhibit the random migration of macrophages. However, recent reports have shown a much broader tissue distribution, including the skin. Functionally, MIF appears to act as an antagonist of anti-inflammatory glucocorticoid action. To elucidate the role of MIF in inflammatory skin diseases, we investigated the production and localization of this cytokine in human skin of patients with psoriasis by means of reverse transcription-polymerase chain reaction, immunohistochemistry and Western blot analysis. In normal skin, our results showed a moderate but homogeneous MIF immunoreactivity in all epidermal layers. Endothelial cells and the outer root sheath of hair follicles were also positive for MIF. In lesional psoriatic human skin, a significant increase in MIF immunoreactivity was visible in suprabasal keratinocytes, especially of the spinous layer. In addition, endothelial cells also showed increased immunolabelling for MIF in psoriatic lesions, indicating a cell-specific upregulation of this mediator in untreated psoriasis. Western blot analysis also revealed a clear increase in MIF in homogenates of lesional skin from psoriasis patients. These results suggest a role for MIF in the inflammatory skin disease psoriasis.

Identification of pituitary adenylate cyclase activating polypeptide (PACAP) and PACAP type 1 receptor in human skin: expression of PACAP-38 is increased in patients with psoriasis.

Morphological and biochemical evidence is presented for the presence of pituitary adenylate cyclase activating peptide (PACAP) and the high-affinity PACAP-1 receptor subtype in human skin. Immunohistochemical analysis revealed PACAP-immunoreactivity (IR) to be present predominantly in dermal nerve fibers close to the dermal-epidermal border, hair follicles, blood vessels and sweat glands. Radioimmunoassay, chromatographic analysis and Western blotting revealed this PACAP-IR to be PACAP-38 whereas the second molecular form, PACAP-27, is absent. In tissue of psoriasis patients significantly more PACAP-38 protein was detected as compared to normal skin. Using RT-PCR, the expression of a high-affinity PACAP-1 receptor in human skin was observed. These results indicate a possible role for PACAP-38 in inflammatory processes of psoriasis.

Trisomy 3 is not a common feature in malignant lymphomas of mucosa-associated lymphoid tissue type.

The genetic background of extranodal marginal zone B-cell non-Hodgkin's lymphoma (NHL) of mucosa-associated lymphoid tissue (MALT) type is poorly understood. In contrast to most entities of primary nodal lymphomas, few cytogenetic data are available, and gene rearrangements frequently encountered in and highly characteristic of certain entities of systemic NHL are absent in this type of lymphoma. Recently, it was suggested that MALT-type NHLs are associated with certain numerical chromosome aberrations and especially with trisomy 3. We performed an extensive study using a sensitive double (bicolor) fluorescence in situ hybridization technique for the analysis of trisomies for chromosomes 3, 7, 12, and 18 in 60 samples of low-grade and 45 high-grade MALT-type tumors. In the low-grade cases, trisomy 3 was found in a frequency of only 20%. High-grade lymphomas of MALT type were associated with trisomies 3, 7, 12, and 18 in 36, 20, 18, and 13% of the cases, respectively. Whereas no difference was encountered for trisomy 3 in primary and secondary/simultaneous high-grade lymphomas, +7 and +12 were associated with primary lymphomas, and a +18 was predominantly found in secondary/simultaneous high-grade NHL. These results challenge earlier reports describing a high frequency of +3 in low-grade MALT-type NHL and indicate a possibly different genetic evolution pattern of primary and secondary/simultaneous high-grade lymphomas of primary mucosal origin.

[Significance of procarbazine in the chemotherapy of Hodgkin's disease--a report of the Cooperative Therapy Study DAL-HD-85]. / Zur Bedeutung des procarbazins in der Chemo therapie des Morbus Hodgkin--Ein Bericht der Kooperativen Therapiestudie DAL-HD-85.

It was the objective of the DAL study HD-85 to examine the possibility of a reduction of chemotherapy, compared to the study HD-82 which had applied a combined treatment strategy resulting in a relapse rate of only 2.5% after 4 years, and a proportion of intercurrent deaths of 1.5%, in a total of 203 patients. Procarbazine was eliminated in the OPPA-therapy (OPA) and replaced by methotrexate in the COPP-cycles (COMP). Chemotherapy consisted in 2 cycles of OPA for stage I/IIA (group 1), 2 cycles of OPA and 2 cycles of COMP for stage IIB/IIIA (including IEA/IIEA) (group 2), and 2 cycles of OPA and 4 cycles of COMP for stage IIIB/IV (group 3). The subsequent radiotherapy was limited to the initially involved fields, the dosage of 35, 30 or 25 Gy depending on the extent of chemotherapy. Regions showing incomplete tumor regression after chemotherapy received another 5 Gy, in patients of groups 2 and 3. Between Jan. 1985 to Nov. 1986, 103 children with Hodgkin's disease from 42 participating hospitals were enrolled in this study. 98 patients were treated according to protocol (59 boys, 39 girls). A specific strategy for the selective indication of laparotomy and splenectomy was applied. With this strategy no laparotomy was performed in 39/98 patients (40%). 67 patients (68%) retained their spleen. 4 patients showed progression of the disease under chemotherapy, all others achieved remission. 16 patients relapsed before Dec. 31, 1987. So far no child of this study has died.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of doxorubicin in man: dose and schedule dependence.

Doxorubicin serum elimination kinetics were measured by HPLC in three different patient groups. A dose of (a) 30 mg/m2; (b) 50 mg/m2, and (c) 4 x 15 mg/m2 every 10 h was administered by bolus injection to (a) 10, (b) 6, and (c) 8 patients. The results obtained provided strong evidence for a nonlinear dependence of doxorubicin serum elimination on the dose and administration schedule used. Comparing the 15 and 30 mg/m2 dose there was no significant increase in early drug levels but a marked increase in terminal half-life. At doses higher than 30 mg/m2, however, there was a steep increase in early drug levels, too. Moreover a marked cumulation of the anthracycline in the central compartment following short-term (4 x 15 mg/m2 every 10 h) consecutive administration was found. To obtain an optimal concentration x time product by single bolus injection a dose equal or higher than 30 mg/m2 should be used. However, in this dose range a steep dose-dependent rise in early drug levels is to be expected. As early high serum levels correlate with congestive heart failure, administration schedules reaching effective concentration x time products without high peak levels such as continuous infusion or consecutive administration of low doses seem to be necessary.

[ATP-dependent and ATP-independent changes in deformability of human erythrocytes]. / ATP-abhängige und ATP-unabhängige Veränderungen der Deformierbarkeit von Humanerythrozyten.

By means of a simple filtration procedure it is shown that the deformability of red blood cells depends indirectly on their relative ATP-concentration. Losses in deformability were observed even with concentrations of ATP, which occur in the course of normal ageing of red blood cells in situ. If erythrocytes are incubated for longer times, their membrane is alterated to such a degree, that the changes cannot be reversed solely by restitution of ATP. The cells remain rigid.

[Studies of the deformability of preserved red blood cells using a simple filtration method]. / Untersuchungen zur Verformbarkeit roter Blutzellen bei Lagerung mit einem einfachen Filtrationsverfahren.

The applied method to measure the filtrability of red blood cells is accurate enough for the study of the effects of the conditions of storage on their deformability. In this work the standard deviation of the method, the mean biological deviation of the deformability of human red blood cells and their deformability in the course of storage in the ACD-AG-medium have been investigated. Considerable loss of deformability occurs towards the end of storage time of the cells, which is not reversible be restitution of ATP alone. The applicability of this method as a simple test of the vitatity of preserved erythrocytes if to be tested.