Design of feedback insensitive InP ring laser

The optical isolators used to protect semiconductor lasers against optical feedback cannot be integrated. Therefore we propose to fabricate a laser that has a strongly reduced sensitivity to feedback. Simulations show that such a device can be realized by employing a ring laser in which the clockwise and counterclockwise modes are not coupled. To achieve unidirectional lasing, this work proposes to use an intra cavity weak optical isolator based on two phase modulators that are driven 90 degrees out of phase. Simulations show up to 3% of intensity feedback can be tolerated without any distinguishable effect on the laser light

Transverse Fluctuations in an Ising Spin-Glass:Fe0.4Mg0.6Cl2

ac-susceptibility and neutron-diffraction experiments show that Fe0.4Mg0.6Cl2 is a three-dimensional Ising spin-glass with a transition temperature Tsg = 3.4 K. Inelastic-scattering experiments show a sharp spin-wave peak at the zone center for all temperature T~<2Tsg. This is the first direct observation of long-wavelength excitation in a spin-glass system. We suggest that it is due to the precession of spin clusters around the easy axis

Magnetic properties of La(FexAl1–x)13 determined via neutron scattering and Mössbauer spectroscopy

La(FexAl1–x)13 pseudobinary intermetallic compounds, which can be stabilized for 0.46<x <0.92, have been studied by neutron diffraction and Mössbauer spectroscopy. Neutron measurements on an antiferromagnetic x =0.91 sample at 4.2 K reveal a long-range-order antiferromagnetic state, consisting of ferromagnetic clusters, coupled antiferromagnetically. Mössbauer-effect measurements show a drop of the hyperfine field at the Fe nucleus at the ferromagnetic-antiferromagnetic phase boundary x ~=0.88. Both these microscopic measurements indicate a transition from α-iron-like ferromagnetism to γ-iron-like antiferromagnetism due to the extremely high coordination of Fe atoms

Specific Heat, Susceptibility and High-Field Magnetisation Experiments on Heavy Fermion UPt3 Alloyed with Pd

Specific heat, susceptibility and high-field magnetisation experiments have been performed on a number of pseudobinary U(Pt1-xPdx)3 compounds with x ≤ 0.30. For low Pd concentrations (x ≤ 0.10) the spin-fluctuation contribution to the specific heat is enhanced with respect to pure UPt3. For x ≥ 0.15 the spin-fluctuation phenomena are lost. On alloying, the anomalies present for UPt3 in the susceptibility at 17 K and in the high-field magnetisation at 21 T (at 4.2 K), shift towards lower temperatures and fields, respectively, and have not been observed in a compound with x = 0.15. Superconductivity has not been found down to 40 mK in a U(Pt0.995Pd0.005)3 sample

Circulating tRNA fragments as a novel biomarker class to distinguish acute stroke subtypes

Early blood biomarkers to diagnose acute stroke could drastically reduce treatment delays. We investigated whether circulating small non-coding RNAs can serve as biomarkers to distinguish between acute ischemic stroke (IS), intracerebral hemorrhage (ICH) and stroke mimics (SM). In an ongoing observational cohort study, we performed small RNA-sequencing in plasma obtained from a discovery cohort of 26 patients (9 IS, 8 ICH and 9 SM) presented to the emergency department within 6 h of symptom onset. We validated our results in an independent dataset of 20 IS patients and 20 healthy controls. ICH plasma had the highest abundance of ribosomal and tRNA-derived fragments, while microRNAs were most abundant in plasma of IS patients. Combinations of four to five tRNAs yielded diagnostic accuracies (areas under the receiver operating characteristics curve) up to 0.986 (ICH vs. IS and SM) in the discovery cohort. Validation of the IS and SM models in the independent dataset yielded diagnostic accuracies of 0.870 and 0.885 to distinguish IS from healthy controls. Thus, we identified tRNA-derived fragments as a promising novel class of biomarkers to distinguish between acute IS, ICH and SM, as well as healthy controls.Development and application of statistical models for medical scientific researc

Superconducting and Magnetic Transitions in the Heavy-Fermion System URu2Si2

The intermetallic compound URu2Si2 can be classified as a heavy-fermion system because of its large linear specific-heat coefficient γ=180 mJ/mol·K2. Susceptibility, magnetization, and specific-heat measurements on single-crystal samples indicate both a magnetic phase transition at 17.5 K and a superconducting transition at 0.8 K. The magnetic and superconducting properties are highly anisotropic

Electron-phonon interaction in C70

The matrix elements of the deformation potential of C$_{70}$ are calculated by means of a simple, yet accurate solution of the electron-phonon coupling problem in fullerenes, based on a parametrization of the ground state electronic density of the system in terms of $sp^{2+x}$ hybridized orbitals. The value of the calculated dimensionless total electron-phonon coupling constant is $\lambda\approx0.1$, an order of magnitude smaller than in C$_{60}$, consistent with the lack of a superconducting phase transition in C$_{70}$A$_3$ fullerite, and in overall agreement with measurements of the broadening of Raman peaks in C$_{70}$K$_4$. We also calculate the photoemission cross section of C$_{70}^-$, which is found to display less structure than that associated with C$_{60}^-$, in overall agreement with the experimental findings.Comment: To be published in Phys. Rev.