Gapped Heisenberg spin chains in a field

We consider the fully anisotropic Heisenberg spin-1/2 antiferromagnet in a uniform magnetic field, whose ground-state is characterized by broken spin rotation symmetry and gapped spinon excitations. We expand on a recent mean-field approach to the problem by incorporating fluctuations in a loop expansion. Quantitative results for the magnetization, excitation gap and specific heat are obtained. We compare our predictions with new DMRG and exact diagonalization data and, for zero field, with the exact solution of the ${XYZ}$ spin chain from the Bethe Ansatz.Comment: 11 pages, 14 figure

Order to disorder transition in the XY-like quantum magnet Cs2CoCl4 induced by noncommuting applied fields

We explore the effects of noncommuting applied fields on the ground-state ordering of the quasi-one-dimensional spin-1/2 XY-like antiferromagnet Cs2CoCl4 using single-crystal neutron diffraction. In zero field interchain couplings cause long-range order below T_N=217(5) mK with chains ordered antiferromagnetically along their length and moments confined to the (b,c) plane. Magnetic fields applied at an angle to the XY planes are found to initially stabilize the order by promoting a spin-flop phase with an increased perpendicular antiferromagnetic moment. In higher fields the antiferromagnetic order becomes unstable and a transition occurs to a phase with no long-range order in the (b,c) plane, proposed to be a spin liquid phase that arises when the quantum fluctuations induced by the noncommuting field become strong enough to overcome ordering tendencies. Magnetization measurements confirm that saturation occurs at much higher fields and that the proposed spin-liquid state exists in the region 2.10 < H_SL < 2.52 T || a. The observed phase diagram is discussed in terms of known results on XY-like chains in coexisting longitudinal and transverse fields.Comment: revtex, 14 figures, 2 tables, to appear in Phys. Rev.

Feasibility of a V-Shaped Magnet Rotor to Convert Vibration into Rotation

Majority of the reported kinetic energy harvesting mechanisms involve translatory transduction mechanisms, which diverges from the long established rotary design for electromagnetic generators. A rotary design can offer a much smaller magnet-coil air gap and clearance guidance that translatory transducers simply cannot physically attain. Therefore, this research investigates the feasibility of implementing a V-shaped magnet rotor for the purpose of coupling base point excitation into rotation, which can eventually be coupled to a generator motor. It was also previously theorised that the nonlinear magnetic coupling can give rise to broadband nonlinear resonant behaviour. The resultant device aims to enhance the overall power conversion efficiency of the captured vibration energy

Anisotropic Quantum Spin Chains

We have studied two models for anisotropic quantum spin chains. (i) XY‐chain with a field in the plane: The magnetization of the ferromagnet behaves as h1/3 for small fields, in agreement with scaling laws. The antiferromagnet shows a critical field at which the ground state is a simple Néel state and which separates power law from exponential decay of spatial correlations. (ii) Anisotropic XY‐chain: The dynamic z‐component spin correlation function can be decomposed into a spin wave and a soliton contribution. The nature of quantum soliton excitations is studied and their form compared to soliton solutions of classical equations of motion

Quasi-one-dimensional anisotropic Heisenberg model in a transverse magnetic field

The phase diagram of weakly coupled $XXZ$ chains in a transverse magnetic field is studied using the mean-field approximation for the interchain coupling and known exact results for an effective one-dimensional model. Results are applied to the quasi-one-dimensional antiferromagnet $Cs_{2}CoCl_{4}$ and the value of interchain interaction in this compound is estimated.Comment: 4 pages, 2 figure

Finite-Size Scaling and Universality in the Spin 1 Quantum XY Chain

The spin-1 XY chain in a transverse field is studied using finite-size scaling. The ground state phase diagram displays a paramagnetic, an ordered ferromagnetic and an ordered oscillatory phase. The paramagnetic-ferromagnetic transition line belongs to the universality class of the 2D Ising model. Along this line, universality is confirmed for the finite-size scaling functions of several correlation lengths and for the conformal operator content.Comment: Latex 8 pages, 2 uucompressed figure

Articulated Multi-Instrument 2D Pose Estimation Using Fully Convolutional Networks

Instrument detection, pose estimation and tracking in surgical videos is an important vision component for computer assisted interventions. While significant advances have been made in recent years, articulation detection is still a major challenge. In this paper, we propose a deep neural network for articulated multi-instrument 2D pose estimation, which is trained on a detailed annotations of endoscopic and microscopic datasets. Our model is formed by a fully convolutional detection-regression network. Joints and associations between joint pairs in our instrument model are located by the detection subnetwork and are subsequently refined through a regression subnetwork. Based on the output from the model, the poses of the instruments are inferred using maximum bipartite graph matching. Our estimation framework is powered by deep learning techniques without any direct kinematic information from a robot. Our framework is tested on single-instrument RMIT data, and also on multi-instrument EndoVis and in vivo data with promising results. In addition, the dataset annotations are publicly released along with our code and model

Quantum renormalization group of XYZ model in a transverse magnetic field

We have studied the zero temperature phase diagram of XYZ model in the presence of transverse magnetic field. We show that small anisotropy (0 =< Delta <1) is not relevant to change the universality class. The phase diagram consists of two antiferromagnetic ordering and a paramagnetic phases. We have obtained the critical exponents, fixed points and running of coupling constants by implementing the standard quantum renormalization group. The continuous phase transition from antiferromagnetic (spin-flop) phase to a paramagnetic one is in the universality class of Ising model in transverse field. Numerical exact diagonalization has been done to justify our results. We have also addressed on the application of our findings to the recent experiments on Cs_2CoCl_4.Comment: 5 pages, 5 figures, new references added to the present versio

Psychotherapie für alle?: Zur Indikation für psychotherapeutische Behandlungen

Zusammenfassung: Hintergrund: Die Wirksamkeit der Psychotherapie zur Behandlung der meisten psychischen Störungen ist empirisch sehr überzeugend belegt. Es gibt aber weltweit bei weitem nicht genügend Therapeuten, um alle Menschen mit psychischen Erkrankungen angemessen psychotherapeutisch behandeln zu können. Fragestellung und Methodik: Es werden Überlegungen zu der Frage dargestellt, welche Krankheiten, Störungen oder Probleme generell psychotherapeutisch behandelt werden sollen, wer diese Behandlungen am besten durchführt und wie die Dissemination evidenzbasierter Ansätze trotz knapper Ressourcen verbessert werden kann. Ergebnisse: Je schwerer eine Gesundheitsstörung ausgeprägt ist, umso höher ist in aller Regel auch der therapeutische Nutzen einer Intervention. Das gilt auch für die Psychotherapie. Aber gerade die schwer kranken Menschen werden heute oft nicht mit wirksamen psychotherapeutischen Interventionen behandelt. Ein Grund hierfür ist, dass es wenig validierte Therapiekonzepte für multimorbide Patienten mit psychischen und somatischen Erkrankungen gibt. Ein weiterer Grund besteht darin, dass deren Behandlung ein spezifisches medizinisches Wissen sowie weitere spezielle Fähigkeiten und Erfahrungen erfordert, die bei weitem nicht alle Psychotherapeuten besitzen. Schlussfolgerungen: Die Indikation zur Psychotherapie soll immer sorgsam, mit Augenmaß, unter Berücksichtigung der verfügbaren wissenschaftlichen Evidenz und klinischer Erfahrungswerte gestellt werden. Zukünftig sollten sich die Ausbildung von Psychotherapeuten, die wissenschaftlichen Untersuchungen von Psychotherapien und die klinischen Angebote verstärkt auf Patienten mit schweren psychischen Störungen und/oder mit psychischen und somatischen Komorbiditäten konzentrieren

EEG synchronization measures are early outcome predictors in comatose patients after cardiac arrest.

Outcome prognostication in comatose patients after cardiac arrest (CA) remains a major challenge. Here we investigated the prognostic value of combinations of linear and non-linear bivariate EEG synchronization measures. 94 comatose patients with EEG within 24h after CA were included. Clinical outcome was assessed at 3months using the Cerebral Performance Categories (CPC). EEG synchronization between the left and right parasagittal, and between the frontal and parietal brain regions was assessed with 4 different quantitative measures (delta power asymmetry, cross-correlation, mutual information, and transfer entropy). 2/3 of patients were used to assess the predictive power of all possible combinations of these eight features (4 measures×2 directions) using cross-validation. The predictive power of the best combination was tested on the remaining 1/3 of patients. The best combination for prognostication consisted of 4 of the 8 features, and contained linear and non-linear measures. Predictive power for poor outcome (CPC 3-5), measured with the area under the ROC curve, was 0.84 during cross-validation, and 0.81 on the test set. At specificity of 1.0 the sensitivity was 0.54, and the accuracy 0.81. Combinations of EEG synchronization measures can contribute to early prognostication after CA. In particular, combining linear and non-linear measures is important for good predictive power. Quantitative methods might increase the prognostic yield of currently used multi-modal approaches