Synchronization of Hamiltonian motion and dissipative effects in optical lattices: Evidence for a stochastic resonance

We theoretically study the influence of the noise strength on the excitation of the Brillouin propagation modes in a dissipative optical lattice. We show that the excitation has a resonant behavior for a specific amount of noise corresponding to the precise synchronization of the Hamiltonian motion on the optical potential surfaces and the dissipative effects associated with optical pumping in the lattice. This corresponds to the phenomenon of stochastic resonance. Our results are obtained by numerical simulations and correspond to the analysis of microscopic quantities (atomic spatial distributions) as well as macroscopic quantities (enhancement of spatial diffusion and pump-probe spectra). We also present a simple analytical model in excellent agreement with the simulations

Brillouin propagation modes in optical lattices: Interpretation in terms of nonconventional stochastic resonance

We report the first direct observation of Brillouin-like propagation modes in a dissipative periodic optical lattice. This has been done by observing a resonant behavior of the spatial diffusion coefficient in the direction corresponding to the propagation mode with the phase velocity of the moving intensity modulation used to excite these propagation modes. Furthermore, we show theoretically that the amplitude of the Brillouin mode is a nonmonotonic function of the strength of the noise corresponding to the optical pumping, and discuss this behavior in terms of nonconventional stochastic resonance

Vortex Pinball Under Crossed AC Drives in Superconductors with Periodic Pinning Arrays

Vortices driven with both a transverse and a longitudinal AC drive which are out of phase are shown to exhibit a novel commensuration-incommensuration effect when interacting with periodic substrates. For different AC driving parameters, the motion of the vortices forms commensurate orbits with the periodicity of the pinning array. When the commensurate orbits are present, there is a finite DC critical depinning threshold, while for the incommensurate phases the vortices are delocalized and the DC depinning threshold is absent.Comment: 4 pages, 4 postscript figure

Spinor Bosonic Atoms in Optical Lattices: Symmetry Breaking and Fractionalization

We study superfluid and Mott insulator phases of cold spin-1 Bose atoms with antiferromagnetic interactions in an optical lattice, including a usual polar condensate phase, a condensate of singlet pairs, a crystal spin nematic phase, and a spin singlet crystal phase. We suggest a possibility of exotic fractionalized phases of spinor BEC and discuss them in the language of topological defect condensation and $Z_2$ lattice gauge theory.Comment: 4 pages, 1 figure included; references adde

Atomic collision dynamics in optical lattices

We simulate collisions between two atoms, which move in an optical lattice under the dipole-dipole interaction. The model describes simultaneously the two basic dynamical processes, namely the Sisyphus cooling of single atoms, and the light-induced inelastic collisions between them. We consider the J=1/2 -> J=3/2 laser cooling transition for Cs, Rb and Na. We find that the hotter atoms in a thermal sample are selectively lost or heated by the collisions, which modifies the steady state distribution of atomic velocities, reminiscent of the evaporative cooling process.Comment: 17 pages, 15 figure

Resting-state functional MRI in multicenter studies on multiple sclerosis: a report on raw data quality and functional connectivity features from the Italian Neuroimaging Network Initiative

The Italian Neuroimaging Network Initiative (INNI) is an expanding repository of brain MRI data from multiple sclerosis (MS) patients recruited at four Italian MRI research sites. We describe the raw data quality of resting-state functional MRI (RS-fMRI) time-series in INNI and the inter-site variability in functional connectivity (FC) features after unified automated data preprocessing. MRI datasets from 489 MS patients and 246 healthy control (HC) subjects were retrieved from the INNI database. Raw data quality metrics included temporal signal-to-noise ratio (tSNR), spatial smoothness (FWHM), framewise displacement (FD), and differential variation in signals (DVARS). Automated preprocessing integrated white-matter lesion segmentation (SAMSEG) into a standard fMRI pipeline (fMRIPrep). FC features were calculated on pre-processed data and harmonized between sites (Combat) prior to assessing general MS-related alterations. Across centers (both groups), median tSNR and FWHM ranged from 47 to 84 and from 2.0 to 2.5, and median FD and DVARS ranged from 0.08 to 0.24 and from 1.06 to 1.22. After preprocessing, only global FC-related features were significantly correlated with FD or DVARS. Across large-scale networks, age/sex/FD-adjusted and harmonized FC features exhibited both inter-site and site-specific inter-group effects. Significant general reductions were obtained for somatomotor and limbic networks in MS patients (vs. HC). The implemented procedures provide technical information on raw data quality and outcome of fully automated preprocessing that might serve as reference in future RS-fMRI studies within INNI. The unified pipeline introduced little bias across sites and appears suitable for multisite FC analyses on harmonized network estimates

Intratumoral CRH modulates immuno-escape of ovarian cancer cells through FasL regulation

Although corticotropin-releasing hormone (CRH) and Fas ligand (FasL) have been documented in ovarian carcinoma, a clear association with tumour progression and immuno-escape has not been established. FasL plays an important role in promoting tumour cells' ability to counterattack immune cells. Here, we examined immunohistochemically the expression of CRH, CRHR1, CRHR2 and FasL in 47 human ovarian cancer cases. The ovarian cancer cell lines OvCa3 and A2780 were further used to test the hypothesis that CRH might contribute to the immune privilege of ovarian tumours, by modulating FasL expression on the cancer cells. We found that CRH, CRHR1, CRHR2 and FasL were expressed in 68.1, 70.2, 63.8 and 63.8% of the cases respectively. Positivity for CRH or FasL expression was associated with higher tumour stage. Finally, CRH increased the expression of FasL in OvCa3 and A2780 cells through CRHR1 thereby potentiated their ability to induce apoptosis of activated peripheral blood lymphocytes. Corticotropin-releasing hormone produced by human ovarian cancer might favour survival and progression of the tumour by promoting its immune privilege. These findings support the hypothesis that CRHR1 antagonists could potentially be used against ovarian cancer

The impact of pre‐operative intravenous iron on quality of life after colorectal cancer surgery: outcomes from the intravenous iron in colorectal cancer‐associated anaemia (IVICA) trial

Anaemia is associated with a reduction in quality of life, and is common in patients with colorectal cancer . Werecently reported thefindings of the intravenous iron in colorectal cancer-associated anaemia (IVICA) trialcomparing haemoglobin levels and transfusion requirements following intravenous or oral iron replacement inanaemic colorectal cancer patients undergoing elective surgery. In this follow-up study, we compared theefficacy of intravenous and oral iron at improving quality of life in this patient group. We conducted amulticentre, open-label randomised controlled trial. Anaemic colorectal cancer patients were randomlyallocated at least two weeks pre-operatively, to receive either oral (ferrous sulphate) or intravenous (ferriccarboxymaltose) iron. We assessed haemoglobin and quality of life scores at recruitment, immediately beforesurgery and at outpatient review approximately three months postoperatively, using the Short Form 36,EuroQoL 5-dimension 5-level and Functional Assessment of Cancer Therapy–Anaemia questionnaires. Werecruited 116 anaemic patients across seven UK centres (oral iron n=61 (53%), and intravenous iron n=55(47%)). Eleven quality of life components increased by a clinically significant margin in the intravenous irongroup between recruitment and surgery compared with one component for oral iron. Median (IQR [range])visual analogue scores were significantly higher with intravenous iron at a three month outpatient review (oraliron 70, (60–85 [20–95]); intravenous iron 90 (80–90 [50–100]), p=0.001). The Functional Assessment ofCancer Therapy–Anaemia score comprises of subscales related to cancer, fatigue and non-fatigue itemsrelevant to anaemia. Median outpatient scores were higher, and hence favourable, for intravenous iron on theFunctional Assessment of Cancer Therapy–Anaemia subscale (oral iron 66 (55–72 [23–80]); intravenous iron 71(66–77 [46–80]); p=0.002), Functional Assessment of Cancer Therapy–Anaemia trial outcome index (oral iron108 (90–123 [35–135]); intravenous iron 121 (113–124 [81–135]); p=0.003) and Functional Assessment ofCancer Therapy–Anaemia total score (oral iron 151 (132–170 [69–183]); intravenous iron 168 (160–174 [125–186]); p=0.005). Thesefindings indicate that intravenous iron is more efficacious at improving quality of lifescores than oral iron in anaemic colorectal cancer patients

Cold bosonic atoms in optical lattices

The dynamics of an ultracold dilute gas of bosonic atoms in an optical lattice can be described by a Bose-Hubbard model where the system parameters are controlled by laser light. We study the continuous (zero temperature) quantum phase transition from the superfluid to the Mott insulator phase induced by varying the depth of the optical potential, where the Mott insulator phase corresponds to a commensurate filling of the lattice (``optical crystal''). Examples for formation of Mott structures in optical lattices with a superimposed harmonic trap, and in optical superlattices are presented.Comment: 4 pages 4 figures New: added references; Postscript version available at: http://th-physics.uibk.ac.at/zoller/Publications/PZListOfPublications.htm