Spin dynamics in a two dimensional quantum gas

We have investigated spin dynamics in a 2D quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimposed angular density modulations. The density distributions depend on the applied magnetic field and are well explained by a simple Bogoliubov model. We show that the two clouds are anti-correlated in momentum space. The observed momentum correlations pave the way towards the creation of an atom source with non-local Einstein-Podolsky-Rosen entanglement.Comment: 5 pages, 4 figure

Spontaneous symmetry breaking in spinor Bose-Einstein condensates

We present an analytical model for the theoretical analysis of spin dynamics and spontaneous symmetry breaking in a spinor Bose-Einstein condensate (BEC). This allows for an excellent intuitive understanding of the processes and provides good quantitative agreement with experimental results in Phys. Rev. Lett. 105, 135302 (2010). It is shown that the dynamics of a spinor BEC initially prepared in an unstable Zeeman state mF=0 (|0>) can be understood by approximating the effective trapping potential for the state |+-1> with a cylindrical box potential. The resonances in the creation efficiency of these atom pairs can be traced back to excitation modes of this confinement. The understanding of these excitation modes allows for a detailed characterization of the symmetry breaking mechanism, showing how a twofold spontaneous breaking of spatial and spin symmetry can occur. In addition a detailed account of the experimental methods for the preparation and analysis of spinor quantum gases is given.Comment: 12 pages, 14 figure

Parametric amplification of matter waves in dipolar spinor Bose-Einstein condensates

Spin-changing collisions may lead under proper conditions to the parametric amplification of matter waves in spinor Bose-Einstein condensates. Magnetic dipole-dipole interactions, although typically very weak in alkalimetal atoms, are shown to play a very relevant role in the amplification process. We show that these interactions may lead to a strong dependence of the amplification dynamics on the angle between the trap axis and the magnetic-field orientation. We analyze as well the important role played by magnetic-field gradients, which also modify strongly the amplification process. Magnetic-field gradients, hence, must be carefully controlled in future experiments, in order to observe clearly the effects of the dipolar interactions in the amplification dynamics. © 2010 The American Physical Society.DFG/SFB/407DFG/EXC/QUESTESF/EuroQUASA

Turbulence and its parameterization in accretion discs

Accretion disc turbulence is investigated in the framework of the shearing box approximation. The turbulence is either driven by the magneto-rotational instability or, in the non-magnetic case, by an explicit and artificial forcing term in the momentum equation. Unlike the magnetic case, where most of the dissipation occurs in the disc corona, in the forced hydrodynamic case most of the dissipation occurs near the midplane. In the hydrodynamic case evidence is presented for the stochastic excitation of epicycles. When the vertical and radial epicyclic frequencies are different (modeling the properties around rotating black holes), the beat frequency between these two frequencies appear to show up as a peak in the temporal power spectrum in some cases. Finally, the full turbulent resistivity tensor is determined and it is found that, if the turbulence is driven by a forcing term, the signs of its off-diagonal components are such that this effect would not be capable of dynamo action by the shear--current effect.Comment: 11 pages, 11 figure

Somatic alpha-synuclein mutations in Parkinson's disease: Hypothesis and preliminary data.

Alpha-synuclein (SNCA) is crucial in the pathogenesis of Parkinson's disease (PD), yet mutations in the SNCA gene are rare. Evidence for somatic genetic variation in normal humans, also involving the brain, is increasing, but its role in disease is unknown. Somatic SNCA mutations, arising in early development and leading to mosaicism, could contribute to PD pathogenesis and yet be absent or undetectable in DNA derived from peripheral lymphocytes. Such mutations could underlie the widespread pathology in PD, with the precise clinical outcome dependent on their type and the timing and location of their occurrence. We recently reported a novel SNCA mutation (c.150T>G, p.H50Q) in PD brain-derived DNA. To determine if there was mosaicism for this, a PCR and cloning strategy was used to take advantage of a nearby heterozygous intronic polymorphism. No evidence of mosaicism was found. High-resolution melting curve analysis of SNCA coding exons, which was shown to be sensitive enough to detect low proportions of 2 known mutations, did not reveal any further mutations in DNA from 28 PD brain-derived samples. We outline the grounds that make the somatic SNCA mutation hypothesis consistent with genetic, embryological, and pathological data. Further studies of brain-derived DNA are warranted and should include DNA from multiple regions and methods for detecting other types of genomic variation. © 2013 Movement Disorder Society

Understanding the complex needs of automotive training at final assembly lines

Automobile final assembly operators must be highly skilled to succeed in a low automation environment where multiple variants must be assembled in quick succession. This paper presents formal user studies conducted at OPEL and VOLVO Group to identify assembly training needs and a subset of requirements; and to explore potential features of a hypothetical game-based virtual training system. Stakeholder analysis, timeline analysis, link analysis, Hierarchical Task Analysis and thematic content analysis were used to analyse the results of interviews with various stakeholders (17 and 28 participants at OPEL and VOLVO, respectively). The results show that there is a strong case for the implementation of virtual training for assembly tasks. However, it was also revealed that stakeholders would prefer to use a virtual training to complement, rather than replace, training on pre-series vehicles

Ultrafast transient absorption spectroscopy: principles and application to photosynthetic systems

The photophysical and photochemical reactions, after light absorption by a photosynthetic pigment–protein complex, are among the fastest events in biology, taking place on timescales ranging from tens of femtoseconds to a few nanoseconds. The advent of ultrafast laser systems that produce pulses with femtosecond duration opened up a new area of research and enabled investigation of these photophysical and photochemical reactions in real time. Here, we provide a basic description of the ultrafast transient absorption technique, the laser and wavelength-conversion equipment, the transient absorption setup, and the collection of transient absorption data. Recent applications of ultrafast transient absorption spectroscopy on systems with increasing degree of complexity, from biomimetic light-harvesting systems to natural light-harvesting antennas, are presented. In particular, we will discuss, in this educational review, how a molecular understanding of the light-harvesting and photoprotective functions of carotenoids in photosynthesis is accomplished through the application of ultrafast transient absorption spectroscopy

A quality oriented approach towards information requirement determination in equivocal situations

Analysis of users’ needs is one of the key determinants of any system’s success and the foundation of requirement determination process. Yet because of the complexity of human’s needs, the process of requirement determination for developing systems to meet human’s needs is often ad hoc and poorly understood (Browne & Ramesh, 2002). Poor execution of Information Requirement Determination (IRD) will almost guarantee the failure of the final project, as a result a significant portion of requirement determination activities are dedicated to determining users’ information level requirements (Hickey & Davis, 2004) which in this study is referred to as IRD. There is no commonly accepted IRD method for all situations and therefore IRD methods are leaning toward specialised methods, designed for specific contexts and situations (Siau & Rossi, 2011). However a significant proportion of IRD literature is focused on organisational context while there are other complex contexts which require researchers’ attention. One such situations for which no specialised IRD method could be found in the literature is the context of “Individual Decision Making in Equivocal Situations (IDMES)” which in this study is defined as: Contexts in which an individual should make important decisions in complex and equivocal situations he/she is not an expert in. Examples of IDMES could be identified in healthcare where a patient who is not a trained healthcare professional has to choose between several available treatments for a serious health problem. Complexity of decisions a patient needs to make is comparable to the complex decisions that a manager must make in an organisation. The differentiation is that patients are not healthcare specialists but managers are specialists of the area in which they make decisions. In such situations providing higher amount of information to users may actually increase the uncertainty they face (e.g. overloading a patient with information). Therefore, in developing information systems for supporting decision making in such contexts, extra attention should be paid to determining other characteristics of users’ information needs, namely: quality and source. To establish a theoretical foundation for the IRD method required in this context, a conceptual model labelled as Quality Requirement Determination (QRD) model has been generated in this study. To develop the QRD model, two concepts of Information Quality (IQ) and Information Seeking Behaviour (ISB) have been leveraged. Although both IQ and ISB are mature topics, their applications in IRD methods are not very well studied (Gharib & Giorgini, 2015; Savolainen, 2007, 2008; Sonnenwald, Wildemuth, & Harmon, 2001). To evaluate the QRD model, it has been applied to the case of parenting children with autism. This case has been selected because it meets all the characteristics of IDMES, namely because: 1) autism cause and cure are unknown and therefore selecting from the array of available interventions “is a nightmare for desperate parents” (Crawford, 2013, p. 53). 2) Parents must individually make decisions in a context in which they are not trained experts even though over time they develop a certain level of practical experience. Seventeen parents were interviewed about their information seeking behaviours when they needed to decide on interventions necessary for a specific problem. The results of the data analysis confirm the existence of the relationships between perceived information needs, source preference behaviour and quality requirements proposed in the QRD model. The information requirements which arose from the case of parenting children with autism is embodied in the QRD presentation matrix. It leverages a nine cell matrix with each cell representing a cognitive role played by the information sources in the users’ information horizon1 . The QRD presentation matrix along with the QRD model and associated data collection and analysis techniques are called QRD method. To evaluate the usability of determined information by the QRD method, results of an instrumental case study were presented to a group of IS practitioners. The selected IS practitioners have been chosen from variety of expertise involved in developing information systems to reflect the maximum variety of opinions. The interview results demonstrated the value of the QRD method for a number of key practical activities in the IRD process, namely: context study, problem definition, quality requirement analysis, quality implementation, designing information flow and user interface design

Type 1 Autoimmune Pancreatitis in Europe: Clinical Profile and Response to Treatment.

Background and aimsAutoimmune pancreatitis (AIP) is an immune-mediated disease of the pancreas with distinct pathophysiology and manifestations. Our aims were to characterize type 1 AIP in a large pan-European cohort and study the effectiveness of current treatment regimens.MethodsWe retrospectively analyzed adults diagnosed since 2005 with type 1 or not-otherwise-specified AIP in 42 European university hospitals. Type 1 AIP was uniformly diagnosed using specific diagnostic criteria. Patients with type 2 AIP and those who had undergone pancreatic surgery were excluded. The primary endpoint was complete remission, defined as the absence of clinical symptoms and resolution of the index radiological pancreatic abnormalities attributed to AIP.ResultsWe included 735 individuals with AIP (69% male; median age 57 years; 85% White). Steroid treatment was started in 634 patients, of whom 9 (1%) were lost to follow-up. The remaining 625 had a 79% (496/625) complete, 18% (111/625) partial, and 97% (607/625) cumulative remission rate, while 3% (18/625) did not achieve remission. No treatment was given in 95 patients, who had a 61% complete (58/95), 19% partial (18/95), and 80% cumulative (76/95) spontaneous remission rate. Higher (≥0.4 mg/kg/day) corticosteroid doses were no more effective than lower ( 2 weeks (OR 0.908; 95%CI 0.818-1.009). Elevated IgG4 levels were independently associated with a decreased chance of complete remission (OR 0.639; 95%CI 0.427-0.955). Relapse occurred in 30% of patients. Relapses within 6 months of remission induction were independent of the steroid tapering duration, induction treatment duration, and total cumulative dose.ConclusionPatients with type 1 AIP and elevated IgG4 level may need closer monitoring. For remission induction, a starting dose of 0.4 mg/kg/day for 2 weeks followed by a short taper period seems effective. This study provides no evidence to support more aggressive regimens