Feedback-enhanced algorithm for aberration correction of holographic atom traps

We show that a phase-only spatial light modulator can be used to generate non-trivial light distributions suitable for trapping ultracold atoms, when the hologram calculation is included within a simple and robust feedback loop that corrects for imperfect device response and optical aberrations. This correction reduces the discrepancy between target and experimental light distribution to the level of a few percent (RMS error). We prove the generality of this algorithm by applying it to a variety of target light distributions of relevance for cold atomic physics.Comment: 5 pages, 4 figure

Topics in Geophysical Fluid Dynamics: I. Natural Convection in Shallow Cavities. II. Studies of a Phenomenological Turbulence Model

Part I The problem of natural convection in a cavity of small aspect ratio with differentially heated end walls is considered. It is shown by use of matched asymptotic expansions that the flow consists of two distinct regimes: a parallel flow in the core region and a second, non-parallel flow near the ends of the cavity. An analytical solution valid at all orders in the aspect ratio, A, is found for the core region, while the first several terms of the appropriate asymptotic expansion are obtained for the end regions. Parametric limits of validity for the parallel flow structure are discussed. Asymptotic expressions for the Nusselt number and the single free parameter of the parallel flow solution, valid in the limit as A → O, are derived. Also presented are numerical solutions of the full Navier-Stokes equations, which cover the parameter range Pr = 6.983, 10 ≤ Gr ≤ 2 X 10⁴ and 0.05 ≤ A ≤ 1. A comparison with the asymptotic theory shows excellent agreement between the analytical and numerical solutions provided that A ≾ 0.1 and Gr²Pr²A³ ~ 10⁵. In addition, the numerical solutions demonstrate the transition between the shallow-cavity limit and the boundary-layer limit, A fixed Gr → ∞. Finally, the effect of upper surface boundary conditions on the flow structure within differentially heated shallow cavities is examined. Matched asymptotic solutions, valid for small cavity aspect ratios are presented for the cases of uniform shear stress with zero heat flux, uniform heat flux with zero shear stress, and a heat flux linearly dependent on surface temperature with zero shear stress. It is shown that these changes in surface boundary conditions have an important influence on temperature and flow structure within the cavity. Part II The rational closure technique proposed by Lumley and Khajeh-Nouri (1974), in which each unknown correlation is represented as an expansion about the homogeneous, isotropic state, is applied to the approximate closure of the mean Reynolds stress tensor, and rate of dissipation equations for turbulent flows. The high Reynolds number turbulence model which results is similar in many respects to that presented by Lumley et al. However, a more detailed effort is made to evaluate systematically the numerous parameters. Particular emphasis is placed on the suitability and quality of the experimental data which is used for the estimation of model parameters and on the uniqueness and universality of the resulting parameters. A quantitative comparison of the present turbulence model to those proposed by Daly and Harlow (1970), Hanjalic and Launder (1972b), Shir (1973) and Wyngaard, Cote and Rao (1973), indicates that the present model gives the best overall prediction of the dynamic response for the homogeneous flows of Uberoi (1956, 1957), Champagne, Harris and Corrsin (1970) and Tucker and Reynolds (1968). A further comparison, which evaluates the ability of these turbulence models to predict profiles of the triple-velocity correlation, the rate of intercomponent transfer and the rate of turbulence energy dissipation for inhomogeneous flows indicates that, of the previous turbulence models, that of Hanjalic and Launder is most consistent with the data examined. However, the present model shows promise to yield an even better approximation to the experimental data.</p

Reviews and bibliographical notices

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PsyCog:A computerised mini battery for assessing cognition in psychosis

Despite the functional impact of cognitive deficit in people with psychosis, objective cognitive assessment is not typically part of routine clinical care. This is partly due to the length of traditional assessments and the need for a highly trained administrator. Brief, automated computerised assessments could help to address this issue. We present data from an evaluation of PsyCog, a computerised, non-verbal, mini battery of cognitive tests. Healthy Control (HC) ( N = 135), Clinical High Risk (CHR) ( N = 233), and First Episode Psychosis (FEP) ( N = 301) participants from a multi-centre prospective study were assessed at baseline, 6 months, and 12 months. PsyCog was used to assess cognitive performance at baseline and at up to two follow-up timepoints. Mean total testing time was 35.95 min (SD = 2.87). Relative to HCs, effect sizes of performance impairments were medium to large in FEP patients (composite score G = 1.21, subtest range = 0.52-0.88) and small to medium in CHR patients (composite score G = 0.59, subtest range = 0.18-0.49). Site effects were minimal, and test-retest reliability of the PsyCog composite was good (ICC = 0.82-0.89), though some practice effects and differences in data completion between groups were found. The present implementation of PsyCog shows it to be a useful tool for assessing cognitive function in people with psychosis. Computerised cognitive assessments have the potential to facilitate the evaluation of cognition in psychosis in both research and in clinical care, though caution should still be taken in terms of implementation and study design. </p

Molecularly Imprinted Polymers for Ochratoxin A Extraction and Analysis

Molecularly imprinted polymers (MIPs) are considered as polymeric materials that mimic the functionality of antibodies. MIPs have been utilized for a wide variety of applications in chromatography, solid phase extraction, immunoassays, and sensor recognition. In this article, recent advances of MIPs for the extraction and analysis of ochratoxins are discussed. Selection of functional monomers to bind ochratoxin A (OTA) with high affinities, optimization of extraction procedures, and limitations of MIPs are compared from different reports. The most relevant examples in the literature are described to clearly show how useful these materials are. Strategies on MIP preparation and schemes of analytical methods are also reviewed in order to suggest the next step that would make better use of MIPs in the field of ochratoxin research. The review ends by outlining the remaining issues and impediments

Negation and the functional sequence

There exists a general restriction on admissible functional sequences which prevents adjacent identical heads. We investigate a particular instantiation of this restriction in the domain of negation. Empirically, it manifests itself as a restriction the stacking of multiple negative morphemes. We propose a principled account of this restriction in terms of the general ban on immediately consecutive identical heads in the functional sequence on the one hand, and the presence of a Neg feature inside negative morphemes on the other hand. The account predicts that the stacking of multiple negative morphemes should be possible provided they are separated by intervening levels of structure. We show that this prediction is borne out

'These Meritorious Objects of the Royal Bounty ...' The administration of the out-pension of the Royal Hospital, Chelsea in the early eighteenth century

This paper explores the establishment and operation of the Chelsea Outpension from 1688 up to 1755. It asks why such rewards for service to the Crown should have been paid to members of the labouring classes distributed across the British Isles, at a time when central government welfare did not exist.It examines the structure and organisation of the Army, with particular emphasis on the recruitment of the Other Ranks, who were the recipients of the pension. It describes the work of soldiering in the early eighteenth century; accounts for the reasons why men reached the conclusion of their military service - whether long or short - and it examines the qualifications that entitled soldiers to a pension or debarred them from it.The process of discharge is rehearsed against the background of statistical examination of length of service and age at discharge along with a major study of the incidence of wounds, illness or injury that terminated soldiers' service.How the pension was paid; what verification procedures were instituted; whether abuses of the system were perpetrated and how it was reformed, occupy the latter part of the narrative. The study concludes with some consideration of the sufficiency of the pension to sustain life and how Out-pensioners managed for the remainder of their days as, mostly elderly and increasingly infirm, civilians.Through this investigation light is shed on concepts such as the 'duty of care' that the State was prepared to adopt in respect of its servants and its willingness and capability to undertake the multitude of tasks required in administering and paying the pension

The Walking Dead: Cross-Channel connections and Funerary Practices c. 1600-1200 BC

Session XXXII-4. Cross-channel connections from the Neolithic to the Bronze AgeInternational audienceThe Middle /early Late Bronze Age (c. 1600-1200 BC) in the cross-channel region is invariably understood through the many close connections evidenced by new metal technologies and object types. These relationships tend to be interpreted as either continuities or developments from Early Bronze Age (c. 2200-1600 BC) cross-channel communities. However, whilst scholarship on the cross-channel connections between Early Bronze Age communities has tended to focus on funerary practices, there been no recent or comparable re-evaluation of cross-channel Middle /Late Bronze Age funerary practices. This paper draws upon a comprehensive dataset of all funerary sites in southern Britain and northern France in order to investigate questions of regionality and the dead