Partial synchronisation of stochastic oscillators through hydrodynamic coupling

Holographic optical tweezers are used to construct a static bistable optical potential energy landscape where a Brownian particle experiences restoring forces from two nearby optical traps and undergoes thermally activated transitions between the two energy minima. Hydrodynamic coupling between two such systems results in their partial synchronisation. This is interpreted as an emergence of higher mobility pathways, along which it is easier to overcome barriers to structural rearrangement.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let

Failed contraception?

The frequency, cost and harms of the procedure must have been weighed up by the British National Health Service (NHS) — usually pretty sensible about their medical recommendations — which proposed 3-yearly screening for women aged between 50 and 64 years. Obviously more cancers would be discovered by 2-yearly rather than 3-yearly screening, and yet more by annual screening. Six-monthly screening, in turn, would clearly yield more cancers than annual screening. This would fit well with Dr Whitehorn’s ‘simple arithmetic’. However a balance has to be found between benefits and harms, and we chose the NHS one. The following organised screening programmes recommend 2- yearly mammography, most of them for women between 50 and 69 years: Australia, Finland, Iceland, Israel, Netherlands, France, Belgium, Canada, Denmark, Ireland, Italy, Norway, Portugal and Greece. Annual mammography, and mammography at an early age are the usual recommendations of interest groups. They are also the recommendation of the correspondence printed above. Like Dr Paul Sneider, we conclude with a quote from Boyle: ‘Every woman has a right to participate in an organised screening program . . .’. This right, alas, does not apply to this country, where other health care priorities make an organised programme an impossibility. However, should a woman have the privilege of medical aid, or be able to afford mammography, it is her choice to undergo it, a choice open to only a minority of South Africans. The majority of South African women would, in our opinion, be well served by an organised programme of ‘breast awareness’, a proposal that Dr Russell Whitehorn finds difficult to fathom

An O(N) symmetric extension of the Sine-Gordon Equation

We discuss an O(N) exension of the Sine-Gordon (S-G)equation which allows us to perform an expansion around the leading order in large-N result using Path-Integral methods. In leading order we show our methods agree with the results of a variational calculation at large-N. We discuss the striking differences for a non-polynomial interaction between the form for the effective potential in the Gaussian approximation that one obtains at large-N when compared to the N=1 case. This is in contrast to the case when the classical potential is a polynomial in the field and no such drastic differences occur. We find for our large-N extension of the Sine-Gordon model that the unbroken ground state is unstable as one increases the coupling constant (as it is for the original S-G equation) and we determine the stability criteria.Comment: 21 pages, Latex (Revtex4) v3:minor grammatical changes and addition

Development and validation of the relational depth frequency scale

OBJECTIVE: The Relational Depth Frequency Scale (RDFS) was developed to measure the frequency of specific moments of profound contact and engagement in psychotherapy. METHOD: Following an initial process of item generation and rating, Three-Step Test Interviews were conducted with eight therapists and clients to further refine potential items. Sixteen relational depth items were then taken forward for psychometric assessment in an online sample of 336 therapists and 220 clients, each divided into separate "shortening" and "checking" subsamples. RESULTS: Following psychometric scale shortening involving confirmatory factor analysis (CFA) and Rasch analysis, we formed a six item RDFS that could be used with both therapists and clients. The parameters of the shortened form replicated well in the independent checking subsamples with good internal consistency (Cronbach's α = .85 and .93 in therapist and clients respectively), acceptable fit statistics in CFA and Rasch analysis, and moderate to high levels of convergent validity against the Working Alliance Inventory (Short Form, Revised) and Relational Depth Inventory (RDI-R2). CONCLUSION: As a brief self-report measure, the RDFS can be used to further assess the relationship between relational depth and therapeutic outcomes. Further research is needed to examine the validity of the RDFS in clinical settings

Ignition column depths of helium-rich thermonuclear bursts from 4U 1728-34

We analysed thermonuclear (type-I) X-ray bursts observed from the low-mass X-ray binary 4U1728-34 by RXTE, Chandra and INTEGRAL. We compared the variation in burst energy and recurrence times as a function of accretion rate with the predictions of a numerical ignition model including a treatment of the heating and cooling in the crust. We found that the measured burst ignition column depths are significantly below the theoretically predicted values, regardless of the assumed thermal structure of the neutron star interior. While it is possible that the accretion rate measured by Chandra is underestimated, due to additional persistent spectral components outside the sensitivity band, the required correction factor is typically 3.6 and as high as 6, which is implausible. Furthermore, such underestimation is even more unlikely for RXTE and INTEGRAL, which have much broader bandpasses. Possible explanations for the observed discrepancy include shear-triggered mixing of the accreted helium to larger column depths, resulting in earlier ignition, or the fractional covering of the accreted fuel on the neutron star surface.Comment: 12 pages, 5 figures, accepted for publication in Ap

Polynomial Nonlinear State Space Identification of an Aero-Engine Structure

Most nonlinear identification problems often require prior knowledge or an initial assumption of the mathematical law (model structure) and data processing to estimate the nonlinear parameters present in a system, i.e. they require the functional form or depend on a proposition that the measured data obey a certain nonlinear function. However, obtaining prior knowledge or performing nonlinear characterisation can be difficult or impossible for certain identification problems due to the individualistic nature of practical nonlinearities. For example, joints between substructures of large aerospace design frequently feature complex physics at local regions of the structure, making a physically motivated identification in terms of nonlinear stiffness and damping impossible. As a result, black-box models which use no prior knowledge can be regarded as an effective method. This paper explores the pragmatism of a black-box approach based on Polynomial Nonlinear State Space (PNLSS) models to identify the nonlinear dynamics observed in a large aerospace component. As a first step, the Best Linear Approximation (BLA), noise and nonlinear distortion levels are estimated over different amplitudes of excitation using the Local Polynomial Method (LPM). Next, a linear state space model is estimated on the non-parametric BLA using the frequency domain subspace identification method. Nonlinear model terms are then constructed in the form of multivariate polynomials in the state variables while the parameters are estimated through a nonlinear optimisation routine. Further analyses were also conducted to determine the most suitable monomial degree and type required for the nonlinear identification procedure. Practical application is carried out on an Aero-Engine casing assembly with multiple joints, while model estimation and validation is achieved using measured sine-sweep and broadband data obtained from the experimental campaign

Social networks and labour productivity in Europe: An empirical investigation

This paper uses firm-level data recorded in the AMADEUS database to investigate the distribution of labour productivity in different European countries. We find that the upper tail of the empirical productivity distributions follows a decaying power-law, whose exponent $\alpha$ is obtained by a semi-parametric estimation technique recently developed by Clementi et al. (2006). The emergence of "fat tails" in productivity distribution has already been detected in Di Matteo et al. (2005) and explained by means of a model of social network. Here we show that this model is tested on a broader sample of countries having different patterns of social network structure. These different social attitudes, measured using a social capital indicator, reflect in the power-law exponent estimates, verifying in this way the existence of linkages among firms' productivity performance and social network.Comment: LaTeX2e; 18 pages with 3 figures; Journal of Economic Interaction and Coordination, in pres

Effector Functions of Natural Killer Cell Subsets in the Control of Hematological Malignancies.

Treatment of hematological malignant disorders has been improved over the last years, but high relapse rate mainly attributable to the presence of minimal residual disease still persists. Therefore, it is of great interest to explore novel therapeutic strategies to obtain long-term remission. Immune effector cells, and especially natural killer (NK) cells, play a crucial role in the control of hematological malignancies. In this regard, the efficiency of allogeneic stem cell transplantation clearly depends on the immune-mediated graft versus leukemia effect without the risk of inducing graft versus host disease. Alloreactive donor NK cells generated following hematopoietic stem cell transplantation ameliorate the outcome of leukemia patients; in addition, in vivo transfer of in vitro expanded NK cells represents a crucial tool for leukemia treatment. To improve NK cell effector functions against resistant leukemia cells, novel immunotherapeutic strategies are oriented to the identification, isolation, expansion, and administration of particular NK cell subsets endowed with multifunctional anti-tumor potential and tropism toward tumor sites. Moreover, the relationship between the emergence and persistence of distinct NK cell subsets during post-graft reconstitution and the maintenance of a remission state is still rather unclear