Screening of the topological charge in a correlated instanton vacuum

Screening of the topological charge due to he fermion-induced interactions is an important phenomenon, closely related with the resolution of the strong CP and U(1) problems. We study the mechanism of such screening in a 'correlated instanton vacuum', as opposed to the 'random' one. Both scalar and pseudoscalar gluonic correlators are analyzed by means of an observable that minimizes finite size effects. Screening of the topological charge is established. This allows us to calculate the $\eta'$ mass without having to invert the Dirac operator. We suggest that this method might be used in lattice QCD calculations as well. Our results for the screening of the topological charge are in agreement with the chiral Ward identities, and the scalar gluonic correlator satisfies a low energy theorem first derived by Novikov et al. \cite{Novikov-etal}. We also propose to evaluate the topological susceptibility in the Witten-Veneziano formula not in an infinite box in an world $without$ fermions but in an infinitesimal box in a world $with$ fermions.Comment: 22 pages + 5 postscript figures, SUNY-NTG/94-25. Corrected LATEX erro

Universal features in the growth dynamics of complex organizations

We analyze the fluctuations in the gross domestic product (GDP) of 152 countries for the period 1950--1992. We find that (i) the distribution of annual growth rates for countries of a given GDP decays with ``fatter'' tails than for a Gaussian, and (ii) the width of the distribution scales as a power law of GDP with a scaling exponent $\beta \approx 0.15$. Both findings are in surprising agreement with results on firm growth. These results are consistent with the hypothesis that the evolution of organizations with complex structure is governed by similar growth mechanisms.Comment: 4 pages, 7 ps figures, using Latex2e with epsf rotate and multicol style files. Submitted to PR

Topology and chiral symmetry breaking in SU(N) gauge theories

We study the low-lying eigenmodes of the lattice overlap Dirac operator for SU(N) gauge theories with N=2,3,4 and 5 colours. We define a fermionic topological charge from the zero-modes of this operator and show that, as N grows, any disagreement with the topological charge obtained by cooling the fields, becomes rapidly less likely. By examining the fields where there is a disagreement, we are able to show that the Dirac operator does not resolve instantons below a critical size of about rho = 2.5 a, but resolves the larger, more physical instantons. We investigate the local chirality of the near-zero modes and how it changes as we go to larger N. We observe that the local chirality of these modes, which is prominent for SU(2) and SU(3), becomes rapidly weaker for larger N and is consistent with disappearing entirely in the limit of N -> infinity. We find that this is not due to the observed disappearance of small instantons at larger N.Comment: 41 pages, 12 figures, RevTe

Hadronic Correlation Functions in the Interacting Instanton Liquid

We study hadronic correlation functions in the interacting instanton liquid model, both at zero and nonzero temperature $T$. At zero $T$ we investigate the dependence of the correlators on the instanton ensemble, in particular the effect of the fermionic determinant. We demonstrate that quark-induced correlations between instantons are important, especially in the repulsive $\eta'$ and $\delta$-meson channels. We also calculate a large number of mesonic and baryonic correlation functions as a function of temperature. We find three different types of behavior as $T\to T_c$. The vector channels $\rho,a_1,\Delta$ show a gradual melting of the resonance contribution and approach free quark behavior near the chiral phase transition. The light pseudoscalars and scalars $\pi,\sigma$, as well as the nucleon show stable resonance contributions, probably even surviving above $T_c$. Correlation functions in the heavy scalar channels $\eta',\delta$ are enhanced as $T\to T_c$.Comment: 34 pages, Revtex, 7 postscript figure

The effectiveness of problem solving therapy in deprived South African communities: results from a pilot study

<p>Abstract</p> <p>Background</p> <p>The majority of South Africans with a DSM-IV diagnosis receive no treatment for their mental health problems. There is a move to simplify treatment for common mental disorders (CMDs) in order to ease access. Brief problem solving therapy (PST) might fill the treatment gap for CMD's in deprived communities in South Africa. This pilot study evaluates the feasibility, acceptability and effectiveness of this PST program for CMD's in deprived communities around Cape Town.</p> <p>Methods</p> <p>A Dutch problem solving program was adapted and translated into English, Xhosa and Afrikaans and thereafter implemented in townships around Cape Town. An initial attempt to recruit participants for online PST proved difficult, and so the program was adapted to a booklet format. Volunteers experiencing psychological distress were invited to participate in the either individually or group delivered 5-week during self-help program. To evaluate the effectiveness, psychological distress was administered through self-report questionnaires. After completion of the intervention participants also rated the program on various acceptability aspects.</p> <p>Results</p> <p>Of 103 participants, 73 completed 5 weeks of brief PST in a booklet/workshop format. There were significantly more dropouts in those who used the booklet individually than in the group. Psychological distress measured on the K-10 and SRQ fell significantly and the program was evaluated positively.</p> <p>Conclusions</p> <p>The results suggest that brief problem solving in a booklet/workshop format may be an effective, feasible and acceptable short-term treatment for people with CMD's in deprived communities. In this setting, group delivery of PST had lower drop-out rates than individual delivery, and was more feasible and acceptable. Randomized controlled trials are needed to evaluate the effect of brief self-help PST more rigorously.</p

Endogenous technological change, innovation diffusion and transitional dynamics in a nonlinear growth model

This paper addresses capital accumulation and capital productivity change in an economy with endogenous technological change and floors and ceilings in activity. The properties of the resulting two-variable nonlinear differential equation system are studied in some detail. The welfare implications are also considered. When discrete lags are introduced, wide-ranging behaviour emerges, which includes convergence to a steady-state, catastrophes, hysteresis, limit cycles and chaos. Simulations illustrate the results. It is found that external shocks, such as the diffusion of innovations from elsewhere, do not just change the level of the steady-state equilibrium but also the dynamical properties of the paths of output and productivity

Making sense of the evolving nature of depression narratives and their inherent conflicts

Originally a psychiatric diagnosis fashioned by Western psychiatry in the 20th Century, depression evolved to encompass varying lineages of discourse and care. This article elucidates some of the current challenges – as well as emerging discourses – influencing the category of depression. Depression-like experiences are shaped by (at times conflicting) subjectivities, claims to knowledge, material realities, social contexts and access to resources. With no unified understanding of the category of ‘depression’ available, lay people, social and neuro scientists, GPs, psychiatrists, talking therapists and pharmaceutical companies all attempt to shape narratives of depression. The current paper focuses on patient narratives about depression – in the context of these wider debates – to better elucidate the ways in which depression discourses are publically developing along varying lines. In conclusion, the paper suggests that we could better conceptualise the resulting ‘depression(s)’ with concepts such as ‘society of mind’ and notions of subjectivity unbounded by individuals

Is it the Income Distribution or Redistribution that Affects Growth?

Hervorming Sociale Regelgevin

Persistent frequent attenders in primary care: costs, reasons for attendance, organisation of care and potential for cognitive behavioural therapeutic intervention

<p><b>Abstract</b></p> <p>Background</p> <p>The top 3% of frequent attendance in primary care is associated with 15% of all appointments in primary care, a fivefold increase in hospital expenditure, and more mental disorder and functional somatic symptoms compared to normal attendance. Although often temporary if these rates of attendance last more than two years, they may become persistent (persistent frequent or regular attendance). However, there is no long-term study of the economic impact or clinical characteristics of regular attendance in primary care. Cognitive behaviour formulation and treatment (CBT) for regular attendance as a motivated behaviour may offer an understanding of the development, maintenance and treatment of regular attendance in the context of their health problems, cognitive processes and social context.</p> <p>Methods/design</p> <p>A case control design will compare the clinical characteristics, patterns of health care use and economic costs over the last 10 years of 100 regular attenders (≥30 appointments with general practitioner [GP] over 2 years) with 100 normal attenders (6–22 appointments with GP over 2 years), from purposefully selected primary care practices with differing organisation of care and patient demographics. Qualitative interviews with regular attending patients and practice staff will explore patient barriers, drivers and experiences of consultation, and organisation of care by practices with its challenges. Cognitive behaviour formulation analysed thematically will explore the development, maintenance and therapeutic opportunities for management in regular attenders. The feasibility, acceptability and utility of CBT for regular attendance will be examined.</p> <p>Discussion</p> <p>The health care costs, clinical needs, patient motivation for consultation and organisation of care for persistent frequent or regular attendance in primary care will be explored to develop training and policies for service providers. CBT for regular attendance will be piloted with a view to developing this approach as part of a multifaceted intervention.</p

Primula vulgaris (primrose) genome assembly, annotation and gene expression, with comparative genomics on the heterostyly supergene

Primula vulgaris (primrose) exhibits heterostyly: plants produce self-incompatible pin- or thrum-form flowers, with anthers and stigma at reciprocal heights. Darwin concluded that this arrangement promotes insect-mediated cross-pollination; later studies revealed control by a cluster of genes, or supergene, known as the S (Style length) locus. The P. vulgaris S locus is absent from pin plants and hemizygous in thrum plants (thrum-specific); mutation of S locus genes produces self-fertile homostyle flowers with anthers and stigma at equal heights. Here, we present a 411 Mb P. vulgaris genome assembly of a homozygous inbred long homostyle, representing ~87% of the genome. We annotate over 24,000 P. vulgaris genes, and reveal more genes up-regulated in thrum than pin flowers. We show reduced genomic read coverage across the S locus in other Primula species, including P. veris, where we define the conserved structure and expression of the S locus genes in thrum. Further analysis reveals the S locus has elevated repeat content (64%) compared to the wider genome (37%). Our studies suggest conservation of S locus genetic architecture in Primula, and provide a platform for identification and evolutionary analysis of the S locus and downstream targets that regulate heterostyly in diverse heterostylous species