Characterisations of Classical and Non-classical states of Quantised Radiation

A new operator based condition for distinguishing classical from non-classical states of quantised radiation is developed. It exploits the fact that the normal ordering rule of correspondence to go from classical to quantum dynamical variables does not in general maintain positivity. It is shown that the approach naturally leads to distinguishing several layers of increasing nonclassicality, with more layers as the number of modes increases. A generalisation of the notion of subpoissonian statistics for two-mode radiation fields is achieved by analysing completely all correlations and fluctuations in quadratic combinations of mode annihilation and creation operators conserving the total photon number. This generalisation is nontrivial and intrinsically two-mode as it goes beyond all possible single mode projections of the two-mode field. The nonclassicality of pair coherent states, squeezed vacuum and squeezed thermal states is analysed and contrasted with one another, comparing the generalised subpoissonian statistics with extant signatures of nonclassical behaviour.Comment: 16 pages, Revtex, One postscript Figure compressed and uuencoded Replaced, minor changes in eq 4.30 and 4.32. no effect on the result

The face validity of an initial sub-typology of people with autism spectrum disorders detained in psychiatric hospitals

Autistic adults who have a history of committing crimes present a major problem for providers of services in terms of legal disposal options and possible interventions, and greater understanding of this group and their associated needs is required. For this reason, we aimed to investigate the face validity of a proposed sub-typology of autistic adults detained in secure psychiatric hospitals in the United Kingdom. Initially, a focus group was completed with psychiatrists, clinical psychologists, healthcare workers, family members, and autistic adults who had been detained in hospital, leading to revisions of the sub-typology. Following this, a consensus rating exercise of ten clinical vignettes based upon this subtypology with three rounds was completed with fifteen psychiatrists and clinical psychologists; revisions to the vignettes to improve clarity were made following each round. The findings indicated these subtypes possess face validity and raters were able to classify all ten clinical case vignettes into the sub-typology and percentage of agreement ranged from 96% to 100% for overall subtype classification. This study suggests that the further validity of the sub-typology should be investigated within a larger study, as these sub-types have the potential to directly inform the hospital care-pathway such that length of stay can be minimised

Nanoindentation and structural studies of MgO-doped congruent LiNbO3 single crystals

The mechanical properties of undoped and 2.0, 4.0 and 6.0 mol% Mg-doped LN single crystals, grown by the Czochralski technique, have been investigated using nanoindentation studies to understand the mechanical deformation behaviour as doping is increased. This has been correlated with structural investigations by powder XRD analysis and Raman spectroscopy. Powder X-ray diffraction measurements show a slight increase in the lattice parameters as the Mg content is increased in the crystal. The lattice strain developed due to the doping has been calculated by the Williamson-Hall relation. The influence of Mg incorporation on lattice vibrations was analysed using Raman spectroscopy, which indicated no shift in the peak positions with doping, and only slight variation in the intensity and width of the peaks. The grown crystals were subjected to nanoindentation and the Young's modulus and hardness values were obtained by using the Oliver-Pharr method. The results reveal the optimal doping levels of Mg which result in enhanced mechanical strength of lithium niobate single crystals.publishe

Understanding Visual Impairment and Its Impact on Patients: A Simulation-Based Training in Undergraduate Medical Education

Introduction: Simulation activities are valuable teaching aids for understanding about living with visual impairment (VI). Our medical students used low-vision simulation spectacles (Sim-specs) to enable learning about VI. Methods: Students made tea and filled dosette boxes using Sim-specs simulating central visual loss (age-related macular degeneration) and navigated using Sim-specs simulating peripheral visual loss (glaucoma). Facilitators recorded errors made for each task. Students completed questionnaires to grade the tasks’ difficulty on a 4-point Likert-type scale. The students also participated in focus groups to discuss how their approach to working with patients may change following this training. Results: In total, 252 out of 254 students participated. Central visual loss provided the greatest challenge when undertaking fine motor skilled activity (dosette box). Highest average number of errors made was for dosette box task (0.70 error), followed by navigation (0.59), then making tea task (0.34). Students scored the most difficult task on average as the dosette box task (3.23 Likert-type points), followed by navigation (2.97), then making tea task (2.63). Our students have shown learning in recognising the challenges of VI and have adapted their approach to patients. Conclusions: Simulation activities are valuable additions to the undergraduate curriculum. Such activities can potentially enable greater empathy for our visually impaired patients

Spin wave analysis to the spatially-anisotropic Heisenberg antiferromagnet on triangular lattice

We study the phase diagram at T=0 of the antiferromagnetic Heisenberg model on the triangular lattice with spatially-anisotropic interactions. For values of the anisotropy very close to J_alpha/J_beta=0.50, conventional spin wave theory predicts that quantum fluctuations melt the classical structures, for S=1/2. For the regime J_beta<J_alpha, it is shown that the incommensurate spiral phases survive until J_beta/J_alpha=0.27, leaving a wide region where the ground state is disordered. The existence of such nonmagnetic states suggests the possibility of spin liquid behavior for intermediate values of the anisotropy.Comment: Revised version, 4 pages, Latex (twocolumn), 4 figures as eps files. To appear in PR

Coherent states for the hydrogen atom: discrete and continuous spectra

We construct the systems of generalised coherent states for the discrete and continuous spectra of the hydrogen atom. These systems are expressed in elementary functions and are invariant under the $SO(3, 2)$ (discrete spectrum) and $SO(4, 1)$ (continuous spectrum) subgroups of the dynamical symmetry group $SO(4, 2)$ of the hydrogen atom. Both systems of coherent states are particular cases of the kernel of integral operator which interwines irreducible representations of the $SO(4, 2)$ group.Comment: 15 pages, LATEX, minor sign corrections, to appear in J.Phys.

Ownership identity, strategy and performance:business group affiliates versus independent firms in India

We consider whether the impact of entrepreneurial orientation on business performance is moderated by the company affiliation with business groups. Within business groups, we explore the trade-off between inter-firm insurance that enables risk-taking, and inefficient resource allocation. Risk-taking in group affiliated firms leads to higher performance, compared to independent firms, but the impact of proactivity is attenuated. Utilizing Indian data, we show that risk-taking may undermine rather than improve business performance, but this effect is not present in business groups. Proactivity enhances performance, but less so in business groups. Firms can also enhance performance by technological knowledge acquisition, but these effects are not significantly different for various ownership categories

What do We Know About Entrepreneurial Finance and its Relationship with Growth?

This article explores what we do (and do not) know about entrepreneurial finance and its relationship with growth. Broadly, there is a need for research to go beyond traditional supply side/market failure issues to better understand the role of entrepreneurial cognition, objectives, ownership types and firm life-cycle stages in financing/investment decisions. We show that little is known about the pivotal relationship between access to external finance and growth due to limitations in current approaches to testing financial constraints. Instead, we propose that the relationship between funding gaps and business performance as a direct and nuanced approach to identifying financial constraints in different entrepreneurial finance markets requires scrutiny. There is also a necessity for research to disentangle cognitive from financial constraints and to better understand the role of financiers in enabling growth. In particular, there is a need to explore the relationship between non-bank sources of finance and growth, shorn of inherent survival and selection bias. We outline an agenda for future research to address gaps in our understanding