From scattering theory to complex wave dynamics in non-hermitian PT-symmetric resonators

I review how methods from mesoscopic physics can be applied to describe the multiple wave scattering and complex wave dynamics in non-hermitian PT-symmetric resonators, where an absorbing region is coupled symmetrically to an amplifying region. Scattering theory serves as a convenient tool to classify the symmetries beyond the single-channel case and leads to effective descriptions which can be formulated in the energy domain (via Hamiltonians) and in the time domain (via time evolution operators). These models can then be used to identify the mesoscopic time and energy scales which govern the spectral transition from real to complex eigenvalues. The possible presence of magneto-optical effects (a finite vector potential) in multichannel systems leads to a variant (termed PTT' symmetry) which imposes the same spectral constraints as PT symmetry. I also provide multichannel versions of generalized flux-conservation laws.Comment: 10 pages, 5 figures, minireview for a theme issue, Philosophical Transactions of the Royal Society

Ca2+-dependent changes in cyclic GMP levels are not correlated with opening and closing of the light-dependent permeability of toad photoreceptors.

We have measured the levels of 3',5'-guanosine monophosphate (cyclic GMP) in isolated retinas from toad to investigate their correlation to the opening and closing of the light-dependent permeability of photoreceptors. When Ca2+-induced changes in cyclic GMP concentration are compared with the Ca2+-induced changes in the permeability of photoreceptor light-dependent channel, four quantitative dissimilarities are noted. First, when extracellular Ca2+ ([Ca2+]o) is reduced from normal physiological levels to between 10(-6) and 10(-7) M, the light-dependent permeability is increased, but cyclic GMP levels are not significantly changed. Second, when [Ca2+]o is increased from 1.8 to 20 mM, the light-dependent permeability is suppressed, but cyclic GMP levels are decreased by only 10-15%, about one-quarter the decrease that can be obtained with bright illumination. Third, when [Ca2+]o is increased from 10(-8) M to 20 mM, the light-dependent permeability is closed rapidly, but the cyclic GMP decrease is slow. Fourth, when [Ca2+]o is lowered to 10(-8) M, the sensitivity of the light-dependent permeability to steady illumination is decreased by three to four orders of magnitude, but the sensitivity of the light-dependent decrease in cyclic GMP is not significantly affected. These observations indicate that there is no simple correlation between cyclic GMP levels and the permeability of the light-dependent channels and that Ca2+ can affect the conductance in the absence of changes in cyclic GMP content

The myth of patient centrality

Purpose: The purpose of this paper is to critically examine the extent of patient centrality within integrated chronic back pain management services and compare policy rhetoric with practice reality. Context: Integrated chronic back pain management services. Data sources: We have drawn on theories of integration and context specific journals related to integration and pain management between 1966 and 2006 to identify evidence of patient centrality within integrated chronic pain management services. Discussions: Despite policy rhetoric and guidelines which promote patient centrality within multidisciplinary services, we argue that evaluations of these services are scant. Many papers have focused on the assessment of pain in multidisciplinary services as opposed to the patient’s experience of these services. Conclusions: A latent measure of the reality of its magnitude needs to be captured through analysis of the patient perspectives. Capturing patient’s thoughts about integrated services will promote patient centrality and support the reality rather than endorse the rhetoric

Oil and international cooperation

The more that states depend on oil exports, the less cooperative they become: they grow less likely to join intergovernmental organizations, to accept the compulsory jurisdiction of international judicial bodies, and to agree to binding arbitration for investment disputes. This pattern is robust to the use of country and year fixed effects, to alternative measures of the key variables, and to the exclusion of all countries in the Middle East. To explain this pattern, we consider the economic incentives that foster participation in international institutions: the desire to attract foreign investment and to gain access to foreign markets. Oil-exporting states, we argue, find it relatively easy to achieve these aims without making costly commitments to international institutions. In other words, natural resource wealth liberates states from the economic pressures that would otherwise drive them toward cooperation

Development of GABAergic and glycinergic transmission in the neonatal rat dorsal horn

Cutaneous spinal sensory transmission appears to lack inhibitory control in the newborn spinal cord, but the properties of GABAergic and glycinergic synapses in the neonatal dorsal horn have not been characterized. Whole-cell patch-clamp recordings from rat superficial dorsal horn neurons in spinal cord slices at postnatal day 0 (P0) to P2, P6 - P7, and P13 - P14 revealed an age-dependent increase in the frequency of spontaneous IPSCs, which were abolished by the GABA(A) receptor (GABA(A)R) antagonist bicuculline between P0 and P7 but not at P14. GABA(A)R-mediated miniature IPSCs (mIPSCs), but not glycinergic mIPSCs, were present at birth, and GABA mIPSCs remained more frequent than glycine mIPSCs at all ages. Sciatic nerve stimulation resulted in IPSCs with both GABAergic and glycinergic components, although a larger contribution arose from GABAA receptors at all ages. In gramicidin perforated patch-clamp recordings, exogenous GABA applications produced depolarization in 40% of neurons at P0 - P2, but the reversal potential of GABA-evoked currents (E-GABA) was consistently more negative than action potential threshold at this age. By P6 - P7, GABA evoked only membrane hyperpolarization. The GABA(B)R agonist baclofen elicited an outward current in all neurons with peak amplitudes observed by P6 - P7 and abolished sciatic nerve-evoked monosynaptic glutamatergic EPSCs in all groups. The results show considerable postnatal development of inhibitory processing in the dorsal horn with GABAergic mechanisms initially dominant over glycinergic events. GABA(A)R-mediated depolarizations during the first postnatal week are likely to be important for the maturation of spinal networks but do not provide a major excitatory drive to the newborn dorsal horn

Explicating the role of partnerships in changing the health and well-being of local communities in urban regeneration areas: evaluation of the Warnwarth conceptual framework for partnership evaluation

This literature review is one of three outputs from a project: Explicating the role of partnerships in changing the health and well-being of local communities, one of a number of projects in a larger Higher Education Funding Council Strategic Development Fund project (HEFCE) entitled: Urban Regeneration: Making a Difference. This was a collaborative venture between Manchester Metropolitan University, Northumbria University, University of Salford and University of Central Lancashire. Bradford University was an affiliated partner

The neuropeptide transcriptome of a model echinoderm, the sea urchin Strongylocentrotus purpuratus

The work reported here was supported by a grant from the University of London Central Research Fun