The Cosmological Constant

This is a review of the physics and cosmology of the cosmological constant. Focusing on recent developments, I present a pedagogical overview of cosmology in the presence of a cosmological constant, observational constraints on its magnitude, and the physics of a small (and potentially nonzero) vacuum energy.Comment: 50 pages. Submitted to Living Reviews in Relativity (http://www.livingreviews.org/), December 199

Transcriptome Analysis of the Vernalization Response in Barley (Hordeum vulgare) Seedlings

Temperate cereals, such as wheat (Triticum spp.) and barley (Hordeum vulgare), respond to prolonged cold by becoming more tolerant of freezing (cold acclimation) and by becoming competent to flower (vernalization). These responses occur concomitantly during winter, but vernalization continues to influence development during spring. Previous studies identified VERNALIZATION1 (VRN1) as a master regulator of the vernalization response in cereals. The extent to which other genes contribute to this process is unclear. In this study the Barley1 Affymetrix chip was used to assay gene expression in barley seedlings during short or prolonged cold treatment. Gene expression was also assayed in the leaves of plants after prolonged cold treatment, in order to identify genes that show lasting responses to prolonged cold, which might contribute to vernalization-induced flowering. Many genes showed altered expression in response to short or prolonged cold treatment, but these responses differed markedly. A limited number of genes showed lasting responses to prolonged cold treatment. These include genes known to be regulated by vernalization, such as VRN1 and ODDSOC2, and also contigs encoding a calcium binding protein, 23-KD jasmonate induced proteins, an RNase S-like protein, a PR17d secretory protein and a serine acetyltransferase. Some contigs that were up-regulated by short term cold also showed lasting changes in expression after prolonged cold treatment. These include COLD REGULATED 14B (COR14B) and the barley homologue of WHEAT COLD SPECIFIC 19 (WSC19), which were expressed at elevated levels after prolonged cold. Conversely, two C-REPEAT BINDING FACTOR (CBF) genes showed reduced expression after prolonged cold. Overall, these data show that a limited number of barley genes exhibit lasting changes in expression after prolonged cold treatment, highlighting the central role of VRN1 in the vernalization response in cereals

Vacuum Topology of the Two Higgs Doublet Model

We perform a systematic study of generic accidental Higgs-family and CP symmetries that could occur in the two-Higgs-doublet-model potential, based on a Majorana scalar-field formalism which realizes a subgroup of GL(8,C). We derive the general conditions of convexity and stability of the scalar potential and present analytical solutions for two non-zero neutral vacuum expectation values of the Higgs doublets for a typical set of six symmetries, in terms of the gauge-invariant parameters of the theory. By means of a homotopy-group analysis, we identify the topological defects associated with the spontaneous symmetry breaking of each symmetry, as well as the massless Goldstone bosons emerging from the breaking of the continuous symmetries. We find the existence of domain walls from the breaking of Z_2, CP1 and CP2 discrete symmetries, vortices in models with broken U(1)_PQ and CP3 symmetries and a global monopole in the SO(3)_HF-broken model. The spatial profile of the topological defect solutions is studied in detail, as functions of the potential parameters of the two-Higgs doublet model. The application of our Majorana scalar-field formalism in studying more general scalar potentials that are not constrained by the U(1)_Y hypercharge symmetry is discussed. In particular, the same formalism may be used to properly identify seven additional symmetries that may take place in a U(1)_Y-invariant scalar potential.Comment: 89 pages, 13 tables and 12 figures (version as to appear in JHEP

Physical, social, psychological and existential trajectories of loss and adaptation towards the end of life for older people living with frailty: a serial interview study

Abstract Background The experiences of people with cancer and organ disease have been described across different dimensions of need as they approach death. Such information is lacking for frail older people approaching death, but could highlight how a palliative approach might be relevant for this population. Methods Cognitively intact, community dwelling adults considered to be moderately or severely frail were recruited from a medical day hospital. Those recruited nominated an informal carer and case-linked professional. Qualitative in-depth serial interviews with older people and their informal carers were conducted over an 18 month period, and single interviews with case-linked healthcare professionals. Interviews were recorded, transcribed and narrative analytical techniques were used to compile case studies. Results Thirty-four participants (13 patients, 13 informal carers and 8 healthcare professionals) completed 40 individual, 14 joint and 8 professional interviews. Five patients died during the study. The analysis highlighted a dynamic balance between losses and adaptations. Three typical patterns of multi-dimensional change emerged. 1) Maintenance of psychological and existential well-being with a gradual social decline mirroring the physical deterioration. 2) a gradual reduction in both psychological and existential well-being. 3) a marked downturn in social, psychological and existential well-being before death. Frail older people sustained their well-being through maintaining a sense-of-self, garnering support from carers and community structures, and focusing on living from day to day. Their well-being lessened when they lost their sense-of-self, feeling alienated from the world, and confused over the cause of their circumstances. Death remained distant and ‘undiagnosed’. Social and community frameworks were essential for supporting their well-being. Conclusions Multidimensional end-of-life trajectories for frail older people differed from those with other conditions. Alleviating psychological, social and existential distress should be a priority of care as frail older people reach the end of life. The current palliative care model is problematic for this group. Care should address future concerns and not necessarily involve a focus on death or place of death