The null energy condition and instability

We extend previous work showing that violation of the null energy condition implies instability in a broad class of models, including gauge theories with scalar and fermionic matter as well as any perfect fluid. Simple examples are given to illustrate these results. The role of causality in our results is discussed. Finally, we extend the fluid results to more general systems in thermal equilibrium. When applied to the dark energy, our results imply that w is unlikely to be less than -1.Comment: 11 pages, 5 figures, Revte

Cooperative Jahn-Teller Effect and Electron-Phonon Coupling in La1−xAxMnO3La_{1-x}A_xMnO_3

A classical model for the lattice distortions of \lax is derived and, in a mean field approximation, solved. The model is based on previous work by Kanamori and involves localized Mn d-electrons (which induce tetragonal distortions of the oxygen octahedra surrounding the Mn) and localized holes (which induce breathing distortions). Parameters are determined by fitting to the room temperature structure of $LaMnO_3$. The energy gained by formation of a local lattice distortion is found to be large, most likely $\approx 0.6$ eV per site, implying a strong electorn-phonon coupling and supporting polaronic models of transport in the doped materials. The structural transition is shown to be of the order-disorder type; the rapid x-dependence of the transition temperature is argued to occur because added holes produce a "random" field which misaligns the nearby sites.Comment: 24 pages. No figures. One Table. Late

Zero Temperature Insulator-Metal Transition in Doped Manganites

We study the transition at T=0 from a ferromagnetic insulating to a ferromagnetic metallic phase in manganites as a function of hole doping using an effective low-energy model Hamiltonian proposed by us recently. The model incorporates the quantum nature of the dynamic Jahn-Teller(JT) phonons strongly coupled to orbitally degenerate electrons as well as strong Coulomb correlation effects and leads naturally to the coexistence of localized (JT polaronic) and band-like electronic states. We study the insulator-metal transition as a function of doping as well as of the correlation strength U and JT gain in energy E_{JT}, and find, for realistic values of parameters, a ground state phase diagram in agreement with experiments. We also discuss how several other features of manganites as well as differences in behaviour among manganites can be understood in terms of our model.Comment: To be published in Europhysics Letter

Ultrahigh Bandwidth Spin Noise Spectroscopy: Detection of Large g-Factor Fluctuations in Highly n-Doped GaAs

We advance all optical spin noise spectroscopy (SNS) in semiconductors to detection bandwidths of several hundred gigahertz by employing an ingenious scheme of pulse trains from ultrafast laser oscillators as an optical probe. The ultrafast SNS technique avoids the need for optical pumping and enables nearly perturbation free measurements of extremely short spin dephasing times. We employ the technique to highly n-doped bulk GaAs where magnetic field dependent measurements show unexpected large g-factor fluctuations. Calculations suggest that such large g-factor fluctuations do not necessarily result from extrinsic sample variations but are intrinsically present in every doped semiconductor due to the stochastic nature of the dopant distribution.Comment: 5 pages, 3 figure

The Journal of the Friends' Historical Society vol. 5 No. 1

1. Notices. 2. Notes and Queries. 3. The Westmorland and Swaledale Seekers in 1651. 4. Extracts from the Minute Book of the Sufferings of Friends in Mansfield. 5. Reminiscences of the Friends' Meeting, Manchester. 6. Women Ministers stopped by Highwaymen. 7. Presentations of Quakers in Episcopal Visitations, 1662-1679. 8. Elisha Bates. 9. Keye-Worsley Marriage Certificate, 1666. 10. Thomas Areskine, Brewer, of Edinburgh. 11. Meeting Records. 12. A Glimpse of Ancient Friends in Dorset I. 13. Distribution of Literature in Cornwall, 1734. 14. William White, M.D. F.R.S. of York. 15. Friends in Barbadoes. 16. Some Quaker Teachers in 1736. 17. Friends in Current Literature. 18. Editors' Note. 19. Anecdote of Obed Cook, Schoolmaster. 20. Early Quaker Booksellers of York

Endo180 modulation by bisphosphonates and diagnostic accuracy in metastatic breast cancer

We thank the patients who participated in this study; Professor Gerry Thomas and the Imperial College Healthcare NHS Trust, Human Biomaterials Resource Centre (Tissue Bank); Professor Clare M Isacke (Institute of Cancer Research, London) for Endo180 antibodies; Dr Richard Harvey (Department of Medical Oncology, Imperial College Healthcare NHS Trust) for CA 15-3 antigen measurement. The Division of Cancer at Imperial College London, Imperial College Healthcare NHS Trust is an Experimental Cancer Medicine Centre (ECMC) supported by funds from Cancer Research UK and the Department of Health (C37/A7283) and forms part of Imperial Cancer Research UK Centre (C42671/A12196). CP is recipient of a CRUK Clinician Scientist award. JW is The Flow Foundation Professor of Oncology at Imperial College London. MPC and GK were supported by donations from Tony and Rita Gallagher and Imperial College NHS Healthcare Trust Special Trustees (to JW and JS). MPC was funded by The Rosetrees Trust (Grant JS16/M59; to JW and JS). A-VF was funded by Fundação para a Ciência e Tecnologia fellowship (project supervisor: JS) and Imperial College NHS Healthcare Special Trustees (to JW and JS). MR-T was funded by the Association of International Cancer Research (Grant 08-0803 to JS)

Evidence for charge localization in the ferromagnetic phase of La_(1-x)Ca_(x)MnO_3 from High real-space-resolution x-ray diffraction

High real-space-resolution atomic pair distribution functions of La_(1-x)Ca_(x)MnO_3 (x=0.12, 0.25 and 0.33) have been measured using high-energy x-ray powder diffraction to study the size and shape of the MnO_6 octahedron as a function of temperature and doping. In the paramagnetic insulating phase we find evidence for three distinct bond-lengths (~ 1.88, 1.95 and 2.15A) which we ascribe to Mn^{4+}-O, Mn^{3+}-O short and Mn^{3+}-O long bonds respectively. In the ferromagnetic metallic (FM) phase, for x=0.33 and T=20K, we find a single Mn-O bond-length; however, as the metal-insulator transition is approached either by increasing T or decreasing x, intensity progressively appears around r=2.15 and in the region 1.8 - 1.9A suggesting the appearance of Mn^{3+}-O long bonds and short Mn^{4+}-O bonds. This is strong evidence that charge localized and delocalized phases coexist close to the metal-insulator transition in the FM phase.Comment: 8 pages, 8 postscript figures, submitted to Phys. Rev.

Forensic interviewing of mentally disordered suspects: The impact of interview style on investigation outcomes.

The investigative interviewing of a vulnerable suspect is a complex and difficult task. Current best practice advocates for the use of open questions in order to elicit a free recall. However, those with mental health conditions have limited cognitive abilities that relate to free recall and episodic memory, and there is emerging evidence that suggests open questions may not always be most suitable for the vulnerable interviewee. As such, the present study examined the impact of two different interview models (best practice v modified interview) on the amount and accuracy of investigation relevant information obtained within an experimental vulnerable ‘suspect’ sample. Participants engaged in two tasks; a minor transgression and a matched non-transgression. Each participant was then subject to either a best practice (containing largely open questions) or a modified interview (containing largely closed questions). Vulnerable participants provided a significantly higher and more accurate amount of investigation relevant information during the modified interview rather than the best practice interview. In addition, participants that have mental health conditions sought more clarifications during the best practice interviews. The type of interview did not impact upon the level of vulnerability displayed. Our findings challenge current best practice in that vulnerable participants performed worse in interviews containing more open questions than closed questions. These findings add to the emerging evidence base that vulnerable individuals may require an alternative method of questioning, including the use of closed questions as ‘scaffolding’ during an investigative interview

Rac1 and Rac3 isoform activation is involved in the invasive and metastatic phenotype of human breast cancer cells

INTRODUCTION: The metastatic progression of cancer is a direct result of the disregulation of numerous cellular signaling pathways, including those associated with adhesion, migration, and invasion. Members of the Rac family of small GTPases are known to act as regulators of actin cytoskeletal structures and strongly influence the cellular processes of integrin-mediated adhesion and migration. Even though hyperactivated Rac proteins have been shown to influence metastatic processes, these proteins have never been directly linked to metastatic progression. METHODS: To investigate a role for Rac and Cdc42 in metastatic breast cancer cell invasion and migration, relative endogenous Rac or Cdc42 activity was determined in a panel of metastatic variants of the MDA-MB-435 metastatic human breast cancer cell line using a p21-binding domain-PAK pull down assay. To investigate the migratory and invasive potential of the Rac isoforms in human breast cancer, namely Rac1 and the subsequently cloned Rac3, we stably expressed either dominant active Rac1 or dominant active Rac3 into the least metastatic cell variant. Dominant negative Rac1 or dominant negative Rac3 were stably expressed in the most metastatic cell variant. Cell lines expressing mutant Rac1 or Rac3 were analyzed using in vitro adhesion, migration and invasion assays. RESULTS: We show that increased activation of Rac proteins directly correlates with increasing metastatic potential in a panel of cell variants derived from a single metastatic breast cancer cell line (MDA-MB-435). The same correlation could not be found with activated Cdc42. Expression of a dominant active Rac1 or a dominant active Rac3 resulted in a more invasive and motile phenotype. Moreover, expression of either dominant negative Rac1 or dominant negative Rac3 into the most metastatic cell variant resulted in decreased invasive and motile properties. CONCLUSION: This study correlates endogenous Rac activity with high metastatic potential and implicates Rac in the regulation of cell migration and invasion in metastatic breast cancer cells. Taken together, these results suggest a role for both the Rac1 and Rac3 GTPases in human breast cancer progression