A young human embryo, showing early differentiation of the primitive streak, together with some observations on the early development of the human embryo

Despite the fact that our knowledge of the normal development of the human embryo in its early stages has increased very substantially in the past twenty years, there are still many points on which further evidence is necessary and which cannot be elucidated until a much larger amount of material is available. The embryo on which this thesis is based is a well-fixed specimen and its detailed description therefore may conceivably contribute a little towards the solution of some of the problems with which the study of Human Embryology is beset.The embryo represents a slightly later stage of development than the beautifully preserved Strahl-Beneke (1910) specimen, and a slightly earlier stage than the Embryo Hugo (1926), with both of which it will be specifically compared. It corresponds in many ways to Grosser's (1931) Embryo H. Schm.10, but as no detailed description has yet been published of this embryo and only a schematic median section has so far been figured, I can only use it occasionally for purposes of comparison. The subject of this thesis will be referred to as H.R.1, as it was obtained at operation by Mr E. Hesketh Roberts, to whom I am deeply indebted for the specimen and for the following clinical notes on the case

Thermodynamic Geometry of the Born-Infeld-anti-de Sitter black holes

Thermodynamic geometry is applied to the Born-Infeld-anti-de Sitter black hole (BIAdS) in the four dimensions, which is a nonlinear generalization of the Reissner-Norstr\"Aom-AdS black hole (RNAdS). We compute the Weinhold as well as the Ruppeiner scalar curvature and find that the singular points are not the same with the ones obtained using the heat capacity. Legendre-invariant metric proposed by Quevedo and the metric obtained by using the free energy as the thermodynamic potential are obtained and the corresponding scalar curvatures diverge at the Davies points.Comment: Latex,19 pages,14 figure

Doping evolution of spin and charge excitations in the Hubbard model

To shed light on how electronic correlations vary across the phase diagram of the cuprate superconductors, we examine the doping evolution of spin and charge excitations in the single-band Hubbard model using determinant quantum Monte Carlo (DQMC). In the single-particle response, we observe that the effects of correlations weaken rapidly with doping, such that one may expect the random phase approximation (RPA) to provide an adequate description of the two-particle response. In contrast, when compared to RPA, we find that significant residual correlations in the two-particle excitations persist up to $40\%$ hole and $15\%$ electron doping (the range of dopings achieved in the cuprates). These fundamental differences between the doping evolution of single- and multi-particle renormalizations show that conclusions drawn from single-particle processes cannot necessarily be applied to multi-particle excitations. Eventually, the system smoothly transitions via a momentum-dependent crossover into a weakly correlated metallic state where the spin and charge excitation spectra exhibit similar behavior and where RPA provides an adequate description.Comment: 5 pages, 4 figures, plus supplementary materia

Discovery of Five Recycled Pulsars in a High Galactic Latitude Survey

We present five recycled pulsars discovered during a 21-cm survey of approximately 4,150 deg^2 between 15 deg and 30 deg from the galactic plane using the Parkes radio telescope. One new pulsar, PSR J1528-3146, has a 61 ms spin period and a massive white dwarf companion. Like many recycled pulsars with heavy companions, the orbital eccentricity is relatively high (~0.0002), consistent with evolutionary models that predict less time for circularization. The four remaining pulsars have short spin periods (3 ms < P < 6 ms); three of these have probable white dwarf binary companions and one (PSR J2010-1323) is isolated. PSR J1600-3053 is relatively bright for its dispersion measure of 52.3 pc cm^-3 and promises good timing precision thanks to an intrinsically narrow feature in its pulse profile, resolvable through coherent dedispersion. In this survey, the recycled pulsar discovery rate was one per four days of telescope time or one per 600 deg^2 of sky. The variability of these sources implies that there are more millisecond pulsars that might be found by repeating this survey.Comment: 15 pages, 3 figures, accepted for publication in Ap

Structure determination from powder data : Mogul and CASTEP

When solving the crystal structure of complex molecules from powder data, accurately locating the global minimum can be challenging, particularly where the number of internal degrees of freedom is large. The program Mogul provides a convenient means to access typical torsion angle ranges for fragments related to the molecule of interest. The impact that the application of modal torsion angle constraints has on the structure determination process of two structure solution attempts using DASH is presented. Once solved, accurate refinement of a molecular structure against powder data can also present challenges. Geometry optimisation using density functional theory in CASTEP is shown to be an effective means to locate hydrogen atom positions reliably and return a more accurate description of molecular conformation and intermolecular interactions than global optimisation and Rietveld refinement alone