Reconstruction of the human foetal pelvis: a study of its development

This work:- The Reconstruction of the Early Foetal Pelvis, with a View to a Studyof its Development, was undertaken at the suggestion of Professor Cunningham and Dr. Waterston and was carried out in the Laboratory of the Anatomy Department. It seemed possible that, by this means of investigation, something of interest might be added to the already known facts about this region of the embryo. That, by supplementing the work done by other methods - particularly the study of sections serially by the microscope - a fuller and more perfect knowledge might be had of this interesting region. Special attention was to be directed to the hard parts, the general shape of the pelvis, and any peculiarities in this or in its constituent elements, seemed to be a very interesting field for research; and, I think I may say, that the results obtained have fully borne this out. Whilst the bony (or, really, cartilaginous) pelvis was the main point of investigation, it seemed to nie that to reconstruct a model, with the viscera in situ, might prove instructive; this, particularly to study the topography of the viscera at this early stage with thieir general form and arrangement. A stud of these in their natural size is of course very difficult and well nigh impossible. Very beautiful models of the tail end of the early embryo have been reconstructed by Professor Keibel cf Freiburg. They do not, however, give a good impression of the topography of the viscera,as organs are only in many cases shown in section, and their limits and relations to the hard parts not made clear. If suitable material were to be had (and I regret that it was not - indeed, there was a great scarcity for one reason and another - everybody seemed to wish his specimens for private museums), it was hoped that something might be done on the development Of the urethra in the male. I particularly desired to investigate the sexual characters of the hard parts and to discover whether there were any differences between male and female at this early period. Unfortunately I have been unable to do so since all my specimens have turned out males. However, with the measurements fully recorded (in one pelvis from a foetus eleven to twelve weeks old) cf this male pelvis, some future workers may be more fortunate with his material and be able to prove that there are or there are not sexual differences at this age. Professor Arthur Thomson (Journal of Anatomy and Physiology, Vol. XXXIII, 1899) has shown that as early as four months there are distinct differences between the pelvis of the two sexes, as distinct as in the adult. its method of investigation was by means of dissection, a much more risky method (as he admits) when dealing, as he had to do, with small and delicate parts. However, the results in the various specimens were uniform and there does seem to be a difference as early, at any rate, as four months. Reconstruction, as a method of investigation in Embryology, did not, it would seem, at first receive the attention it merited. Its value is not apparent in many cases at first sight and so the method has, until comparatively recently, been neglected; except perhaps by those under the immediate influence and direction cf the originator, Professor His. When we consider, however, it is clear that this method must be of great service in dealing with very early embryos when we wish to study the form and make measurements cf these embryos or any particular organ. By magnifying the structure and modelling it in its enlarged form we can not only make more accurate observations as to the form and size of any structure at any age, but also study the development of that structure from its first appearance up to the stage when it can be studied accurately in its natural condition. A study of serial sections cf a structure has, of course, its own particular value and much may be made out by the aid of the microscope and other aids even as to the form of the structure. This indeed was what this did in his earliest reconstruction models - models which are famous. He studied a complete series of sections of an embryo so carefully that he was able to model the embryo freely in wax or clay. This, to his with his great powers cf observation, must have been a very difficult task and it is not, as Professor Peter Thompson says, for the ordinary man. One may be allowed to doubt whether such models were, in their finer points, strictly accurate. For myself I have studied these serial sections pretty closely and have often been amazed at the appearance after reconstruction. Taking the cartilaginous pelvis as an example it seems to me well nigh impossible to form an accurate idea of such a structure with its many processes and fossae, or what are the correct shape and dimensions of such processes and fossae, by a mere study of sections. In any case, in such a study, the investigator alone would have the mental picture complete, which he could give to others by description; but where we can reconstruct a model we have a visual picture for all to study from. The value cf this method therefore lies mainly in this, that, where we wish to study form, at any particular stage in a developing structure, we have an accurate, enlarged, visual image of the structure so that we can handle it and measure it and note the relations cf one part to another. So much for the advantages of this method of investigation. That are its disadvantages? The most important is that it consumes much time; though after working at it for some time one gets along much more rapidly than at first. There is always, of course, much of interest in the work; but in certain parts the procedure is very tedious and a good. deal of patience is required to keep steadily at the work from day to day. The other disadvantage, or rather difficulty, is that there is a good deal of risk in certain parts of the technique. Everything must work smoothly during the process until the sections are safely mounted. For example, the tissue must be in good order for cutting so that the sections will be complete; the microtome must therefore also be cutting well; draughts have to be avoided when handling the sections for fear of mixing them; the sections must stick well to the slides; etc. But after all,these difficulties can be overcome by careful technique, so that there is nothing much to be said against the method, nothing that will weigh against the advantages, for time is required in all methods of investigation

A next-generation inverse-geometry spallation-driven ultracold neutron source

The physics model of a next-generation spallation-driven high-current ultracold neutron (UCN) source capable of delivering an extracted UCN rate of around an-order-of-magnitude higher than the strongest proposed sources, and around three-orders-of-magnitude higher than existing sources, is presented. This UCN-current-optimized source would dramatically improve cutting-edge UCN measurements that are currently statistically limited. A novel "Inverse Geometry" design is used with 40 L of superfluid $^4$He (He-II), which acts as a converter of cold neutrons (CNs) to UCNs, cooled with state-of-the-art sub-cooled cryogenic technology to $\sim$1.6 K. Our design is optimized for a 100 W maximum heat load constraint on the He-II and its vessel. In our geometry, the spallation target is wrapped symmetrically around the UCN converter to permit raster scanning the proton beam over a relatively large volume of tungsten spallation target to reduce the demand on the cooling requirements, which makes it reasonable to assume that water edge-cooling only is sufficient. Our design is refined in several steps to reach $P_{UCN}=2.1\times10^9\,/$s under our other restriction of 1 MW maximum available proton beam power. We then study effects of the He-II scattering kernel as well as reductions in $P_{UCN}$ due to pressurization to reach $P_{UCN}=1.8\times10^9\,/$s. Finally, we provide a design for the UCN extraction system that takes into account the required He-II heat transport properties and implementation of a He-II containment foil that allows UCN transmission. We estimate a total useful UCN current from our source of $R_{use}=5\times10^8\,/$s from a 18 cm diameter guide 5 m from the source. Under a conservative "no return" approximation, this rate can produce an extracted density of $>1\times10^4\,/$cm$^3$ in $<$1000~L external experimental volumes with a $^{58}$Ni (335 neV) cut-off potential.Comment: Submitted to Journal of Applied Physic

The epigenetic clock is correlated with physical and cognitive fitness in the Lothian Birth Cohort 1936

Background: The DNA methylation-based 'epigenetic clock' correlates strongly with chronological age, but it is currently unclear what drives individual differences. We examine cross-sectional and longitudinal associations between the epigenetic clock and four mortality-linked markers of physical and mental fitness: lung function, walking speed, grip strength and cognitive ability. Methods: DNA methylation-based age acceleration (residuals of the epigenetic clock estimate regressed on chronological age) were estimated in the Lothian Birth Cohort 1936 at ages 70 (n=920), 73 (n=299) and 76 (n=273) years. General cognitive ability, walking speed, lung function and grip strength were measured concurrently. Cross-sectional correlations between age acceleration and the fitness variables were calculated. Longitudinal change in the epigenetic clock estimates and the fitness variables were assessed via linear mixed models and latent growth curves. Epigenetic age acceleration at age 70 was used as a predictor of longitudinal change in fitness. Epigenome-wide association studies (EWASs) were conducted on the four fitness measures. Results: Cross-sectional correlations were significant between greater age acceleration and poorer performance on the lung function, cognition and grip strength measures (r range: -0.07 to -0.05, P range: 9.7 x 10 to 0.024). All of the fitness variables declined over time but age acceleration did not correlate with subsequent change over 6 years. There were no EWAS hits for the fitness traits. Conclusions: Markers of physical and mental fitness are associated with the epigenetic clock (lower abilities associated with age acceleration). However, age acceleration does not associate with decline in these measures, at least over a relatively short follow-up

Representation in Westminster in the 1990s : The ghost of Edmund Burke

Why are 'trustee' notions of representation still invoked in the UK House of Commons in the 1990s? In answering this question this article analyses the premises of Burkean theory and the arguments that these premises are of little relevance in the late twentieth century. Despite these dismissals of trusteeship, Burkean ideas are still articulated in the Commons some 200 years after they were first voiced. The idea of trusteeship can prove extremely useful to justify the actions of representatives when those actions conflict with constituency 'opinion', party policy or the wishes of interest groups. Examples of the occasions when Burkean notions have been invoked in the 1990s are provided

Measurement of the half-life of the T=12\frac{1}{2} mirror decay of 19^{19}Ne and its implication on physics beyond the standard model

The $\frac{1}{2}^+ \rightarrow \frac{1}{2}^+$ superallowed mixed mirror decay of $^{19}$Ne to $^{19}$F is excellently suited for high precision studies of the weak interaction. However, there is some disagreement on the value of the half-life. In a new measurement we have determined this quantity to be $T_{1/2}$ = $17.2832 \pm 0.0051_{(stat)}$ $\pm 0.0066_{(sys)}$ s, which differs from the previous world average by 3 standard deviations. The impact of this measurement on limits for physics beyond the standard model such as the presence of tensor currents is discussed.Comment: 5 pages, 3 figures, 1 tabl

Search for the Neutron Decay n→\rightarrow X+γ\gamma where X is a dark matter particle

In a recent paper submitted to Physical Review Letters, Fornal and Grinstein have suggested that the discrepancy between two different methods of neutron lifetime measurements, the beam and bottle methods can be explained by a previously unobserved dark matter decay mode, n$\rightarrow$ X+$\gamma$ where X is a dark matter particle. We have performed a search for this decay mode over the allowed range of energies of the monoenergetic gamma ray for X to be a dark matter particle. We exclude the possibility of a sufficiently strong branch to explain the lifetime discrepancy with greater than 4 sigma confidence.Comment: 6 pages 3 figure

Status of the UCNτ experiment

The neutron is the simplest nuclear system that can be used to probe the structure of the weak interaction and search for physics beyond the standard model. Measurements of neutron lifetime and β-decay correlation coefficients with precisions of 0.02% and 0.1%, respectively, would allow for stringent constraints on new physics. The UCNτ experiment uses an asymmetric magneto-gravitational UCN trap with in situ counting of surviving neutrons to measure the neutron lifetime, τ_n = 877.7s (0.7s)_(stat) (+0.4/−0.2s)_(sys). We discuss the recent result from UCNτ, the status of ongoing data collection and analysis, and the path toward a 0.25 s measurement of the neutron lifetime with UCNτ

A boron-coated CCD camera for direct detection of Ultracold Neutrons (UCN)

A new boron-coated CCD camera is described for direct detection of ultracold neutrons (UCN) through the capture reactions $^{10}$B (n,$\alpha$0$\gamma$)$^7$Li (6%) and $^{10}$B(n,$\alpha$1$\gamma$)$^7$Li (94%). The experiments, which extend earlier works using a boron-coated ZnS:Ag scintillator, are based on direct detections of the neutron-capture byproducts in silicon. The high position resolution, energy resolution and particle ID performance of a scientific CCD allows for observation and identification of all the byproducts $\alpha$, $^7$Li and $\gamma$ (electron recoils). A signal-to-noise improvement on the order of 10$^4$ over the indirect method has been achieved. Sub-pixel position resolution of a few microns is demonstrated. The technology can also be used to build UCN detectors with an area on the order of 1 m$^2$. The combination of micrometer scale spatial resolution, few electrons ionization thresholds and large area paves the way to new research avenues including quantum physics of UCN and high-resolution neutron imaging and spectroscopy.Comment: 10 pages, 8 figure