The X-ray eclipse of OY Car resolved with XMM-Newton: X-ray emission from the polar regions of the white dwarf

We present the XMM-Newton X-ray eclipse lightcurve of the dwarf nova OY Car. The eclipse ingress and egress are well resolved for the first time in any dwarf nova placing strong constraints on the size and location of the X-ray emitting region. We find good fits to a simple linear eclipse model, giving ingress/egress durations of 30+/-3 sec. Remarkably this is shorter than the ingress/egress duration of the sharp eclipse in the optical as measured by Wood et al. (1989) and ascribed to the white dwarf (43+/-2 sec). We also find that the X-ray eclipse is narrower than the optical eclipse by 14+/-2 sec, which is precisely the difference required to align the second and third contact points of the X-ray and optical eclipses. We discuss these results and conclude that X-ray emission in OY Car most likely arises from the polar regions of the white dwarf. Our data were originally reported by Ramsay et al (2001), but they did not make a quantitative measurement of eclipse parameters. We have also corrected important timing anomalies present in the data available at that time.Comment: 6 pages, 5 figures; accepted for publication in MNRA

The Why and Wherefore of the Methodist Episcopal Church

EVERY organization of individuals should be able to justify its own existence. Justification depends upon the spirit, aim, and characteristics of the body, which, in the case of professing Christians, should be in harmony with the mind and will of God, and with the best interests of the human race.https://place.asburyseminary.edu/ecommonsatsdigitalresources/1090/thumbnail.jp

LIFE: Costing the digital preservation lifecycle

Having confidence in the permanence of a digital resource requires a deep understanding of the preservation activities that will need to be performed throughout its lifetime, and an ability to plan and resource for those activities. The LIFE (Lifecycle Information for E-Literature) Project1 has advanced understanding of the short and long-term costs in this complex area, facilitating better planning, comparison and evaluation of digital lifecycles. The LIFE Project created a digital lifecycle model based on previous work undertaken on the lifecycles of paper-based materials. It applied the model to real-life collections, modelling their lifecycles and studying their constituent processes. The results were then used to estimate the costs of each element of the digital lifecycle. Organisations can now apply this process, enabling evaluation and refinement of their existing lifecycles and facilitating more effective planning for the preservation of newly acquired content. Phase 2 of the LIFE Project began in February 2007. It is evaluating and refining the models and methodology developed in the first phase of the project and developing lifecycle costings for a range of further case studies

Single site observations of \textit{TESS} single transit detections

Context: TESS has been successfully launched and has begin data acquisition. To expedite the science that may be performed with the resulting data it is necessary to gain a good understanding of planetary yields. Given the observing strategy employed by TESS the probability of detecting single transits in long period systems is increased. These systems require careful consideration. Aims: To simulate the number of TESS transit detections during its 2 year mission with a particular emphasis on single transits. Additionally, to determine the feasibility of ground-based follow-up observations from a single site. Methods: A distribution of planets is simulated around the $\sim$ 4 million stars in the TESS Candidate Target List. These planets are tested for detectable transits and characterised. Based on simulated parameters the single transit detections are further analysed to determine which are amenable to ground-based follow-up. Results: TESS will discover an approximate lower bound of 4700 planets with around 460 being single transits. A large fraction of these will be observable from a single ground-based site. This paper finds that, in a single year, approximately 1000 transit events of around 320 unique TESS single transit detections are theoretically observable. Conclusions: As we consider longer period exoplanets the need for exploring single transit detections increases. For periods $\gtrsim45$ days the number of single transit detections outnumber multitransits by a factor of 3 (82$\pm$18 and 25$\pm$7 respectively) a factor which only grows as longer period detections are considered. Therefore, it is worth expending the extra effort required to follow-up these more challenging, but potentially very rewarding, discoveries. Additionally, we conclude that a large fraction of these targets can be theoretically observed from just a single ground-based site.Comment: 12 pages, 19 figures. To be published in Astronomy and Astrophysic

Machine learning for non-additive intermolecular potentials: from quantum chemistry to first-principles predictions

Prediction of thermophysical properties from molecular principles requires accurate potential energy surfaces (PES). We present a widely-applicable method to produce first-principles PES from ab initio quantum chemistry calculations. Our approach accurately interpolates ab initio calculations of three-body non-additive interactions, using the machine learning technique, Gaussian Processes (GP). Significantly, no bespoke modification of the GP approach is required when the number or type of molecules is changed. Our method produces highly accurate interpolation from significantly fewer training points per PES than typical approaches, meaning ab-initio calculations can be performed at higher accuracy. As an exemplar we compute the PES for all cross interactions for CO2−Ar mixtures up to three-body non-additive interactions. From our PES we calculate the CO2−Ar virial coefficients up to 5th order. The resulting virial equation of state (EoS) is convergent for densities up to the critical density. Where convergent, the EoS makes accurate first-principles predictions for a range of useful thermophysical properties for CO2−Ar mixtures, including the compressibility factor, speed of sound and Joule-Thomson coefficient. Our method has great potential to make wide-ranging first-principles predictions for many mixtures of comparably sized molecules. Such predictions can replace the need for expensive, laborious and repetitive experiments and inform the continuum models that are required for applications

Blueshift and intramolecular tunneling of NH[sub 3] umbrella mode in [sup 4]He[sub n] clusters

International audienceWe present diffusion Monte Carlo calculations of the ground and first excited vibrational states of NH(3) (4)He(n) for n< or =40. We use the potential energy surface developed by one of us [M. P. Hodges and R. J. Wheatley, J. Chem. Phys. 114, 8836 (2001)], which includes the umbrella mode coordinate of NH(3). Using quantum Monte Carlo calculations of excited states, we show that this potential is able to reproduce qualitatively the experimentally observed effects of the helium environment, namely, a blueshift of the umbrella mode frequency and a reduction of the tunneling splittings in ground and first excited vibrational states of the molecule. These basic features are found to result regardless of whether dynamical approximations or exact calculations are employed

Interpolation of intermolecular potentials using Gaussian processes

A procedure is proposed to produce intermolecular potential energy surfaces from limited data. The procedure involves generation of geometrical configurations using a Latin hypercube design, with a maximin criterion, based on inverse internuclear distances. Gaussian processes are used to interpolate the data, using over-specified inverse molecular distances as covariates, greatly improving the interpolation. Symmetric covariance functions are specified so that the interpolation surface obeys all relevant symmetries, reducing prediction errors. The interpolation scheme can be applied to many important molecular interactions with trivial modifications. Results are presented for three systems involving CO2, a system with a deep energy minimum (HF - HF) and a system with 48 symmetries (CH4 - N2). In each case the procedure accurately predicts an independent test set. Training this method with high-precision ab initio evaluations of the CO2 - CO interaction enables a parameter-free, first-principles prediction of the CO2 - CO cross virial coefficient that agree very well with experiments

Relationship between the Linear Ringing Frequencies in 3He-A and 3He-B near the Polycritical Point

New measurements of parallel ringing in a quasi-ideal geometry for 3He-B near the temperature and pressure of the polycritical point suggest fB2/fA2∼5/2, where fB and fA are the linear parallel-ringing frequencies at a given temperature near Tc. This result approaches the prediction of theory using the Anderson-Brinkman-Morel and Balian-Werthamer states to describe 3He-A and 3He-B, respectively, and hence the results of Osheroff at melting pressure, but disagrees with earlier observations at pressures near the polycritical point

Reflections on the responsible conduct of cancer research

Most cancer researchers regularly practice the responsible conduct of research (RCR) without consciously considering it. As professional scientists, we simply do what we are trained to do. However, as we train a new generation of cancer researchers in our laboratories, we must be vigilant against undue complacency. In an age when misconduct in research is receiving more media attention than ever before, we should periodically take a moment of pause and reflect upon the meaning and practice of responsibly conducting research. Rather than meeting minimum standards in a compliance-driven manner, we should practice forethought and periodically consider how we can improve. We, as leaders in cancer research, must then push our peers to do the same. By embedding RCR into the culture of cancer research through a multilayer approach, including regular assessment at the levels of individual research groups, departmentally, and institutionally, we will become a model discipline in the responsible conduct of research

Simulation of the Raman spectroscopy of multi-layered carbon nanomaterials

Multi-layered carbon nanomaterials can have an important role in modern nanotechnology. Raman spectroscopy is a widely used analytical technique that is used to characterise the structure of these materials. In this work, an approach based upon an empirical potential for the simulation of the Raman spectroscopy of carbon nanomaterials [Carbon, 113 (2017) 299] is extended through the addition of a term to describe the Van der Waals interaction between layers of sp2 hybridised carbons. The resulting model accurately describes the properties of the shearing modes of few layer graphene and is used to characterise the low frequency modes of multi-walled carbon nanotubes and carbon nanofibres