Sound propagation over mixed impedances

Outdoor propagation of surface transportation noise is strongly influenced by reflections from the ground surface due to the creation of an intereference pattern. The result is an attenuation with distance over and above that expected from simple spherical divergence and atmospheric absorption. A review of literature shows that ground effects can be characterised by a spherical wave reflection coefficient and a normal surface impedance. Theoretical solutions of point to point propagation over three different ground surface models (local reaction, extended reaction and a rigid backed layer) are described and the first two are shown to give good estimates of the excess attenuation as a function of distance. Methods for measuring the normal surface impedance are discussed and experimental measurements reported. It is concluded that an indirect method employing the local reaction theoretical solution gives reasonable estimates over the frequency range 1-70 kHz. For practical applications the homogeneous ground surface is modified to include the effects of impedance discontinuities. The theoretical solutions are compared with the results obtained from experiments on laboratory models built to a notional scale of 1:100. In the case of the source over a rigid surface and receiver over an acoustically soft ground surface, it is shown that (a) for a low noise source (e.g. cars) the impedance discontinuity has negligible effect and (b) that for elevated sources (e.g. lorries) the excess attenuation is increased relative to that of a homogeneous surface. The double discontinuity introduced by a rigid strip in an acoustically soft ground surface is also examined. Experimental results indicate the effect of the strip is insignificant for strip widths less than 10% of the source receiver separation distance. For wider strips it is found that prediction can be improved by postulating an increased average surface impedance

All-Sky spectrally matched UBVRI-ZY and u'g'r'i'z' magnitudes for stars in the Tycho2 catalog

We present fitted UBVRI-ZY and u'g'r'i'z' magnitudes, spectral types and distances for 2.4M stars, derived from synthetic photometry of a library spectrum that best matches the Tycho2 BtVt, NOMAD Rn and 2MASS JHK_{2/S} catalog magnitudes. We present similarly synthesized multi-filter magnitudes, types and distances for 4.8M stars with 2MASS and SDSS photometry to g<16 within the Sloan survey region, for Landolt and Sloan primary standards, and for Sloan Northern (PT) and Southern secondary standards. The synthetic magnitude zeropoints for BtVt, UBVRI, ZvYv, JHK_{2/S}, JHK_{MKO}, Stromgren uvby, Sloan u'g'r'i'z' and ugriz are calibrated on 20 calspec spectrophotometric standards. The UBVRI and ugriz zeropoints have dispersions of 1--3%, for standards covering a range of color from -0.3 < V-I < 4.6; those for other filters are in the range 2--5%. The spectrally matched fits to Tycho2 stars provide estimated 1-sigma errors per star of ~0.2, 0.15, 0.12, 0.10 and 0.08 mags respectively in either UBVRI or u'g'r'i'z'; those for at least 70% of the SDSS survey region to g<16 have estimated 1-sigma errors per star of ~0.2, 0.06, 0.04, 0.04, 0.05 in u'g'r'i'z' or UBVRI. The density of Tycho2 stars, averaging about 60 stars per square degree, provides sufficient stars to enable automatic flux calibrations for most digital images with fields of view of 0.5 degree or more. Using several such standards per field, automatic flux calibration can be achieved to a few percent in any filter, at any airmass, in most workable observing conditions, to facilitate inter-comparison of data from different sites, telescopes and instruments.Comment: 36 pages, 30 figures, 3 printed tables, several electronic tables, accepted PASP Dec 201

Deaths in people from Black, Asian and minority ethnic communities from both COVID-19 and non-COVID causes in the first weeks of the pandemic in London: a hospital case note review

Objective To undertake a case review of deaths in a 6-week period during the COVID-19 pandemic commencing with the first death in the hospital from COVID-19 on 12th of March 2020 and contrast this with the same period in 2019. Setting A large London teaching hospital. Participants Three groups were compared: group 1—COVID-19-associated deaths in the 6-week period (n=243), group 2—non-COVID deaths in the same period (n=136) and group 3—all deaths in a comparison period of the same 6 weeks in 2019 (n=194). Primary and secondary outcome measures This was a descriptive analysis of death case series review and as such no primary or secondary outcomes were pre-stipulated. Results Deaths in patients from the Black, Asian and minority ethnic (BAME) communities in the pandemic period significantly increased both in the COVID-19 group (OR=2.43, 95% CI=1.60–3.68, p<0.001) and the non-COVID group (OR=1.76, 95% CI=1.09–2.83, p=0.02) during this time period and the increase was independent of differences in comorbidities, sex, age or deprivation. While the absolute number of deaths increased in 2020 compared with 2019, across all three groups the distribution of deaths by age was very similar. Our analyses confirm major risk factors for COVID-19 mortality including male sex, diabetes, having multiple comorbidities and background from the BAME communities. Conclusions There was no evidence of COVID-19 deaths occurring disproportionately in the elderly compared with non-COVID deaths in this period in 2020 and 2019. Deaths in the BAME communities were over-represented in both COVID-19 and non-COVID groups, highlighting the need for detailed research in order to fully understand the influence of ethnicity on susceptibility to illness, mortality and health-seeking behaviour during the pandemic

Fundamental Properties of O-Type Stars

We present a comprehensive analysis of high-resolution, far-UV HST/STIS, FUSE, and optical spectra of 17 O stars in the SMC. Our analysis is based on NLTE metal line-blanketed model atmospheres calculated with our NLTE code TLUSTY. We systematically explore the sensitivity of various UV and optical lines to different stellar parameters. We have obtained consistent fits of the UV and the optical spectrum to derive the effective temperature, surface gravity, surface composition, and microturbulent velocity of each star. Stellar radii, masses, luminosities and ages then follow. Similarly to more limited recent studies, we derive cooler temperatures than the standard Teff calibration of O stars. We propose a new calibration between the spectral type and effective temperature based on our results from UV metal lines as well as optical hydrogen and helium lines. For stars of the same spectral subtype, we find a general good agreement between Teff determinations obtained with TLUSTY, CMFGEN, and FASTWIND models. We derive ionizing luminosities that are smaller by a factor of 3 compared to luminosities inferred from previous standard calibrations. The chemical composition analysis reveals that the surface of about 3/4 of the program stars is moderately to strongly enriched in nitrogen, while showing the original helium, carbon, and oxygen abundances. Our results support the new stellar evolution models that predict that the surface of fast rotating stars becomes N-rich during the main sequence phase because of rotationally-induced mixing. Most stars exhibit the ``mass discrepancy'' problem. This discrepancy too is a result of fast rotation which lowers the measured effective gravity. Our study thus emphasizes the importance of rotation in our understanding of the properties of massive stars. (abridged)Comment: Submitted to Astrophysical Journal; 69 page

Paraphrases and summaries: A means of clarification or a vehicle for articulating a preferred version of student accounts?

The use of group discussions as a means to facilitate learning from experiences is well documented in adventure education literature. Priest and Naismith (1993) assert that the use of the circular discussion method, where the leader poses questions to the participants, is the most common form of facilitation in adventure education. This paper draws on transcripts of facilitation sessions to argue that the widely advocated practice of leader summaries or paraphrases of student responses in these sessions functions as a potential mechanism to control and sponsor particular knowledge(s). Using transcripts from recorded facilitation sessions the analysis focuses on how the leader paraphrases the students’ responses and how these paraphrases or ‘formulations’ function to modify or exclude particular aspects of the students’ responses. I assert that paraphrasing is not simply a neutral activity that merely functions to clarify a student response, it is a subtle means by which the leader of the session can, often inadvertently or unknowingly, alter the student’s reply with the consequence of favouring particular knowledge(s). Revealing the subtle work that leader paraphrases perform is of importance for educators who claim to provide genuine opportunities for students to learn from their experience

Elastic and anelastic relaxation behaviour of perovskite multiferroics II: PbZr0.53_{0.53}Ti0.47_{0.47}O3_3 (PZT)–PbFe0.5_{0.5}Ta0.5_{0.5}O3_3 (PFT)

Elastic and anelastic properties of ceramic samples of multiferroic perovskites with nominal compositions across the binary join PbZr$_{0.53}$Ti$_{0.47}$O$_3$–PbFe$_{0.5}$Ta$_{0.5}$O$_3$ (PZT–PFT) have been assembled to create a binary phase diagram and to address the role of strain relaxation associated with their phase transitions. Structural relationships are similar to those observed previously for PbZr$_{0.53}$Ti$_{0.47}$O$_3$–PbFe$_{0.5}$Nb$_{0.5}$O$_3$ (PZT–PFN), but the magnitude of the tetragonal shear strain associated with the ferroelectric order parameter appears to be much smaller. This leads to relaxor character for the development of ferroelectric properties in the end member PbFe$_{0.5}$Ta$_{0.5}$O$_3$. As for PZT–PFN, there appear to be two discrete instabilities rather than simply a reorientation of the electric dipole in the transition sequence cubic–tetragonal–monoclinic, and the second transition has characteristics typical of an improper ferroelastic. At intermediate compositions, the ferroelastic microstructure has strain heterogeneities on a mesoscopic length scale and, probably, also on a microscopic scale. This results in a wide anelastic freezing interval for strain-related defects rather than the freezing of discrete twin walls that would occur in a conventional ferroelastic material. In PFT, however, the acoustic loss behaviour more nearly resembles that due to freezing of conventional ferroelastic twin walls. Precursor softening of the shear modulus in both PFT and PFN does not fit with a Vogel–Fulcher description, but in PFT there is a temperature interval where the softening conforms to a power law suggestive of the role of fluctuations of the order parameter with dispersion along one branch of the Brillouin zone. Magnetic ordering appears to be coupled only weakly with a volume strain and not with shear strain but, as with multiferroic PZT–PFN perovskites, takes place within crystals which have significant strain heterogeneities on different length scales.RUS facilities in Cambridge were established with funding from the Natural Environment Research Council (Grants NE/B505738/1, NE/F017081/1). The present work was supported by Grant No. EP/ I036079/1 from the Engineering and Physical Sciences Research Council. We thank Dr. Sam Crossley for his assistance with dielectric analysis and the use of his software to run those measurements. JAS gratefully acknowledges the hospitality of the Max Planck Institute for Chemical Physics of Solids. The Nanopaleomagnetism lab has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007– 2013)/ERC Grant Agreement 320750. SED and HS acknowledge support from the Winton Programme for the physics of sustainability. HS also acknowledges support from the Funai Foundation for Information Technology and the British Council Japan Association. Part of the work was carried out at the University of Puerto Rico, supported by the DOEEBSCoR project DEG02-ER46526

Social preferences, accountability, and wage bargaining

We assess the extent of preferences for employment in a collective wage bargaining situation with heterogeneous workers. We vary the size of the union and introduce a treatment mechanism transforming the voting game into an individual allocation task. Our results show that highly productive workers do not take employment of low productive workers into account when making wage proposals, regardless of whether insiders determine the wage or all workers. The level of pro-social preferences is small in the voting game, while it increases as the game is transformed into an individual allocation task. We interpret this as an accountability effect

The uptake of different tillage practices in England

Reduced tillage systems have been argued to provide several potential benefits to soil, environment and to farm incomes. In England, while many farms have partially adopted such practices, a large proportion of arable farmers do not undertake reduced tillage in any form. This paper analyses the rationale for and uptake of different cultivation techniques, including analysis of the barriers to adoption of reduced tillage, aiming to benefit policy makers and researchers and increase the spread of smart agricultural practices. Based on a postal questionnaire, we estimated that 47.6% of English arable land is cultivated using minimum‐tillage and 7% under no‐tillage. As farm size increased, so did the probability of reduced tillage uptake. Furthermore, farms growing combinable crops were more likely to utilise reduced tillage approaches than other farm types. Soil type, weed control and weather conditions were noted as the main drivers for ‘strategic' and ‘rotational' ploughing, constraining continuous reduced tillage use. To effect greater reduced tillage uptake, greater communication between researchers and farmers is needed to facilitate the implementation of sustainable soil management solutions, supported by current legislation permitting responsible herbicide use in arable production. Financial support to access reduced tillage machinery may also be required for farmers operating smaller holdings. Adopting reduced tillage is a continuous learning process requiring ongoing training and information‐gathering; supporting a network of reduced tillage ‘farmer champions' would facilitate practical knowledge exchange, allow farmers to observe soil improvements, understand transition phase barriers, and ultimately encourage increased reduced tillage uptake