Phonon-assisted decoherence in the production of polarization-entangled photons in a single semiconductor quantum dot

We theoretically investigate the production of polarization-entangled photons through the biexciton cascade decay in a single semiconductor quantum dot. In the intermediate state the entanglement is encoded in the polarizations of the first emitted photon and the exciton, where the exciton state can be effectively ``measured'' by the solid state environment through the formation of a lattice distortion. We show that the resulting loss of entanglement becomes drastically enhanced if the phonons contributing to the lattice distortion are subject to elastic scatterings at the device boundaries, which might constitute a serious limitation for quantum-dot based entangled-photon devices.Comment: 4 pages, 3 figure, to appear in Physical Review Letter

Dating Nathan: The Oldest Stained Glass Window in England?

Relatively little is known about stained glass windows in England predating c. 1170; however, art-historical evaluation by Caviness (1987) argued that four figures from the “Ancestors series” of Canterbury Cathedral, usually dated to the late 12th and early 13th century, in fact date earlier (c. 1130–1160). This would place them amongst the earliest stained glass in England, and the world. Building on our previous work, we address Caviness’s hypothesis using a methodology based upon analysis of a few, well-measured heavy trace elements and a 3D-printed attachment for a pXRF spectrometer that facilitates in situ analysis. The results confirm two major periods of “recycling” or re-using medieval glass. The first is consistent with Caviness’s argument that figures predating the 1174 fire were reused in the early 13th century. The results suggest that in addition to figures, ornamental borders were reused, indicating the presence of more early glass than previously thought. In the second period of recycling (1790s), surviving figures from the Ancestors series were removed and adapted into rectangular panels for insertion into large Perpendicular-style windows elsewhere in the cathedral. The results show that the glasses used to adapt the panels to a rectangular shape were broadly contemporary with the glasses used to glaze the original Ancestors windows, again representing a more extensive presence of medieval glass in the windows

Perfect magnetohydrodynamics as a field theory

We propose the generally covariant action for the theory of a self-coupled complex scalar field and electromagnetism which by virtue of constraints is equivalent, in the regime of long wavelengths, to perfect magnetohydrodynamics (MHD). We recover from it the Euler equation with Lorentz force, and the thermodynamic relations for a prefect fluid. The equation of state of the latter is related to the scalar field's self potential. We introduce 1+3 notation to elucidate the relation between MHD and field variables. In our approach the requirement that the scalar field be single valued leads to the quantization of a certain circulation in steps of $\hbar$; this feature leads, in the classical limit, to the conservation of that circulation. The circulation is identical to that in Oron's generalization of Kelvin's circulation theorem to perfect MHD; we here characterize the new conserved helicity associated with it. We also demonstrate the existence for MHD of two Bernoulli-like theorems for each spacetime symmetry of the flow and geometry; one of these is pertinent to suitably defined potential flow. We exhibit the conserved quantities explicitly in the case that two symmetries are simultaneously present, and give examples. Also in this case we exhibit a new conserved MHD circulation distinct from Oron's, and provide an example.Comment: RevTeX, 16 pages, no figures; clarifications added and typos corrected; version to be published in Phys. Rev.

World caf\ue9 method to engage smart energy-district project partners in assessing urban co-benefits

Urban energy-district projects introduce outstanding technological innovation in buildings and energy systems increasing sustainability in city neighborhoods. Such projects generate additional co-benefits for the city beyond changes in physical elements and development of social and institutional relationships (e.g. local employment, environmental quality, public health, property values, innovation attitude, etc.). Since exceeding main declared goals or not always clearly foreseen in the early project phase, these co-benefits are often not properly understood and considered. However, only their explicit recognition will make possible their inclusion in the assessment of the whole project\u2019s performance. From these considerations, this study faces the issue of engaging project partners in assessing co-benefits in order to consider a broad spectrum of relevant, positive effects in the evaluation process. Group knowledge and group thinking of this complex topic are investigated through the world caf\ue9 method, providing an atmosphere of trust and open discussions among participants. This empirical work lays the foundations to go beyond the mere economic measure as the sole criterion for assessing project effects, also including changes in end-user behavior and intangible asset

'Will the Paris Agreement protect us from hydro-meteorological extremes?'

Multi-hazard assessment is needed to understand compound risk. Yet, modelling of multiple climate hazards has been limitedly applied at the global scale to date. Here we provide a first comprehensive assessment of global population exposure to hydro-meteorological extremes—floods, drought and heatwaves—under different temperature increase targets. This study shows how limiting temperature increase to 1.5 and 2 °C, as for the goals of the Paris Agreement, could substantially decrease the share of global population exposed compared to a 3 °C scenario. In a 2 °C world, population exposure would drop by more than 50%, in Africa, Asia and the Americas, and by about 40% in Europe and Oceania. A 1.5 °C stabilization would further reduce exposure of about an additional 10% to 30% across the globe. As the Parties of the Paris Agreement are expected to communicate new or updated nationally determined contributions by 2020, our results powerfully indicate the benefits of ratcheting up both mitigation and adaptation ambition

Investigation of nucleon - unbound states in 29 Si and 29 P by the reaction 28 Si (d, pn)

The deuteron break-up reaction is a good tool to study nucleon unbound states o f atomic nuclei [1, 2]. In the present paper we are studying the proton unbound states o f 29P and the neutron unbound states o f 29Si via the 28Si(d, p n )28Si reaction. The experimental results and an analysis limited to the most prominent peaks in the spectra o f this reaction were published in an earlier work [3], Now an extended analysis is presented, based on the “ summed spectra” method [4] which enables us to identify even weak states in complicated spectra

Ion species fractions in the far-field plume of a high-specific impulse Hall thruster

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76418/1/AIAA-2003-5001-731.pd

Survival following parathyroidectomy among United States dialysis patients

Survival following parathyroidectomy among United States dialysis patients.BackgroundSecondary hyperparathyroidism (SHPTH) is highly prevalent among persons with end-stage renal disease (ESRD). SHPTH has been linked to uremic bone disease, vascular calcification, and a higher risk of death. Parathyroidectomy (PTX) can dramatically reduce parathyroid hormone (PTH) and phosphate levels; however, the relationship between PTX and survival is not known.MethodsWe conducted an observational matched cohort study utilizing data from the United States Renal Database System (USRDS) in which 4558 patients undergoing a first PTX while on hemodialysis or peritoneal dialysis were individually matched by age, race, gender, cause of ESRD, dialysis duration, prior transplantation status, and dialysis modality to 4558 control patients who did not undergo PTX. Patients were followed from the date of PTX until they died or were lost to follow-up.ResultsThe 30-day postoperative mortality rate following PTX was 3.1%. Long-term relative risks of death among patients undergoing PTX were estimated to be 10% to 15% lower than those of matched control patients not undergoing surgery. Survival curves between the 2 groups crossed 587 days following PTX. Median survival was 53.4 months (95% CI: 51.2–56.4) in the PTX group, and 46.8 months (95% CI: 44.7–48.9) in the control group.ConclusionPTX was associated with higher short-term, and lower long-term, mortality rates among U.S. patients receiving chronic dialysis. Measures to attenuate SHPTH may play an important role in reducing mortality among patients with end-stage renal disease