Absence of boron aggregates in superconducting silicon confirmed by atom probe tomography

Superconducting boron-doped silicon films prepared by gas immersion laser doping (GILD) technique are analyzed by atom probe tomography. The resulting three-dimensional chemical composition reveals that boron atoms are incorporated into crystalline silicon in the atomic percent concentration range, well above their solubility limit, without creating clusters or precipitates at the atomic scale. The boron spatial distribution is found to be compatible with local density of states measurements performed by scanning tunneling spectroscopy. These results, combined with the observations of very low impurity level and of a sharp two-dimensional interface between doped and undoped regions show, that the Si:B material obtained by GILD is a well-defined random substitutional alloy endowed with promising superconducting properties.Comment: 4 page

The Modern Movement and Sustainability: Yesterday, Today and in the Future

Concern for the environment and a focus on the conservation of our natural resources have in general over the last couple of decades, entered into the dialogue around architecture and preservation. In the last decade this focused more specifically on the more recent architecture. In some instances, the discussion about sustainability has begun to overshadow the preservation issues. Many countries have developed elaborate rating systems for buildings, whether new or old, that take into account a large number of factors to gauge and assess their impact. While these systems are intended to assist in deciding what actions can and should be undertaken, the discussion has remained quite limited and largely focused on the operational aspects of buildings and on new construction

Evaluating the pronunciation of proper names by four French grapheme-to-phoneme converters

International Speech Communication Association (Isca) - International Astronautical Federation.ISBN : 13 9781604234480.This article reports on the results of a cooperative evaluation of grapheme-to-phoneme (GP) conversion for proper names in French. This work was carried out within the framework of a general evaluation campaign of various speech and language processing devices, including text-to-speech synthesis. The corpus and the methodology are described. The results of 4 systems are analysed: with 12-20% word error rates on a list of 8,000 proper names, they give a fairly accurate picture of the progress achieved, the state-of-the-art and the problems still to be solved, in the domain of GP conversion in French. In addition, the resources and collected data will be made available to the scientific and industrial community, in order to be re-used in future bench-marks

Art, Architecture and Public Space in New York, 1950–1970

In the decades after World War II there was much discussion about the need for collaboration between the architect and artist either as embodied in one or as distinctly different creative talents working closely but creatively independently together. Many saw little actual collaboration and questioned the relationship artistically or saw art as a cover for otherwise bland architecture. However, architects like Wallace K. Harrison, Gordon Bunshaft, and others worked regularly with artists like Josef Albers, Isamu Noguchi, Gyorgy Kepes or Richard Lippold. While many of those art installations remain today, they are under constant pressure because of real estate changes, renovations or simply neglect

Low temperature transition to a superconducting phase in boron-doped silicon films grown on (001)-oriented silicon wafers

We report on a detailed analysis of the superconducting properties of boron-doped silicon films grown along the 001 direction by Gas Immersion Laser Doping. The doping concentration cB has been varied up to approx. 10 at.% by increasing the number of laser shots to 500. No superconductivity could be observed down to 40mK for doping level below 2.5 at.%. The critical temperature Tc then increased steeply to reach 0.6K for cB = 8 at%. No hysteresis was found for the transitions in magnetic field, which is characteristic of a type II superconductor. The corresponding upper critical field Hc2(0) was on the order of 1000 G, much smaller than the value previously reported by Bustarret et al. in Nature (London) 444, 465 (2006).Comment: 4 pages including 4 figures, submitted to PRB-Rapid Communicatio

Preservation and public housing in the United States

Public housing is an important part of the heritage of the 20th century that deserves preservation, but is in danger of being demolished or unrecognizably altered. The United States, which saw the construction of such government sponsored projects, largely between 1930 and 1975, is no exception. In the last four decades government efforts have continued to shift towards financial incentives for private initiatives for design, construction and property management. This housing legacy, if being preserved, still needs to be improved so it can continue to serve as affordable housing in the 21st century

Thickness dependence of the superconducting critical temperature in heavily doped Si:B epilayers

International audienceWe report on the superconducting properties of a series of heavily doped Si:B epilayers grown by gas immersion laser doping with boron content (nB) ranging from ∼3 × 1020 cm−3 to ∼6 × 1021cm−3 and thickness (d) varying between ∼20 nm and ∼210 nm. We show that superconductivity is only observed for nB values exceeding a threshold value (nc,S ) which scales as nc,S ∝ 1/d. The critical temperature (Tc) then rapidly increases with nB, largely exceeding the theoretical values which can be estimated by introducing the electron-phonon coupling constant (λe-ph) deduced from ab initio calculations into the McMillan equation. Surprisingly Tc(nB,d) is fully determined by the boron dose (nB × d) and can be well approximated by a simple Tc(nB,d) ≈ Tc,0[1 − A/(nB.d)] law, with Tc,0 ∼ 750 mK and A ∼ 8(±1) × 1015 cm−2

From the onset of illness to potential recovery:Empirical economic analysis of health, disability and work

Despite a series of reforms between 1996 and 2006 aimed at reducing the inflow into disability insurance in the Netherlands, a substantial share (7%) of the Dutch labor force still receives disability benefits. To gain insights into which groups are most at risk of entering DI, what measures can be taken to prevent this, and how to support them to return to work, this dissertation consists of four chapters that empirically analyse the process from the onset of health problems, through the DI application until the potential recovery of DI recipients in the Netherlands. All chapters of this thesis confirm that while experiencing health issues might be a necessary condition for applying for DI, it is certainly not a sufficient condition to explain differentials in the inflow into DI or work resumption across groups. Even though DI inflow rates in the Netherlands have been reduced by a number of drastic reforms, contextual factors (also non-health related) still matter substantially for both the inflow and the potential outflow out of the DI system. The adequate and timely provision of treatments in the sickness period, the commitment of employers to provide preventative and reintegration activities, labor market prospects, and benefit conditions of the DI benefit scheme itself all make a difference when it comes to the application for and receipt of DI benefits and (partial) work resumption. In terms of targeting, this does not imply that “wrong” (relatively healthy) individuals end up receiving DI in the current system. Groups with higher DI application risks due to these contextual factors exhibit very similar health trajectories leading up to their DI application, compared to groups with lower DI application risks. These contextual factors affect individuals across the entire health spectrum. For example, a DI applicant with a temporary contract might be deemed fully and permanently disabled, while this individual might not have had to apply for DI at all if they had a permanent contract. Improvements of the DI system thus also have the potential to affect a large share of the individuals who might apply for DI. From a policy perspective, this suggests that there is still room for improvements in the design and implementation of the health care and DI systems in order to retain people in the workforce and reduce the number of DI recipients. The analysis in this dissertation has shown that more stringent screening and increased employer incentives have been effective tools. However, the analyses have also shown that despite these tools being in place, a weak labor market attachment can still result in a substantial DI risk. This can be seen in the elevated risks for workers with temporary contracts and UI recipients, but also in the larger impacts of waiting time for mental health treatments on individuals with a migration background and lower educational attainment. Interventions aimed at improving labor market attachment might thus also be effective in reducing DI inflow. Lastly, there still exist considerable disincentives to return to the workforce once DI recipients recover. It should become more favourable to return to work for DI recipients, to ensure that disability benefit receipt becomes a lay-over station instead of an end station

The Superconducting Transition in Boron Doped Silicon Films

International audienceWe report on a detailed analysis of the superconducting properties of boron-doped silicon films grown along the 001 direction by gas immersion laser doping. This technique is proved to be a powerful technique to dope silicon in the alloying range 2-10 at.% where superconductivity occurs. The superconducting transitions are sharp and well defined both in resistivity and magnetic susceptibility. The variation of Tc on the boron concentration is in contradiction with a classical exponential dependence on superconducting parameters. Electrical measurements were performed in magnetic field on the sample with cB = 8 at.% (400 laser shots) which has the highest Tc (0.6 K). No hysteresis was found for the transitions in magnetic field, which is characteristic of a type-II superconductor. The corresponding upper critical field was on the order of 1000 G at low temperatures, much smaller than the value previously reported. The temperature dependence of Hc2 is very well reproduced by the linearized Gorkov equations neglecting spin effects in the very dirty limit. These measurements in magnetic field allow an estimation of the electronic mean-free path, the coherence length, and the London penetration depth within a simple two-band free electron model