Characterization of Carbon-Contaminated B4C-Coated Optics after Chemically Selective Cleaning with Low-Pressure RF Plasma

Boron carbide (B4C) is one of the few materials that is expected to be mostly resilient with respect to the extremely high brilliance of the photon beam generated by free electron lasers (FELs) and is thus of considerable interest for optical applications in this field. However, as in the case of many other optics operated at modern light source facilities, B4C-coated optics are subject to ubiquitous carbon contaminations. These contaminations represent a serious issue for the operation of high performance FEL beamlines due to severe reduction of photon flux, beam coherence, creation of destructive interference, and scattering losses. A variety of B4C cleaning technologies were developed at different laboratories with varying success. We present a study regarding the low-pressure RF plasma cleaning of carbon contaminated B4C test samples via inductively coupled O2/Ar, H2/Ar, and pure O2 RF plasma produced following previous studies using the same IBSS GV10x downstream plasma source. Results regarding the chemistry, morphology as well as other aspects of the B4C optical coating before and after the plasma cleaning are reported. We conclude from these comparative plasma processes that pure O2 feedstock plasma only exhibits the required chemical selectivity for maintaining the integrity of the B4C optical coating.Comment: 27 pages, 15 figure

Productivity in Knowledge Worker Teams

The use of Information and Communication Technologies in work pro- cesses has not brought the expected productivity improvement. Some studies even suggest that the always-on model decreases productivity. This article proposes work teams as a new unit for knowledge worker productivity analysis in organizations. Organizations? ability to adopt new analysis measures is analyzed in three case studies

Study through Geant4, for Time Resolution characterization of different detectors arrays coupled with two SiPMs, as a function of: the scintillator plastic material, its volumetric dimensions and the location of the radiation emission source

The high time resolution detectors are relevant in those experiments or simulations were the particles to detect, have a very short time of flight (TOF), and due this it´s required that the detections times are ranged between ns. & ps.Using Geant4 software, it was made thirty simulations of coupled detectors to plastic scintillators with two silicon photomultipliers (SiPMs) located on the scintillator’s central sides. To characterize the time resolution, it was required to quantify the optical photons that reach the Score in a certain time, which are generated by muons on the surface of the plastic scintillator. Different configurations of muon beams were simulated at energy of 1 GeV, to interact with the configuration of the scintillator material of its corresponding arrangement. The simulations were made varying three parameters: the scintillator material “BC404 & BC422”, its size, and the location of the radiation source. Fifteen simulations correspond to BC404 material & fifteen simulations to BC422 material respectively. The first five simulations consisted in varying the scintillator’s volumetric size and collocate the muons beam guided randomly distributed over it, the next five simulations differentiate from setting up a directly centered beam, and the last five simulations for guide the beam on the left lower corner of each scintillator.The best time resolution achieved was σ= 8.67 +/− 0.26 ps., reported by the detector with BC422 scintillator material which has a volume of 20x20x3 mm3

Modeling sapling distribution over time using a functional predictor in a generalized additive model

[Key message], The effect of adult trees on sapling density distribution during the regeneration fellings is determined in a Pinus sylvestris L. Mediterranean forest using generalized additive models. [Context], Spatial pattern of adult trees determines the number of new individuals after regeneration fellings, which modify the light and air temperature under tree canopy. [Aims], We proposed a novel spatiotemporal model with a functional predictor in a generalized additive model framework to describe nonlinear relationships between the size of the adult trees and the number of saplings of P. sylvestris and to determine if the spatial pattern of the number of saplings remained constant or changed in time. [Methods], In 2001, two plots (0.5 ha) were set up in two phases of regeneration fellings under the group shelterwood method. We mapped the trees and saplings and measured their diameter and height. The inventories were repeated in 2006, 2010, and 2014. [Results], We found a negative association between the diameter of adult trees and number of saplings up to 7–8 m. Beyond these distances, the diameter of adult trees was not associated with the number of saplings. Our results indicate that the spatial pattern of the number of saplings remained quite constant in time. [Conclusion ], The generalized additive models are a flexible tool to determine the distance range of inhibition of saplings by adult trees

Validation of a rapid antigen test as a screening tool for SARS-CoV-2 infection in asymptomatic populations. Sensitivity, specificity and predictive values

Background: Early diagnosis of SARS-CoV-2 infection is essential to reduce disease spread. Rapid antigen tests have not been sufficiently evaluated in asymptomatic patients to be used as massive population screening tools. Methods: Head-to-head evaluation of Roche SARS-CoV-2 Rapid Antigen Test and real-time reverse transcription polymerase chain reaction (RT-PCR) as SARS-CoV-2 screening tools performed in asymptomatic adults from a semi-closed community in University of Navarra (Spain) from November 2020 to January 2021. Sensitivity, specificity and predictive values were calculated using RT-PCR as reference method. Findings: Roche SARS-CoV-2 Rapid Antigen Test was performed on 2542 asymptomatic adults in a community with a SARS-CoV-2 incidence of 1·93%. It showed a sensitivity of 71·43% (CI 95%: 56·74 – 83·42) and a specificity of 99·68% (CI 95%: 99·37 - 99·86). Positive Predictive Value was 81·4 (CI 95% 66·6 – 91·61) and Negative Predictive Value was 99·44 (CI 95% 99·06 – 99·69). Test sensitivity was related to viral load, with higher sensitivity in RT-PCR cycle threshold (Ct) values under 25 (93·75%, CI 95%: 71·96 – 98·93), that dropped to 29·41% (CI 95%: 10·31- 55·96) in RT-PCR Ct values above 25. Interpretation: This study suggests that rapid antigen tests are less effective in asymptomatic population, when compared with RT-PCR. Further studies are needed to evaluate different options to improve screenings based on rapid antigen test, such as the use of clinical questionnaires to select higher risk-participants, the confirmation of negative results with RT-PCR or the use of repetitive sequential testing

Ozone production by corona discharge using a hollow needle-plate electrode system

Ozone generation using a hollow needle-to-plate corona reactor has been investigated using both positive and negative polarities and various flow rates. Oxygen could be introduced in the reactor either through the needle electrode or through a port on the lateral wall. This configuration al-lowed studying the effect of the flow direction on ozone production

Changes in plant diversity in a water‑limited and isolated high‑mountain range (Sierra Nevada, Spain)

Open Access funding provided by University of Natural Resources and Life Sciences Vienna (BOKU). This study was funded by the Austrian Academy of Sciences (project MEDIALPS-Disentangling anthropogenic drivers of climate change impacts on alpine plant species: Alps vs. Mediterranean mountains).Supplementary Information The online version contains supplementary material available at https ://doi.org/10.1007/s0003 5-021-00246 -x.We thank Manfred Bardy-Durchhalter for managing the database, Imran Nadeem for discussing climate data preparation, and National Park and Andalusian Environmental Agency staff for their assistance in the field in 2015 and 2019, and answering our questions.Climate change impacts are of a particular concern in small mountain ranges, where cold-adapted plant species have their optimum zone in the upper bioclimatic belts. This is commonly the case in Mediterranean mountains, which often harbour high numbers of endemic species, enhancing the risk of biodiversity losses. This study deals with shifts in vascular plant diversity in the upper zones of the Sierra Nevada, Spain, in relation with climatic parameters during the past two decades. We used vegetation data from permanent plots of three surveys of two GLORIA study regions, spanning a period of 18 years (2001–2019); ERA5 temperature and precipitation data; and snow cover durations, derived from on-site soil temperature data. Relationships between diversity patterns and climate factors were analysed using GLMMs. Species richness showed a decline between 2001 and 2008, and increased thereafter. Species cover increased slightly but significantly, although not for endemic species. While endemics underwent cover losses proportional to non-endemics, more widespread shrub species increased. Precipitation tended to increase during the last decade, after a downward trend since 1960. Precipitation was positively related to species richness, colonisation events, and cover, and negatively to disappearance events. Longer snow cover duration and rising temperatures were also related to increasing species numbers, but not to cover changes. The rapid biotic responses of Mediterranean alpine plants indicate a tight synchronisation with climate fluctuations, especially with water availability. Thus, it rather confirms concerns about biodiversity losses, if projections of increasing temperature in combination with decreasing precipitation hold true.University of Natural Resources and Life Sciences Vienna (BOKU) - Austrian Academy of Science

Relativistically extended Blanchard recurrence relation for hydrogenic matrix elements

General recurrence relations for arbitrary non-diagonal, radial hydrogenic matrix elements are derived in Dirac relativistic quantum mechanics. Our approach is based on a generalization of the second hypervirial method previously employed in the non-relativistic Schr\"odinger case. A relativistic version of the Pasternack-Sternheimer relation is thence obtained in the diagonal (i.e. total angular momentum and parity the same) case, from such relation an expression for the relativistic virial theorem is deduced. To contribute to the utility of the relations, explicit expressions for the radial matrix elements of functions of the form $r^\lambda$ and $\beta r^\lambda$ ---where $\beta$ is a Dirac matrix--- are presented.Comment: 21 pages, to be published in J. Phys. B: At. Mol. Opt. Phys. in Apri