Biotic pump of atmospheric moisture: A conceptual model

The Biotic Pump Theory, as described by Drs. Makarieva and Gorshkov (M&G), defines the mechanism by which water vapour is transported from areas of low evaporation to areas of high evaporation, conveniently termed “donor” and “acceptor” regions, respectively, and where only the latter exhibits condensation. The implications of such a theory are critical, especially to moisture regulation of tropical rainforests, yet highly controversial. Unfortunately, most of the theory’s physics cannot be evaluated due to the lack of atmospheric observations over such areas. This study aims at building a conceptual model of the theory over the Amazon basin as to quantitatively assess the existence and determine the properties of donor and acceptor regions statistically through their respective condensation rates. The model uses the predictive capabilities of Time-Delayed Neural Networks to downscale available atmospheric observations to calculate condensation rates at a scale suited for this analysis. Validation of the downscaling model reveals monthly Mean Absolute Errors to range between 0.022 m s-1 and 2.76 m s-1 in the predictions of vertical velocity and zonal wind speed, respectively. Findings quantitatively support the existence of a biotic mechanism regulating the transport of water vapour as these clearly show the presence of donor and acceptor regions. These regions have average spatial distributions of 42% - 58%, respectively, over the whole study area and correlations are found between wind speeds and condensation rates. Mean annual condensation rate for the Amazon basin is calculated to be of 0.23E-06 mol m-3 s-1. Results also show an increase in average condensation rate (0.06E-06 mol m-3 s-1) for the last 9 years, which does not strictly adhere to M&G’s views on the impacts of deforestation on precipitation. Outcomes hence also suggest a more complex relationship between evaporation and condensation, and therefore highlight the necessity to further refine this novel theory

The ground-based solar observations database BASS 2000

BASS 2000 is the French solar database for ground-based instruments. We describe hereafter our organization, our tasks and the products we can deliver to the international community. Our prospects cover data mining into the THeMIS archive, a participation to the EST endeavour and the creation and curation of the ESPaDOnS/NARVAL stellar spectra database.Comment: 3 pages, 1 figure (to appear in the Procs. of Solar Polarization Workshop #5, eds. Berdyugina, Nagendra and Ramelli

Towards nonlinearity measurement and simulation using common EMC equipment

International audienceIntegrated circuit (IC) models that predict functional failure are necessary for predicting the immunity of systems to electromagnetic interference (EMI). The integrated circuit immunity model for conducted immunity (ICIM-CI) of IEC 62433-4 assumes that the IC terminals still behave linearly at injection power levels that cause susceptibility. This hypothesis should be systematically verified when modelling integrated circuits for EMC, but this is not always straightforward. A simple measurement set-up using a directional coupler and a spectrum analyser is demonstrated to verify this linearity hypothesis using commonly available equipment. The measured reflected spectrum can be transformed into the |X11| parameter, which is the non-linear extension of the S11 parameter. X-parameters may be the key to predict susceptibility by simulation when the linearity hypothesis is invalid

Design of a 20 GHz DPI method for SOIC8

International audienceThe direct power injection (DPI) test defined in IEC 62132-4 measures the conducted immunity of integrated circuits (ICs) up to 1GHz. As the frequency of functional and interference signals is increasing, we would like to characterise immunity for higher frequencies as well. In this paper, we show why typical IEC 62132-4 compliant DPI set-ups become inaccurate when going up to 20GHz. We propose to determine the power Ptrans actually transmitted to the device under test (DUT) by using offline short-open-load-thru (SOLT) or thru-reflect-line (TRL) calibration. Furthermore, we design a low-cost FR4 printed circuit board (PCB) that allows for testing of SOIC8-packaged ICs. We verify that this board has acceptable and reproducible losses up to 20 GHz, as well as acceptable crosstalk

Design of a 20 GHz DPI method for SOIC8

The direct power injection (DPI) test defined in IEC 62132-4 measures the conducted immunity of integrated circuits (ICs) up to 1 GHz. As the frequency of functional and interference signals is increasing, we would like to characterise immunity for higher frequencies as well. In this paper, we show why typical IEC 62132-4 compliant DPI set-ups become inaccurate when going up to 20 GHz. We propose to determine the power Ptrans actually transmitted to the device under test (DUT) by using offline short-open-load-thru (SOLT) or thru-reflect-line (TRL) calibration. Furthermore, we design a low-cost FR4 printed circuit board (PCB) that allows for testing of SOIC8-packaged ICs. We verify that this board has acceptable and reproducible losses up to 20 GHz, as well as acceptable crosstalk.Peer ReviewedPreprin

Forces on Dust Grains Exposed to Anisotropic Interstellar Radiation Fields

Grains exposed to anisotropic radiation fields are subjected to forces due to the asymmetric photon-stimulated ejection of particles. These forces act in addition to the ``radiation pressure'' due to absorption and scattering. Here we model the forces due to photoelectron emission and the photodesorption of adatoms. The ``photoelectric'' force depends on the ambient conditions relevant to grain charging. We find that it is comparable to the radiation pressure when the grain potential is relatively low and the radiation spectrum is relatively hard. The calculation of the ``photodesorption'' force is highly uncertain, since the surface physics and chemsitry of grain materials are poorly understood at present. For our simple yet plausible model, the photodesorption force dominates the radiation pressure for grains with size >~0.1 micron exposed to starlight from OB stars. We find that the anisotropy of the interstellar radiation field is ~10% in the visible and ultraviolet. We estimate size-dependent drift speeds for grains in the cold and warm neutral media and find that micron-sized grains could potentially be moved across a diffuse cloud during its lifetime.Comment: LaTeX(41 pages, 19 figures), submitted to Ap

Fire History of the Appalachian Region: A Review and Synthesis

The importance of fire in shaping Appalachian vegetation has become increasingly apparent over the last 25 years. This period has seen declines in oak (Quercus) and pine (Pinus) forests and other fire-dependent ecosystems, which in the near-exclusion of fire are being replaced by fire-sensitive mesophytic vegetation. These vegetation changes imply that Appalachian vegetation had developed under a history of burning before the fire-exclusion era, a possibility that has motivated investigations of Appalachian fire history using proxy evidence. Here we synthesize those investigations to obtain an up-to-date portrayal of Appalachian fire history. We organize the report by data type, beginning with studies of high-resolution data on recent fires to provide a context for interpreting the lower-resolution proxy data. Each proxy is addressed in a subsequent chapter, beginning with witness trees and continuing to fire-scarred trees, stand age structure, and soil and sediment charcoal. Taken together, these proxies portray frequent burning in the past. Fires had occurred at short intervals (a few years) for centuries before the fire-exclusion era. Indeed, burning has played an important ecological role for millennia. Fires were especially common and spatially extensive on landscapes with large expanses of oak and pine forest, notably in the Ridge and Valley province and the Blue Ridge Mountains. Burning favored oak and pine at the expense of mesophytic competitors, but fire exclusion has enabled mesophytic plants to expand from fire-sheltered sites onto dry slopes that formerly supported pyrogenic vegetation. These changes underscore the need to restore fire-dependent ecosystems

What influences the speed of prototyping? An empirical investigation of twenty software startups

It is essential for startups to quickly experiment business ideas by building tangible prototypes and collecting user feedback on them. As prototyping is an inevitable part of learning for early stage software startups, how fast startups can learn depends on how fast they can prototype. Despite of the importance, there is a lack of research about prototyping in software startups. In this study, we aimed at understanding what are factors influencing different types of prototyping activities. We conducted a multiple case study on twenty European software startups. The results are two folds, firstly we propose a prototype-centric learning model in early stage software startups. Secondly, we identify factors occur as barriers but also facilitators for prototyping in early stage software startups. The factors are grouped into (1) artifacts, (2) team competence, (3) collaboration, (4) customer and (5) process dimensions. To speed up a startups progress at the early stage, it is important to incorporate the learning objective into a well-defined collaborative approach of prototypingComment: This is the author's version of the work. Copyright owner's version can be accessed at doi.org/10.1007/978-3-319-57633-6_2, XP2017, Cologne, German

Properties of LiMnBO3 glasses and nanostructured glass-ceramics

Polycrystalline LiMnBO3 is a promising cathode material for Li-ion batteries. In this work, we investigated the thermal, structural and electrical properties of glassy and nanocrystallized materials having the same chemical composition. The original glass was obtained via a standard meltquenching method. SEM and 7Li solid-state NMR indicate that it contains a mixture of two distinct glassy phases. The results suggest that the electrical conductivity of the glass is dominated by the ionic one. The dc conductivity of initial glass was estimated to be in the order of 10-18 S.cm-1 at room temperature. The thermal nanocrystallization of the glass produces a nanostructured glass-ceramics containing MnBO3 and LiMnBO3 phases. The electric conductivity of this glass-ceramics is increased by 6 orders of magnitude, compared to the starting material at room temperature. Compared to other manganese and borate containing glasses reported in the literature, the conductivity of the nanostructured glass ceramics is higher than that of the previously reported glassy materials. Such improved conductivity stems from the facilitated electronic transport along the grain boundaries

HI and CO in the circumstellar environment of the oxygen-rich AGB star RX Lep

Circumstellar shells around AGB stars are built over long periods of time that may reach several million years. They may therefore be extended over large sizes (~1 pc, possibly more), and different complementary tracers are needed to describe their global properties. In the present work, we combined 21-cm HI and CO rotational line data obtained on an oxygen-rich semi-regular variable, RX Lep, to describe the global properties of its circumstellar environment. With the SEST, we detected the CO(2-1) rotational line from RX Lep. The line profile is parabolic and implies an expansion velocity of ~4.2 km/s and a mass-loss rate ~1.7 10^-7 Msun/yr (d = 137 pc). The HI line at 21 cm was detected with the Nancay Radiotelescope on the star position and at several offset positions. The linear shell size is relatively small, ~0.1 pc, but we detect a trail extending southward to ~0.5 pc. The line profiles are approximately Gaussian with an FWHM ~3.8 km/s and interpreted with a model developed for the detached shell around the carbon-rich AGB star Y CVn. Our HI spectra are well-reproduced by assuming a constant outflow (Mloss = 1.65 10^-7 Msun/yr) of ~4 10^4 years duration, which has been slowed down by the external medium. The spatial offset of the HI source is consistent with the northward direction of the proper motion, lending support to the presence of a trail resulting from the motion of the source through the ISM, as already suggested for Mira, RS Cnc, and other sources detected in HI. The source was also observed in SiO (3 mm) and OH (18 cm), but not detected. The properties of the external parts of circumstellar shells around AGB stars should be dominated by the interaction between stellar outflows and external matter for oxygen-rich, as well as for carbon-rich, sources, and the 21-cm HI line provides a very useful tracer of these regions.Comment: 15 pages, 9 figures, accepted for publication in A&