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Le MIR au service du végétal : de la thermographie à l’imagerie spectrale
No full textNous présentons ici les applications de systèmes d’imagerie optique opérant dans le Moyen Infra Rouge (MIR) au domaine du végétal. Nous passons en revue l’application la plus populaire qu’est la thermographie, qui a donné lieu à de nombreux cas d’usage dans les cultures végétales. Nous poursuivons par une étude prospective d’imagerie à haute résolution spectrale, sur la base de lasers largement accordables, entre 3 et 10 μm. Ces diagnostics ouvrent la voie à une caractérisation précoce des pathologies
Le dichroïsme circulaire : une sonde dynamique de la conformation des molécules
No full textLe dichroïsme circulaire, une propriété optique des molécules chirales, permet d’obtenir des informations uniques sur la conformation tridimensionnelle des molécules. Nous montrons comment on peut utiliser cet effet dans des expériences résolues en temps pour déterminer la dynamique des changements de conformation de molécules chimiques ou biologiques
IoT-based Multimodal Borewell Monitoring
No full textExcessive groundwater extraction has led to a significant decline in water tables, highlighting the need for continuous monitoring. This study presents an Internet of Things (IoT)-based approach for real-time estimation of groundwater levels in borewells. In addition to water level measurements, parameters such as motor current and rainfall are tracked to evaluate their influence on groundwater dynamics. To assess practical feasibility, five monitoring nodes were deployed across a small educational campus in Hyderabad, India. Data collected over a two-month period indicate that the proposed low-cost system is both reliable and effective in real-world conditions, while also revealing interesting correlations between groundwater level variations and the monitored parameters
On the dual formulation of Russell measure model
No full textThe Russell Measure Model (RM), a nonlinear data envelopment analysis (DEA) model for evaluating decision-making units (DMUs), allows for independent and disproportionate inputs and outputs, which makes it superior and more accurate than the radial models. The model is formulated as a second-order cone programming (SOCP) problem, and its dual is derived using SOCP duality. Previous studies have noted the complexity and limited interpretability of this dual formulation and have proposed an alternative using semidefinite programming (SDP) problem. This paper demonstrates the equivalence of these dual formulations through variable transformations. In addition, a new SOCP formulation of the dual RM model is introduced, which is in the usual form of multiplier models without any variable transformations. It is shown that this new formulation is equivalent to the SDP model. Moreover, using the conic model, a new approach is proposed to identify the unique maximal reference set and projection by solving one model, thereby improving upon the existing two-stage approach. Two examples demonstrate the advantages of the proposed models
The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)
No full textContext. Asymmetries in debris discs provide unique clues to understand the evolution and architecture of planetary systems. Previous studies of debris discs at (sub)millimetre wavelengths have suggested the presence of asymmetries in a wide variety of systems, yet the lack of sufficiently sensitive high-resolution observations means that the typical properties of debris disc asymmetries have not been studied at the population level. The aim of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is to expand our understanding of radial and vertical dust structures, as well as gas distributions and kinematics, in debris discs. The ARKS sample of 24 highly resolved targets in ALMA’s Bands 6 and 7 (1.1–1.4 mm and 0.8–1.1 mm, respectively) provided a unique opportunity to study their asymmetries.
Aims. Here, in ARKS VI, we present a systematic analysis of the asymmetries and stellocentric offsets present in the ALMA continuum data for the ARKS survey. Our aims are to (i) identify asymmetries in debris disc dust distributions, (ii) quantify debris disc asymmetry properties, and (iii) discuss the potential origins of debris disc asymmetries. This work is the first systematic analysis of asymmetries in a large sample of well-resolved discs at (sub)millimetre wavelengths.
Methods. We utilised empirical methods to identify emission asymmetries (relative to disc major and minor axes, and azimuthal disc locations) and the presence of offset emission between disc centres and the locations of the host stars, via an analysis of their calibration procedures and disc properties. We associated observational asymmetry types (offset, major and/or minor axis, azimuthal) and plausible physical classes (arcs, eccentricities, and possible clumps and warps) associated with each source.
Results. We show that there are ten systems, almost half of the ARKS sample, that host either a continuum emission asymmetry or offset emission. Three systems host offsets (HD 15115, HD 32297, and HD 109573 (HR 4796)), four host azimuthal asymmetries (HD 9672 (49 Ceti), HD 92945, HD 107146, and HD 121617), two host an asymmetry in their major axis (HD 10647 (q1 Eri), and HD 39060 (β Pic)), and one hosts an asymmetry in their minor axis (HD 61005). We attribute the offset asymmetries to non-zero eccentricities, and three of the azimuthal asymmetries to arcs. The presence of an asymmetry or offset in the ARKS sample appears to be correlated with the fractional luminosity of cold dust. We tentatively suggest that continuum asymmetries are more prevalent in CO-rich debris discs, suggesting that gas interactions may drive debris dust asymmetries. We identify seven other tentative asymmetries, including four in distinct ARKS systems and three in systems with otherwise significant asymmetries.
Conclusions. This study demonstrates that debris disc asymmetries in the ARKS sample are common, and plausibly so in the wider population of debris discs at (sub)-millimetre wavelengths. This means that (sub)-millimetre asymmetries plausibly await discovery in debris discs as we probe these with higher sensitivity and resolution. Throughout, we highlight future studies to further investigate the origins of debris disc asymmetries, and build on the work presented here
Toward solar many-line inversions of high-resolution spectropolarimetric data
No full textContext. For the analysis of highly resolved solar spectra the simultaneous observation and interpretation (inversion) of only a few (often only one) spectral lines is still the norm. With modern instruments spatially highly resolved spectropolarimetric data covering many lines are available.
Aims. For the first time we combine the information from 85 simultaneously observed absorption lines in spatially highly resolved data to test a proposed solar many-line inversion strategy.
Methods. We inverted full Stokes spectra recorded with the FISS spectro-polarimeter (FISS-SP) at the 1.6-m Goode Solar Telescope in California, using the SPINOR code. We contrasted two different setups: one following the traditional approach of using a line doublet, and a new method inverting many-lines simultaneously.
Results. Compared to results from an inversion using two lines of a line doublet, we discovered more fine-structure and better constrained values using the many-line technique. An average quiet Sun spectrum was successfully reproduced using a model atmosphere, but when inverting spatially resolved data, uncertainties in line parameters and blend configurations did not average out. Thus, a deliberate selection process of lines and line blends was required, in order to make the many-line case converge to a physically expected and coherent atmosphere. We successfully developed and tested such a selection method.
Conclusions. Our results highlight that the many-line inversions method delivers more coherent results with superior line of sight (LOS) resolution of the atmospheric structure. Moreover, it effectively detects and utilizes even weak polarimetric signals in noisy data and thereby partly circumvents low noise requirements. It reveals uncertainties in atomic parameters of individual spectral lines and models, as the degree of freedom to compensate for these uncertainties by compromising the inferred atmospheric parameters is considerably reduced. It is thereby pointing to a need for improved atomic data, including log(gf) values, of many lines in the solar spectrum. The many-line method presents significant potential for solar physics and may become the preferred option for future observations with upcoming spectrographs
Joint optimization of inventory replenishment and transportation decisions: Models and solution algorithms
No full textThe joint optimization of transportation and inventory replenishment related decisions promises to yield significant cost savings coupled with higher customer satisfaction levels. This paper investigates a supply chain system consisting of a single supplier replenishing a single retailer, where the primary focus is on the retailer's decision-making process, aimed at determining the most efficient operational policy. This includes identifying the optimal replenishment quantity from the supplier and selecting the appropriate mix and size of the truck fleet under different situations. At first, the scenario whereby the retailer exclusively operates its limited fleet of trucks for inbound transportation is considered. An efficient solution procedure along with closed form expressions for the optimal ordering quantity and the number of trucks are devised. Subsequently, the problem is extended to incorporate environmental considerations under carbon tax and carbon cap policies. We propose a computationally efficient algorithm for generating the optimal operational policy following the carbon cap policy. Finally, to better resemble reality, the scope of the operational optimization model is extended via allowing the retailer the option to lease trucks from the external market. The conducted numerical experiments demonstrate that this flexibility can lead to significant cost reductions that are increasing with demand
Tissue stress measurements with Bayesian inversion stress microscopy
No full textCells within biological tissue are constantly subjected to dynamic mechanical forces. Measuring the internal stress of tissues has proven crucial for our understanding of the role of mechanical forces in fundamental biological processes like morphogenesis, collective migration, cell division or cell elimination and death. Previously, we have introduced Bayesian inversion stress microscopy (BISM), which is relying on measuring cell-generated traction forces in vitro and has proven particularly useful to measure absolute stresses in confined cell monolayers. We further demonstrate the applicability and robustness of BISM across various experimental settings with different boundary conditions, ranging from confined tissues of arbitrary shape to monolayers composed of different cell types. Importantly, BISM does not require assumptions on cell rheology. Therefore, it can be applied to complex heterogeneous tissues consisting of different cell types, as long as they can be grown on a flat substrate. Finally, we compare BISM to other common stress measurement techniques using a coherent experimental setup, followed by a discussion on its limitations and further perspectives
Modification of PCBM electron transport layer (ETL) by potassium iodide in inverted type perovskite solar cells
No full textOver the past decade, perovskite solar cells have garnered significant attention owing to their exceptional optoelectronic properties. The performance of perovskite solar cells is highly dependent on the efficient operation of both hole transport layers and electron transport layers, making the selection of cost-effective and compatible charge transport materials critically important. Phenyl-C61-butyric acid methyl ester (PCBM) is widely utilized as an electron transport layer (ETL) in perovskite solar cells; however, several limitations persist, including low electron mobility, challenges in the deposition of uniform and high-quality films, and considerable interfacial recombination losses. In this study, potassium iodide (KI) doping of PCBM was investigated to enhance the photovoltaic parameters of perovskite solar cells. The incorporation of KI was found to enhance photovoltaic performance by optimizing surface morphology. Characterization techniques such as space charge limited current (SCLC) measurements confirmed a decrease in trap-state density within the perovskite layer, thereby mitigating charge recombination and contributing to improved device efficiency
Wavelength-Dispersive Micro X-Ray Fluorescence (WDμXRF) Analysis with the microprobe
No full textAn Electron Probe Microanalyser (EPMA) determines the element distribution by detection of the electron beam excited characteristic X-rays using wavelength-dispersive spectrometers (WDS). This study evaluates the benefits of implementing a micro-focus X-ray source into the EPMA as an alternative excitation of X-Ray fluorescence (WDuXRF). Since XRF does not generate a Bremsstrahlung background, a higher detection limit is anticipated for elements with atomic numbers greater than 20 [1]. However, differing excitation probabilities and space constraints may result in lower overall signal intensity and a higher signal-to-noise ratio (SNR). This paper reports the mechanical integration of a IFG-IMOX X-ray source into a JEOL JXA-8530F electron microprobe. The signal-to-noise ratio (SNR) shows that WDμXRF performs comparably to conventional WD-EPMA under standard beam conditions of 20 kV and 500 nA. However, when using a fresh electron source with higher beam currents (1.9 μA) or increased accelerating voltages (30 kV), WD-EPMA exhibits superior SNR at identical measuring times, resulting in improved detection limits. We identify key parameters to enhance WDμXRF performance. Additional advantages of WDμXRF are also discussed, including the suitability for insulating materials, layered structures, rough surfaces, and beam-sensitive specimens. These factors make WDμXRF an attractive alternative, even in cases where the signal-to-noise ratio is lower compared to WD-EPMA