Point Source Research Articles

Controlled Discovery and Localization of Signals via Bayesian Linear Programming

Scientists often must simultaneously localize and discover signals. For instance, in genetic fine-mapping, high correlations between nearby genetic variants make it hard to identify the exact locations of causal variants. So the statistical task is to output as many disjoint regions containing a signal as possible, each as small as possible, while controlling false positives. Similar problems arise, for example, when locating stars in astronomical surveys and in changepoint detection. Common Bayesian approaches to these problems involve computing a posterior distribution over signal locations. However, existing procedures to translate these posteriors into credible regions for the signals fail to capture all the information in the posterior, leading to lower power and (sometimes) inflated false discoveries. We introduce Bayesian Linear Programming (BLiP), which can efficiently convert any posterior distribution over signals into credible regions for signals. BLiP overcomes an extremely high-dimensional and nonconvex problem to verifiably nearly maximize expected power while controlling false positives. Applying BLiP to existing state-of-the-art analyses of UK Biobank data (for genetic fine-mapping) and the Sloan Digital Sky Survey (for astronomical point source detection) increased power by 30%–120% in just a few minutes of additional computation. BLiP is implemented in pyblip (Python) and blipr (R). Supplementary materials for this article are available online, including a standardized description of the materials available for reproducing the work.

A Note on Exact Closed-Form Solutions for Lamb’s Problem with an Arbitrary Poisson’s Ratio

Abstract Lamb’s Problem, a cornerstone in theoretical seismology, investigates the displacement of an elastic half-space due to surficial or buried point sources. Although the exact closed-form solution for surface displacements from surficial sources is well established, the solutions for buried sources in the 3D case have remained limited, either confined to integral forms or applicable only for certain Poisson’s ratios. This study addresses this gap by generalizing the existing closed-form solutions to accommodate Poisson’s ratio for buried sources. Our solutions are expressed in terms of elementary algebraic expressions, elliptic integrals, and Gauss hypergeometric functions. The derived solution is validated by numerical tests. With the newly derived solution, we also explore the properties of the leaking mode, which stems from the complex conjugate roots of the Rayleigh equation.

Probabilistic and progressive deblended far-infrared and sub-millimetre point source catalogues. I. Methodology and first application in the COSMOS field

Probabilistic and progressive deblended far-infrared and sub-millimetre point source catalogues. I. Methodology and first application in the COSMOS field

A study on decompression wave propagation characteristics during CO2 pipeline leakage with consideration of gas‐liquid transition

AbstractPipelines stand as the most cost‐effective method for large‐scale transportation of CO2 from a source point to the storage site, especially over extensive distances. The potential for crack propagation following a pipeline rupture highlights the need for precise analysis of decompression wave propagation. To accurately model this, understanding the decompression wave's propagation laws becomes imperative. Although previous studies have predominantly focused on pipeline leaks within the dense phase or supercritical state, the transition from liquid to gas during leakage significantly affects the decompression wave propagation. When a gaseous CO2 pipeline ruptures, the high Joule‐–Thomson coefficient causes a swift temperature plunge, potentially leading to a gas–liquid transition. However, research on how this phase transition impacts the decompression wave characteristics is limited. To address this gap, this study proposes a transition computational fluid dynamics model to predict the decompression wave behavior. The model is validated with an industrial‐scale full‐bore rupture experiment. The results reveal that the gaseous CO2 leakage induces a pressure plateau at a certain distance from the leakage due to the gas‐liquid phase transition. The influences of initial conditions on this pressure plateau and decompression wave are also explored. This study provides valuable insights into understanding the decompression wave behaviors of gaseous CO2 pipelines, which are essential for ensuring the safety and reliability of CO2 transportation within the carbon capture and storage technology chain. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Periodicity from X-ray sources within the inner Galactic disk

Aims. For many years it had been claimed that the Galactic ridge X-ray emission at the Galactic Center (GC) is truly diffuse in nature. However, with the advancement of modern X-ray satellites, it has been found that most of the diffuse emission actually comprises thousands of previously unresolved X-ray point sources. Furthermore, many studies suggest that a vast majority of these X-ray point sources are magnetic cataclysmic variables (CVs) and active binaries. One unambiguous way to identify these magnetic CVs and other sources is by detecting their X-ray periodicity. Therefore, we systematically searched for periodic X-ray sources in the inner Galactic disk, including the GC region. Methods. We used data from our ongoing XMM-Newton Heritage Survey of the inner Galactic disk (350° ≲l ≲ +7° and −1° ≲b ≲ +1°) plus archival XMM-Newton observations of the GC. We computed the Lomb-Scargle periodogram for the soft (0.2–2 keV), hard (2–10 keV), and total (0.2–10 keV) band light curves to search for periodicities. Furthermore, we modeled the power spectrum using a power-law model to simulate 1000 artificial light curves and estimate the detection significance of the periodicity. We fitted the energy spectra of the sources using a simple power-law model plus three Gaussians, at 6.4, 6.7, and 6.9 keV, for the iron K emission complex. Results. We detected periodicity in 26 sources. For 14 of them, this is the first discovery of periodicity. For the other 12 sources, we found periods similar to those already known, indicating no significant period evolution. The intermediate polar (IP) type sources display relatively hard spectra compared to polars. We also searched for the Gaia counterparts of the periodic sources to estimate their distances using the Gaia parallax. We found a likely Gaia counterpart for seven sources. Conclusions. Based on the periodicity, hardness ratio, and the equivalent width of Fe K line emission, we have classified the sources into four categories: IPs, polars, neutron star X-ray binaries, and unknown. Of the 14 sources for which we detect the periodicity for the first time, four are likely IPs, five are likely polars, two are neutron star X-ray binaries, and three are of an unknown nature.

Assessing a semi-empirical model performance to predict the wetting patterns in subsurface drip irrigation

ContextBecause of the complexity of soil water distribution, accurate prediction of wetting pattern is not easily accessible and this has led to a inefficiency in some proposed models in the literature. These models do not consider the hydraulic characteristics of the irrigation system and are developed solely on the basis of the water volume or infiltration rate, soil hydrodynamic properties, and other conditions of the percolation environment. ObjectiveDue to the importance of the estimation of wetting front beneath Subsurface Drip Irrigation (SDI) laterals, a semi-empirical model using easily accessible data of the SDI system is proposed to predict the wetting patterns in both distribution and redistribution phases. The aforementioned model has been developed based on a novel approach that couples the governing equations of the lateral hydraulics with empirical equations derived by dimensional analysis. MethodsTo develop the model and evaluate its performance, three 16-mm drip line pipes with 0.2, 0.4, and 0.5 m emitter spacing, and 2–5 l/h discharge were placed at 0.20 m depth in a soil box filled with clay loam soil. Water was applied for 3 hours at 50, 100, and 150 kPa operating pressures, and the wetting patterns’ geometries were measured in each lateral after 1, 2, 3, and 24 h. The performance of the model was then assessed and compared with that of three other models. Results and conclusionThe result demonstrated that the proposed model provides the most accurate estimations of the wetting depths and widths. RMSE and MAE statistical indexes of the wetting depth were 0.001–0.002 m and 0.004–0.009 m, respectively, whereas those associated with the wetting width were 0.001–0.003 m and 0.005–0.016 m, respectively. These values resulted in the lowest error when compared with the corresponding obtained from other well-known models. Consequently, the model allows acceptable predictions of the wetting patterns using accessible hydraulic parameters of the SDI system. SignificanceUniquely, the results of the lateral hydraulic analysis were applied to determine the wetting front dimensions in this study. Also, the results demonstrated that the model was successful in wetting pattern prediction beneath the lateral as a line source. While other models usually are used to estimate the wetting front around a point source.

Perspectives on total phosphorus response in rivers: Examining the influence of rainfall extremes and post-dry rainfall

Eutrophication is a significant environmental problem caused by nutrient loads from both point and non-point sources. Weather variables, particularly precipitation, affect the concentration of nutrients in water bodies, particularly those from non-point sources, in two contrasting ways. Heavy precipitation causes surface runoff which transports pollutants to rivers and increases nutrient concentration. Conversely, increased river flow can dilute the concentration, lowering it. This study investigates the impact of extreme precipitation, prolonged precipitation, and precipitation after a dry period on the total phosphorus concentration in the Moehne and Erft rivers in Germany, given the projected increase in frequency of extreme precipitation events and long drought periods due to climate change. The study comprises two parts: selecting extreme weather days from 2001 to 2021 and comparing observed Total Phosphorus concentrations with estimated concentrations derived from Generalized Additive Models and linear regression based on the discharge-concentration relationship. Changes in river TP concentration in response to continuous precipitation and precipitation after a dry period were also studied. Our results showed that during wet extreme and post-dry period rainfall events, TP concentration consistently surpassed expected values, underscoring the profound influence of intense rainfall on nutrient mobilization. However, we observed the impact of continuous rainfall to be non-unidirectional. Our work is distinguished by three key innovations: 1) addressing limitations in studying the effects of extreme weather on water quality due to limited temporal resolution, 2) incorporating both linear and non-linear modeling approaches for discharge-concentration relationships, and 3) performing a comprehensive analysis of temporal and spatial patterns of Total Phosphorus concentrations in response to varying rainfall patterns.

Structural, radiation shielding, thermal and dynamic mechanical analysis for waste rubber/EPDM rubber composite loaded with Fe2O3 for green environment

Increasing waste rubber recycling produces a specious range of products for many valuable applications. Waste Rubber/EPDM composite with different concentrations was prepared. Infrared spectroscopy (FTIR) is used to identify the chemical composition. A water absorption test, Dynamic mechanical analysis (DMA), and Thermal Gravimetric Analysis (TGA) were performed. The (75/25) WR/EPDM rubber composite exhibited the best behavior with the highest mechanical performance. Fe2O3 was added to (75/25) WR/EPDM rubber composite. Water absorption, FTIR, TGA, and DMA were investigated. The composite performance was improved with increasing Fe2O3 content. The linear attenuation coefficients (μ) were also measured as a function of the concentrations of Fe2O3 for γ-ray energy 662 keV by using 137Cs point source; the radiation shielding can be denoted by numbers of parameters like mass attenuation coefficient (μm), half value layer (HVL), Tenth value layer TVL and radiation protection efficiency (RPE%), radiation protection efficiency increased as Fe2O3 increased.

Improved drinking water planning challenges in Urban Households’ in Bamenda city, Cameroon

Access to improved drinking water remains a fundamental need and a basic human right vital for the dignity and health of all people. There is an urgent need to increase access to improved drinking water in urban households in Bamenda city where a low proportion currently appears to be having access. There also exist marked disparity in access amongst the different Sub-divisions which is still to be scientifically investigated. This study sets out to investigate the improved drinking water planning challenges in urban households in Bamenda, Cameroon. The study used systematic field observation, household surveys and administration of 520 copies of questionnaire to urban household heads as primary sources of data collection. The administration of the 520 copies of questionnaire was carried out using purposive and simple random sampling techniques within Bamenda I, II and III Sub-Divisions. Primary data were matched with secondary source information obtained from WHO, UNICEF, UN, CDC, UNDP, PAHO and The University of Bamenda Central Library. Findings revealed that standpipes (41.3%), protected dug well (51.9%), piped water connected to households (54.8%), boreholes (61.9%), rain water collection (63.3%) and spring water harnessed to households (38.6%) constitutes the main urban households improved drinking water sources. Also, natural factors (33.67%) and planning-related challenges (63.33%) work together to limit access to improved drinking water to households. Field observation and measurements revealed that less than 5 urban households share a common water source, while other 42.88% cover <50m to get to the nearest improved drinking water source point. The study highlights that improved drinking water in Bamenda city is currently a limited and non-basic service. The study recommends the expansion of improved drinking water infrastructure by the relevant stakeholders, systematic data collection on factors affecting access to improved drinking water by urban households for better decision making, seek ways to increase accessibility of improved drinking water by the government via MINEE and MINDUH and finally, households should build water towers to store water for continuous use.

Modelling future coastal water pollution: impacts of point sources, socio-economic developments & multiple pollutants

Urbanisation is happening worldwide. In 2100, over 70% of the population is projected to live in highly urbanised areas. As a result, urban wastewater discharge may increase. This may add multiple pollutants to rivers and coastal waters. However, current knowledge on how urbanisation-related socio-economic developments affect coastal water pollution is limited. In this study, we analysed individual and combined impacts of wastewater treatment improvements, economic growth and city expansion on future coastal water pollution from point sources (sewage and open defecation) by sub-basin taking a multi-pollutant approach. We improved the existing MARINA-Multi model (version Global-1.0) by integrating hydrology and pollutant retentions in order to quantify river exports of total dissolved nitrogen, total dissolved phosphorus, microplastics and triclosan to coastal waters for 2010 and 2100 using scenario analysis. Globally, river exports from point sources are projected to more than double by 2100 for all pollutants, especially in Africa and Asia. Wastewater treatment improvements, economic growth and city expansion can have a positive (less pollution) or negative (more pollution) impact on future coastal water pollution. These impacts differ among pollutants and sub-basins. Wastewater treatment improvements may globally reduce multi-pollutant issues (−30% to −38% change on average) compared to the reference scenario (positive impact). Economic growth and city expansion may globally enhance multi-pollutant issues (+15% to +25% and +28% to +33% change on average, respectively) compared to the reference scenario (negative impact). A combined scenario, accounting for all three socio-economic developments simultaneously, may globally reduce or enhance pollutant issues (−21% to +50% change on average) compared to the reference scenario. In the combined scenario, the reinforcements of positive and negative impacts are pollutant- and region-dependent. Our study gives insights into future coastal water pollution, which aids in identifying management strategies for urban areas, hence contributing to reaching Sustainable Development Goal 14.

Sludge degradation, nutrient removal and reduction of greenhouse gas emission by a Chironomus-Azolla wastewater treatment cascade.

Wastewater treatment plants (WWTPs) are a point source of nutrients, emit greenhouse gases (GHGs), and produce large volumes of excess sludge. The use of aquatic organisms may be an alternative to the technical post-treatment of WWTP effluent, as they play an important role in nutrient dynamics and carbon balance in natural ecosystems. The aim of this study was therefore to assess the performance of an experimental wastewater-treatment cascade of bioturbating macroinvertebrates and floating plants in terms of sludge degradation, nutrient removal and lowering GHG emission. To this end, a full-factorial experiment was designed, using a recirculating cascade with a WWTP sludge compartment with or without bioturbating Chironomus riparius larvae, and an effluent container with or without the floating plant Azolla filiculoides, resulting in four treatments. To calculate the nitrogen (N), phosphorus (P) and carbon (C) mass balance of this system, the N, P and C concentrations in the effluent, biomass production, and sludge degradation, as well as the N, P and C content of all compartments in the cascade were measured during the 26-day experiment. The presence of Chironomus led to an increased sludge degradation of 44% compared to 25% in the control, a 1.4 times decreased transport of P from the sludge and a 2.4 times increased transport of N out of the sludge, either into Chironomus biomass or into the water column. Furthermore, Chironomus activity decreased methane emissions by 92%. The presence of Azolla resulted in a 15% lower P concentration in the effluent than in the control treatment, and a CO2 uptake of 1.13 kg ha-1 day-1. These additive effects of Chironomus and Azolla resulted in an almost two times higher sludge degradation, and an almost two times lower P concentration in the effluent. This is the first study that shows that a bio-based cascade can strongly reduce GHG and P emissions simultaneously during the combined polishing of wastewater sludge and effluent, benefitting from the additive effects of the presence of both macrophytes and invertebrates. In addition to the microbial based treatment steps already employed on WWTPs, the integration of higher organisms in the treatment process expands the WWTP based ecosystem and allows for the inclusion of macroinvertebrate and macrophyte mediated processes. Applying macroinvertebrate-plant cascades may therefore be a promising tool to tackle the present and future challenges of WWTPs.

Log-Linear Model and Delivery Load Analysis for Improvements in Water Quality through TMDL in the Gyeongan Stream Watershed, Republic of Korea

The effectiveness of implementing the total maximum daily load (TMDL) in the Gyeongan stream watershed was evaluated to assess its impact on water quality. The relationships between water quality and flow rate and load and water quality were reinterpreted using a log-linear model and the delivery load, respectively. To estimate annual water quality trends and analyze the effects of water quality improvement in each parameter, an improved multivariable log-linear model addressing the limitations of the traditional L-Q equation was applied to analyze the relationship between water quality and flow rate, excluding the effects of flow rate and seasonality. The effect of total phosphorus (T-P) was particularly prominent. A new delivery load was developed and applied to address the limitations of the original unit-based delivery load. Evaluations showed that water quality continuously improved across all parameters, and all methods (excluding the influence of flow rate on water quality fluctuations) were highly effective in estimating water quality changes attributable to anthropogenic pollution sources. The analysis of pollutant contributions revealed that managing point sources is necessary for controlling the biochemical oxygen demand and total nitrogen, while point and non-point sources require T-P management. Future policy development should consider this when formulating management strategies.

In-fiber illumination-detection-synchronized confocal microscopy for high-precision fast axial scanning

Confocal microscopy remains a major workhorse in the 3D surface topography measurement owing to its reliability and compatibility for workpieces with various reflectance, which, however, suffers from slow scanning speed and limited axial resolution. Commercial confocal microscopy primarily relies on the axial movement of a sample or objective lens to create a series of 2D image stacks, and then reconstruct 3D map. Nevertheless, most samples and objective lens are too bulky to scan rapidly, let alone that multiple scans are required to increase the signal-to-noise ratio (SNR). To address this issue, an original approach named illumination-detection-synchronized confocal microscopy was developed, which enabled high-precision fast axial scanning via a compact fiber-multiplexed port with the high-speed synchronous motion of point source and point detection. The approach can effectively improve the peak localization precision while not requiring a high-precision motion stage. Theoretically, via controlling the magnification of the optical system M > 1, the total peak localization precision of axial light intensity response curve can be improved by M3 times. Experiments show that the single-point repeat measurement precision by this approach is improved by 4 times, and the profile measurement precision is enhanced by 2.3 times. Moreover, this approach can effectively avoid collisions between the sample and objective lens, and has the potential to design a low-cost single-point confocal sensor or confocal profilometer.

Unidirectional focusing Rayleigh waves EMAT for plate surface defect Inspection

ABSTRACT Electromagnetic ultrasonic Rayleigh waves are commonly used for detecting surface or near-surface defects, but they still exhibit the drawback of low energy conversion efficiency. In this study, based on the Huygens principle and the discrete point source method, a double curving meander line coils EMAT (DC-MLCs EMAT) which generate unidirectional focusing Rayleigh waves is designed. Firstly, a simulation model of the transducer is established using COMSOL Multiphysics. Then, the impacts of magnet and coise defect detection efficiency is validated by numerical simulation method. Finally, a physical transducer is made, an experimental system is built, and the defect specimens are tested using this experimental system. The simulation and experimental results show that the optimised DC-MLCs EMAT significantly improves ultrasound focusing effect. Compared with the existing single constant length meander line coil（SCL-MLC）EMAT, the signal strength increases by 164.36%. This DC-MLCs EMAT shows good application prospects in the field of fixed focal length measurement.

A three-dimensional, discrete-continuum model of blood pressure in microvascular networks.

We present a 3D discrete-continuum model to simulate blood pressure in large microvascular tissues in the absence of known capillary network architecture. Our hybrid approach combines a 1D Poiseuille flow description for large, discrete arteriolar and venular networks coupled to a continuum-based Darcy model, point sources of flux, for transport in the capillary bed. We evaluate our hybrid approach using a vascular network imaged from the mouse brain medulla/pons using multi-fluorescence high-resolution episcopic microscopy (MF-HREM). We use the fully-resolved vascular network to predict the hydraulic conductivity of the capillary network and generate a fully-discrete pressure solution to benchmark against. Our results demonstrate that the discrete-continuum methodology is a computationally feasible and effective tool for predicting blood pressure in real-world microvascular tissues when capillary microvessels are poorly defined.

Antibiotic Resistance Genes and Faecal Sterols in Marine Sediments: An Evidence of Their Presence away from Point Sources–Kuwait’s Example

Coastal areas are vital ecosystems, supporting diverse marine life and providing resources essential to human well-being. However, sewage pollution poses a significant threat to these delicate environments, impacting water quality, biodiversity, and public health. Antimicrobial resistance (AMR) has gained importance. We believe the presence of faecal sterols in coastal and marine sediments is a reliable indicator of sewage contamination. At most sites, the faecal contamination was observed with ranges from <dl to 18713 ng g−1 dw. The coprostanol/cholesterol ratio was >0.2 at 68% of the sampling sites, suggesting a large spatial distribution of sewage contamination beyond the discharge points. The positive correlation of faecal sterols with AMR provides an insight that antibiotic resistance genes (ARGs) can spread to areas away from point sources. We propose that sterol ratios be considered as a screening tool for selecting the sites for AMR assessment. The analyses of sterols will be less time and cost-intensive compared to pharmaceutical analyses and can be a reliable indicator for AMR studies in areas where prior knowledge and experience are lacking.

Frequencies of Warm Debris Disks Based on Point Source Catalogs of Spitzer, WISE, and Gaia

More than a thousand warm debris disks have been detected as infrared excess at mid-infrared wavelengths, and their frequencies have been obtained for various spectral types of stars. However, the dependence of the frequencies on spectral type is still debated because the number of stars with significant and detectable infrared excess is limited. Herein, we present the largest systematic search for infrared excess using data from Gaia, WISE, and Spitzer. We identified 373, 485, and 255-reliable infrared excesses in the mid-infrared archival data at wavelengths of 12, 22, and 24 μm for WISE/W3, W4, and Spitzer/MIPS ch1, respectively. Although we confirmed that more massive stars tend to show higher frequencies of debris disks, these disk frequencies are relatively flat for both low- and intermediate-mass stars, with a jump at 7000 K for all three wavelengths. Assuming that bright, warm debris disks have lifetimes of a few to several hundred million years, the disk frequency can be understood as the ratio between the timescale and the upper limits of the sample ages. We also found that intermediate-mass stars with infrared excess tend to be bluer and fainter along the evolutionary track than those without, implying that massive stars hosting debris disks are relatively young, with an isochronal age of approximately 500 Myr. These tendencies are reasonably explained by a standard scenario in which debris disks are likely to be produced by collisions of planetesimals in the early stages of stellar evolution, such as the Late Heavy Bombardment.

Enhancing gamma radiation shielding properties of iron metal and natural rubber composites

AbstractA comparative study was conducted to investigate the gamma and neutron radiation shielding properties of composites made from iron metal (micro and nano) dispersed within natural rubber (NR). The aim was to attenuate neutron and γ‐rays. The study utilized the gamma spectroscopy technique and the Monte Carlo FLUKA code. To assess the gamma ray shielding, a 3×3 Nal (Tl) detector and radioactive point sources were employed. Two comparative studies were carried out, one using Fe loaded NR (Fe/NR) composites in microsize and the other using Fe/NR composites in nanosize. The objective was to determine the impact of iron nanoparticles on the shielding ability of the composites. The findings revealed that the Fe/NR composites in nanosize exhibited superior gamma radiation shielding ability compared with the Fe/NR composites in microsize. These results were supported by the FLUKA Monte Carlo code, which demonstrated good agreement with both the experimental and theoretical XCOM data.

Implementing robust outlier detection to enhance estimation accuracy of GNSS-IR based seasonal snow depth retrievals

ABSTRACT Monitoring snow depth variations aligned with the seasonal cycle is crucial for studies on climate change and its impacts due to global warming. Especially in terms of snow hydrology, the determination and continuous monitoring of snow depth to determine snow water equivalent is a priority in climate, water science, drought, flood, and inundation prediction studies, particularly in the water cycle. Recently, the so-called Global Navigation Satellite Systems – Interferometric Reflectometry (GNSS-IR) method enables to extract environmental radiometric and geometric characteristics of surface where the signals transmitted from the satellites reflect. The reflected signal follows an extra path than the direct one and causes a major error source for accurate point positioning but a useful tool for sensing the environment. However, outliers remain a challenge in long-term GNSS-IR estimations. In this study, we proposed a median-based robust outlier detection (ROD) approach for identifying outliers in long-term GNSS-IR snow depth estimations. To validate our approach, we analysed 5-year GNSS L1 SNR and L2 SNR data from 1 January 2015 to 31 December 2019 provided by AB33 and AB39 GNSS stations in Alaska, U.S.A. using the GNSS-IR method. We validated GNSS-IR estimations using snow depth measurements from the Coldfoot and Fort Yukon stations in the SNOTEL network. Applying ROD to long-term snow depth estimates increased the highest correlation from 91.58% to 94.93%, and reduced the lowest RMSE from 8.6 cm to 6.7 cm. In addition, the improvement rates calculated to assess the contribution of ROD to the results showed improvements of up to 6.9% in correlation and 26.1% in RMSE. Overall, the results demonstrate that ROD can be effectively used to detect outliers in long-term GNSS-IR snow depth time series.

Multi-purpose InSTRument for Astronomy at Low-resolution: MISTRAL at the Observatoire de Haute-Provence

Multi-purpose InSTRument for Astronomy at Low-resolution (MISTRAL) is the new Faint Object Spectroscopic Camera mounted at the folded Cassegrain focus of the 1.93m telescope of the Haute-Provence Observatory (OHP). We describe the design and components of the instrument and give some details about its operation. We emphasize in particular the various observing modes and the performance of the detector. A short description of the working environment is also provided. Various types of objects, including stars, nebulae, comets, novae, and galaxies, have been observed during various test phases to evaluate the performance of the instrument. The instrument covers the range of 4000 to 8000 AA with the blue setting, or from 6000 to 10000 AA with the red setting, at an average spectral resolution of 700. Its peak efficiency is about 22$<!PCT!>$ at 6000 AA . In spectroscopy, a limiting magnitude of rsim 19.5 can be achieved for a point source in one hour with a signal-to-noise ratio of 3 in the continuum (and better when emission lines are present). In imaging mode, limiting magnitudes of 20-21 can be obtained in 10-20mn (with average seeing conditions of 2.5 arcsec at the OHP). The instrument is very user-friendly and can be put into operations in less than 15mn (rapid change-over from the other instrument in use) if required by the science (e.g. for gamma-ray bursts). Some first scientific results are described for various types of objects, and in particular, for the follow-up of gamma-ray bursts. While some further improvements are still under way, in particular, to facilitate the switch from blue to red setting and add more grisms or filters, MISTRAL is ready for the follow-up of transients and other variable objects, in the soon-to-come era of the Space-based multi-band astronomical Variable Objects Monitor (SVOM) satellite and of the Rubin telescope, for instance.