Bernard Grobety

Bernard Grobety
Université de Fribourg · Department of Geosciences

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103
Publications
25,182
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2,651
Citations
Citations since 2017
12 Research Items
1231 Citations
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200

Publications

Publications (103)
Conference Paper
Eclogite-hosted metamorphic veins mark former fluid migration pathways during a subduction- exhumation cycle, and allow to trace fluid-mediated element transfer across lithologies, to ultimately metasomatize the mantle wedge. Fluids can be generated by dehydration reactions at different P-T conditions in various lithologies, all influencing how dif...
Conference Paper
In the absence of strong fluid-rock interactions, stable isotopes of oxygen (δ18OV-SMOW) and iron (δ56FeIRMM-524a) are thought to behave conservatively during subduction zone metamorphism. High-pressure minerals may attain isotopic equilibrium, and preserve it in case of limited diffusion. High-Fe3+/ΣFe minerals tend to enrich heavy Fe isotopes com...
Conference Paper
Stable Fe isotope fractionation (δ56Fe = [(56Fe/54Fe)sample/(56Fe/54Fe)IRMM-524a standard − 1] × 1000) is sensitive to redox processes. Under equilibrium conditions, the heavy Fe isotopes tend to partition into more oxidized phases as Fe3+, but the bonding environment can also play a substantial role. We investigate Fe isotope fractionation between...
Article
Full-text available
Eclogites, metagabbros, and paragneisses from the Variscan Münchberg Massif record a complex succession of igneous, hydrothermal and metamorphic processes. The geodynamic setting related to the protolith formation and the impact of different types of fluid-rock interactions have been uncertain up to now. We use major and trace element chemistry as...
Conference Paper
The Münchberg Massif (German Bohemian Massif) is an allochthonous nappe pile within the Saxothuringian zone of the Variscan orogen. Its uppermost nappe (Hangendserie) contains eclogites and paragneisses which were both affected by early Variscan high-pressure metamorphism. A dark, kyanite-free eclogite (Mg# ~45–70, Al2O3 ~13–16 wt.%) can be disting...
Conference Paper
Fe isotopes provide a promising tool to trace fluid-rock interactions and mass transfer in subducting lithosphere due to redox-sensitive isotope fractionation (phases rich in Fe3+ preferentially incorporate the heavier isotopes). Our study aims at understanding to which extent the Fe isotopes in the subducted crust reflect (1) igneous protolith for...
Conference Paper
Fe isotopes provide a promising tool to trace fluid-rock interactions and mass transfer in subducting oceanic lithosphere due to redox-sensitive isotope fractionation (phases rich in Fe3+ preferentially incorporate the heavier isotopes). Our study aims at understanding to which extent the Fe isotope signatures of eclogites reflect (1) igneous proto...
Article
The subduction-related volcanic front in Nicaragua consists of the Tertiary “Coyol” member in the eastern highlands and the Quaternary to recent volcanic arc within the Nicaraguan depression. Although the Holocene to recent explosive volcanism has been studied extensively no detailed work has been done on the products of explosive volcanism from Qu...
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Computer controlled scanning electron microscopy (CCSEM) is a widely-used method for single airborne particle analysis. It produces extensive chemical and morphological data sets, whose processing and interpretation can be very time consuming. We propose an automated two-stage particle classification procedure based on elemental compositions of ind...
Article
We describe the synthesis of hybrid magnetic ellipsoidal nanoparticles that consist of a mixture of two different iron oxide phases, hematite (α-Fe2O3) and maghemite (γ-Fe2O3), and characterize their magnetic field-driven self-assembly. We demonstrate that the relative amount of the two phases can be adjusted in a continuous way by varying the reac...
Article
Einige Mikroorganismen zeigen anaerobe mineralische Respiration, bei der sie Metallionen zu Metallnanopartikeln reduzieren. Hierbei werden Peptide als Medium für den Elektronentransfer (ET) verwendet. Diese Reaktionsklasse wird anhand eines Modellpeptids und Silber als Metall diskutiert. Erstaunlicherweise können Silberionen, die von Peptiden mit H...
Article
Some microorganisms perform anaerobic mineral respiration by reducing metal ions to metal nanoparticles, using peptide aggregates as medium for electron transfer (ET). Such a reaction type is investigated here with model peptides and silver as the metal. Surprisingly, Ag(+) ions bound by peptides with histidine as the Ag(+) -binding amino acid and...
Article
The morphology of small volcanic ash particles is fundamental to our understanding of magma fragmentation, and in transport modeling of volcanic plumes and clouds. Until recently, the analysis of 3D features in small objects (< 250 μm) was either restricted to extrapolations from 2D approaches, partial stereo-imaging, or CT methods having limited s...
Article
The Eifel region in western central Germany is the type locality for maar volcanism, which is classically interpreted to be the result of explosive eruptions due to shallow interaction between magma and external water (i.e. phreatomagmatic eruptions). Sedimentary structures, deposit features and particle morphology found in many maar deposits of th...
Conference Paper
Full-text available
The recently calibrated Zr-in-rutile geothermometer (e.g. Watson et al., 2006; Zack et al., 2004) could be very suitable to identify and investigate UHT terranes (Ewing et al. 2013). It is based on the incorporation of Zr (as a trace element) into rutile, which is a common accessory mineral in a wide variety of metamorphic rocks including UHT rocks...
Article
We have synthesized hematite cube-shaped nanoparticles using different synthesis paths to examine the effect of the intermediate product akaganeite (β-FeOOH) on the size and shape of the final hematite particles. Akaganeite spindles and hematite nanocubes are prepared using forced hydrolysis of iron chloride (FeCl3) salt. We use a combination of tr...
Article
The dehydroxylation reactions of chrysotile Mg3Si2O5(OH)4 and brucite Mg(OH)2 were studied under inert nitrogen atmosphere using isothermal and non-isothermal approaches. The brucite decomposition was additionally studied under CO2 in order to check the influence of a competing dehydroxylation/carbonation/decarbonisation reaction on the reaction ki...
Article
Full-text available
Alburnite, ideally Ag8GeTe2S4, was discovered in the Cârnicel vein from the Roşia Montana epithermal Au-Ag ore deposit, Apuseni Mountains, Romania The new mineral is associated with tetrahedrite, galena, pyrite, sphalerite, chalcopyrite and tellurides (hessite, altaite and sylvanite). Associated gangue minerals are rhodochrosite, quartz, calcite an...
Article
Dense and gastight dead-end tubular Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) membranes were fabricated by thermoplastic extrusion. Optimal feedstocks for the extrusion of dead-end tubular structures were obtained for a feedstock consisting of 89.83 wt% BSCF powder, 5.63 wt% ethylene vinyl acetate (EVA), 3.56 wt% paraffin wax (PW), and 0.98 wt% stearic acid...
Article
Fine particles were sampled both inside the chimneys and in the near-field of an Fe-Mn-alloy manufacturing plant. The transfer from one point to another point in the environment, as well as the bioavailability and toxicity of these two metals, depend above all on their speciation. The oxidation states of iron and manganese in the collected particle...
Article
This paper presents the processing steps for producing thin planar and tubular oxygen separation membranes by thermoplastic forming of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) with polystyrene (PS) and stearic acid (SA) as binder. The influence of powder content on the shape stability of thin membranes (tubular and planar structures) during the thermoplasti...
Article
One of the most important mechanisms releasing water in subducting slabs of oceanic crust is connected to the dehydration of serpentinized oceanic rocks. This study reports on a detailed investigation of the transition from chrysotile-an important serpentine mineral-to forsterite through the release of water. The dehydroxylation of natural chrysoti...
Article
The ion conductivity of two series of porous ceramic diaphragms impregnated with caustic potash was investigated by electrochemical impedance spectroscopy. To understand the impact of the pore structure on ion conductivity, the three-dimensional (3-D) pore geometry of the diaphragms was characterized with synchrotron x-ray absorption tomography. Io...
Article
Full-text available
The aim of the present investigation is to define microstructure parameters, which control the effective transport properties in porous materials for energy technology. Recent improvements in 3D-imaging (FIB-nanotomography, synchrotron X-ray tomography) and image analysis (skeletonization and graph analysis, transport simulations) open new possibil...
Article
In the present study, we address the interaction between a thermoplastic binder system and Ba(0.5) Sr(0.5) Co(0.8) Fe(0.2) O(3-δ) (BSCF) during thermal treatment of the thermoplastic feedstock. BSCF powder was coated with different amounts of stearic acid (SA) acting as a surfactant. Oxygen release from the uncoated BSCF surface changes the decompo...
Article
Ambient airborne particulate matter is known to cause various adverse health effects in humans. In a recent study on the environmental impacts of coal and tire combustion in a thermal power station fine crystals of PbSO4 (anglesite), ZnSO4•H2O (gunningite), and CaSO4 (anhydrite) were identified in the stack emissions. Here, we have studied the toxi...
Article
Full-text available
The alkaline electrolyzer industry is facing the imminent necessity of replacing the asbestos diaphragms with a separator made of a new environmentally friendly material. The influence of a diaphragm's material and porosity on the ionic conductivity was studied for asbestos, zirconium dioxide, wollastonite and olivine diaphragms. Developed electroc...
Article
A temperature-dependent in situ micro-FTIR and micro-Raman spectroscopic investigation was performed on powdered (FTIR, Raman) and single-crystal (Raman) lizardite-1T samples between room temperature and 819 degrees C. Between room temperature and 665 degrees C, the OH stretching bands shift to lower wavenumbers, demonstrating a weak expansion of t...
Article
Full-text available
During the time period of the eruption of the Icelandic volcano Eyjafjallajökull in April/May 2010 the Duesseldorf University of Applied Sciences has performed 14 research flights in situations with and without the volcanic ash plume over Germany. In parallel to the research flights in Germany three measurement flights have been performed by the Un...
Article
Polymeric binder burnout during thermoplastic processing of yttria stabilized zirconia (YSZ) ceramics were analyzed using thermogravimetric analysis (TGA). The debinding kinetics of the stearic acid/polystyrene binder have been described using model free methods and compared with the decomposition rate of the pure polymers. The apparent activation...
Article
Full-text available
Laser ablation of metals in liquid helium results in the formation of metal filaments with diameters on the order of 2–10 nanometres and of spherical nanoparticles. In superfluid helium these nanowires aggregate into centimeter-sized networks. We study the morphology and the electric conductivity of these large aggregates, as well as extinction spe...
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Full-text available
Cr-rich clinozoisite with up to 0.89 Cr3+ apfu and additional 0.23 V3+ apfu originating from the Outokumpu copper mine, Finland, was studied by electron microprobe analyses, laser ablation inductively coupled-plasma mass spectrometry, single-crystal X-ray structure refinement of natural crystals and after step-wise annealing to a maximum temperatur...
Article
Oxygen permeability measurements of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) disk shaped membranes fabricated by thermoplastic processing and sintered at different temperatures (1000–1100°C), showed no influence of the grain size on the oxygen permeation fluxes. To further investigations, Electron Backscattered Diffraction (EBSD) and Conductive mode (CM) mi...
Article
Airborne particulate matter (PM) of varying size and composition is known to cause health problems in humans. The iron oxide Fe(3)O(4) (magnetite) may be a major anthropogenic component in ambient PM and is derived mainly from industrial sources. In the present study, we have investigated the effects of four different size fractions of magnetite on...
Article
Until now, the adverse effects of toner powders on humans have been considered to be minimal. However, several recent reports have suggested possible significant adverse health effects from toner dust inhalation. The aim of this study was to evaluate the genotoxic potential of black toner powders in vitro. For the study of DNA damage, A549 cells we...
Article
Full-text available
Magnetic properties of particles are generally determined from randomly oriented ensembles and the influence of the particle orientation on the magnetic response is neglected. Here, we report on the magnetic characterization of anisotropic spindle-type hematite particles. The easy axis of magnetization is within the basal plane of hematite, which i...
Article
Particulate matter is an important constituent of our atmosphere and has a critical impact on natural processes and human health. Although they are a minor component of the average global mass flux, anthropogenic particles are abundant in the urban environment, where they contribute substantially to air pollution. Particulate matter is routinely mo...
Conference Paper
Air quality measurements of German health and recreation resorts are based on specific quality standards and are licensed by state regulations. For this purpose easy and cost-effective passive sampling techniques are in use. Apart from measuring gaseous pollutants, fine and coarse particulate matter is sampled and analyzed. For collection of the co...
Conference Paper
During 2008, Saharan dust reached southern Germany during several events, increasing significantly the weekly levels of particulate matter. The aim of this study was to characterize these dust events by using aerosol samples collected at an urban site in Freiburg, Germany. These samples were compared to non-event conditions at the same site. Using...
Article
Computed X-ray tomography was used to characterise distribution and sphericity of Ti granules within highly porous (>35%) Al2O3 powder compacts, as they are key parameters for a successful infiltration by Fe-based alloys. Setting of reconstruction constraints, image editing as well as data processing are the most challenging parts of computed X-ray...
Article
Full-text available
We demonstrate that laser ablation of a gold target immersed in superfluid and normal fluid helium leads to the formation of elongated gold nano-fragments. In the superfluid phase these nano-fragments aggregate into filaments with extremely large aspect ratios displaying metallic electric conductivity. We attribute this unusual structure to the coa...
Article
High-temperature steam electrolysis by solid oxide electrolysis cells (SOEC) is a method with great potential for transforming clean and renewable energy from non-fossil sources to synthetic fuels such as hydrogen, methane or dimethyl ether, which have been identified as promising alternative energy carriers. With the same technology, fuel gas can...
Article
Apatites derived from different rock types have distinctive absolute and relative abundances of trace elements including rare-earth elements (REE). [1] In this study, apatite inclusions in natural gem-quality corundum and spinel were analysed. They originate from the world’s most important mining areas including Myanmar, Vietnam, Sri Lanka, Ma...
Article
Solid oxide electrolyser cells (SOECs) have great potential for efficient and economical production of hydrogen fuel. Element diffusion between the Ni-cermet electrode and the metal substrate of metal supported cells (MSC) is a known problem in fuel cell and electrolysis technology. In order to hinder this unintentional mass transport, different ce...
Article
Diesel and wood combustion are major sources of carbonaceous particles in the atmosphere. It is very hard to distinguish between the two sources by looking at soot particle morphology, but clear differences in the chemical structure of single particles are revealed by C(1s) NEXAFS (near edge X-ray absorption fine structure) microspectroscopy. Soot...
Article
Activation mechanism and infiltration kinetic for pressureless melt infiltration of Ti activated Al 2O 3 preforms by high melting alloy, was reported. Porous alumina preforms were prepared with fine and coarse alumina powders mixed with different amounts of either fine or coarse titanium activator. Pressed pellets of powder mixtures A100T40-i and A...
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Full-text available
The influence of Cu(II) on the hydrothermal and thermal transformations of a synthetic hectorite was investigated by a combined approach using mainly X-ray diffraction, thermal analyses, and electron paramagnetic resonance spectroscopy. The presence of Cu(II) during hydrothermal treatment increased the crystallite size. Copper (II) was both structu...
Article
A carbon nanotube/perovskite composite material was developed as material for air electrodes in fuel cells or zinc-air batteries. For this purpose, carbon nanotubes were directly grown on the perovskite La0.6Sr0.4CoO3 impregnated with Fe solution which acted as substrate. The synthesis was carried out in a fluidised bed reactor. The carbon source w...
Article
The distributions of general and coincidence site lattice (CSL) grain boundaries (GBs) in texture-free alumina and zirconia ceramics sintered at two different temperatures were investigated based on electron backscatter diffraction (EBSD) measurements. Results were compared with the distributions obtained from random 2D spatial models and with calc...
Article
A novel activation mechanism for the pressureless infiltration in the Non-wetting Steel-Alumina metal matrix composites (MMC) systems was demonstrated by conducting a series experiments. The MMC system studied is made of Alumina and high melting iron based alloys and meet the requirement for certain application in food, pharmaceutical and automotiv...
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Full-text available
In this article, the potential of a thermophoretic sampling device to derive quantitative particle size distributions and number concentrations of aerosols based on microscopic single particle analysis is explored. For that purpose a plate-to-plate thermophoretic precipitator to collect ultrafine atmospheric particles for TEM (transmission electron...
Article
For two decades, considerable efforts have been made to explain the formation of snowball garnets by either the rotational or non-rotational models. On the basis of morphological, chemical and crystallographic evidence, this paper presents new data on snowball garnets showing that the formation of these microstructures can be explained by the combi...
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We present a recently developed method using a field emission scanning electron microscope (FEG) to view and photograph microfossil specimens that are not coated by conductive material. The FEG microscope provides high electron flux and offers the option to capture images at low beam voltage. Balancing incident energy with absorbed energy from the...
Article
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X-ray computed micro tomography (CT) is an alternative technique to the classical methods such as mercury intrusion (MIP) and gas pycnometry (HP) to obtain the porosity, pore-size distribution, and density of porous materials. Besides the advantage of being a nondestructive method, it gives not only bulk properties, but also spatially resolved info...
Article
Submicronic aerosol particles were collected in two sampling campaigns during CLACE-4 and -5 ("the Cloud and Aerosol Characterisation Experiment in the Free Troposphere") at the high alpine research station on top of Jungfraujoch (altitude: 3580 m.a.s.l.). The particles were deposited directly on transmission electron microscopy (TEM) grids placed...
Article
We investigated the mechanical behaviour and microstructural evolution of a dolomite marble from Mt. Frerone (Adamello, N-Italy) during decarbonation to calcite and periclase in torsion experiments. Tests were performed in a Paterson gas-medium apparatus on cylindrical samples of 10 mm diameter and 10 mm length. Experiments were conducted at 800 °C...
Article
Many authors have considered pottery manufacturing constraints and sociocultural elements as factors in change in past civilizations over time. The main issue of this research is to better understand the reasons for changes, or choices, in pottery raw materials. The very precise and detailed stratigraphy and cultural succession of occupations is ba...
Article
The Tláloc volcano (TV) is a 4125 m high stratovolcano of the Trans Mexican Volcanic Belt (TMVB) and is located in the northern end of the N-S trending Sierra Nevada, 30 km NE of Mexico City. Few data on the petrological and temporal evolution of TV have been published to date. Recently dated deposits gave ages between 32'000 and 34'500±500 years B...
Article
We present a petrophysical analysis of upper mantle xenoliths, collected in the Quaternary alkali basalt fields (Series III and IV) from the island of Lanzarote. The samples consist of eight harzburgite and four dunite nodules, 5 to 15 cm in size, and exhibit a typical protogranular to porphyroclastic texture. An anomalous foliation resulting from...
Article
The goal of this study was to identify and quantify particles emitted from railway traffic. For that purpose PM10 samples were collected near a busy railway line using a wind direction and speed controlled sampling equipment consisting of five devices. Measurements taken perpendicular to the railway lines at 10, 36 and 120 m distance enable an iden...
Article
Ruddlesden-Popper (RP) compounds are composed of alternating perovskite-type and rocksalt-type structural elements. MgSiO3 and MgO are found as separate phases in Earth's lower mantle. Both structural elements occur also in the hypothetical RP-series MgO(MgSiO3)n. It is interesting to explore the high pressure-high temperature stability of such RP-...
Article
The Earth's mantle is divided into five layers with four major phase transitions at 410, 520, 660 and ˜2600-km depths, due to a structural and chemical changes of its main constituent minerals. MgSiO3 is believed to be a predominant mineral, at least in the upper part of the lower mantle. MgSiO3 has a structural sequence from corundum-type ilmenite...
Article
We performed torsion experiments using a Paterson rig apparatus on cylindrical (diam = 1cm; H = 1cm) samples of natural specimen of pure dolomite (
Article
High Resolution Transmission and Analytical Electron Microscopy (HRTEM-AEM) of phlogopite crystals from the Finero lherzolite (Italian Western Alps) revealed nanometric intergrowths of graphite-like layers. The intergrowths consist of 4 to 6 graphite-like layers (c approximate to 3.3 Angstrom) with the basal plane parallel to (001) of the phlogopit...
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Pezzottaite is a new mineral from the Sakavalana pegmatite, located 25 km south of the village of Mandosonoro, southwest of the town of Antsirabe, 140 km southwest of Ambatofinandrahana, in Fianarantsoa province, central Madagascar. It usually occurs as isolated crystals that can have three distinct habits: (1) irregularly shaped flat masses that f...
Article
Tellurium nanotubes and nanorods were synthesized by physical vapor deposition (PVD) in an induction furnace for reaction times between 25 and 35 min. The growth morphologies depended on the reaction times and the atmosphere in the induction furnace. Nanotubes grew only under argon atmosphere (1 mbar). Under vacuum, tellurium blades and nanorods we...
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The crystal structure of the rare hexagonal mineral painite [a = 8.724(1), c = 8.464(2) Å] from Mogok (Myanmar), with the ideal composition CaZrB[Al9O18], was re-determined by single-crystal X-ray diffraction. Structure refinements were performed in space groups P63/m and P63. The centrosymmetric P63/m model yielded excellent agreement (R1 = 1.44%,...
Article
A hot stage in an environmental scanning electron microscope (ESEM) was used for in situ infiltration experiments. Pressureless infiltration of a porous Ti-activated Al(2)O(3) preform has been investigated at temperatures up to 1530 degrees C under two atmospheres (He and H(2)O((g))). A brief description of the operating and the experimental set-up...
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In 2002, a new gem mineral of commercial importance was discovered. In accordance with the need for all new mineral discoveries to be scientifically characterized (see Nickel and Grice, 1998), the gemological community anxiously awaited the results of tests to positively identify the new mineral (Hawthorne et al., 2003, Hawthorne et al., submitted...
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Ultramafic rocks are a major component of the oceanic lithosphere and are commonly exposed near and along slow-and ultra-spreading ridges and in other tectonically active environments. The serpentinization of mantle material is a fun-damental process that has significant geophysical, geochemical and biological importance for the global marine syste...
Article
Carbon nanotubes (CNTs) have been grown by the decomposition of C2H2 over a thin catalyst film in order to investigate the growth mechanism of CNTs by chemical vapour deposition (CVD). The catalyst was prepared from an iron nitrate precursor solution that was spin-coated on an aluminium substrate. The density (mg cm−2) and the length of the CNTs we...
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Pezzottaite, ideally Cs(Be2Li)Al2Si6O18, is a new gem mineral that is the Cs,Li-rich member of the beryl group. It was discovered in November 2002 in a granitic pegmatite near Ambatovita in central Madagascar. Only a few dozen kilograms of gem rough were mined, and the deposit appears nearly exhausted. The limited number of transparent faceted ston...
Article
Olivine with oriented ilmenite inclusions occurs in garnet peridotites and in basic layered intrusions. In all cases, the ilmenite inclusions are elongated parallel to [010](ol) but exhibit different morphology (rods versus platelets). These morphological differences observed for ilmenite inclusions in olivine can be correlated with variations in t...
Article
The late crystallisation stages of Campiglia Marittima skarn are characterised by an increase in Mn-activity at the metasomatic front. Mn-pyroxenoids became stable with respect to johannsenite. The pyroxene-pyroxenoid textures indicate either pyroxenoid overgrowths on johannsenite or pyroxenoid pseudomorphs after johannsenite. TEM investigation of...
Article
The dehydroxylation kinetics of phengite 3T were investigated under both oxidizing (air) and reducing (CO_2/H_2 = 1/4) atmospheres by in-situ