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Multiple-step nucleation pathways have been observed during mineral formation in both inorganic and biomineral systems. These pathways can involve precursor aqueous species, amorphous intermediates, or metastable phases. Despite the widespread occurrence of these processes, elucidating the precise nucleation steps and the transformation mechanisms between each step remains a challenging task. Using a suite of potentiometric, microscopic, and spectroscopic tools, we studied the nucleation pathway of SrSO4 as a function of the physico-chemical solution parameters. Our observations reveal that below a threshold supersaturation, nucleation is driven by bound species, akin to the prenucleation cluster model, which directly leads to the formation of the stable phase celestine, SrSO4. At higher supersaturations, this situation is altered, with nucleation dominated by the consumption of free ions. Importantly, this change in nucleation mechanism is coupled to the formation of a hemihydrate metastable phase, SrSO4 · 1/2H2O, which eventually transforms into celestine, adhering to Ostwald's rule of stages. This transformation is a solution-mediated process, also occurring in the presence of a fluid film and is controlled by the physico-chemical parameters of the surrounding environment. It proceeds through the dissolution of the metastable phase and the de novo crystallization of the final phase. Overall, our results reveal that ion association taking place during the prenucleation stage dictates whether the nucleation pathway goes through an intermediate phase or not. This also underlines that although Ostwald's rule of stages is a common process, it is not a prerequisite for mineral formation—even in systems where it can occur. [ABSTRACT FROM AUTHOR]

The International Association for the Properties of Water and Steam has adopted new formulations for the thermodynamic and transport properties of heavy water. This manuscript describes the development of a formulation for the thermal conductivity of heavy water that was adopted as an international standard in 2021. It is consistent with the equation of state adopted in 2017, revised slightly in 2018, and is valid for fluid states up to 825 K and 250 MPa with uncertainties ranging from 1.5% to 6% depending on the state point. Comparisons with experimental data and with an earlier thermal-conductivity formulation are presented. The 2021 formulation accounts for the critical enhancement of the thermal conductivity, which was not incorporated in the previous formulation. Furthermore, in the zero-density limit, the 2021 formulation is based on thermal conductivity values at temperatures from 250 to 2500 K obtained from the kinetic theory of polyatomic gases. In addition, the 2021 formulation is applicable in a larger range of pressures than the previous formulation. [ABSTRACT FROM AUTHOR]

Copyright of Annales Françaises de Médecine d'Urgence is the property of John Libbey Eurotext Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The binary isotropic and anisotropic collision-induced light scattering spectra of gaseous methane at room temperature are analyzed in terms of a recent ab initio intermolecular potential and interaction-induced pair polarizability trace and anisotropy models, using quantum line-shapes computations. The translational spectra at relatively low frequencies are determined largely by the effects of bound and free transitions. At intermediate frequencies the spectra are sensitive to both the attractive part of the potential and the short-range part of the polarizability trace and anisotropy. The high frequency wings are discussed in terms of the collision-induced rotational Raman effect and estimates for the dipole-quadrupole polarizability A and the dipole-octopole polarizability E are obtained and checked with recent ab initio theoretical values. [ABSTRACT FROM AUTHOR]

In this study, the authors report on femtosecond laser direct generation of microchannels inside poly(methyl methacrylate) with variable dimensions ranging from a channel height of 20 to 350 μm and an aspect ratio down to 1.2. Focused ultrashort laser pulses are used to trigger a material modification in the focal area which can be selectively opened by a subsequent annealing process. A 3D microchannel architecture can easily be realized by moving the specimen using motorized stages, allowing freely chosen complex shaped channel layouts. While the laser wavelength is identified as one of the main parameters determining process effectiveness, another core of this study is the variation of channel dimensions by the numerical aperture of the applied objective to focus the laser. The authors find that both size and shape of the modified region and the resulting microchannel can be controlled by altering the numerical aperture. [ABSTRACT FROM AUTHOR]

Copyright of Annales Françaises de Médecine d'Urgence is the property of John Libbey Eurotext Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Annales Françaises de Médecine d'Urgence is the property of John Libbey Eurotext Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We demonstrate a novel temperature referenced polymer Bragg grating (BG) sensor structure in planar cyclo-olefin copolymer (COC) substrate for tensile and compressive strain sensing. The sensor is based on two serial BGs UV-written into a specially designed planar COC substrate using a 248-nm-KrF laser. Successively, the temperature sensitivity and the behavior toward the tensile and compressive strain of both BGs are evaluated. Furthermore, we calculate the strain distribution in the COC specimen using a numerical simulation and discuss it with regard to the experimental results. [ABSTRACT FROM PUBLISHER]

Discusses present time-resolved photoluminescence studies of perpendicular transport and the subsequent capture of photoexcited carriers in II-VI semiconductor superlattices. Use of a cadmium telluride quantum well; Overview of Bloch-type perpendicular transport in electron and heavy-hole minibands; Temporal characteristics of the collection process.

A newly developed concept for a miniaturized optical shape sensor is demonstrated. The sensor consists of a flexible polymer bending beam with two integrated optical waveguide Bragg gratings spatially staggered to each other. We report on the basic layout and the fabrication process and characterize the fundamental sensing response by an elaborate testing scheme. The polymer shape sensor reveals a pronounced spectral shift of the Bragg wavelength of several nanometers upon deformation with a distinct directionality. In conjunction with an undiscernible hysteresis, these results highlight the general applicability of the polymer Bragg grating-based bending beam as a shape sensor. [ABSTRACT FROM PUBLISHER]

We study pulsed fiber laser back side ablation of silicon carbide diodes. With the objective to thin the SiC substrate thickness without damaging the semiconductor device or altering its electrical characteristics, we investigate the ablation characteristics of silicon carbide and determine the ablation threshold, rate and quality as well as the material composition at the ablated surface. Based on optimized process parameters, including track distance, laser repetition rate and scanning velocity, we micro structure the substrate of SiC diodes and compare its electrical characteristic to an unprocessed device. Our results prove that the typical diode characteristic and built-in voltage are not affected by the laser ablation process. Fiber laser back side ablation therefore offers a precise and efficient micro structuring approach for substrate thinning in silicon carbide technology. [ABSTRACT FROM AUTHOR]

We present a comprehensive experimental study on the influence of laser cutting on the flexural strength of 0.63 mm thick alumina sheets. In this study ceramic specimens are cut to a size of 24×3 mm2 with the flexural strength being measured using a 3 point bending test. Based on a design of experiments approach the results reveal that among the experimental parameters the laser focus position has the highest influence on the flexural strength, reducing it by 63 MPa. Cutting alumina at 300 mm/s yields a flexural strength of 395 MPa, which is significantly lower as compared with reference samples produced by scribe and break having a flexural strength of 520 MPa. Yet, a comparable flexural strength of 311 MPa using a CO2 laser is achieved at only 20 mm/s. To cut small con-tours, digital modulation of the fiber laser output power is employed leading to a flexural strength of 506 MPa at 1 mm/s and 469 MPa at 10 mm/s. Further results show that additional outer contours can halve the flexural strength and the lack of rounding reduces the flexural strength further. Inner contours especially with corners are also decreasing the flexural strength drastically while an inner circle causes only low strength reduction. [ABSTRACT FROM AUTHOR]

Introduction: The differences in bulk elemental compositions, stable-isotope ratios, mineralogy, and structures of chondrites demonstrate the variations in time/space of their formation regions in the solar nebula and the subsequent evolution of their parent body. Naturally, one may expect to find some variations in chondritic organics reflecting their different reservoirs in the solar nebula and the secondary modifications on asteroids [1]. Chondrite soluble organic matter (SOM) is complex, and the aqueous reactions on asteroids are thought to be where it was synthesized [2]. Also, thermal alterations could have produced organo-metallic complexes [3]. Our previous study of Tagish Lake meteorite showed that the primordial SOM could be distinguished from the parent body's secondary alteration through mass distribution. Also, we concluded that the complex nature of the primordial SOM was established before severe alteration on the asteroid and later became simplified on the asteroid [4]. However, it is still unclear if the secondary processes recorded in the Tagish Lake SOM can be generalized and applied to other chondrite groups. Recently, organic extracts from the asteroid Ryugu regolith materials brought to Earth by the JAXA Hayabusa 2 mission were analyzed and revealed the nature of terrestrially uncontaminated CI organic materials [5]. Although Ryugu extracts and other chondrite extracts are not identical, it appears to have only subtle variations in their parameters to explain their overall alkyl homologous series' mass distribution [6]. Relative to this first-order similarity, the secondary modifications we observed in the Tagish Lake meteorite are indeed minor. In this study, we focused on the relatively small variations/potential specific chemical differences among different chondrite groups and petrologic types using the model from our previous study to further clarify the secondary processes on the asteroids. Sample and Methods: Tarda (C2 ungrouped), Orgueil (CI), Murchison (CM2), EET 96029 (CM2), GRO 95577 (CR1), EET 92159 (CR2), GRA 06100 (CR2), GRO 03116 (CR2), and MIL 090657 (CR2) meteorite SOM were compared with experimental products from mineral-organic co-alteration under hydrothermal conditions [7]. We analyzed the methanol/toluene extract from meteorites with the high-resolution Orbitrap mass spectrometer located at the Institut de Planétologie et d'Astrophysique de Grenoble (IPAG). We directly injected and ionized the SOM and its solvent by using an Electrospray Ionization (ESI) source. After spectra acquisition, post-processing data analysis tools with the name Attributor [8], which were developed in-house, were employed. Results and Discussion: Tarda and the other type 2 chondrites' SOM mass distribution were well fit by using the model interpreted as the primordial SOM distribution in Tagish Lake. This match among the distribution patterns from different chondrite types implies the presence of a common organic reservoir or a common mechanism for SOM formation, as discussed in Orthous-Daunay et al.'s abstract at the same conference [6]. The model fits better to Tarda SOM distribution than Tagish Lake ones; this implies that Tarda was less altered in the parent body than Tagish Lake, consistent with their studies of inorganic matter [9]. Orgueil and GRO 95577 (CR1) share the common shape in their mass distribution of a few alkyl homologous series, and these unique features are apparent in Orgueil, CR1. Such characteristic mass-distributions were not reported by the Ryugu extract studies (analyzed by the HPLC) [5], or other type-2 meteorites (analyzed by direct infusion). However, its similar bimodal distribution appeared in the organic extracts from the hydrothermal mineral-organic co-alteration experimental products. In contrast to the mass distribution, SOM's elemental abundance was distinct among the different chondrite groups. In this presentation, we will discuss standard features of SOM among the chondrite groups based on the Wesslau model [6] and chemical formulae of detected ions. We discuss the organic chemical processes that are unique to the small bodies by listing stoichiometric formulae and mass distributions that are recognized as anomalies from the Wesslau model [6]. Finally, we hope to discuss the mechanisms of chemical reactions that produced specific organic compounds in the context of chemical evolution in the early solar system. [ABSTRACT FROM AUTHOR]

To obtain ohmic contacts on silicon carbide semicondanneuctors commonly a thin metal layer is deposited onto the semiconductor wafer, followed by a rapid thermal process to transform the resulting Schottky diode into an ohmic contact. Here, we report on an alternative laser based process replacing the conventional rapid thermal treatment. A continuous wave infrared fiber laser is employed to locally alloy nickel coated silicon carbide to an ohmic contact. Our results show that ohmic contacts are achieved with laser powers between 100 W and 300 W over an irradiated area on the order of 7 mm diameter. Electrical resistances of the generated ohmic contacts are measured down to 6.5 Ω, depending on laser power. Temperature dependent measurements of the resistance reveal a negative temperature coefficient of 11 mΩ/K. [ABSTRACT FROM AUTHOR]