Prismatic to asbestiform offretite from Northern Italy. Occurrence, morphology and crystal-chemistry of a new potentially hazardous zeolite

A multi-methodological approach, based upon field investigation, morphological characterization, chemical analysis and structure refinement was applied to different samples of fibrous offretite, a new potentially hazardous zeolite recently discovered in northern Italy. Their morphology ranges from stocky-prismatic to asbestiform. All the investigated fibers may be considered as "inhalable", and they are well within the range of the "more carcinogenic fibers" regarding diameter. As regards the length, the main mode observed in the asbestiform samples is 20-25 mu m, and similar to 93% of the measured fibers are >5 mu m and may be significantly associated with carcinogenesis also in terms of lengths. The chemical-structural features of the investigated fibers are comparable: the extra-framework cations K+, Mg2+ and Ca2+ are present in all samples in similar proportions, and refined cell parameters are similar among the samples. Offretite occurs in 60% of the investigated sites, with an estimated amount up to 75 vol % of the associated minerals. The presence of this mineral could be of concern for risk to human health, especially if one considers the vast number of quarries and mining-related activities that are operating in the zeolite host rocks

Chrysotile within calcite veins from Northern Apennines

In the Northern Apennines several olistoliths made up of serpentinites, calpionelle limestones and ophiolitic breccias have been recognized within the Porcellara Complex, Monte Cassio Unit. These olistoliths are frequently crossed by a dense network of centimeter to decimeter veins generally filled by carbonate minerals (e.g. La Costa, Berceto, PR). Morphological and compositional data (SEM-EDS and XRPD) have revealed that these carbonate minerals consist mainly of well-formed, white to milky calcite crystals, strictly associated with chrysotile. This mineral is found as white thin fibers (< 1 micron), grew up in intimate association with calcite crystals. These fibers may be very rare and randomly scattered within the crystals of calcite, or can be grouped into bundles of millimeter to centimeter size. At times, the chrysotile can get to completely fill the vein. Chrysotile fibers are well-formed and euhedral at all scales from hand specimen to electron microscope images. In some cases, individual fibers of chrysotile are not visible in hand specimen or under the petrographic microscope; however, SEM images show the characteristic elongate crystal morphology. The fibers are also characteristically curved at the millimeter scale. It is important to note that the fibers of chrysotile appear, frequently, as a physical extension of calcite crystals, without any evident morphological discontinuity in the transition from a massive (calcite) to a fibrous (chrysotile) appearence. The results of detailed SEM-EDS elemental analyses carried out in various segments of the contact areas between calcite and chrysotile crystals seem to show a gradual transition in chemical composition from pure calcite to pure chrysotile phases, passing through various intermediate arrangements

Stepwise dehydration of thomsonite (THO) with disordered Si/Al distribution: a new partially hydrated phase

The structural transformations occurring as a function of increasing temperature in zeolites are of interest because the porous structure, and therefore the physical properties, can significantly change. Zeolites with THO framework type are small-pore materials, which received attention because of their applications in catalytic processes. The majority of THO zeolites (synthetic and natural) are characterized by an ordered distribution of the cations at the tetrahedral sites. To date, few cases of disordered thomsonite have been reported. In this study, we investigated the dehydration behavior of a natural thomsonite with disordered Si/Al distribution and chemical composition Ca3.34Na2.66Si11Al9O40∙12H2O. The structure was determined from room temperature (RT) to 698 K in order to compare the thermal behavior with that reported for the ordered variety. Accurate structural analysis was performed by in situ single crystal X-ray diffraction. The dehydration starts at 348 K. Up to 498 K, thomsonite gradually releases four H2O. From 498 to 573 K, additional four H2O are lost and the space group changes from orthorhombic (Pbmn) to monoclinic (P21/n). This partially hydrated phase is characterized by a unit-cell volume contraction of -3% with respect to the RT phase and by a rearrangement of the extraframework cations in the zeolitic pores. The thermally treated thomsonite is able to reabsorb 50% of the lost H2O and transform to the orthorhombic phase, equivalent to that observed at lower temperatures. However, the diffraction pattern analysis indicated a high degree of mosaicity, most probably due to the residual stress accumulated during the phase transformation

Prismatic to asbestiform offretite from Northern Italy. Occurrence, morphology and crystal-chemistry of a new potentially hazardous zeolite

A multi-methodological approach, based upon field investigation, morphological characterization, chemical analysis and structure refinement was applied to different samples of fibrous offretite, a new potentially hazardous zeolite recently discovered in northern Italy. Their morphology ranges from stocky-prismatic to asbestiform. All the investigated fibers may be considered as "inhalable", and they are well within the range of the "more carcinogenic fibers" regarding diameter. As regards the length, the main mode observed in the asbestiform samples is 20-25 mu m, and similar to 93% of the measured fibers are >5 mu m and may be significantly associated with carcinogenesis also in terms of lengths. The chemical-structural features of the investigated fibers are comparable: the extra-framework cations K+, Mg2+ and Ca2+ are present in all samples in similar proportions, and refined cell parameters are similar among the samples. Offretite occurs in 60% of the investigated sites, with an estimated amount up to 75 vol % of the associated minerals. The presence of this mineral could be of concern for risk to human health, especially if one considers the vast number of quarries and mining-related activities that are operating in the zeolite host rocks

NR V2X Communications at Millimeter Waves: An End-to-End Performance Evaluation

3GPP NR V2X represents the new 3GPP standard for next-generation vehicular systems which, among other innovations, supports vehicle-to-vehicle (V2V) operations in the millimeter wave (mmWave) spectrum to address the communication requirements of future intelligent automotive networks. While mmWaves will enable massive data rates and low latency, the propagation characteristics at very high frequencies become very challenging, thereby calling for accurate performance evaluations as a means to properly assess the performance of such systems. Along these lines, in this paper MilliCar, the new ns-3 module based on the latest NR V2X specifications, is used to provide an end-to-end performance evaluation of mmWave V2V networks. We investigate the impact of different propagation scenarios and system parameters, including the inter-vehicle distance, the adopted frame numerology, and the modulation and coding scheme, and provide guidelines towards the most promising V2V deployment configurations.Comment: 6 pages, 7 figures. Submitted to IEEE Globecom 202

Minimizing Energy Consumption for 5G NR Beam Management for RedCap Devices

In 5G New Radio (NR), beam management entails periodic and continuous transmission and reception of control signals in the form of synchronization signal blocks (SSBs), used to perform initial access and/or channel estimation. However, this procedure demands continuous energy consumption, which is particularly challenging to handle for low-cost, low-complexity, and battery-constrained devices, such as RedCap devices to support mid-market Internet of Things (IoT) use cases. In this context, this work aims at reducing the energy consumption during beam management for RedCap devices, while ensuring that the desired Quality of Service (QoS) requirements are met. To do so, we formalize an optimization problem in an Indoor Factory (InF) scenario to select the best beam management parameters, including the beam update periodicity and the beamwidth, to minimize energy consumption based on users' distribution and their speed. The analysis yields the regions of feasibility, i.e., the upper limit(s) on the beam management parameters for RedCap devices, that we use to provide design guidelines accordingly