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Rotary kilns are widely used for various high temperature industrial applications, e.g., quicklime and cement production. Most of these operations rely on fossil fuels like coal; however, there is growing interest in increasing the share of biomass fuels. During the high-temperature combustion process, ash transport onto, and reactions with, refractory bricks can significantly influence refractory wear. Ash infiltration may impair refractory performance through chemical reactions and exacerbated cracking caused by structural changes in combination with thermal shock. Analysis of spent refractory materials provides valuable insights for understanding and predicting corrosion mechanisms. In the present study, three MgO-based spent refractory bricks were collected from different locations within the burn zone of a rotary lime kiln that was cofired with a mixture of coal, olive pomace (a potassium-rich biomass), and oil. Infiltrated ash and reaction products within the refractory bricks were sampled and characterized using SEM-EDX for elemental mapping and morphology analysis. EBSD analysis was employed to measure the grain size distributions. Micrographic images revealed that all three spent refractory bricks were more sintered and cracked on their hot sides compared to their middle sections and cold sides. Si-rich and K-rich ashes from the coal and biomass fuels, respectively, all infiltrated into the refractories as well as Ca-rich constituents from the limestone/quicklime. XRD analyses revealed the formation of phases such as Mg2SiO4, Ca12Al14O33, and Ca2SiO4. No potassium from the fuel ash was found on the hot side of the refractory bricks, but some were detected deeper within the middle section and cold side of the bricks. The combined use of analytical techniques enabled detailed mapping of ash-forming elements and identification of newly formed phases from the reactions between refractory bricks, ash, and quicklime. These findings provide critical insights into fuel-specific interactions and highlight potential risks for refractory degradation.

Purpose: Cerebrospinal fluid (CSF) flow oscillations have emerged as a potentially important marker related to brain clearance, but their acquisition often relies on specialized imaging MRI sequences. The purpose of this work was to enable quantitative assessment of CSF flow associated with cardiac, respiratory, and low-frequency cycles using widely available functional magnetic resonance imaging (fMRI) acquisitions.

Methods: A method was developed to translate fMRI-derived CSF inflow signals into quantitative flow rates. This approach modeled the spin-history of an oscillating ensemble of molecules. Validation was performed using phantom experiments with cardiac-, respiratory-, and low-frequency-like oscillatory flow. The method was further applied to resting-state data from 48 older adults (68–82 years, 19 women) to characterize CSF flow at the foramen magnum.

Results: Phantom experiments demonstrated excellent correlations between estimated and true velocities for cardiac- and respiratory-like frequencies (r = 0.94 and 0.97, respectively) and moderate correlation for the low-frequency-like oscillation (r = 0.58). In the population cohort, median CSF stroke volumes were 0.77 [0.57, 1.09] mL for the cardiac cycle, 0.38 [0.26, 0.88] mL for the respiratory cycle, and 0.26 [0.14, 0.39] mL for the low-frequency cycle.

Conclusion: The proposed spin-history modeling method enabled quantitative estimation of CSF flow components using a conventional fMRI dataset and showed that the cardiac cycle dominates CSF motion at the foramen magnum.

Prostate cancer treatment depends on whether the cancer exists only inside the gland or within the prostate capsule or on the outside surface of the gland. The presence on the outside surface indicates migration of the cancer to adjacent organs. This study presents a novel method for detecting prostate cancer (PCa) on the surface of excised prostate glands using Raman spectroscopy and stiffness measurements. The workflow involves assessing the location and extent of PCa via MRI before surgery, followed by 3D scanning of the excised prostate. Key positions on ten excised prostates, 211 positions with 56 deemed as cancer, are measured using Raman spectroscopy and stiffness probes. The results are mapped onto a digital representation of the prostate to aid surgical decision-making. Statistical analysis of the Raman data indicates that spectra could be divided into two components, one more related to cancer and one more related to normal tissue. A stiffness parameter was calculated from resonance measurements from the stiffness probe. The Raman components and stiffness parameters were converted to z-scores. Logistic generalized linear mixed modelling revealed that the stiffness parameter was statistically associated with cancer presence in prostate regions (p = 0.009). The scanning equipment is easy to handle and makes further larger studies possible. This method holds promise for providing real-time support during surgery, reducing the need for post-surgical therapies and minimizing patient distress.

Refractory liner bricks in the hot zone of rotary lime kilns can sustain wear and corrosion during contact with fuel ashes and quicklime (QL), a product composed mainly of CaO. The effects on a MgO-based refractory after exposure at 1400 °C for 96 h to olive pomace ash (OPA) and coal ash (CA), with and without QL, were investigated. Exposure of the refractory to only OPA caused slag intrusion with no ash deposits remaining on top, while CaMgSiO4 (monticellite) was also identified as a new phase. When exposed to only CA, the refractory exhibited dissolution into the molten slag and 0.5–2 mm cracks were found on the surface interfacing the ash. Mg2SiO4 (forsterite) and CaMgSiO4 were identified as new formed phases. Exposure of the refractory to OPA + QL and CA + QL caused less slag intrusion and substantial amounts of ash/QL deposit remained afterwards. No new phases were identified. The differences in interactions between the exposure materials and refractory were supported by thermochemical equilibrium analysis. Apparent Ca-Si–rich or Ca-rich melts were found in all the exposed samples, but potassium (K) was found to be depleted in all samples, including those involving OPA, which was rich in K. Furthermore, with the exception of exposure to only CA, the other exposures caused the cold crushing strength (CCS) of the refractory to increase compared to its original value. This was attributed to the sintering of the refractory microstructure. The CCS of the refractory decreased after exposure to only CA. The findings of this study enhance understanding of how CA and OPA impact MgO refractories in lime kilns, supporting initiatives aiming at reducing fossil fuel use. The results are encouraging and motivate further investigation.

Doping β-tricalcium phosphate (β-TCP) with copper (Cu²⁺) has great potential in various applications due to its rich chemistry. However, the doping characteristics are rarely studied in detail and are yet to be fully understood, creating a gap in the existing knowledge of these multifunctional materials. In this work, a series of Cu²⁺ doped β-TCP (Cu_x-TCPs) were prepared and comprehensively characterized to investigate the correlation between Cu²⁺ doping and the material properties. Also, the synthesis of Cu_x-TCPs was modeled using thermodynamic equilibrium calculations to investigate their formation pathways. The calculations predicted a possible inclusion of Cu²⁺ in intermediate phosphate phases during the material synthesis, depending on the temperature. The structural analyses revealed lattice shrinkage due to the Cu²⁺ doping and that Cu²⁺ occupied Ca4 and Ca5 sites in the β-TCP crystal. The vibrational spectroscopy of the Cu_x-TCPs showed noticeable deformation of ν₁ band of PO₄³⁻ ligand. The ultraviolet-visible absorption analysis revealed a reduction in the band gap energy induced by Cu²⁺ doping. Photoluminescence spectroscopy demonstrated an enhanced emission tunability of Cu_x-TCPs in the blue and orange–red regions depending on Cu²⁺ concentration. These findings are a step toward a deeper understanding of the structure–property relationships of Cu²⁺ doped β-TCPs and can play a significant role in their multidisciplinary applications.

Variations in cerebral blood flow and blood volume interact with intracranial pressure and cerebrospinal fluid dynamics, all of which play a crucial role in brain homeostasis. A key physiological modulator is respiration, but its impact on cerebral blood flow and volume has not been thoroughly investigated. Here we used 4D flow MRI in a population-based sample of 65 participants (mean age = 75 ± 1) to quantify these effects. Two gating approaches were considered, one using respiratory-phase and the other using respiratory-time (i.e. raw time in the cycle). For both gating methods, the arterial inflow was significantly larger during exhalation compared to inhalation, whereas the venous outflow was significantly larger during inhalation compared to exhalation. The cerebral blood volume variation per respiratory cycle was 0.83 [0.62, 1.13] ml for respiratory-phase gating and 0.78 [0.59, 1.02] ml for respiratory-time gating. For comparison, the volume variation of the cardiac cycle was 1.01 [0.80, 1.30] ml. Taken together, our results clearly demonstrate respiratory influences on cerebral blood flow. The corresponding vascular volume variations appear to be of the same order of magnitude as those of the cardiac cycle, highlighting respiration as an important modulator of cerebral blood flow and blood volume.

In this study, the impact of Zn2+ doping on β-Ca3(PO4)2 characteristics was investigated with particular focus on its influence on the surface, structure, and photocatalytic properties. Zn2+ doped β-Ca3(PO4)2 (Znx-TCPs) were synthesized using a solid-state method and were thoroughly studied to evaluate the modification induced by cationic substitution. The structural analysis revealed a noticeable shrinkage in the lattice parameters a and c and the unit cell volume induced by Zn2+ doping. Minor spectral changes in the vibrational modes of PO43− were also observed in the infrared and Raman spectra of Znx-TCPs. The influence of doping on the materials’ morphology was insignificant; however, molten grain boundaries were noticeable at high Zn concentration, x ≥ 1. X-ray photoelectron spectroscopy (XPS) revealed that the surface of the doped materials was rich in Zn. Optical absorption measurements indicated that Zn2+ doping slightly affects the optical bandgap of β-Ca3(PO4)2. The photocatalytic activities of the materials were investigated for the degradation of Rhodamine B (RB) and Methylene blue (MB). The photocatalytic experiments were carried out in the presence of hydrogen peroxide and under simulated solar light. The samples exhibited enhanced catalytic activity compared to β-Ca3(PO4)2, and the Zn0.5-TCP sample demonstrated the highest degradation efficiency. This sample showed excellent stability during the reusability tests, which suggests the suitability of Zn0.5-TCP for use as an efficient photocatalyst. Surface defects are believed to play an important role in the production of active species during the photocatalytic reaction.

Magnesium oxide (MgO)-based refractories are commonly used in quicklime and cement rotary kilns. At the high temperatures in the kiln burn zone, the infiltration of molten fuel ash into the refractory can occur. Subsequent chemical interactions can cause refractory wear that inflicts high maintenance costs and loss of production. To improve refractory reliability, it is necessary to increase the understanding of the interactions between fuel ash slag and refractory liner materials. Three commercially available MgO-based refractory materials were exposed to coal ash at 1200 °C and 1400 °C for between 15 and 60 min under a CO₂-rich gaseous environment. Hot slag from the coal ash infiltrated the refractories and the infiltration depths were estimated with scanning electron microscope with energy dispersive X-ray spectroscopy. Based on detailed elemental and microstructure analyses, the interactions between ash and refractory were examined. Molten silicates infiltrated the refractory through grain boundaries and pores into depths of up to 2.8 mm. Powder X-ray diffraction of the exposed refractory samples indicated that MgO grains reacted with SiO₂-containing phases to form Mg₂SiO₄. This was identified as a corrosion product whose formation was supported by thermochemical equilibrium calculations. Elevated Mg content was found in the ash residue on top of the samples, indicating the dissolution or dislocation of refractory components. In addition, phases such as MgO were identified in the ash residue.

MgO-based refractories are used in lime kilns to withstand the high temperature and chemical environment. Efforts to reduce CO₂ emissions have led to an increased interest to use bio-based fuels as alternatives to traditional fossil sources. The potential for refractory corrosion from a potassium-rich biomass ash was investigated by studying the infiltration of olive pomace ash into magnesia/spinel refractories. Refractory samples were exposed to the ash at up to 1400 °C for 15–60 min in a CO₂–rich atmosphere. Molten ash infiltrated the refractories through pores and grain boundaries to a depth of up to 9.6 mm, which was quantified with a new systematic procedure. The phase KAlO₂ was identified inside the refractories after exposure, indicating an attack of spinel components by potassium. Phases found in the ash residues also indicated the migration of refractory constituents. Thermochemical equilibrium calculations were also used to investigate the ash/refractory chemistry.