Local Structure and Spin Transition in Fe2O3 Hematite at High-Pressure

The pressure evolution of the local structure of Fe2O3 hematite has been determined for the first time by extended x-ray absorption fine structure up to 79 GPa. The comparison to the different high-pressure forms proposed in the literature suggests that the orthorhombic structure with space group Aba2 is the most probable. The crossover from Fe high-spin to low-spin states with pressure increase has been monitored from the pre-edge region of the Fe K-edge absorption spectra. The "simultaneous" comparison with the local structural changes allows us to definitively conclude that it is the electronic transition that drives the structural transition and not viceversa

ERAS® protocol improves survival after radical cystectomy: A single-center cohort study.

To evaluate Enhanced recovery after surgery (ERAS®) protocol on oncological outcomes for patients treated with radical cystectomy (RC) for urothelial carcinoma of the bladder (UCB). A prospectively maintained single-institutional database comprising 160 consecutive UCB patients who underwent open RC from 2012 to 2020 was analyzed. Patients receiving chemotherapy and those with a urinary diversion other than ileal conduit were excluded. Patients were divided into two groups according to the perioperative management (ERAS® and pre-ERAS®). The study aimed to evaluate the impact of the ERAS® protocol on survival at five years after surgery using a Kaplan-Meier log-rank test. A multivariable Cox proportional hazards model was used to identify prognostic factors for cancer-specific (CSS) and overall survival (OS). Of the 107 patients considered for the final analysis, 74 (69%) were included in the ERAS® group. Median follow-up for patients alive at last follow-up was 28 months (interquartile range [IQR] 12-48). Five-years CSS rate was 74% for ERAS® patients, compared to 48% for the control population (P = 0.02), while 5-years OS was 31% higher in the ERAS® (67% vs. 36%, P = .003). In the multivariable analysis, ERAS® protocol and tumor stage were independent factors of CSS, while ERAS®, tumor stage so as total blood loss were independent factors for OS. A dedicated ERAS® protocol for UCB patients treated with RC has a significant impact on survival. Reduction of stress after a major surgery and its potential improvement of perioperative patient's immunity may explain these data

Inclusions in super-deep diamonds

Super-deep diamonds may originate from a depth of between 300 and 800 km, although their precise depth of origin remains uncertain. When growing, they trap other minerals from their surroundings, which remain unaltered in their diamond capsule on their journey up to the surface of our planet. Through the study of these inclusions it is thus possible to reveal the secrets of deep unseen environments. In this study we aim to determine the formation pressure of super- deep diamonds for the first time by characterising two types of inclusions: CaSiO3-walstromite and ferropericlase. To achieve this goal we investigated CaSiO3-walstromite inclusions by a combination of in situ single-crystal X-ray diffraction, \u201csingle-inclusion elastic barometry\u201d and in situ micro-Raman spectroscopy and we obtained an apparent entrapment pressure of 3c7.1 GPa, corresponding to 3c250 km, at a temperature of 1500 K. In addition, thermodynamic calculations suggested that single inclusions of CaSiO3-walstromite cannot derive from CaSiO3-perovskite. Preliminary X-ray micro-tomography and nuclear resonance scattering data were also collected on ferropericlase-bearing diamonds in order to detect micro-fractures around the inclusions and to determine whether the Fe3+/ 11Fe ratios are in agreement with lower mantle values or not

First in-situ measurements of Fe3+/Fetot for oxides and silicates included in natural diamonds with Synchrotron M\uf6ssbauer Source

Diamond is the paramount phase to understand the evolution and the physico- chemical condition of the deep portions of the Earth\u2019s mantle, mainly because: (i) it is the stable phase through which carbon is stored in the deep mantle for long geologic time; (ii) it does contain and preserve different types of inclusions (fluid, mineral, etc.); (iii) it is the only material sampling the mantle to depths of 800 km (e.g. Harte, 2010), although the majority of the mined diamonds worldwide derive from shallower depth (150 to 250 km). The study of mineral inclusions trapped in diamonds allows the retrieval of different pieces of information about the Earth\u2019s interior and its active geodynamics, providing important clues on the initiation of subduction processes (Shirey & Richardson, 2011; Smart et al., 2016), tracking the transfer of material through the mantle transition zone (Stachel et al., 2005; Walter et al., 2011), recording the timing of ingress of fluids to the continental lithosphere (e.g. Shirey et al., 2004), preserving carbonatitic fluid that trigger deep mantle melting (e.g. Schrauder & Navon, 1994; Kopylova et al., 2010), providing samples of primordial noble gases (e.g. Ozima & Igarashi, 2000), and capturing the redox state of the mantle (e.g. Rohrbach & Schmidt, 2011). Unfortunately the majority of the techniques used so far to study the mineral inclusions are destructive. It is only in the last decade that the studies on inclusions in diamond have started to use non-destructive techniques, providing new information which would otherwise be lost using earlier destructive techniques. Such an example is the rim fluids around inclusions in diamonds. In this study we present details of the experimental setup on the determination of Fe3+/Fetot ratios of mineral inclusions whilst still within the diamonds by a non-destructive approach using the Synchrotron M\uf6ssbauer Source (SMS; Potapkin et al., 2012) at the Nuclear Resonance beamline SOURCE ID18 (R\ufcffer & Chumakov, 1996), European Synchrotron Radiation Facility (ESRF), Grenoble. The extremely small X-ray spot size (10 7 15 \u3bcm2) is perfectly suited for our purposes as some inclusions are smaller than 30-50 \u3bcm and the Fe3+/Fetot variation over the same inclusion cannot be performed by using standard laboratory radioactive sources because of the larger beam size. The average collection time for thicker inclusions (~ 200 \u3bcm) was 2 hours per spectrum, whilst the smallest inclusion (~ 30 730 730 \u3bcm3) required a collection time of approximately 10-12 hours in order to get a spectrum with nicely distinguishable features and a high signal-to-noise ratio. In general, application to a suite of silicate and oxide inclusions in diamonds produced comparable results with respect to those obtained using conventional M\uf6ssbauer sources (e.g. McCammon et al., 2004)

Synchrotron M\uf6ssbauer Source technique for in situ measurement of iron-bearing inclusions in natural diamonds

Natural diamonds containing silicate, oxide and sulfide inclusions are a popular focus of investigation as they uniquely provide a window into the conditions of the Earth\u2019s interior at extreme depths. Recent discoveries based on investigations of deep diamonds have considerably improved our knowledge of the Earth\u2019s deep carbon and water cycles and the oxygen fugacity of the Earth\u2019s interior. Super deep diamonds are those that are believed to have formed at depths of at least 300 km and some evidence suggests depths of at least 800 km. A common inclu- sion in these diamonds is ferropericlase, (Mg,Fe2+)O. Ferropericlase is the second most abundant mineral in the lower mantle, constituting up to about 20 mol% of its volume. The Fe3+/Fetot of ferropericlase is a strong func- tion of oxygen fugacity, and provides a measure of the most recent redox conditions under which it equilibrated. Conventional M\uf6ssbauer spectroscopy using a 57Co point source has been used in the past decades to study the Fe3+/Fetot content in inclusions still trapped in their diamond\u2019s host, however its limitations are the low spatial resolution (not below 3c100 \u3bcm2) and the long acquisition time. The Flank method was also proposed, it is fast, it has high spatial resolution (down to 3c20 \u3bcm2) but it measures the bulk value of Fe3+/Fetot since it cannot distinguish between different phases. An ideal method to measure Fe3+/Fetot values of ferropericlase would com- bine (1) the advantage of M\uf6ssbauer spectroscopy to distinguish Fe3+ in different phases and measure inclusions while still in the diamond, with (2) the advantage of the Flank method to conduct rapid measurements with high spatial resolution. The only method that offers the possibility to satisfy all these requirements is the Synchrotron M\uf6ssbauer Source (SMS). We used the SMS for the first time, to study the iron content and iron distribution in ferropericlase inclusion still contained within its diamond host from Juina (Brazil). This definitive non-destructive technique with extremely high spatial resolution ( 3c15 \u3bcm2) enabled measurements in multiple regions of the 150 7 150 \u3bcm2 inclusion to be sampled and showed that while Fe3+/Fetot values in ferropericlase were below the detection limit (0.02) overall, there was a magnetic component whose abundance varied systematically across the inclusion. Hyperfine parameters of the magnetic component are consistent with magnesioferrite, and the absence of superparamagnetism allows the minimum particle size to be estimated as 3c30 nm. Bulk Fe3+/Fetot values are similar to those reported for other ferropericlase inclusions from Juina. Their variation across the inclusion can provide constraints on its history, and ultimate on the deep carbon processes behind diamonds formation and their exhumation from the transition zone and shallow lower mantle regions

Stability of Fe,Al-bearing bridgmanite in the lower mantle and synthesis of pure Fe-bridgmanite

The physical and chemical properties of Earth’s mantle, as well as its dynamics and evolution, heavily depend on the phase composition of the region. On the basis of experiments in laser-heated diamond anvil cells, we demonstrate that Fe,Al-bearing bridgmanite (magnesium silicate perovskite) is stable to pressures over 120 GPa and temperatures above 3000 K. Ferric iron stabilizes Fe-rich bridgmanite such that we were able to synthesize pure iron bridgmanite at pressures between ~45 and 110 GPa. The compressibility of ferric iron–bearing bridgmanite is significantly different from any known bridgmanite, which has direct implications for the interpretation of seismic tomography data

Direct tomography imaging for inelastic x-ray scattering experiments at high pressure

A method to separate the non-resonant inelastic X-ray scattering signal of a micro-metric sample contained inside a diamond anvil cell (DAC) from the signal originating from the high-pressure sample environment is described. Especially for high-pressure experiments, the parasitic signal originating from the diamond anvils, the gasket and/or the pressure medium can easily obscure the sample signal or even render the experiment impossible. Another severe complication for high-pressure non-resonant inelastic X-ray measurements, such as X-ray Raman scattering spectroscopy, can be the proximity of the desired sample edge energy to an absorption edge energy of elements constituting the DAC. It is shown that recording the scattered signal in a spatially resolved manner allows these problems to be overcome by separating the sample signal from the spurious scattering of the DAC without constraints on the solid angle of detection. Furthermore, simple machine learning algorithms facilitate finding the corresponding detector pixels that record the sample signal. The outlined experimental technique and data analysis approach are demonstrated by presenting spectra of the Si L-2,L-3-edge and O K-edge of compressed alpha-quartz. The spectra are of unprecedented quality and both the O K-edge and the Si L-2,L-3-edge clearly show the existence of a pressure-induced phase transition between 10 and 24 GPa.Peer reviewe