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The crystal chemistry and crystal structure of the rare earth element phosphates, monazite-(Ce), Ce(PO4), and xenotime-(Y), Y(PO4), as well as the arsenates, gasparite-(Ce), Ce(AsO4), and chernovite-(Y), Y(AsO4), from the hydrothermal quartz-bearing fissures, related to pegmatites overprinted by amphibolite facies, cropping out at Mt. Cervandone, Western Alps, Piedmont, Italy, have been investigated by means of electron microprobe analysis in wavelength dispersion mode and single-crystal X-ray diffraction. The chemical data reveal the occurrence of a full solid solution among the isostructural chernovite-(Y) and xenotime-(Y) with tetragonal symmetry, whereas a wide miscibility gap is observed for the isostructural gasparite-(Ce) and monazite-(Ce) of Mt. Cervandone, with monoclinic symmetry. A significant chemical heterogeneity has been observed for several investigated samples, especially related to the Th content, which is locally enriched in ThSiO4 grains. The analysis of the refined structural models demonstrates the significant control played by the composition of the tetrahedrally-coordinated (As,P)-bearing sites on the bulk unit-cell volume, and on the size and shape of the (REE)-coordination polyhedra.

We report the synthesis, at 7 GPa and 923 K, and the thermoelastic characterization, up to 16 GPa and 850 K, of a single crystal of Mg-sursassite, Mg5Al5Si6O21(OH)7. In situ high-pressure and high-temperature single-crystal diffraction allowed the study of structural variation at non-ambient conditions and the determination of bulk elastic properties. The refined parameters of a second-order Birch-Murnaghan equation of state (BM-II EoS) are V0 = 446.02(1) Å3 and KT0 = 135.6(7) GPa. The thermal expansion coefficients of a Berman-type EoS are α0 = 3.14 (5) × 10−5 K−1, α1 = 2.50(16) × 10−8 K−2, and V0 = 445.94(3). For comparison, the P-V EoS is determined for a natural sursassite sample, ideally Mn4Al6Si6O22(OH)6. The refined parameters of BM-II EoS [V0 = 470.2(3) Å3, KT0 = 128(4) GPa] indicate that composition has a minimal effect on elastic properties. The similarity of density and bulk properties of Mg-sursassite if compared to olivine and other anhydrous mantle minerals suggests that this phase could be overseen by geophysical methods.

Background: Mandibular fractures (MF) are a daily problem in maxillofacial surgery. A staging system for classifying MF is of paramount importance to plan surgery, to define prognosis, and to exchange information among trauma centers. In this article, a classification for MF is proposed. Methods: The mandible is divided into six sites (symphysis, body, angle, ramus, coronoid, and condyle) and the mandibular nerve divides the alveolar process (i.e., the upper part containing teeth) from the basal bone (placed caudally with respect to the nerve). MF can be summarized using three abbreviations: A = alveolar, B = basal, and C = complete. Consequently, MFs are staged as follows: F in situ = a greenstick fracture; F1 = a single mobile fragment of alveolar or basal bone; F2 = double mobile fractures of the alveolar or basal portion or a single complete separation of the mandibular arch continuity; F3 = a complete double separation of the mandibular arch continuity; F4 = triple or more mandibular arch fragments. To evaluate the suitability of the proposed classification, a retrospective study on a series of 128 patients (and 205 MFs) was performed. Age, gender, stage, clinical diagnosis at admission, type of surgery, and outcome were considered. Results: A good correlation between the proposed classification and the studied variables was detected. Conclusions: The new classification is a simple and precise method for staging MF. It can summarize MFs and be used in daily practice. It is our understanding, however, that a multicenter study should be performed before the effectiveness of the proposed classification can be clearly stated.

The midfacial region (MR) is located in the middle-third of the face, composed of several bones and surrounded by complex anatomical structures so that MR fractures (MRFs) often involve other parts of the face. A staging system for classifying MRFs is of paramount importance in order to exchange information among trauma centers. Le Fort described three lines of fractures but still there is no scoring method to stage MRFs. In this article, a classification for MRFs is proposed. It is based on Le Fort’s three lines and it defines seven facial units. MRFs can be staged as follows: F in situ = a fracture line without fragment mobility (i.e. greensticked); F1 = a fracture involving one MR unit (MRU); F2 = a fracture involving two MRUs; F3 = a fracture involving three MRUs; F4 = a fracture involving four or more MRUs or neighboring anatomical regions (i.e. mandible, orbit and skull). To evaluate the suitability of the proposed classification a retrospective study on a series of 117 MRFs was performed. Age, gender, new stage, clinical diagnosis at admission, type of surgery, and outcome were considered. A good correlation between the proposed classification and the studied variables was detected. In conclusion, the proposed classification is a simple and precise method of staging MRFs. It can summarize MRFs and be used in daily practice. It is our understanding, however, that a multi-centers study should be performed before the effectiveness of the proposed classification can be clearly stated.