Preclinical evaluation of a new synthetic carbonate apatite bone substitute on periodontal regeneration in intrabony defects.

OBJECTIVE To evaluate the potential of a novel synthetic carbonate apatite bone substitute (CO3 Ap-BS) on periodontal regeneration. BACKGROUND The use of various synthetic bone substitutes as a monotherapy for periodontal regeneration mainly results in a reparative healing pattern. Since xenografts or allografts are not always accepted by patients for various reasons, a synthetic alternative would be desirable. METHODS Acute-type 3-wall intrabony defects were surgically created in 4 female beagle dogs. Defects were randomly allocated and filled with CO3 Ap-BS (test) and deproteinized bovine bone mineral (DBBM) or left empty (control). After 8 weeks, the retrieved specimens were scanned by micro-CT, and the percentages of new bone, bone substitute, and soft tissues were evaluated. Thereafter, the tissues were histologically and histometrically analyzed. RESULTS Healing was uneventful in all animals, and defects were present without any signs of adverse events. Formation of periodontal ligament and cementum occurred to varying extent in all groups without statistically significant differences between the groups. Residues of both bone substitutes were still present and showed integration into new bone. Histometry and micro-CT revealed that the total mineralized area or volume was higher with the use of CO3 Ap-BS compared to control (66.06 ± 9.34%, 36.11 ± 6.40%; p = .014, or 69.74 ± 2.95%, 42.68 ± 8.68%; p = .014). The percentage of bone substitute surface covered by new bone was higher for CO3 Ap-BS (47.22 ± 3.96%) than for DBBM (16.69 ± 5.66, p = .114). CONCLUSIONS CO3 Ap-BS and DBBM demonstrated similar effects on periodontal regeneration. However, away from the root surface, more new bone, total mineralized area/volume, and higher osteoconductivity were observed for the CO3 Ap-BS group compared to the DBBM group. These findings point to the potential of CO3 Ap-BS for periodontal and bone regeneration

Transport of Mass and Energy in Mercury’s Plasma Sheet

We examined the transport of mass and energy in Mercury’s plasma sheet (PS) using MESSENGER magnetic field and plasma measurements obtained during 759 PS crossings. Regression analysis of proton density and plasma pressure shows a strong linear relationship. We calculated the polytropic index γ for Mercury’s PS to be ~0.687, indicating that the plasma in the tail PS behaves nonadiabatically as it is transported sunward. Using the average magnetic field intensity of Mercury’s tail lobe as a proxy for magnetotail activity level, we demonstrated that γ is lower during active time periods. A minimum in γ was observed at R ~ 1.4 RM, which coincides with previously observed location of Mercury’s substorm current wedge. We suggest that the nonadiabatic behavior of plasma as it is transported into Mercury’s nearâ tail region is primarily driven by particle precipitation and particle scattering due to large loss cone and particle acceleration effect, respectively.Plain Language SummaryThe transport process of mass and energy within Mercury’s magnetotail remains unexplored until now. The availability of in situ magnetic field and plasma measurements from National Aeronautics and Space Administration’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft provides us with the first opportunity to study the thermodynamic properties of particles within sunward convecting closed flux tubes in the plasma sheet. In this study, we study how mass and energy are transported in Mercury’s magnetotail by investigating the relationship between the thermal pressure and number density of the plasma in Mercury’s plasma sheet given by the equation of state in magnetohydrodynamics theory. We determined, for the first time, that the plasma behaves nonadiabatically as it is transported sunward toward Mercury. We suggest that precipitation of particles due to Mercury’s large loss cone and demagnetization of particles due to finite gyroradius effect contributes to this nonadiabatic behavior of plasma in the plasma sheet. Our results have major implications in our understanding of particle sources and sinks mechanisms in Mercury’s magnetotail.Key PointsWe calculated the value of polytropic index γ for Mercury’s plasma sheet to be ~0.687, which is smaller than 5/3 (adiabatic)Nonadiabatic plasma behavior is driven by ion precipitation and ion demagnetization due to large loss cone and finite gyroradius effectWe demonstrated that γ is lower during active time and determined a relationship between γ and the location of flow breaking regionPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147033/1/grl58293_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147033/2/grl58293.pd

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb carbonate geochronology: strategies, progress, and limitations

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb geochronology of carbonate minerals, calcite in particular, is rapidly gaining popularity as an absolute dating method. The high spatial resolution of LA-ICP-MS U–Pb carbonate geochronology has benefits over traditional isotope dilution methods, particularly for diagenetic and hydrothermal calcite, because uranium and lead are heterogeneously distributed on the sub-millimetre scale. At the same time, this can provide limitations to the method, as locating zones of radiogenic lead can be time-consuming and “hit or miss”. Here, we present strategies for dating carbonates with in situ techniques, through imaging and petrographic techniques to data interpretation; our examples are drawn from the dating of fracture-filling calcite, but our discussion is relevant to all carbonate applications. We review several limitations to the method, including open-system behaviour, variable initial-lead compositions, and U–daughter disequilibrium. We also discuss two approaches to data collection: traditional spot analyses guided by petrographic and elemental imaging and image-based dating that utilises LA-ICP-MS elemental and isotopic map data

Ion‐scale structure in Mercury’s magnetopause reconnection diffusion region

The strength and time dependence of the electric field in a magnetopause diffusion region relate to the rate of magnetic reconnection between the solar wind and a planetary magnetic field. Here we use ~150 ms measurements of energetic electrons from the Mercury Surface, Space Environment, GEochemistry, and Ranging (MESSENGER) spacecraft observed over Mercury’s dayside polar cap boundary (PCB) to infer such small‐scale changes in magnetic topology and reconnection rates. We provide the first direct measurement of open magnetic topology in flux transfer events at Mercury, structures thought to account for a significant portion of the open magnetic flux transport throughout the magnetosphere. In addition, variations in PCB latitude likely correspond to intermittent bursts of ~0.3–3 mV/m reconnection electric fields separated by ~5–10 s, resulting in average and peak normalized dayside reconnection rates of ~0.02 and ~0.2, respectively. These data demonstrate that structure in the magnetopause diffusion region at Mercury occurs at the smallest ion scales relevant to reconnection physics.Key PointsEnergetic electrons at Mercury map magnetic topology at ~150 msFirst direct observation of flux transfer event open‐field topology at MercuryModulations of the reconnection rate at Mercury occur at ion kinetic scalesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/133575/1/grl54476_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133575/2/grl54476.pd

FOREWORD

We analyzed MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) magnetic field and plasma measurements taken during 319 crossings of Mercury’s crossâ tail current sheet. We found that the measured BZ in the current sheet is higher on the dawnside than the duskside by a factor of â 3 and the asymmetry decreases with downtail distance. This result is consistent with expectations based upon MHD stress balance. The magnetic fields threading the more stretched current sheet in the duskside have a higher plasma beta than those on the dawnside, where they are less stretched. This asymmetric behavior is confirmed by mean current sheet thickness being greatest on the dawnside. We propose that heavy planetary ion (e.g., Na+) enhancements in the duskside current sheet provides the most likely explanation for the dawnâ dusk current sheet asymmetries. We also report the direct measurement of Mercury’s substorm current wedge (SCW) formation and estimate the total current due to pileup of magnetic flux to be â 11 kA. The conductance at the foot of the field lines required to close the SCW current is found to be â 1.2 S, which is similar to earlier results derived from modeling of Mercury’s Region 1 fieldâ aligned currents. Hence, Mercury’s regolith is sufficiently conductive for the current to flow radially then across the surface of Mercury’s highly conductive iron core. Mercury appears to be closely coupled to its nightside magnetosphere by mass loading of upward flowing heavy planetary ions and electrodynamically by fieldâ aligned currents that transfer momentum and energy to the nightside auroral oval crust and interior. Heavy planetary ion enhancements in Mercury’s duskside current sheet provide explanation for crossâ tail asymmetries found in this study. The total current due to the pileup of magnetic flux and conductance required to close the SCW current is found to be â 11 kA and 1.2 S. Mercury is coupled to magnetotail by mass loading of heavy ions and fieldâ aligned currents driven by reconnectionâ related fast plasma flow.Key PointsHeavy planetary ion enhancements in Mercury’s duskside current sheet provide explanation for crossâ tail asymmetries found in this studyThe total current due to the pileup of magnetic flux and conductance required to close the SCW current is found to be almost equal to 11 kA and 1.2 SMercury is coupled to magnetotail by mass loading of heavy ions and fieldâ aligned currents driven by reconnectionâ related fast plasma flowPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138879/1/jgra53698.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138879/2/jgra53698_am.pd

Phylogenetic Relationships in Pterodroma Petrels Are Obscured by Recent Secondary Contact and Hybridization

The classification of petrels (Pterodroma spp.) from Round Island, near Mauritius in the Indian Ocean, has confounded researchers since their discovery in 1948. In this study we investigate the relationships between Round Island petrels and their closest relatives using evidence from mitochondrial DNA sequence data and ectoparasites. Far from providing clear delimitation of species boundaries, our results reveal that hybridization among species on Round Island has led to genetic leakage between populations from different ocean basins. The most common species on the island, Pterodroma arminjoniana, appears to be hybridizing with two rarer species (P. heraldica and P. neglecta), subverting the reproductive isolation of all three and allowing gene flow. P. heraldica and P. neglecta breed sympatrically in the Pacific Ocean, where P. arminjoniana is absent, but no record of hybridization between these two exists and they remain phenotypically distinct. The breakdown of species boundaries in Round Island petrels followed environmental change (deforestation and changes in species composition due to hunting) within their overlapping ranges. Such multi-species interactions have implications not only for conservation, but also for our understanding of the processes of evolutionary diversification and speciation

Hadley circulation and precipitation changes control black shale deposition in the Late Jurassic Boreal Seaway

New climate simulations using the HadCM3L model with a paleogeography of the Late Jurassic [155.5 Ma], and proxy-data corroborate that warm and wet tropical-like conditions reached as far north as the UK sector of the Jurassic Boreal Seaway [~35oN]. This is associated with a northern hemisphere Jurassic Hadley cell and an intensified subtropical jet which both extend significantly polewards than in the modern (July-September). Deposition of the Kimmeridge Clay Formation [KCF] occurred in the shallow, storm-dominated, epeiric Boreal Seaway. High resolution paleo-environmental proxy data from the Kimmeridge Clay Formation [KCF; ~155–150 Ma], UK are used to test for the role of tropical atmospheric circulation on meter-scale heterogeneities in black shale deposition. Proxy and model data show that the most organic-rich section [eudoxus to mid-hudlestoni zones] is characterised by a positive δ13Corg excursion and up to 37 wt% total organic carbon [%TOC]. Orbital-modulation of organic carbon burial primarily in the long eccentricity power band combined with a clear positive correlation between %TOC carbonate-free and the kaolinite/illite ratio supports peak organic carbon burial under the influence of very humid climate conditions, similar to the modern tropics. This re-interpretation of large-scale climate relationships, supported by independent modelling and geological data, has profound implications for atmospheric circulation patterns and processes affecting marine productivity and organic carbon burial further north along the Boreal Seaway, including the Arctic

MESSENGER and Mariner 10 flyby observations of magnetotail structure and dynamics at Mercury

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94896/1/jgra21525.pd

The Earth: Plasma Sources, Losses, and Transport Processes

This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, 1999) are addressed