In vitro Validation of Quantitative Light-Induced Fluorescence for the Diagnosis of Enamel Fluorosis in Permanent Teeth

This study aimed to validate quantitative light-induced fluorescence (QLF) as a diagnostic tool for mild and moderate enamel fluorosis in permanent teeth, comparing it to visual diagnosis and histological assessment completed using polarized light microscopy (PLM). The buccal surfaces of 139 teeth were visually classified using the Thylstrup and Fejerskov Index (TFI) into sound (TFI 0; n = 17), mild (TFI 1-2; n = 69), and moderate (TFI 3-4; n = 43) fluorosis. Fluorosis was then assessed with QLF (variables ΔF, A, and ΔQ at 5-, 15-, and 30-radiance thresholds) using as reference areas the entire surface and a region of interest (ROI), identified as the most representative region of a fluorosis lesion. PLM images of longitudinal thin sections including the ROI were assessed for histological changes. Correlations among TFI, PLM, and QLF were determined. A receiver-operating characteristic curve was conducted to determine QLF's diagnostic accuracy when compared to the TFI and PLM assessments. This was used to assess the probability that the images were correctly ranked according to severity as determined by PLM and TFI. A positive correlation was found between QLF and PLM, and between QLF and TFI. QLF showed the highest sensitivity and specificity for the diagnosis of mild fluorosis. There was also a strong agreement between TFI and PLM. The selection of a ROI resulted in a stronger correlation with TFI and PLM than when the entire surface was used. The study results indicate that defining an ROI for QLF assessments is a valid method for the diagnosis of mild and moderate enamel fluorosis

Blood levels of lead and dental caries in permanent teeth

ObjectivesThe purpose of this study was to determine whether there is an association between lead exposure within the ages of 1- 4- years and dental caries in the permanent dentition between ages 9- 17 among Mexican youth.MethodsData were collected for the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort from a group of 490 children born and reared in Mexico City. Among ages 1- 4- years, blood lead levels were measured in micrograms of lead per deciliter of blood (μg/dL) and the presence of caries in adolescence was determined using the International Caries and Detection and Assessment System (ICDAS). The relationship between blood levels of lead and decayed, missing, or filled surfaces (DMFS) was examined using negative binomial regression. Covariates were selected based on previous studies and included age, gender, socioeconomic status, oral hygiene, body mass index, and diet. The nonlinear relationship between lead and DMFS was examined using smoothing splines.ResultsThe mean overall blood lead level (BLL) was 4.83- μg/dL (S.D. of 2.2). The mean overall caries level (DMFS) was 4.1. No statistically significant association was found between early childhood blood lead levels and dental caries in adolescence.ConclusionThis study shows a lack of association between exposure to lead between the ages of 1- 4- years of age and dental caries in permanent dentition later in life. Other covariates, such as age and sugar consumption, appeared to play a more prominent role in caries development.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163870/1/jphd12384.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163870/2/jphd12384_am.pd

A chromosome-scale assembly reveals chromosomal aberrations and exchanges generating genetic diversity in Coffea arabica germplasm

In order to better understand the mechanisms generating genetic diversity in the recent allotetraploid species Coffea arabica, here we present a chromosome-level assembly obtained with long read technology. Two genomic compartments with different structural and functional properties are identified in the two homoeologous genomes. The resequencing data from a large set of accessions reveals low intraspecific diversity in the center of origin of the species. Across a limited number of genomic regions, diversity increases in some cultivated genotypes to levels similar to those observed within one of the progenitor species, Coffea canephora, presumably as a consequence of introgressions deriving from the so-called Timor hybrid. It also reveals that, in addition to few, early-occurring exchanges between homoeologous chromosomes, there are numerous recent chromosomal aberrations including aneuploidies, deletions, duplications and exchanges. These events are still polymorphic in the germplasm and could represent a fundamental source of genetic variation in such a lowly variable species

Observation of the nonlinear Hall effect under time reversal symmetric conditions

The electrical Hall effect is the production of a transverse voltage under an out-of-plane magnetic field. Historically, studies of the Hall effect have led to major breakthroughs including the discoveries of Berry curvature and the topological Chern invariants. In magnets, the internal magnetization allows Hall conductivity in the absence of external magnetic field. This anomalous Hall effect (AHE) has become an important tool to study quantum magnets. In nonmagnetic materials without external magnetic fields, the electrical Hall effect is rarely explored because of the constraint by time-reversal symmetry. However, strictly speaking, only the Hall effect in the linear response regime, i.e., the Hall voltage linearly proportional to the external electric field, identically vanishes due to time-reversal symmetry. The Hall effect in the nonlinear response regime, on the other hand, may not be subject to such symmetry constraints. Here, we report the observation of the nonlinear Hall effect (NLHE) in the electrical transport of the nonmagnetic 2D quantum material, bilayer WTe2. Specifically, flowing an electrical current in bilayer WTe2 leads to a nonlinear Hall voltage in the absence of magnetic field. The NLHE exhibits unusual properties sharply distinct from the AHE in metals: The NLHE shows a quadratic I-V characteristic; It strongly dominates the nonlinear longitudinal response, leading to a Hall angle of about 90 degree. We further show that the NLHE directly measures the "dipole moment" of the Berry curvature, which arises from layer-polarized Dirac fermions in bilayer WTe2. Our results demonstrate a new Hall effect and provide a powerful methodology to detect Berry curvature in a wide range of nonmagnetic quantum materials in an energy-resolved way

Mars Science Laboratory Observations of the 2018/Mars Year 34 Global Dust Storm

Mars Science Laboratory Curiosity rover observations of the 2018/Mars year 34 global/planetâ encircling dust storm represent the first in situ measurements of a global dust storm with dedicated meteorological sensors since the Viking Landers. The Mars Science Laboratory team planned and executed a science campaign lasting approximately 100 Martian sols to study the storm involving an enhanced cadence of environmental monitoring using the rover’s meteorological sensors, cameras, and spectrometers. Mast Camera 880â nm optical depth reached 8.5, and Rover Environmental Monitoring Station measurements indicated a 97% reduction in incident total ultraviolet solar radiation at the surface, 30K reduction in diurnal range of air temperature, and an increase in the semidiurnal pressure tide amplitude to 40 Pa. No active dustâ lifting sites were detected within Gale Crater, and global and local atmospheric dynamics were drastically altered during the storm. This work presents an overview of the mission’s storm observations and initial results.Plain Language SummaryThe 2018 Mars global dust storm was observed by six spacecraft in orbit and two rovers on the surface. This paper provides an overview and description of the Mars Science Laboratory Curiosity rover’s observations during the storm. For approximately 100 Martian days (sols), the rover conducted an enhanced cadence of environmental observations to study the storm. These are the first observations of a Martian global dust storm with meteorological sensors near the equator. Atmospheric opacity reached a peak of 8.5, attenuating ~97% of the total solar ultraviolet radiation at the surface. Most of the dust was sourced from outside Gale Crater, with no indications of dust lifting within the crater during the height of the storm. Meteorological conditions were substantially altered, with changes to the pressure, temperature, and humidity patterns. Dust devil activity ceased for several weeks due to the reduction in temperature contrast between the surface and atmosphere. There was no indication of unusual aeolian transport, suggesting Martian global dust storms are not a major cause of sand dune movement.Key PointsThe Curiosity rover conducted a dedicated science campaign to study the 2018 Mars global dust stormAtmospheric opacity reached a peak of 8.5, and horizontal visibility dropped to 2.7 kmMeteorological conditions in Gale Crater were substantially altered, with changes to the pressure, temperature, and humidity cyclesPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147828/1/grl58365_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147828/2/grl58365.pd

Mars Science Laboratory Observations of the 2018/Mars Year 34 Global Dust Storm

Mars Science Laboratory Curiosity rover observations of the 2018/Mars year 34 global/planet-encircling dust storm represent the first in situ measurements of a global dust storm with dedicated meteorological sensors since the Viking Landers. The Mars Science Laboratory team planned and executed a science campaign lasting approximately 100 Martian sols to study the storm involving an enhanced cadence of environmental monitoring using the rover's meteorological sensors, cameras, and spectrometers. Mast Camera 880-nanometer optical depth reached 8.5, and Rover Environmental Monitoring Station measurements indicated a 97 percent reduction in incident total ultraviolet solar radiation at the surface, 30 degrees Kelvin reduction in diurnal range of air temperature, and an increase in the semidiurnal pressure tide amplitude to 40 pascals. No active dust-lifting sites were detected within Gale Crater, and global and local atmospheric dynamics were drastically altered during the storm. This work presents an overview of the mission's storm observations and initial results

Abiotic Input of Fixed Nitrogen by Bolide Impacts to Gale Crater During the Hesperian : Insights From the Mars Science Laboratory

We acknowledge the NASA Mars Science Laboratory Program, Centre National d'Études Spatiales, the Universidad Nacional Autónoma de México (PAPIIT IN109416, IN111619, and PAPIME PE103216), and the Consejo Nacional de Ciencia y Tecnología de México (CONACyT 220626) for their support. We thank Fred Calef for constructing Figure 4 and appreciate the interest and support received from John P. Grotzinger and Joy A. Crisp throughout the Curiosity mission. The authors are grateful to the SAM and MSL teams for successful operation of the SAM instrument and the Curiosity rover. The data used in this paper are listed in the supporting information, figures, and references. SAM Data contained in this paper are publicly available through the NASA Planetary Data System at http://pds‐geosciences.wustl.edu/missions/msl/sam.htm. We would like to express gratitude to Pierre‐Yves Meslin from the Research Institute in Astrophysics and Planetology at Toulouse, France, and five anonymous reviewers whose comments/suggestions on earlier drafts helped improve and clarify this manuscript. The authors declare no conflicts of interests.Peer reviewedPublisher PD

Secular Climate Change on Mars: An Update Using MSL Pressure Data

The South Polar Residual Cap (SPRC) on Mars is an icy reservoir of CO2. If all the CO2 trapped in the SPRC were released to the atmosphere the mean annual global surface pressure would rise by approx. 20 Pa. Repeated MOC and HiRISE imaging of scarp retreat rates within the SPRC have led to the suggestion that the SPRC is losing mass. Estimates for the loss rate vary between 0.5 Pa per Mars Deacde to 13 Pa per Mars Decade. Assuming 80% of this loss goes directly to the atmosphere, and that the loss is monotonic, the global annual mean surface pressure should have increased between approx. 1-20 Pa since the Viking mission (19 Mars years ago)