Precise Age Estimates Research Articles

BS-clock, advancing epigenetic age prediction with high-resolution DNA methylation bisulfite sequencing data.

DNA methylation patterns provide precise and accurate estimates of biological age due to their robustness and predictable changes associated with aging processes. Although several methylation aging clocks have been developed in recent years, they are primarily designed for DNA methylation array data, which has limited CpG coverage and detection sensitivity compared to bisulfite sequencing data. Here, we present BS-clock, a novel DNA methylation clock for human aging based on bisulfite sequencing data. Using BS-seq data from 529 samples retrieved from four tissues, our BS-clock achieves higher correlations with chronological age in multiple tissue types compared to existing array-based clocks. Our study revealed age-dependent aging rates across different age stages and disease conditions, and overall low cross-tissue prediction capability by applying the model trained on one tissue type to others. In summary, BS-clock overcomes limitations of array-based techniques, offering genome-wide CpG site coverage and more robust and accurate aging quantification. This research paves the way for advanced epigenetic studies of aging and holds promise for developing targeted interventions to promote healthy aging. All analysis codes for reproducing the results of the study are publicly available at https://github.com/hucongcong97/BS-clock. Supplementary data are available at Bioinformatics online.

Age estimation of Phormia regina pupae based on ATR-FTIR and chemometrics

Accurate postmortem interval estimation is vital in the investigation of homicides, suicides, and accidental deaths. It is key in narrowing suspect lists, improving crime-solving efficiency, and offering solace to bereaved families. The intra-puparial period, comprising about half of a fly’s developmental cycle, presents challenges for morphological age estimation. External changes are limited to color shifts and the appearance of respiratory horns on the puparium only within several hours after pupariation, while detailed internal development analysis often requires invasive methods like removing the puparium, which can be damaging. Additionally, these techniques usually depend on a forensic entomologist’s expertise, which lead to subjective biases. This study employed attenuated total reflection-fourier transform infrared spectroscopy, a rapid, non-destructive method for analyzing proteins, chitosan, and chitin in puparia. Data showed a consistent reduction in the concentration of the amide I band within the puparium during the intra-puparial development at five constant temperatures (19 °C, 22 °C, 25 °C, 28 °C and 31 °C). This trend in the spectral data effectively distinguishes pupae at various stages of intra-puparial development, facilitating precise age estimation, which is critical for the estimation of the minimum postmortem interval (PMImin). Finally, this work combined the total reflection-fourier transform infrared spectroscopy with chemometric analysis and successfully developed a partial least squares discriminant analysis model and a random forest model, with accuracies of 88 % and 81 %, respectively. These models enable the non-invasive age estimation of P. regina in its intra-puparial period, a stage traditionally difficult to assess morphologically, thus laying the groundwork for PMImin estimation using fly pupae.

Dynamical traceback age of the Octans young stellar association

Context. Octans is one of the most distant (d ∼ 150 pc) young stellar associations of the solar neighbourhood, and it has not yet been sufficiently explored. Its age is still poorly constrained in the literature and requires further investigation. Aims. We take advantage of the state-of-the-art astrometry delivered by the third data release of the Gaia space mission combined with radial velocity measurements obtained from high-resolution spectroscopy to compute the 3D positions and 3D spatial velocities of the stars and derive the dynamical traceback age of the association. Methods. We created a clean sample of cluster members by removing potential outliers from our initial list of candidate members. We then performed an extensive traceback analysis using different subsamples of stars, different metrics to define the size of the association, and different models for the Galactic potential to integrate the stellar orbits in the past. Results. We derive a dynamical age of $ 34^{+2}_{-2} $ Myr that is independent from stellar models and represents the most precise age estimate currently available for the Octans association. After correcting the radial velocity of the stars for the effect of gravitational redshift, we obtain a dynamical age of $ 33^{+3}_{-1} $ Myr, which is in very good agreement with our first solution. This shows that the effect of gravitational redshift is small for such a distant young stellar association. Our result is also consistent with the less accurate age estimates obtained in previous studies from lithium depletion (30–40 Myr) and isochrones (20–30 Myr). By integrating the stellar orbits in time, we show that the members of Octans and Octans-Near had different locations in the past, which indicates that the two associations are unrelated despite the close proximity in the sky. Conclusions. This is the first reliable and precise dynamical age result for the Octans young stellar association. Our results confirm that it is possible to derive precise dynamical ages via the traceback method for ∼30 Myr old stellar clusters at about ∼150 pc with the same precision level that has been achieved in other studies for young stellar groups within 50 pc of the Sun. This represents one more step towards constructing a self-consistent age scale based on the 3D space motion of the stars in the young stellar clusters of the solar neighbourhood.

Age Estimation in Libyan Children Based on Dental Panoramic Radiography

Background: Age estimation plays a key role in the human identification process, and in guiding police investigations. Tooth development is widely used in determining age and state of maturity. Dental age (DA) is of high importance in forensic and pediatric dentistry and also orthodontic treatment planning. Objective: The aim of this study was to assess the accuracy of the Cameriere method in estimating chronological age (CA) of a Libyan sample of 6-year-old up to 13-year-old children through analysis of panoramic radiographs on teeth, considering the relationship between age and measurements of open apices teeth. Materials and methods: Orthopantomographic images of 156 radiographs were selected for the study of which 76 belonged to boys and 80 girls children. The dental age of the subjects was determined through the Cameriere method. Differences and correlations between chronological and dental ages were assessed by paired t-tests and Pearson’s correlation analysis, respectively. Multiple regression analysis was used to predict chronologic age in Libyan from 6-13 years children population. Results: A high positive correlation was found between chronologic age and dental age (as assessed by Cameriere's formula) with r values 0.882, 0.975, and 0.758 for the total, girls and boys study population, respectively. The mean dental age assessed by Cameriere's method was significantly lower than the chronologic age in the Libyan population with boys and the total study population (p < 0.05). Six out of nine parameters were significantly associated with chronologic age (R2=0.996, F (6,155)= 2792.023, p<0.01). Conclusion: Our findings demonstrate that Cameriere’s method is a robust tool for age estimation. These results underscore the high accuracy and importance of assessing dental development for precise age estimation. Based on this research, we can conclude that Cameriere’s method is suitable for dental age estimation in Libyan children.

Exploiting the Greenland volcanic ash repository to date caldera-forming eruptions and widespread isochrons during the Holocene

Polar ice-cores have long been recognised as unrivalled repositories of past volcanic events. Although tephra products from local eruptions tend to dominate these records, improvements in micro-sampling and analytical techniques are uncovering a growing number of cryptotephras erupted from exceptionally distant volcanoes. We present a series of nine Middle Holocene cryptotephra deposits detected within the NGRIP ice-core that originate from five different volcanic regions across the Northern Hemisphere (Alaska, Cascades, Iceland, Japan, Kamchatka). Unique compositional signatures are employed to identify ash from three large caldera-forming events in Kamchatka (KS2 from Ksudach), the Cascades (Mazama) and North East Japan (Mashu), along with ash from the Hekla 4 eruption in Iceland. High-precision ice-core ages (adopting a 1950 CE datum for the GICC05 timescale assigned to the Greenland ice cores) are derived for each eruption: Hekla 4 (4325 ± 8 a b1.95k), KS2 (7089 ± 26 a b1.95k), Mashu (i-f) (7473 ± 33 a b1.95k) and Mazama (7562 ± 35 a b1.95k), all of which can be employed as chronological fix-points in other proxy records where these deposits are also preserved. Four further cryptotephra deposits and one macro-deposit are also identified and traced to sources in Iceland and Alaska. The cryptotephra originating from Alaska is correlated to a deposit identified in lake records from the Kenai Peninsula, thought to originate from Redoubt Volcano. The remaining four deposits are typical of the products of Katla, Grímsvötn and Veiðivötn in Iceland. This ensemble of Middle Holocene tephra deposits highlights the pivotal position of the Greenland ice-sheet and its ice-cores to capture deposition from the convergence of several far-travelled ash clouds. Precise age estimates derived from the annually resolved ice-core record greatly enhances the value of these tephra isochrons.

AI As the New Age Estimator: Pioneering Customized Facial Surgery Outcomes

Abstract Goals/Purpose The imperative for precision in aesthetic surgery necessitates a robust framework for evaluating the impact of facial interventions on perceived age. Our study introduces a cutting-edge AI model aimed at discerning an individual's perceived age from facial characteristics. This tool is designed to augment the assessment of various plastic surgery procedures, facilitating the tailoring of interventions to each patient's unique facial aging pattern. Methods/Technique We harnessed a deep convolutional neural network (DCNN), pre-trained on the extensive ImageNet dataset, and further refined using 523,051 pre-annotated facial images from the IMBD-WIKI database, normalized as per the Mathias et al. face detection paradigm. Faces were processed into a 299x299 pixel matrix, maintaining a 40% margin around the face for uniformity. The Xception architecture was employed for its advanced feature extraction capabilities. The model was refined and tested against a diverse set of 100 patient faces from the Mayo Clinic's database, categorized by demographic and procedural data. The AI model employed regression analysis and softmax probability for precise age estimation. Results/Complications The AI model exhibited a remarkable accuracy rate of 92.5% in age estimation for pre procedural patients, with a standard deviation of 3.2 years. It significantly outperformed traditional methods in identifying fine-grained age-related features. The AI model discerned an average perceived age reduction of 3.5 years across all patients post-procedure, with a notable variance among different types of surgeries. Certain procedures, such as rhytidectomy and blepharoplasty, showed a more pronounced age-reduction effect. Conclusion The AI model presents an accurate and objective method for quantifying perceived age, serving as a significant benchmark in facial aesthetic evaluation. By illustrating measurable age reduction following various procedures, with some surgeries yielding more substantial changes in perceived age, the model stands as a testament to the effectiveness of plastic surgery interventions. The precision of our model in predicting age pre- and post-procedure underscores its potential to assist surgeons in custom-tailoring surgeries to individual aging patterns. This innovation is poised to refine the decision-making process in aesthetic surgery, ensuring treatments are aligned with the desired outcomes for rejuvenation and patient-specific needs, ultimately advancing the frontier of personalized plastic surgery.

Comparing a common clavicle maturation-based age estimation method to ordinary regression analyses with quadratic and sex-specific interaction terms in adolescents

Established methods of age estimation are based on correlating defined maturation stages of bony structures with tables representing the observed range of biological ages in the majority of cases. In this retrospective monocentric study in southwestern Germany, common age estimation methodology was assessed in n = 198 subjects at the age of 25 or younger by analyzing the influence of age, quadratic age, biological sex and age-sex interaction on the ossification stages of the medial epiphysis fugue. Three readers (ICC ≥ 0.81 for left/right side) evaluated routine care computed tomography images of the clavicle with a slice thickness of 1 mm. By using least square regression analyses, to determine the real biological age a quadratic function was determined corrected for the age estimated by established methods and sex (R2 = 0.6 each side), reducing the mean absolute error and root mean squared error in the age estimation of women (2.57 and 3.19) and men (2.57 and 3.47) to 1.54 and 1.82 for women, and 1.54 and 2.25 for men. In women, the medial clavicle epiphysis seem to fuse faster, which was particularly observable from approximately 18 years of age. Before that age, the estimation method was relatively close to the ideal correlation between assessed and real age. To conclude, the presented new method enables more precise age estimation in individuals and facilitates the determination and quantification of additional variables, quantifying their influence on the maturation of the medial clavicle epiphysis based on the established ossification stages.

A Bayesian astrochronology for the Cambrian first occurrence of trilobites in West Gondwana (Morocco)

Abstract The first occurrence of trilobites at ca. 520 Ma is an iconic feature of the Cambrian Explosion. Developing a robust evolutionary view on early Cambrian life is generally hindered by large uncertainties in the ages of fossil finds and their global stratigraphic correlation. We developed an astrochronological interpretation for the Tiout section in Morocco that features some of the oldest trilobite fossils. Our novel approach to incorporating individual astronomical cycle durations in an integrated radioisotopic and astrochronological Bayesian age-depth model results in an age estimate of 519.62 Ma (519.70–519.54 Ma 95% highest posterior distribution) for the first occurrence of trilobites in West Gondwana. This level of precise age estimation is exceptional for biological events in deep time and demonstrates the power of our novel approach.

Asteroseismic age estimate of the open cluster NGC 6866 using Kepler and Gaia

Context. Asteroseismic investigations of solar-like oscillations in giant stars allow for the derivation of their masses and radii. For members of open clusters, this allows us to obtain an age estimate of the cluster that is expected to be identical to the age estimate given by the colour-magnitude diagram, but independent of the uncertainties that are present for that type of analysis. Thus, a more precise and accurate age estimate can be obtained. Aims. We aim to identify and measure the asteroseismic properties of oscillating giant members of the open cluster NGC 6866 and utilise them for a cluster age estimate. Model comparisons also allow constraints to be placed on the stellar physics. Here, we investigate the efficiency of convective-core overshoot during the main sequence evolution, which has a significant influence on the age estimations for these relatively massive giants. The effects of rotation and core overshoot are similar, but not identical, and so, we also investigated the potential of our measurements to distinguish between these effects. Methods. We identified six giant members of NGC 6866 via photometry, proper motions, and parallaxes from Gaia, and spectroscopic literature measurements. These were combined with asteroseismic measurements, which we derived using photometric data from the Kepler mission for five of the stars. Comparisons to stellar-model isochrones constrained the convective-core overshoot and enable a more precise and accurate age estimate than previously possible. Results. A significant amount of differential reddening is found for NGC 6866. Asteroseismology establishes the helium-core burning evolutionary phase for the giants, which have a mean mass of 2.8 M⊙. Their radii are significantly smaller than predicted by current 1D stellar models unless the amount of convective-core overshoot on the main sequence is reduced to αov ≤ 0.1 ⋅ Hp in the step-overshoot description. Our measurements also suggest that rotation has affected the evolution of the stars in NGC 6866 in a way that is consistent with 3D simulations, but not with current 1D stellar models. The age of NGC 6866 is estimated to be 0.43 ± 0.05 Gyr, which is significantly younger and more precise than most previous estimates. Conclusions. We derive a precise cluster age while constraining convective-core overshooting and the effects of rotation in the stellar models. A comparison to age estimates from machine learning methods of the same and similar giant stars uncovers potential biases for automated asteroseismic and non-asteroseismic age estimates of helium-core burning stars.

Improved age estimation from semen using sperm-specific age-related CpG markers

Accurate age estimation from semen has the potential to greatly narrow the pool of unidentified suspects in sexual assault investigations. However, previous efforts utilizing semen age-related CpG (AR-CpG) markers have shown lower accuracy compared to blood AR-CpG-based methods. This discrepancy may be attributed to DNA methylation (DNAm) interferences from “round cells” such as leukocytes and immature sperm cells in semen. This study aimed to develop age calculators based on sperm-specific AR-CpG markers and to achieve performance-improved age estimates from sperm DNA. Through an analysis of publicly available MethylationEPIC microarray data from 90 sperm samples of healthy males aged 22–51 years, we identified 31 sperm-specific AR-CpG markers with absolute Pearson’s R values > 0.5 and Benjamini-Hochberg adjusted p values < 0.013. The top 19 AR-CpG markers with the largest absolute R values and beta ranges > 0.10, along with 3 reported semen AR-CpG markers (cg06304190, cg06979108, and cg12837463), were integrated into two methylation SNaPshot panels (Ⅰ and Ⅱ), each containing 11 markers. The 21 qualified AR-CpG markers showed absolute R values ≥ 0.427 in an independent validation cohort of 253 sperm DNA samples (22–67 years), with cg21843517 exhibiting the strongest age correlation (R = 0.853). The optimal models, constructed using sperm DNAm data of the training set (n = 214, 22–67 years) and markers from panel Ⅰ (n = 11), panel Ⅱ (n = 10), or both panels, achieved mean absolute errors (MAEs) of 2.526–4.746, 3.890–5.715, and > 9.800 years on the test sets of sperm (n = 39, 23–64 years), semen (same donors as the sperm test set), and whole blood (n = 40, 22–65 years), respectively. The simplified models incorporating 3, 5, 9, or 14 AR-CpG markers (MAE = 2.918–4.139 years for sperm) still outperformed the Lee et al. original model (MAE = 6.444 years for semen) and the reconstructed panel Lee model (MAE = 6.011 years for sperm). The final models, utilizing all sperm DNAm data (n = 253) and markers from panel Ⅰ, panel Ⅱ, or both panels, yielded mean MAEs of 2.587, 2.766, and 2.200 years, respectively, on the 50 test sets generated by 5 repeats of 10-fold cross-validations. Additionally, multiple markers in both panels demonstrated the ability to discern sperm or semen from blood with 100% accuracy. In summary, our study substantiates the potential of sperm-specific AR-CpG markers for precise age estimation from sperm DNA, providing an improved toolset for forensic investigations.

An evaluation of the Gilbert-McKern pubic symphyseal age estimation method using Bayesian statistics and principal component analysis: A computed tomographic exploration in an Indian population.

Age of an individual constitutes a primary facet of human identification. In cases where skeletal remains present for examination, bony markers distributed throughout the skeletal framework are employed for age estimation. Amongst these markers, the pubic symphysis constitutes one of the more commonly utilized structures. Gilbert-McKern's pubic symphyseal age estimation method was derived to complement the original three component method, and permit accurate age estimation in females. However, subsequent investigations with the Gilbert-McKern method are limited, and completely lacking for an Indian population. In the present study, CT scans of 380 consenting individuals (190 males and 190 females) undergoing CT examinations for therapeutic purposes, aged 10 years and above, were scored according to Gilbert-McKern's three component method. A significant sexual dimorphism was observed with the scoring of the ventral rampart and symphyseal rim. An overall accuracy of 29.50% was obtained in females, indicating that the method lacks forensic utility in its primal form. Highest posterior density and highest posterior density region values were computed for each component using Bayesian analysis in both sexes, to enable age estimation from individual components, whilst overcoming issues of age mimicry. Amongst the three components, symphyseal rim furnished the most accurate and precise estimates of age, whereas the ventral rampart garnered highest error computations, in both sexes. Principal component analysis was utilized for multivariate age estimation by taking into consideration this differential contribution of individual components. Weighted summary age models, derived using principal component analysis, furnished inaccuracy values of 12.19 years and 12.30 years in females and males, respectively. Bayesian error computations obtained with the symphyseal rim in both sexes were even lower than those obtained with weighted summary age models, demonstrating its suitability as an independent age marker. Despite the use of statistical modalities of Bayesian inference and principal component analysis for age estimation, the method did not yield significantly reduced error rates in females, demonstrating its limited forensic applicability. While, statistically significant sex differences were observed with the scoring of Gilbert-McKern's components, concordant correlations, comparable accuracy and absolute error values were obtained for both sexes, indicating that the Gilbert-McKern method can be utilized to age either sex. However, inaccuracy and bias values obtained with different statistical modalities, as well as broad age intervals furnished with Bayesian analysis demonstrate the overall limited applicability of the Gilbert-McKern method in aging males and females of an Indian population.

Calibrating epigenetic clocks with training data error.

Animal age data are valuable for management of wildlife populations. Yet, for most species, there is no practical method for determining the age of unknown individuals. However, epigenetic clocks, a molecular-based method, are capable of age prediction by sampling specific tissue types and measuring DNA methylation levels at specific loci. Developing an epigenetic clock requires a large number of samples from animals of known ages. For most species, there are no individuals whose exact ages are known, making epigenetic clock calibration inaccurate or impossible. For many epigenetic clocks, calibration samples with inaccurate age estimates introduce a degree of error to epigenetic clock calibration. In this study, we investigated how much error in the training data set of an epigenetic clock can be tolerated before it resulted in an unacceptable increase in error for age prediction. Using four publicly available data sets, we artificially increased the training data age error by iterations of 1% and then tested the model against an independent set of known ages. A small effect size increase (Cohen's d >0.2) was detected when the error in age was higher than 22%. The effect size increased linearly with age error. This threshold was independent of sample size. Downstream applications for age data may have a more important role in deciding how much error can be tolerated for age prediction. If highly precise age estimates are required, then it may be futile to embark on the development of an epigenetic clock when there is no accurately aged calibration population to work with. However, for other problems, such as determining the relative age order of pairs of individuals, a lower-quality calibration data set may be adequate.

A variational encoder–decoder approach to precise spectroscopic age estimation for large Galactic surveys

ABSTRACT Constraints on the formation and evolution of the Milky Way Galaxy require multidimensional measurements of kinematics, abundances, and ages for a large population of stars. Ages for luminous giants, which can be seen to large distances, are an essential component of studies of the Milky Way, but they are traditionally very difficult to estimate precisely for a large data set and often require careful analysis on a star-by-star basis in asteroseismology. Because spectra are easier to obtain for large samples, being able to determine precise ages from spectra allows for large age samples to be constructed, but spectroscopic ages are often imprecise and contaminated by abundance correlations. Here we present an application of a variational encoder–decoder on cross-domain astronomical data to solve these issues. The model is trained on pairs of observations from APOGEE and Kepler of the same star in order to reduce the dimensionality of the APOGEE spectra in a latent space while removing abundance information. The low dimensional latent representation of these spectra can then be trained to predict age with just ∼1000 precise seismic ages. We demonstrate that this model produces more precise spectroscopic ages ($\sim 22~{{\ \rm per\ cent}}$ overall, $\sim 11~{{\ \rm per\ cent}}$ for red-clump stars) than previous data-driven spectroscopic ages while being less contaminated by abundance information (in particular, our ages do not depend on [α/M]). We create a public age catalogue for the APOGEE DR17 data set and use it to map the age distribution and the age-[Fe/H]-[α/M] distribution across the radial range of the Galactic disc.

Precision of Structures Used to Estimate Age and Growth of Apache Trout from Arizona

Abstract Obtaining reliable information on the age structure of fish populations is important for making conservation and management decisions. We sought to evaluate precision and reader confidence in age estimates from scales (two body locations), sectioned fin rays (pectoral, pelvic, anal), and sectioned sagittal otoliths from Apache Trout Oncorhynchus apache (n = 78 fish) sampled from the East Fork White River, Arizona, in 2017. Two experienced readers without prior knowledge of fish length aged structures independently. Each reader provided a confidence rating of 0 (no confidence) to 3 (completely confident) as a measure of readability. Both readers were unable to estimate age from scales collected from the area just posterior to the insertion of the pectoral fin. We used scales removed from an area just dorsal to the lateral line and posterior to the dorsal fin in all analyses. Percentage of exact agreement between readers was highest for scales and otoliths (&amp;gt;72.0%) and lowest for fin rays (31.8–58.1%). Average confidence rating was highest for sectioned otoliths (mean ± SE, 2.1 ± 0.07), and lowest for anal fin rays (0.3 ± 0.06) and scales (0.7 ± 0.05). We compared consensus ages from otoliths to the other structures. Percentage of exact agreement with otolith age was low and varied from 21.6 to 35.7% among structures. Similarly, percentage of agreement within 1 y was also low among structures (58.0–70.2%). Scales consistently underestimated age of age-4 and older fish (based on otolith age), whereas fin rays tended to overestimate age of younger fish and underestimate age of older Apache Trout. Although sectioned otoliths require lethal sampling, they produced the most precise age estimates for Apache Trout with the highest reader confidence. Dorsal scales may be a suitable nonlethal alternative to otoliths if ages for only young fish (age 3 and younger) meet study objectives.

An integrated proximal-distal radiocarbon dating approach provides improved age constraints for a key Holocene tephra isochron

Volcanic ash (tephra) horizons are an essential tool for the spatial and temporal correlation of many natural archives. However, tephrochronology is accompanied by age uncertainties that often limit its capacity to effectively constrain age models. This is particularly problematic for paleoseismology in complex tectonic settings such as New Zealand, where the accuracy and precision of earthquake ages is important for interpreting past fault interactions and earthquake sequences. We use the widespread Waimihia tephra, erupted at ∼3.4 ka from Taupō volcano, as a case study for generating improved age constraints for Holocene tephra isochrons. Our dating strategy minimizes uncertainties by (i) conducting detailed assessments to identify the most reliable dateable material, (ii) using precise AMS dating techniques, and (iii) constructing Bayesian age models. By applying consistent procedures to date tephra deposits at proximal, onshore distal and offshore distal locations, we also facilitate the detection of any geographic radiocarbon bias. Based on high agreement between the independently derived tephra ages from each location, we demonstrate no offsets in radiocarbon results between proximal and distal deposits, precluding bias from near-vent magmatic degassing. Our integrated age model exploits the benefits of each individual dating approach and uses the full suite of 42 new radiocarbon dates to yield an age of 3574–3478 cal yr BP (highest 95% range) for the Waimihia eruption. Compared to previous estimates, this older and more precise age has implications for refining existing paleoearthquake correlations and other chronologies that rely on the Waimihia isochron to provide age control. We recommend applying this multi-location approach to existing tephrochronologies where possible, to achieve more accurate and precise eruption age estimates that allow for the detection of radiocarbon bias.

Curriculum classification network based on margin balancing multi-loss and ensemble learning

In this paper, we propose a curriculum classification network based on margin-balancing multi-loss and ensemble learning method, which solves the problems of difficult classification in different age groups and uneven distance within ages groups on the basis of the orthopantomograms. Firstly, due to the characteristics of teeth development, a curriculum learning framework is proposed and divides the sample ”easily” into high-age and low-age groups, which reduces the error of dividing low-age into high-age groups or vice versa. Secondly, owing to minor differences of teeth development in the high-age group, the margin-balancing multi-loss is proposed to optimize the classification interface. Thirdly, considering the distinguishable characteristics in the low-age group and large range and non-concentrated features, an ensemble feature learning method is proposed to improve the classification reliability. Extensive experimental results on the orthopantomograms dataset demonstrate that the proposed method can perform well on different networks and accomplish precise age estimation.

A &gt;200 ka U‐Th Based Chronology From Lacustrine Evaporites, Searles Lake, CA

AbstractWell‐dated lacustrine records are essential to establish the timing and drivers of regional hydroclimate change. Searles Basin, California, records the depositional history of a fluctuating saline‐alkaline lake in the terminal basin of the Owens River system draining the eastern Sierra Nevada. Here, we establish a U‐Th chronology for the ∼76‐m‐long SLAPP‐SLRS17 core collected in 2017 based on dating of evaporite minerals. Ninety‐eight dated samples comprising nine different minerals were evaluated based on stratigraphic, mineralogic, textural, chemical, and reproducibility criteria. After the application of these criteria, a total of 37 dated samples remained as constraints for the age model. A lack of dateable minerals between 145 and 110 ka left the age model unconstrained over the penultimate glacial termination (Termination II). We thus established a tie point between plant wax δD values in the core and a nearby speleothem δ18O record at the beginning of the Last Interglacial. We construct a Bayesian age model allowing stratigraphy to inform sedimentation rate inflections. We find that the &gt;210 ka SLAPP‐SRLS17 record contains five major units that correspond with prior work. The new dating is broadly consistent with previous efforts but provides more precise age estimates and enables a detailed evaluation of evaporite depositional history. We also offer a substantial revision of the age of the Bottom Mud‐Mixed Layer contact, shifting it from ∼130 ka to 178 ± 3 ka. The new U‐Th chronology documents the timing of mud and salt layers and lays the foundation for climate reconstructions.

Uncertainties in asteroseismic grid-based estimates of the ages of halo stars

Context. Stellar age determinations for field stars are crucial for studying the evolutionary history of the Galaxy. The vast majority of the research in this area has so far been focused on stars with typical disk characteristics. Aims. Nowadays, the availability of high-quality asteroseismic data for stars with typical halo characteristics makes it possible to extend such investigations. The aim of this paper is to study the precision and theoretical biases in the age determinations of halo stars adopting both asteroseismic and classic observational constraints. Methods. We adopt the well-tested SCEPtER pipeline, covering evolutionary phases up to the red giant branch (RGB). The fitting grids contain stars with mass in the range of [0.7; 1.0] M⊙ and metallicity [Fe/H] from −2.5 to −0.5, which are typical ranges seen in the halo population. We investigate several scenarios characterised by different adopted observational uncertainties. We also assess the impact of systematic discrepancies between the recovery grid models and target stars by computing several synthetic grids of stellar models with perturbed input physics. Results. We achieve more precise asteroseismic age estimates for old metal-poor stars than for more metallic stars. In our reference scenario (errors in Δν and νmax of 2.5% and 5% respectively), we recover ages for stars in the main sequence (MS) or subgiant branch (SGB) with a typical 10%−20% precision, while we recover those of RGB stars with a precision of about 60%. However, recent observations allow tighter constraints on asteroseismic parameters by about a factor of 3. With this assumption, the age precision in RGB improved to 20%, while few modifications occur in the other analysed evolutionary phases. Our investigation of the relevance of systematic discrepancies between grid models and target stars shows that a mismatch in the mixing-length parameter value between grids and targets (from 1.9 to 1.74) leads to significant bias in the age estimations for MS stars (about 10%), but this bias is smaller for SGB and RGB stars. Neglecting the microscopic diffusion effect in the recovery grid leads to a typical 40% bias in age estimates for stars on the MS. Finally, we applied the age estimation technique to stars in globular clusters, adopting typical observational uncertainties from the literature. We find a precision in age estimates of around 20% for MS stars and up to 40% for RGB stars. These uncertainties are greater than those obtained with classical methods, which are therefore still to be preferred. We also applied the SCEPtER pipeline to the age determination of the stars of the cluster M4, relying on asteroseismic data for seven RGB stars from the literature. We obtain a cluster age of 11.9 ± 1.5 Gyr and a mass at the turn-of off 0.86 ± 0.04 M⊙, which are in good agreement with literature results.

Pupal Age Estimation of Sarcophaga peregrina (Diptera: Sarcophagidae) at Different Constant Temperatures Utilizing ATR-FTIR Spectroscopy and Cuticular Hydrocarbons

Sarcophaga peregrina (Robineau-Desvoidy, 1830) (Diptera: Sarcophagidae) is a forensically important flesh fly that has potential value in estimating the PMImin. The precise pupal age estimation has great implications for PMImin estimation. During larval development, the age determination is straightforward by the morphological changes and variation of length and weight, however, the pupal age estimation is more difficult due to anatomical and morphological changes not being visible. Thus, it is necessary to find new techniques and methods that can be implemented by standard experiments for accurate pupal age estimation. In this study, we first investigated the potential of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and cuticular hydrocarbons (CHCs) for the age estimations of S. peregrina pupae at different constant temperatures (20 °C, 25 °C, and 30 °C). The orthogonal projections latent structure discrimination analysis (OPLS-DA) classification model was used to distinguish the pupae samples of different developmental ages. Then, a multivariate statistical regression model, partial least squares (PLS), was established with the spectroscopic and hydrocarbon data for pupal age estimations. We identified 37 CHCs with a carbon chain length between 11 and 35 in the pupae of S. peregrina. The results of the OPLS-DA model show a significant separation between different developmental ages of pupae (R2X > 0.928, R2Y > 0.899, Q2 > 0.863). The PLS model had a satisfactory prediction with a good fit between the actual and predicted ages of the pupae (R2 > 0.927, RMSECV < 1.268). The results demonstrate that the variation tendencies of spectroscopy and hydrocarbons were time-dependent, and ATR-FTIR and CHCs may be optimal for the age estimations of pupae of forensically important flies with implications for PMImin estimation in forensic practice.

Comparison of age estimates and population characteristics for green sunfish using two otolith methods

AbstractDependent on the specific fishery, green sunfish (Lepomis cyanellus) can be viewed as a benefit or a detriment. Regardless, effective management of this species relies on precise age estimation, which is critical to detail age structure, growth and recruitment rates of their populations. To determine the most precise method for age estimation, estimated ages of whole and cracked otoliths of 422 green sunfish were compared from three small impoundments (0.6–16.2 ha) in Oklahoma. Green sunfish ages ranged from 0 to 7 for cracked otoliths and 0 to 6 for whole‐viewed otoliths, depending on the population. High precision between readers was observed for whole (per cent agreement = 85%–96%; mean CV = 3.4%–4.8%; and average per cent error = 2.4%–3.4%) and cracked otoliths (per cent agreement = 92%–96%; mean CV = 0.3%–6.3%; and average per cent error = 0.3%–4.4%). Limited bias was observed for young fish (≤age 3) for evaluating between‐reader precision using whole otoliths. When bias was present, ages generally exceeded the 1:1 line of equivalency. Final consensus ages for older fish (≥age 5) were sometimes underestimated using whole otoliths, compared to cracked otoliths. Fair agreement for final consensus ages (73%–87%) between whole and cracked otoliths was observed, compared to other otolith ageing studies in the literature. However, the results of the present study indicated no significant differences in growth or age‐frequency estimates using ages derived from whole and cracked otoliths, suggesting the moderate level of consensus agreement was not sufficiently low to significantly impact population characteristics and subsequent management decisions. Green sunfish growth rates in Oklahoma appear sufficiently high to allow the use of whole otoliths for age estimation to age seven, unless slow growth is expected. To ensure precise age estimation, however, it is suggested that otoliths from green sunfish ≥age 5 be cracked, regardless of growth rates.