The past few hundred years have seen large fluctuations in atmospheric
14C concentration. In part, these have been the result of natural factors, including the climatic changes of the Little Ice Age, ...and the Spörer and Maunder solar activity minima. In addition, however, changes in human activity since the middle of the 19th century have released
14C-free CO
2 to the atmosphere. Moreover, between c. 1955 and c. 1963, atmospheric nuclear weapon testing resulted in a dramatic increase in the concentration of
14C in the atmosphere. This was followed by a significant decrease in atmospheric
14C as restrictions on nuclear weapon testing began to take effect and as rapid exchange occurred between the atmosphere and other carbon reservoirs. The large fluctuations in atmospheric
14C that occurred prior to 1955 mean that a single radiocarbon date may yield an imprecise calibrated age consisting of several possible age ranges. This difficulty may be overcome by obtaining a series of
14C dates from a sequence and either wiggle-matching these dates to a radiocarbon calibration curve or using additional information on dated materials and their surrounding environment to narrow the calibrated age ranges associated with each
14C date. For the period since 1955 (the bomb-pulse period), significant differences in atmospheric
14C levels between consecutive years offer the possibility of dating recent samples with a resolution of from one to a few years. These approaches to dating the recent past are illustrated using examples from peats, lake and salt marsh sediments, tree rings, marine organisms and speleothems.
Early researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve ...for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 14C yrs older.
H3 K27‐altered diffuse midline glioma is a highly lethal pediatric‐type tumor without efficacious treatments. Recent findings have highlighted the heterogeneity among diffuse midline gliomas with ...different locations and ages. Compared to tumors located in the brain stem and thalamus, the molecular and clinicopathological features of H3 K27‐altered spinal cord glioma are still largely elusive, thus hindering the accurate management of patients. Here we aimed to characterize the clinicopathological and molecular features of H3 K27M‐mutant spinal cord glioma in 77 consecutive cases. We found that the H3 K27M‐mutant spinal cord glioma, with a median age of 35 years old, had a significantly better prognosis than H3 K27M‐mutant brain tumors. We noticed a molecular heterogeneity of H3 K27M‐mutant spinal cord astrocytoma via targeted sequencing with 34 cases. TP53 mutation which occurred in 58.8% of cases is mutually exclusive with PPM1D (26%) and NF1 (44%) mutations. The TP53‐mutant cases had a significantly higher number of copy number variants (CNV) and a marginally higher proportion of pediatric patients (age at diagnosis <18 years old, p = 0.056). Cox regression and Kaplan–Meier curve analysis showed that the higher number of CNV events (≥3), chromosome (Chr) 9p deletion, Chr 10p deletion, ATRX mutation, CDK6 amplification, and retinoblastoma protein (RB) pathway alteration are associated with worse survival. Cox regression analysis with clinicopathological features showed that glioblastoma histological type and a high Ki‐67 index (>10%) are associated with a worse prognosis. Interestingly, the histological type, an independent prognostic factor in multivariate Cox regression, can also stratify molecular features of H3 K27M‐mutant spinal cord glioma, including the RB pathway, KRAS/PI3K pathway, and chromosome arms CNV. In conclusion, although all H3 K27M‐mutant spinal cord diffuse glioma were diagnosed as WHO Grade 4, the histological type, molecular features representing chromatin instability, and molecular alterations associated with accelerated cell proliferative activity should not be ignored in clinical management.
In a large cohort (n=77), we characterized the molecular, clinicopathological, and prognostic characteristics of H3 K27M‐mutant spinal cord diffuse glioma. ATRX mutation, CDK6 amplification, RB pathway alteration, a higher number of Copy number variant (CNV) events, chromosome (Chr) 9p deletion, and Chr 10p deletion is associated with worse survival. Glioblastoma histological type and a high Ki‐67 index (>10%) are associated with a worse prognosis. Interestingly, the histological type, an independent prognostic factor in multivariate Cox regression, can stratify molecular features of H3 K27M‐mutant spinal cord glioma, including the RB pathway and PI3K pathway.
The practices of head and neck surgical oncologists must evolve to meet the unprecedented needs placed on our health care system by the Coronavirus disease 2019 (COVID‐19) pandemic. Guidelines are ...emerging to help guide the provision of head and neck cancer care, though in practice, it can be challenging to operationalize such recommendations. Head and neck surgeons at Wuhan University faced significant challenges in providing care for their patients. Similar challenges were faced by the University of Toronto during the severe acute respiratory syndrome (SARS) pandemic in 2003. Herein, we outline our combined experience and key practical considerations for maintaining an oncology service in the midst of a pandemic.
When European colonists arrived in the late 19th century, large villages dotted the coastline of the Gulf of Papua (southern Papua New Guinea). These central places sustained long-distance exchange ...and decade-spanning ceremonial cycles. Besides ethnohistoric records, little is known of the villages’ antiquity, spatiality, or development. Here we combine oral traditional and 14C chronological evidence to investigate the spatial history of two ancestral village sites in Orokolo Bay: Popo and Mirimua Mapoe. A Bayesian model composed of 35 14C assays from seven excavations, alongside the oral traditional accounts, demonstrates that people lived at Popo from 765–575 cal BP until 220–40 cal BP, at which time they moved southwards to Mirimua Mapoe. The village of Popo spanned ca. 34 ha and was composed of various estates, each occupied by a different tribe. Through time, the inhabitants of Popo transformed (e.g., expanded, contracted, and shifted) the village to manage social and ceremonial priorities, long-distance exchange opportunities and changing marine environments. Ours is a crucial case study of how oral traditional ways of understanding the past interrelate with the information generated by Bayesian 14C analyses. We conclude by reflecting on the limitations, strengths, and uncertainties inherent to these forms of chronological knowledge.
The time of arrival of people in Australia is an unresolved question. It is relevant to debates about when modern humans first dispersed out of Africa and when their descendants incorporated genetic ...material from Neanderthals, Denisovans and possibly other hominins. Humans have also been implicated in the extinction of Australia's megafauna. Here we report the results of new excavations conducted at Madjedbebe, a rock shelter in northern Australia. Artefacts in primary depositional context are concentrated in three dense bands, with the stratigraphic integrity of the deposit demonstrated by artefact refits and by optical dating and other analyses of the sediments. Human occupation began around 65,000 years ago, with a distinctive stone tool assemblage including grinding stones, ground ochres, reflective additives and ground-edge hatchet heads. This evidence sets a new minimum age for the arrival of humans in Australia, the dispersal of modern humans out of Africa, and the subsequent interactions of modern humans with Neanderthals and Denisovans.
Gene function studies benefit from the availability of mutants. In plants, Agrobacterium‐mediated genetic transformation is widely used to create mutants. These mutants, also called transformants, ...contain one or several transfer‐DNA (T‐DNA) copies in the host genome. Quantifying the copy number of T‐DNA in transformants is beneficial to assess the number of mutated genes. Here, we developed a competitive polymerase chain reaction (PCR)‐based method to detect a single copy of a T‐DNA insertion in transformants. The competitor line BHK−‐1 that contains a single copy of competitor BHK− (BHK, Basta, Hygromycin, Kanamycin‐resistant genes) was crossed with test transformants and the genomic DNA of F1 plants was subjected to competitive PCR. By analyzing the gray ratio between two PCR products, we were able to determine whether or not the test transformants contained a single copy of T‐DNA insertion. We also generated the control lines BHK±1:1 and BHK±2:1, which contain the target (BHK+) and competitor (BHK−) in a ratio of 1:1 and 2:1, respectively. The ratios of their PCR products are useful references for quantitative analysis. Overall, this method is reliable and simple in experimental manipulations and can be used as a substitute for Southern‐blot analysis to identify a single copy of T‐DNA insertion in transformants.
This paper presents a compilation of atmospheric radiocarbon for the period 1950–2019, derived from atmospheric CO2 sampling and tree rings from clean-air sites. Following the approach taken by Hua ...et al. (2013), our revised and extended compilation consists of zonal, hemispheric and global radiocarbon (14C) data sets, with monthly data sets for 5 zones (Northern Hemisphere zones 1, 2, and 3, and Southern Hemisphere zones 3 and 1–2). Our new compilation includes smooth curves for zonal data sets that are more suitable for dating applications than the previous approach based on simple averaging. Our new radiocarbon dataset is intended to help facilitate the use of atmospheric bomb 14C in carbon cycle studies and to accommodate increasing demand for accurate dating of recent (post-1950) terrestrial samples.
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