An unprecedented sea ice retreat in the Weddell Sea driving an overall decrease of the Antarctic sea-ice extent over the 20th century

Sea-ice extent is predicted to decrease in a warming climate. However, despite global warming over the past century, total Antarctic sea ice remained relatively stable from 1979 until 2015, before strongly melting. Here we explore the long-term sea ice variability by reconstructing Antarctic sea ice since 1700 CE, based on paleoclimate records and data assimilation. Our results indicate a decline in southern hemisphere sea-ice extent over the 20th century, driven by a reduction of 0.26 million km2 in the Weddell Sea that reached values at the end of the century lower than any other reconstructed period. The Ross Sea experienced an increasing sea-ice cover trend due to a low-pressure system located off the Amundsen Sea coast, offset by a decreasing trend in the Bellingshausen-Amundsen Sea. Models failed to account for the Ross Sea increase, resulting in an overly uniform estimate of Antarctic sea ice loss over the 20th century

Ice Core Chronologies from the Antarctic Peninsula: The Palmer, Jurassic, and Rendezvous Age-Scales

In this study, we present the age scales for three Antarctic Peninsula (AP) ice cores: Palmer, Rendezvous, and Jurassic. The three cores are all intermediate-depth cores, in the 133–141 m depth range. Non-sea-salt sulfate ([nssSO42−]) and hydrogen peroxide (H2O2) display marked seasonal variability suitable for annual-layer counting. The Palmer ice core covers 390 years, 1621–2011 C.E., and is one of the oldest AP cores. Rendezvous and Jurassic are lower elevation high-snow accumulation sites and therefore cover shorter intervals, 1843–2011 C.E. and 1874–2011 C.E., respectively. The age scales show good agreement with known volcanic age horizons. The three chronologies’ start and end dates of volcanic events are compared to the volcanic events in the published WAIS Divide core. The age difference for the Palmer age scale is ±6 months, Rendezvous ±9 months, and Jurassic ±7 months. Our results demonstrate the advantage of dating several cores from the same region at the same time. Additional confidence can be gained in the age scales by evaluating and finding synchronicity of [nssSO42−] peaks amongst the sites.</jats:p

A combined HM-PCR/SNuPE method for high sensitive detection of rare DNA methylation

<p>Abstract</p> <p>Background</p> <p>DNA methylation changes are widely used as early molecular markers in cancer detection. Sensitive detection and classification of rare methylation changes in DNA extracted from circulating body fluids or complex tissue samples is crucial for the understanding of tumor etiology, clinical diagnosis and treatment. In this paper, we describe a combined method to monitor the presence of methylated tumor DNA in an excess of unmethylated background DNA of non-tumorous cells. The method combines heavy methyl-PCR, which favors preferential amplification of methylated marker sequence from bisulfite-treated DNA with a methylation-specific single nucleotide primer extension monitored by ion-pair, reversed-phase, high-performance liquid chromatography separation.</p> <p>Results</p> <p>This combined method allows detection of 14 pg (that is, four to five genomic copies) of methylated chromosomal DNA in a 2000-fold excess (that is, 50 ng) of unmethylated chromosomal background, with an analytical sensitivity of > 90%. We outline a detailed protocol for the combined assay on two examples of known cancer markers (SEPT9 and TMEFF2) and discuss general aspects of assay design and data interpretation. Finally, we provide an application example for rapid testing on tumor methylation in plasma DNA derived from a small cohort of patients with colorectal cancer.</p> <p>Conclusion</p> <p>The method allows unambiguous detection of rare DNA methylation, for example in body fluid or DNA isolates from cells or tissues, with very high sensitivity and accuracy. The application combines standard technologies and can easily be adapted to any target region of interest. It does not require costly reagents and can be used for routine screening of many samples.</p

Unintentional p-type conductivity in intrinsic Ge-rich SiGe/Ge heterostructures grown on Si(001)

In this work, we investigate the effective background charge density in intrinsic Si0.06Ge0.94/Ge plastically relaxed heterostructures deposited on Si(001). Hall effect measurements and capacitance–voltage profiling reveal a p-type conductivity in the nominally intrinsic layer with a hole concentration in the mid 1015 cm−3 range at temperatures between 50 and 200 K. In view of the carrier freeze out that we observe below 50 K, we attribute the origin of these carriers to the ionization of shallow acceptor-like defect states above the valence band. In addition, one dominant hole trap located at mid-gap position is found by deep level transient spectroscopy. Carrier trapping kinetics measurements can be interpreted as due to a combination of point defects, likely trapped in the strain field of extended defects, i.e., the threading dislocation

Current leakage mechanisms related to threading dislocations in Ge-rich SiGe heterostructures grown on Si(001)

This work investigates the role of threading dislocation densities (TDD) in the low density regime on the vertical transport in Si0.06Ge0.94 heterostructures integrated on Si(001). The use of unintentionally doped Si0.06Ge0.94 layers enables the study of the impact of grown-in threading dislocations (TD) without interaction with processing-induced defects originating, e.g., from dopant implantation. The studied heterolayers, while equal in composition, the degree of strain relaxation, and the thickness feature three different values for the TDD as 3 × 106, 9 × 106, and 2 × 107 cm−2. Current–voltage measurements reveal that leakage currents do not scale linearly with TDD. The temperature dependence of the leakage currents suggests a strong contribution of field-enhanced carrier generation to the current transport with the trap-assisted tunneling via TD-induced defect states identified as the dominant transport mechanism at room temperature. At lower temperatures and at high electric fields, direct band-to-band tunneling without direct interactions with defect levels becomes the dominating type of transport. Leakage currents related to emission from mid-gap traps by the Shockley–Read–Hall (SRH) generation are observed at higher temperatures (&gt;100 °C). Here, we see a reduced contribution coming from SRH in our material, featuring the minimal TDD (3 × 106 cm−2), which we attribute to a reduction in point defect clusters trapped in the TD strain fields

Ice core chemistry database: an Antarctic compilation of sodium and sulfate records spanning the past 2000 years

Changes in sea ice conditions and atmospheric circulation over the Southern Ocean play an important role in modulating Antarctic climate. However, observations of both sea ice and wind conditions are limited in Antarctica and the Southern Ocean, both temporally and spatially, prior to the satellite era (1970 onwards). Ice core chemistry data can be used to reconstruct changes over annual, decadal, and millennial timescales. To facilitate sea ice and wind reconstructions, the CLIVASH2k (CLimate Variability in Antarctica and the Southern Hemisphere over the past 2000 years) working group has compiled a database of two species, sodium [Na+] and sulfate [SO2− 4 ], commonly measured ionic species. The database (https://doi.org/10.5285/9E0ED16E-F2AB4372-8DF3-FDE7E388C9A7; Thomas et al., 2022) comprises records from 105 Antarctic ice cores, containing records with a maximum age duration of 2000 years. An initial filter has been applied, based on evaluation against sea ice concentration, geopotential height (500 hPa), and surface wind fields to identify sites suitable for reconstructing past sea ice conditions, wind strength, or atmospheric circulation

SHOX2 DNA Methylation is a Biomarker for the diagnosis of lung cancer based on bronchial aspirates

<p>Abstract</p> <p>Background</p> <p>This study aimed to show that SHOX2 DNA methylation is a tumor marker in patients with suspected lung cancer by using bronchial fluid aspirated during bronchoscopy. Such a biomarker would be clinically valuable, especially when, following the first bronchoscopy, a final diagnosis cannot be established by histology or cytology. A test with a low false positive rate can reduce the need for further invasive and costly procedures and ensure early treatment.</p> <p>Methods</p> <p>Marker discovery was carried out by differential methylation hybridization (DMH) and real-time PCR. The real-time PCR based HeavyMethyl technology was used for quantitative analysis of DNA methylation of SHOX2 using bronchial aspirates from two clinical centres in a case-control study. Fresh-frozen and Saccomanno-fixed samples were used to show the tumor marker performance in different sample types of clinical relevance.</p> <p>Results</p> <p>Valid measurements were obtained from a total of 523 patient samples (242 controls, 281 cases). DNA methylation of SHOX2 allowed to distinguish between malignant and benign lung disease, i.e. abscesses, infections, obstructive lung diseases, sarcoidosis, scleroderma, stenoses, at high specificity (68% sensitivity [95% CI 62-73%], 95% specificity [95% CI 91-97%]).</p> <p>Conclusions</p> <p>Hypermethylation of SHOX2 in bronchial aspirates appears to be a clinically useful tumor marker for identifying subjects with lung carcinoma, especially if histological and cytological findings after bronchoscopy are ambiguous.</p

Ice core chemistry database: an Antarctic compilation of sodium and sulfate records spanning the past 2000 years

Changes in sea ice conditions and atmospheric circulation over the Southern Ocean play an important role in modulating Antarctic climate. However, observations of both sea ice and wind conditions are limited in Antarctica and the Southern Ocean, both temporally and spatially, prior to the satellite era (1970 onwards). Ice core chemistry data can be used to reconstruct changes over annual, decadal, and millennial timescales. To facilitate sea ice and wind reconstructions, the CLIVASH2k (CLimate Variability in Antarctica and the Southern Hemisphere over the past 2000 years) working group has compiled a database of two species, sodium [Na+] and sulfate [SO2− 4 ], commonly measured ionic species. The database (https://doi.org/10.5285/9E0ED16E-F2AB4372-8DF3-FDE7E388C9A7; Thomas et al., 2022) comprises records from 105 Antarctic ice cores, containing records with a maximum age duration of 2000 years. An initial filter has been applied, based on evaluation against sea ice concentration, geopotential height (500 hPa), and surface wind fields to identify sites suitable for reconstructing past sea ice conditions, wind strength, or atmospheric circulation