Experimental study on retardation of a heavy NAPL vapor in partially saturated porous media

Non-aqueous-phase liquid (NAPL) contaminants introduced into the unsaturated zone spread as a liquid phase; however, they can also vaporize and migrate in a gaseous state. Vapor plumes migrate easily and thus pose a potential threat to underlying aquifers. Large-scale column experiments were performed to quantify partitioning processes responsible for the retardation of carbon disulfide (CS2) vapor in partially saturated porous media. The results were compared with a theoretical approach taking into account the partitioning into the aqueous phase as well as adsorption to the solid matrix and to the air–water interface. The experiments were conducted in large, vertical columns (i.d. of 0.109 m) of 2 m length packed with different porous media. A slug of CS2 vapor and the conservative tracer argon was injected at the bottom of the column followed by a nitrogen chase. Different seepage velocities were applied to characterize the transport and to evaluate their impact on retardation. Concentrations of CS2 and argon were measured at the top outlet of the column using two gas chromatographs. The temporal-moment analysis for step input was employed to evaluate concentration breakthrough curves and to quantify dispersion and retardation. The experiments conducted showed a pronounced retardation of CS2 in moist porous media which increased with water saturation. The comparison with an analytical solution helped to identify the relative contributions of partitioning processes to retardation. Thus, the experiments demonstrated that migrating CS2 vapor is retarded as a result of partitioning processes. Moreover, CS2 dissolved in the bulk water is amenable to biodegradation. The first evidence of CS2 decay by biodegradation was found in the experiments. The findings contribute to the understanding of vapor-plume transport in the unsaturated zone and provide valuable experimental data for the transfer to field-like conditions

Acceleration of dynamic ice loss in Antarctica from satellite gravimetry

The dynamic stability of the Antarctic Ice Sheet is one of the largest uncertainties in projections of future global sea-level rise. Essential for improving projections of the ice sheet evolution is the understanding of the ongoing trends and accelerations of mass loss in the context of ice dynamics. Here, we examine accelerations of mass change of the Antarctic Ice Sheet from 2002 to 2020 using data from the GRACE (Gravity Recovery and Climate Experiment; 2002–2017) and its follow-on GRACE-FO (2018-present) satellite missions. By subtracting estimates of net snow accumulation provided by re-analysis data and regional climate models from GRACE/GRACE-FO mass changes, we isolate variations in ice-dynamic discharge and compare them to direct measurements based on the remote sensing of the surface-ice velocity (2002–2017). We show that variations in the GRACE/GRACE-FO time series are modulated by variations in regional snow accumulation caused by large-scale atmospheric circulation. We show for the first time that, after removal of these surface effects, accelerations of ice-dynamic discharge from GRACE/GRACE-FO agree well with those independently derived from surface-ice velocities. For 2002–2020, we recover a discharge acceleration of -5.3 ± 2.2 Gt yr−2 for the entire ice sheet; these increasing losses originate mainly in the Amundsen and Bellingshausen Sea Embayment regions (68%), with additional significant contributions from Dronning Maud Land (18%) and the Filchner-Ronne Ice Shelf region (13%). Under the assumption that the recovered rates and accelerations of mass loss persisted independent of any external forcing, Antarctica would contribute 7.6 ± 2.9 cm to global mean sea-level rise by the year 2100, more than two times the amount of 2.9 ± 0.6 cm obtained by linear extrapolation of current GRACE/GRACE-FO mass loss trends

Разработка и исследование алгоритмов решения геодезических задач с использованием Web-технологий

Объектом исследования данной работы являются базовые задачи геодезии. Цель работы – разработка и введение в эксплуатацию Web-приложения выполняющего вычисления возникающие при решении базовых задач геодезии с максимальной автоматизацией.Research and modification of algorithms for solving basic problems of geodesy. Development web-based applications based on compiled algorithms

Late Holocene Glacial Fluctuations of Schiaparelli Glacier at Monte Sarmiento Massif, Tierra del Fuego (54°24′ S)

The Magallanes–Tierra del Fuego region, Southern Patagonia (53–56° S) features a plethora of fjords and remote and isolated islands, and hosts several thousand glaciers. The number of investigated glaciers with respect to the multiple Neoglacial advances is based on a few individual studies and is still fragmentary, which complicates the interpretation of the glacial dynamics in the southernmost part of America. Schiaparelli Glacier (54°24′ S, 70°50′ W), located at the western side of the Cordillera Darwin, was selected for tree-ring-based and radiocarbon dating of the glacial deposits. One focus of the study was to address to the potential dating uncertainties that arise by the use of Nothofagus spp. as a pioneer species. A robust analysis of the age–height relationship, missing the pith of the tree (pith offset), and site-specific ecesis time revealed a total uncertainty value of ±5–9 years. Three adjacent terminal moraines were identified, which increasingly tapered towards the glacier, with oldest deposition dates of 1749 ± 5 CE, 1789 ± 5 CE, and 1867 ± 5 CE. Radiocarbon dates of trunks incorporated within the terminal moraine system indicate at least three phases of cumulative glacial activity within the last 2300 years that coincide with the Neoglacial phases of the Southern Patagonian Icefield and adjacent mountain glaciers. The sub-recent trunks revealed the first evidence of a Neoglacial advance between ~600 BCE and 100 CE, which so far has not been substantiated in the Magallanes–Tierra del Fuego region

DESENVOLVIMENTO HIDROLÓGICO E FENOLOGIA DE LAGOS DA PENÍNSULA FILDES – ANTÁRTICA: Hydrological development and phenology of lakes of the Fildes Peninsula - Antarctica

This paper evaluates the freezing and thawing dynamics of the Fildes Peninsula lakes using TerraSAR-X (TSX) images from February to April 2011, and the correlation of the open water surface area with temperature, precipitation and wind. The open water surface area was obtained from the TSX images classification using the MAXVER classifier for 12 images from 2011. The correlation of atmospheric air temperature with the area, determined by the Pearson and Spearman correlation method, demonstrates a significant correlation pattern in 7 of the 15 lakes, while precipitation is an important variable for the formation of open water in 11 of the 15 lakes. All lakes facing the Drake Passage show significant correlation with wind direction. It is possible that the wind acts causing waves on the liquid surface, which in turn cause the surface ice to break. As for wind direction, this variable may be linked to changes in the duration of the ablation period for the Fildes peninsula. In general, the TSX images allowed an unprecedented temporal detailing for the study area, making it possible to map the lakes from February to April 2011.Este artigo avalia a dinâmica de congelamento e descongelamento dos lagos da península Fildes, utilizando imagens TerraSAR-X (TSX) entre fevereiro e abril de 2011, e a correlação da área de superfície líquida com as variáveis temperatura, precipitação e vento. A área de superfície líquida foi obtida a partir de classificação de imagem TSX, utilizando o classificador MAXVER, para 12 imagens do ano de 2011. A correlação de temperatura do ar atmosférico com a área, determinada pelo método de correlação de Spearman e Pearson, demonstra padrão de correlação significativa em 7 dos 15 lagos, enquanto a precipitação é uma importante variável na formação da superfície líquida em 11 dos 15 lagos. Todos os lagos voltados para a passagem de Drake mostram correlação significativa coma direção do vento que atua causando ondas na superfície líquida e que, por sua vez, provocam a quebra do gelo na superfície. Quanto à direção dos ventos, esta variável pode estar ligada à mudanças na duração do período de ablação para a península Fildes. De forma geral, as imagens TSX permitiram um detalhamento temporal inédito para a área de estudo, possibilitando mapear os lagos no período entre fevereiro e abril de 2011

Fractures in glaciers - Crack tips and their stress fields by observation and modeling

High-resolution optical camera systems are opening new opportunities to studyfractures in ice. Here, we present data obtained from the Modular Aerial CameraSystem camera system operated onboard of Alfred Wegener Institute HelmholtzCentre for Polar and Marine Research (AWI) polar aircraft in northeast Green-land in 2022. In addition, we are using optical and radar satellite imagery. Thestudy area is the 79N Glacier (Nioghalvfjerdsbræ, 79NG), an outlet glacier of theNortheast Greenland Ice Stream. We found that crack tips are exhibiting addi-tional isolated cracks ahead of the main crack. Subsequent crack propagationis starting from those isolated cracks, leading to an advance of the crack, withbridges between crack faces. The bridges provide information of the episodiccrack propagation. Fractures have typically a length scale of kilometers andthe distance of crack faces is in the order of meters to tenths of meters. Frac-ture modes will be inferred from stress fields computed by an inverse modelingapproach using the Ice Sheet and Sea Level System Model. To this end, a surfacevelocity field derived from satellite remote sensing is used for the optimal controlmethod that constrains model parameters, for example, basal friction coefficientor rheology

Cardiac output states in patients with severe functional tricuspid regurgitation: impact on treatment success and prognosis

Aims To investigate whether there is evidence for distinct cardiac output (CO) based phenotypes in patients with chronic right heart failure associated with severe tricuspid regurgitation (TR) and to characterize their impact on TR treatment and outcome. Methods and results A total of 132 patients underwent isolated transcatheter tricuspid valve repair (TTVR) for functional TR at two centres. Patients were clustered according to k-means clustering into low [cardiac index (CI)  2.6 L/min/m2) clusters. All-cause mortality and clinical characteristics during follow-up were compared among different CO clusters. Mortality rates were highest for patients in a low (24%) and high CO state (42%, log-rank P < 0.001). High CO state patients were characterized by larger inferior vena cava diameters (P = 0.003), reduced liver function, higher incidence of ascites (P = 0.006) and markedly reduced systemic vascular resistance (P < 0.001) as compared to TTVR patients in other CO states. Despite comparable procedural success rates, the extent of changes in right atrial pressures (P = 0.01) and right ventricular dimensions (P < 0.001) per decrease in regurgitant volume following TTVR was less pronounced in high CO state patients as compared to other CO states. Successful TTVR was associated with the smallest prognostic benefit among low and high CO state patients. Conclusions Patients with chronic right heart failure and severe TR display distinct CO states. The high CO state is characterized by advanced congestive hepatopathy, a substantial decrease in peripheral vascular tone, a lack of response of central venous pressures to TR reduction, and worse prognosis. These data are relevant to the pathophysiological understanding and management of this important clinical syndrome. Graphical Abstract Proposed mechanism of hypercirculatory tricuspid regurgitation. Tricuspid regurgitation related backward failure causes liver congestion and dysfunction with portal hypertension and reduced washout of vasoactive substances. Consequent splanchnic and peripheral vasodilatation alongside with reduced renal blood flow results in renin–angiotensin–aldosterone system (RAAS) activation and sympathetic overactivation. The sympathetic drive and volume retention lead to further capacitance depletion and volume overload, eventually resulting in a high cardiac output state, with limited preload reduction and prognostic benefit following transcatheter tricuspid valve repair. The alterations in the graph should be interpreted as simultaneous interaction rather than a timeline. Continuous lines indicate findings in the present study. Dashed lines express currently accepted mechanistical considerations. AP, alkaline phosphatase; γGT, gamma-glutamyl-transferase; RA, right atrium; RV, right ventricle

Spektroskopische Eigenschaften eines biologisch‐relevanten [Fe2(μ‐O)2] Diamond‐Core‐Motivs mit einem kurzen Eisen‐Eisen‐Abstand

Dieisen-Kofaktoren in Enzymen vollziehen diverse anspruchsvolle Transformationen. Die Strukturen hoch-valenter Intermediate (Q in der löslichen Methanmonooxygenase und X in der Ribonukleotidreduktase) sind Gegenstand aktueller Diskussionen, seit Fe-Fe-Abstände von 2.1–3.4 Å eine Zuordnung zu geöffneten und geschlossen Kernen mit verbrückenden oder terminalen Oxido-Gruppen in den aktiven Zentren ermöglichen. In dieser Studie berichten wir die kristallografische und spektroskopische Charakterisierung eines FeIII2(μ-O)2-Komplexes (2) mit tetraedrischen (4C) Zentren sowie einem geringen Fe-Fe-Abstand (2.52 Å), der in Lösungsmitteln beständig ist. 2 zeigt eine große Fe-K-Vorkanten-Intensität. Diese resultiert aus der starken Asymmetrie an den TD-FeIII-Zentren bedingt durch die kurzen Fe-μ-O-Bindungen. Während ein Fe-Fe-Abstand von ≈2.5 Å für sechsfach-koordinierte Zentren in Q und X unwahrscheinlich ist, könnte ein Fe2(μ-O)2-Kern mit vierfacher (oder möglicherweise auch fünffacher) Koordination flexibel genug sein, um eine kurze Fe-Fe-Separierung mit großer Vorkanten-Intensität zu ermöglichen. Diese Erkenntnis kann dazu beitragen, dass weitere Modelle für die Strukturen der hoch-valenten Dieisen-Intermediate, die sich im Zuge der biologischen O2-Aktivierung bilden, in Betracht gezogen werden

Spektroskopische Eigenschaften eines biologisch‐relevanten [Fe2(μ‐O)2] Diamond‐Core‐Motivs mit einem kurzen Eisen‐Eisen‐Abstand

Dieisen-Kofaktoren in Enzymen vollziehen diverse anspruchsvolle Transformationen. Die Strukturen hoch-valenter Intermediate (Q in der löslichen Methanmonooxygenase und X in der Ribonukleotidreduktase) sind Gegenstand aktueller Diskussionen, seit Fe-Fe-Abstände von 2.1–3.4 Å eine Zuordnung zu geöffneten und geschlossen Kernen mit verbrückenden oder terminalen Oxido-Gruppen in den aktiven Zentren ermöglichen. In dieser Studie berichten wir die kristallografische und spektroskopische Charakterisierung eines FeIII2(μ-O)2-Komplexes (2) mit tetraedrischen (4C) Zentren sowie einem geringen Fe-Fe-Abstand (2.52 Å), der in Lösungsmitteln beständig ist. 2 zeigt eine große Fe-K-Vorkanten-Intensität. Diese resultiert aus der starken Asymmetrie an den TD-FeIII-Zentren bedingt durch die kurzen Fe-μ-O-Bindungen. Während ein Fe-Fe-Abstand von ≈2.5 Å für sechsfach-koordinierte Zentren in Q und X unwahrscheinlich ist, könnte ein Fe2(μ-O)2-Kern mit vierfacher (oder möglicherweise auch fünffacher) Koordination flexibel genug sein, um eine kurze Fe-Fe-Separierung mit großer Vorkanten-Intensität zu ermöglichen. Diese Erkenntnis kann dazu beitragen, dass weitere Modelle für die Strukturen der hoch-valenten Dieisen-Intermediate, die sich im Zuge der biologischen O2-Aktivierung bilden, in Betracht gezogen werden.Peer Reviewe

Regional Brain and Spinal Cord Volume Loss in Spinocerebellar Ataxia Type 3

Background: Given that new therapeutic options for spinocerebellar ataxias are on the horizon, there is a need for markers that reflect disease-related alterations, in particular, in the preataxic stage, in which clinical scales are lacking sensitivity. Objective: The objective of this study was to quantify regional brain volumes and upper cervical spinal cord areas in spinocerebellar ataxia type 3 in vivo across the entire time course of the disease. Methods: We applied a brain segmentation approach that included a lobular subsegmentation of the cerebellum to magnetic resonance images of 210 ataxic and 48 preataxic spinocerebellar ataxia type 3 mutation carriers and 63 healthy controls. In addition, cervical cord cross-sectional areas were determined at 2 levels. Results: The metrics of cervical spinal cord segments C3 and C2, medulla oblongata, pons, and pallidum, and the cerebellar anterior lobe were reduced in preataxic mutation carriers compared with controls. Those of cervical spinal cord segments C2 and C3, medulla oblongata, pons, midbrain, cerebellar lobules crus II and X, cerebellar white matter, and pallidum were reduced in ataxic compared with nonataxic carriers. Of all metrics studied, pontine volume showed the steepest decline across the disease course. It covaried with ataxia severity, CAG repeat length, and age. The multivariate model derived from this analysis explained 46.33% of the variance of pontine volume. Conclusion: Regional brain and spinal cord tissue loss in spinocerebellar ataxia type 3 starts before ataxia onset. Pontine volume appears to be the most promising imaging biomarker candidate for interventional trials that aim at slowing the progression of spinocerebellar ataxia type 3. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society