Airfall volume of the 15 January 2022 eruption of Hunga volcano estimated from ocean color changes.

On 15 January 2022, Hunga volcano erupted, creating an extensive and high-reaching umbrella cloud over the open ocean, hindering traditional isopach mapping and fallout volume estimation. In MODIS satellite imagery, ocean surface water was discolored around Hunga following the eruption, which we attribute to ash fallout from the umbrella cloud. By relating intensity of ocean discoloration to fall deposit thicknesses in the Kingdom of Tonga, we develop a methodology for estimating airfall volume over the open ocean. Ash thickness measurements from 41 locations are used to fit a linear relationship between ash thickness and ocean reflectance. This produces a minimum airfall volume estimate of 1.8-0.4+0.3 km3. The whole eruption produced > 6.3 km3 of uncompacted pyroclastic material on the seafloor and a caldera volume change of 6 km3 DRE. Our fall estimates are consistent with the interpretation that most of the seafloor deposits were emplaced by gravity currents rather than fall deposits. Our proposed method does not account for the largest grain sizes, so is thus a minimum estimate. However, this new ocean-discoloration method provides an airfall volume estimate consistent with other independent measures of the plume and is thus effective for rapidly estimating fallout volumes in future volcanic eruptions over oceans. Supplementary Information: The online version contains supplementary material available at 10.1007/s00445-024-01744-6.

The effects of bathymetry on the long-term carbon cycle and CCD.

The shape of the ocean floor (bathymetry) and the overlaying sediments provide the largest carbon sink throughout Earth's history, supporting ~one to two orders of magnitude more carbon storage than the oceans and atmosphere combined. While accumulation and erosion of these sediments are bathymetry dependent (e.g., due to pressure, temperature, salinity, ion concentration, and available productivity), no systemic study has quantified how global and basin scale bathymetry, controlled by the evolution of tectonics and mantle convection, affects the long-term carbon cycle. We reconstruct bathymetry spanning the last 80 Myr to describe steady-state changes in ocean chemistry within the Earth system model LOSCAR. We find that both bathymetry reconstructions and representative synthetic tests show that ocean alkalinity, calcite saturation state, and the carbonate compensation depth (CCD) are strongly dependent on changes in shallow bathymetry (ocean floor ≤600 m) and on the distribution of the deep marine regions (>1,000 m). Limiting Cenozoic evolution to bathymetry alone leads to predicted CCD variations spanning 500 m, 33 to 50% of the total observed variations in the paleoproxy records. Our results suggest that neglecting bathymetric changes leads to significant misattribution to uncertain carbon cycle parameters (e.g., atmospheric CO2 and water column temperature) and processes (e.g., biological pump efficiency and silicate-carbonate riverine flux). To illustrate this point, we use our updated bathymetry for an Early Paleogene C cycle case study. We obtain carbonate riverine flux estimates that suggest a reversal of the weathering trend with respect to present-day, contrasting with previous studies, but consistent with proxy records and tectonic reconstructions.

Microscopic defect dynamics during a brittle-to-ductile transition.

Deformation of all materials necessitates the collective propagation of various microscopic defects. On Earth, fracturing gives way to crystal-plastic deformation with increasing depth resulting in a "brittle-to-ductile" transition (BDT) region that is key for estimating the integrated strength of tectonic plates, constraining the earthquake cycle, and utilizing deep geothermal resources. Here, we show that the crossing of a BDT in marble during deformation experiments in the laboratory is accompanied by systematic increase in the frequency of acoustic emissions suggesting a profound change in the mean size and propagation velocity of the active defects. We further identify dominant classes of emitted waveforms using unsupervised learning methods and show that their relative activity systematically changes as the rocks cross the brittle-ductile transition. As pressure increases, long-period signals are suppressed and short-period signals become dominant. At higher pressures, signals frequently come in avalanche-like patterns. We propose that these classes of waveforms correlate with individual dominant defect types. Complex mixed-mode events indicate that interactions between the defects are common over the whole pressure range, in agreement with postmortem microstructural observations. Our measurements provide unique, real-time data of microscale dynamics over a broad range of pressures (10 to 200 MPa) and can inform micromechanical models for semi-brittle deformation.

Is Hypoglycemia Secondary to Metastatic Retroperitoneal Sarcoma - A Therapeutic Challenge? Case Report and Review of Literature.

Most soft tissue sarcomas afflict the extremities; however, the retro peritoneum can also be affected rarely. Retroperitoneal sarcomas are relatively asymptomatic. Although tumor-induced hypoglycemia is rare in tumors other than insulinomas, extrapancreatic tumors are a subset that displays this phenomenon. The occurrence of hypo-insulinemic hypoglycemia with low GH and IGF-1 should prompt consideration of the secretion of a hypoglycemic substance impeding the secretion of insulin and GH, such as IGF-2 or one of its related substances. The present case report is of a 38-year-old male with retroperitoneal round cell sarcoma with liver metastasis with severe symptomatic hypoglycemia who was managed with multipronged symptomatic therapy and oncological management after which he had shown significant improvement in hypoglycemic episodes and symptom profile. A literature review revealed our case report to be the first reported case of a young male (preponderance in the older population) with hypoglycemia associated with retroperitoneal sarcoma which presented with liver metastasis and the only one treated with Gemcitabine /Docetaxel. The presence of these features might point toward a poorer prognosis in a disease with an already dismal course. All these points towards the need for further research regarding intensified oncological treatment after evidence-based prognostication of high-risk groups and modalities for the management of symptomatic hypoglycemia such as Somatostatin analogs and glucagon which aid in symptom control.

Disseminated tuberculosis presenting as cutaneous leucocytoclastic vasculitis.

Cutaneous leucocytoclastic vasculitis (CLV) is a type of small vessel vasculitis, predominantly presenting with palpable purpuras and sometimes with systemic manifestations. The following report describes the case of a woman, who presented with fever, anorexia and maculopapular lesions over both lower limbs. Skin biopsy revealed CLV. CT scan demonstrated bilateral pulmonary nodules, ileocecal wall thickening and generalised lymphadenopathy. Colonoscopy guided biopsy obtained from ileocecal valve ulcer showed epitheloid cell granuloma with Langhans-type giant cells and caseous necrosis. Rapid clinical improvement was seen with anti-tubercular therapy. Among infectious causes, although rare and an uncommon presentation, Mycobacterium tuberculosis should be considered as an important cause of CLV.

How does salinity shape ocean circulation and ice geometry on Enceladus and other icy satellites?

Of profound astrobiological interest, Enceladus appears to have a global saline subsurface ocean, indicating water-rock reaction at present or in the past, an important mechanism in the moon's potential habitability. Here, we investigate how salinity and the partition of heat production between the silicate core and the ice shell affect ocean dynamics and the associated heat transport-a key factor determining equilibrium ice shell geometry. Assuming steady-state conditions, we show that the meridional overturning circulation of the ocean, driven by heat and salt exchange with the poleward-thinning ice shell, has opposing signs at very low and very high salinities. Regardless of these differing circulations, heat and fresh water converge toward the equator, where the ice is thick, acting to homogenize thickness variations. Among scenarios explored here, the pronounced ice thickness variations observed on Enceladus are most consistent with heating that is predominantly in the ice shell and a salinity of intermediate range.

Calcium isotope evidence for early Archaean carbonates and subduction of oceanic crust.

Continents are unique to Earth and played a role in coevolution of the atmosphere, hydrosphere, and biosphere. Debate exists, however, regarding continent formation and the onset of subduction-driven plate tectonics. We present Ca isotope and trace-element data from modern and ancient (4.0 to 2.8 Ga) granitoids and phase equilibrium models indicating that Ca isotope fractionations are dominantly controlled by geothermal gradients. The results require gradients of 500-750 °C/GPa, as found in modern (hot) subduction-zones and consistent with the operation of subduction throughout the Archaean. Two granitoids from the Nuvvuagittuq Supracrustal Belt, Canada, however, cannot be explained through magmatic processes. Their isotopic signatures were likely inherited from carbonate sediments. These samples (> 3.8 Ga) predate the oldest known carbonates preserved in the rock record and confirm that carbonate precipitation in Eoarchaean oceans provided an important sink for atmospheric CO2. Our results suggest that subduction-driven plate tectonic processes started prior to ~3.8 Ga.

Ca isotopes record rapid crystal growth in volcanic and subvolcanic systems.

Kinetic calcium isotope effects can be used as growth-rate proxies for volcanic and subvolcanic minerals. Here, we analyze Ca isotopic compositions in experimental and natural samples and confirm that large kinetic effects (>2‰) can occur during magmatic plagioclase crystallization. Experiments confirm theoretical predictions that disequilibrium isotope effects depend mainly on the rates for crystal growth relative to liquid phase Ca diffusivity (R/D). Plagioclase phenocrysts from the 1915 Mount Lassen rhyodacite eruption, the ∼650-y-old Deadman Creek Dome eruption, and several mafic subvolcanic orbicules and plagioclase comb layers from Northern California have disequilibrium Ca isotopic compositions that suggest rapid crystal growth rates (>1 cm/y to 15 cm/y). The Ca isotope results, combined with complementary crystal-size distribution analyses, suggest that magmatic rejuvenation (and eruption) events, as reflected in crystal growth times, can be as short as ∼10-3 y. Although mafic systems are predicted to have shorter magmatic rejuvenation periods, we find similarly short timescales in both mafic and silicic systems. These results are consistent with a growing body of evidence suggesting that dominantly crystalline volcanic magma reservoirs can be rapidly reactivated by the injection of fresh magma prior to eruption. By focusing on a common mineral such as plagioclase, this approach can be applied across all major magmatic compositions, suggesting that Ca isotopes can be used as a tool for investigating the dynamics and timing of volcanic eruptions.

The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary.

Late Cretaceous records of environmental change suggest that Deccan Traps (DT) volcanism contributed to the Cretaceous-Paleogene boundary (KPB) ecosystem crisis. However, testing this hypothesis requires identification of the KPB in the DT. We constrain the location of the KPB with high-precision argon-40/argon-39 data to be coincident with changes in the magmatic plumbing system. We also found that the DT did not erupt in three discrete large pulses and that >90% of DT volume erupted in <1 million years, with ~75% emplaced post-KPB. Late Cretaceous records of climate change coincide temporally with the eruption of the smallest DT phases, suggesting that either the release of climate-modifying gases is not directly related to eruptive volume or DT volcanism was not the source of Late Cretaceous climate change.

Executive Functions are not Affected by 24 Hours of Sleep Deprivation: A Color-Word Stroop Task Study.

BACKGROUND: Sleep is an important factor affecting cognitive performance. Sleep deprivation results in fatigue, lack of concentration, confusion and sleepiness along with anxiety, depression and irritability. Sleep deprivation can have serious consequences in professions like armed forces and medicine where quick decisions and actions need to be taken. Color-Word Stroop task is one of the reliable tests to assess attention and it analyzes the processing of information in two dimensions i.e., reading of words and naming of colour. The evidence regarding the effect of sleep deprivation on Stroop interference is conflicting. The present study evaluated the effect of 24 hours of sleep deprivation on reaction time and interference in Stroop task. MATERIALS AND METHODS: The present study was done on 30 healthy male medical student volunteers in the age group of 18-25 years after taking their consent and clearance from Institute Ethics Committee. Recordings of Stroop task were at three times: baseline (between 7-9 am), after 12 hours (7-9 pm) and after 24 hours (7-9 am, next day). The subjects were allowed to perform normal daily activities. RESULTS: The study revealed a significant increase in reaction time after 24 hours of sleep deprivation in comparison to baseline and after 12 hours of sleep deprivation. There was no significant change in interference and facilitation after sleep deprivation in comparison to baseline. The number of errors also did not show any significant change after sleep deprivation. CONCLUSION: The study indicated that there was slowing of responses without change in executive functions after 24 hours of sleep deprivation. It is probable that 24 hours of sleep deprivation does not bring about change in areas of brain affecting executive functions in healthy individuals who have normal sleep cycle. The present study indicated that in professions like armed forces and medicine working 24 hours at a stretch can lead to decrease in motor responses without affecting information processing and judgment ability.

Sex determination from buccal mucosa scrapes.

Establishing individuality is an imperative aspect in any investigation procedure. At times, it becomes necessary to determine the sex of the individual to establish identity, and saliva stains found at the scene of crime are of major help in such cases. In the present study, we have determined the sex of the individual from buccal mucosal scrapings. Buccal smears prepared from 100 men and 100 women were stained by the Papanicolaou staining method. Cells were observed for Barr bodies under oil immersion with a compound microscope, and the percentage of Barr-body-positive cells was determined. It was observed that 1.14% of buccal mucosal cells in men (range = 0-4%) and 39.29% of buccal mucosal cells in women (range = 20-78%) showed Barr bodies. Inferences from the study show that the presence of Barr body in buccal mucosal cells can be demonstrated with a fair degree of accuracy using Papanicolaou staining. The sex of the individual can be determined accurately, as two non-overlapping ranges for the percentage of Barr-body-positive cells has been obtained for men and women. This method not only proves to be accurate but is also simple and economic.