Saturated Fraction Research Articles

About “Paleozoic roots” of the oils of the Eastern Ciscaucasia

The paper considers geochemical data on the biomarker composition of oils from the fields of the Terek-Caspian oil and gas basin. Samples of oils from the fields of the main oil and gas bearing regions of the Eastern Ciscaucasia – Terek-Sunzha zone, Prikumsky swell, Piedmont Dagestan and the Middle Caspian Sea were studied. To determine the “geochemical” age of oils, the ratios of regular steranes in saturated oil fractions were analyzed. It was found that the value of the biomarker parameter St28/St29, which determines the geological age of the original organic matter for oils, varies widely – 0.36–1.47. The most “ancient” age (Devonian-Carboniferous) was determined for the oils of the Prikumsky swell and the water area of the Middle Caspian; in the Terek-Sunzha zone and Piedmont Dagestan, an increase in the proportion of St28 sterane is recorded in oils, which indicates a younger generation age (up to the Paleogene). The data obtained can be used to clarify the history of the formation of hydrocarbon accumulations in this region.

Molecular and carbon isotope composition of hydrocarbons from ambers of the Eocene Shenbei coalfield (Liaoning Province, NE China)

The molecular and (bulk and compound-specific) stable carbon isotope composition of ambers from the Shenbei coalfield, northeastern China, were analysed to determine their origin and palaeobotanical affinitions. The applicability of the δ13C data of saturated diterpenoid hydrocarbons for palaeoenvironmental reconstruction was addressed by comparison with published carbon isotope ratios of diterpenoids from adjacent areas. The detected sesquiterpenoids are common biomarkers for the gymnosperm families of Pinaceae and Cupressaceae. The diterpenoids dominate the saturated hydrocarbon fraction with high abundances of kaurane-type compounds. Abietane-type, cadalene-type and alkylated compounds are the main biomarkers in the aromatic hydrocarbons in the ambers. Proposed typical biomarkers for amber (e.g., amberene and homoamberene) have also been detected and probably derived from the diagenesis of the abietane-type terpenoids in the studied ambers. The biomarker composition suggest that the ambers probably originated from gymnosperms such as Taxodium and Pinus. The δ13C values of bulk amber and individual compounds fall within the range of ancient ambers, but the δ13C values of bulk amber are isotopically more enriched than modern ambers. The δ13C values of compounds in hydrocarbon fractions vary in broad ranges. In the saturated hydrocarbon fraction, the δ13C value of sesquiterpenoids (–28.0‰ to –24.5‰) fluctuates more than that of diterpenoids (–22.5‰ to –21.8‰), and the average δ13C value of the latter is approximately 4‰ higher than the former. Aromatic hydrocarbons are on average enriched in 13C by around 2‰ compared to the δ13C of non-aromatic compounds, the result is influenced by isotopically light sesquiterpenoids in the saturated fraction. The similar carbon isotope compositions of aromatic abietane-type compounds and abietane confirm that progressive aromatization does not have a significant impact on the δ13C value of compounds. The obtained higher δ13C values of saturated diterpenoids in contrast to that of lower Eocene lignite from the nearby regions provide evidence for growth of the precursor plants of the amber in dryer habitats or differences in precipitation distribution between different locations and ages.

On the impact of dropsondes on the ECMWF Integrated Forecasting System model (CY47R1) analysis of convection during the OTREC (Organization of Tropical East Pacific Convection) field campaign

Abstract. The Organization of Tropical East Pacific Convection (OTREC) field campaign, conducted August through October 2019, focuses on studying convection in the eastern Pacific and the Caribbean. An unprecedented number of dropsondes were deployed (648) during 22 missions to study the region of strong sea surface temperature (SST) gradients in the eastern Pacific region, the region just off the coast of Columbia, and in the uniform SST region in the southwestern Caribbean. The dropsondes were assimilated in the European Centre for Medium-Range Weather Forecasts (ECMWF) model. This study quantifies departures, observed minus the model value of a variable, in dropsonde denial experiments and studies time series of convective variables, saturation fraction which measures moisture and instability index and deep convective inhibition which quantify atmospheric stability and boundary layer stability to convection, respectively. Departures are small whether dropsondes are assimilated or not, except in a special case of developing convection and organization prior to Tropical Storm Ivo where wind departures are significantly larger when dropsondes are not assimilated. Departures are larger in cloudy regions compared to cloud-free regions when comparing a vertically integrated departure with a cloudiness estimation. Abovementioned variables are all well represented by the model when compared to observations, with some systematic deviations in and above the boundary layer. Time series of these variables show artificial convective activity in the model, in the eastern Pacific region off the coast of Costa Rica, which we hypothesize occurs due to the overestimation of moisture content in that region.

Random sequential adsorption of rounded rectangles, isosceles and right triangles

We studied random sequential adsorption (RSA) of three classes of polygons with rounded corners: rectangles, isosceles triangles, and orthogonal triangles. Using the algorithm that enables the generation of strictly saturated RSA packing, we systematically determined the mean saturated packing fraction for RSA configurations built by these shapes. The main aim was to find the figure that forms the densest random configuration. Although for rounded rectangles the packing fractions were lower than for discorectangles, the densities reached for some rounded isosceles and right triangles exceeded the highest known two-dimensional packing fraction for configurations built of unoriented monodisperse objects. The microstructural properties of several packings were discussed in terms of the two-point density autocorrelation function.

Geochemical Investigation of the Cretaceous Crude Oil Reservoirs and Source Rock Samples in One of the Abadan Plain Oilfields, SW Iran

AbstractCrude oil and source rock samples from one of the main oilfields of the Abadan Plain, Zagros, Iran were analyzed geochemically. Rock‐Eval pyrolysis was conducted on Kazhdumi (Upper Cretaceous) and Gadvan (Lower Cretaceous) formations, which are the probable source rocks for the oil in the region. The results indicated that the Kazhdumi Formation can be classified as a fair‐to‐excellent source rock, while the Gadvan Formation can be identified as having poor‐to‐good source rock in the basin. Based on the cross‐plots of HI versus OI and S2 versus TOC, types II and III kerogen were identified from studied source samples in the area. Determination of the main fraction percentages of the Sarvak and Fahliyan crude oils represented that the oils from the Sarvak reservoir are paraffinic‐naphthenic and aromatic‐intermediate, whilst that from the Fahliyan reservoir is paraffinic and paraffinic‐naphthenic. Biomarker ratios of the saturated fractions of oil from both reservoirs indicate that the source rocks formed in reducing marine environments with carbonate‐shale lithology. Furthermore, biomarker data helped to distinguish the degree of biodegradation in the studied oils. According to geochemical analysis, oil samples from the Fahliyan reservoir were generated at a higher thermal maturity than the Sarvak reservoir samples.

Precipitation‐Moisture Coupling Over Tropical Oceans: Sequential Roles of Shallow, Deep, and Mesoscale Convective Systems

AbstractPrecipitation over tropical oceans rapidly increases when the environmental column saturation fraction (CSF) increases past a critical value of ∼0.7. Past studies suggested that increased stratiform rainfall greatly contributes to the rapid rainfall enhancement. In this study, the sequential roles of non‐deep convection, deep convection, and mesoscale convective system (MCS) in precipitation‐moisture interactions are examined using 19 years of satellite observations. When CSF is below ∼0.5, non‐deep convection dominates total rainfall, and predominantly contributes to moistening of the environment. Between the CSF range of 0.5–0.7, transition to deep convective rainfall begins. Meanwhile, MCS contribution to total rain rapidly increases, and the environment is further moistened. MCS becomes the major rainfall type above the critical CSF value (∼0.7), with the rapid increase of total rain mostly explained by the rapid increase in MCS rain area. Rainfall reduction at high CSF values is jointly contributed by MCS and non‐deep convection.

Organic geochemical evidence for the transition of Aptian-Albian hypersaline environments into marine restricted seas: The South Atlantic oceanic northern gateway and its implications for the pre-salt deposits

The transition between Aptian and Albian stages of the Lower Cretaceous (∼113 Ma) was a critical moment in the development of the proto–South Atlantic Ocean. At this time, marine ingressions in Brazilian sedimentary basins occurred in the northeastern region and deposited organic-rich mudstones and sulfate evaporites. However, the paleogeographic configuration that controlled sedimentation and biota dynamics remains poorly understood. This study presents new paleogeographic insights based on tectonic reconstructed Gplate models and a high-resolution chemostratigraphic framework. We explore new isotopic data of bulk organic carbon and nitrogen as well as saturated fraction biomarkers collected from a well-preserved section in the eastern part of the Brazilian northeastern Parnaíba Basin (Codó Formation). We also present new biomarker data for samples from the Barra Velha Formation from a well in the Santos Basin, which belongs to the same local stage of the Codó Formation (Alagoas Stage). For the Parnaíba Basin section, geochemical proxies subdivide the environmental evolution into five stages. These stages reflect a transition from a highly saline environment (stage A) that experienced transient marine influxes and eventually transitioned into a closed evaporitic system (stage B). A major marine ingression established an epicontinental anoxic sea (Stage C) that subsequently experienced an increase in water circulation and water depth; turning into an oxic marine environment (Stage D). Interruption of the connection with the sea and constant terrestrial input led to a continentalization process establishing a lacustrine/continental environment (Stage E). For the Santos Basin section (Barra Velha Formation), we measured the occurrence of the C30 tetracyclic polyprenoids which are consistent with a dominant lacustrine saline environment. Our paleogeographic model suggests that marine ingressions towards the southern basins, during the first stages of Pangea breakup, occurred through the northern portion of the Borborema Province and produced an interior seaway that possibly connected the Brazilian northeastern with the southeastern basins through the Recôncavo/Tucano rift system. Our findings and the environmental interpretations for stratigraphic correlated units from the southern continental basins infers that the greater marine influence in the northeastern areas shifted from hypersaline environments into restricted marine environments that resulted in the deposition of shales and mesohaline/penesaline salts. Concomitantly, the existence of a Brazilian-African landbridge acted as a barrier point for the first marine inflows towards the south. The restricted marine connection transformed south alkaline environments into extensive areas of superhaline conditions that resulted in giant thick salt successions of the South Atlantic basins. Finally, further tectonic evolution and complete breakup of Pangea terminated the Brazilian-African landbridge and shutoff interior marine routes that later became terrestrial environments. As the continents steadily became rifted-segments, the proto-South Atlantic Ocean expanded leaving a marine record in the southern basins.

Cooling Effects Revealed by Modeling of Wetlands and Land‐Atmosphere Interactions

AbstractWetlands are important ecosystems—they provide vital hydrological and ecological services such as regulating floods, storing carbon, and providing wildlife habitat. The ability to simulate their spatial extents and hydrological processes is important for valuing wetlands' function. The purpose of this study is to dynamically represent the spatial extents and hydrological processes of wetlands and investigate their feedback to regional climate in the Prairie Pothole Region (PPR) of North America, where a large number of wetlands exist. In this study, we incorporated a wetland scheme into the Noah‐MP land surface model with two major modifications: (a) modifying the subgrid saturation fraction for spatial wetland extent and (b) incorporating a dynamic wetland storage to simulate hydrological processes. This scheme was evaluated at a fen site in central Saskatchewan, Canada and applied regionally in the PPR with 13‐year climate forcing produced by a high‐resolution convection‐permitting model. The differences between wetland and no‐wetland simulations are significant, with increasing latent heat and evapotranspiration while suppressing sensible heat and runoff in the wetland scheme. Finally, the dynamic wetland scheme was applied in the Weather Research and Forecasting (WRF) model. The wetlands scheme not only modifies the surface energy balance but also interacts with the lower atmosphere, shallowing the planetary boundary layer height and promoting cloud formation. A cooling effect of 1–3°C in summer temperature is evident where wetlands are abundant. In particular, the wetland simulation shows reduction in the number of hot days for >10 days over the summer of 2006, when a long‐lasting heatwave occurred. This research has great implications for land surface/regional climate modeling and wetland conservation, especially in mitigating extreme heatwaves under climate change.

The Brazilian soil Mid-infrared Spectral Library: The Power of the Fundamental Range

Brazil plays an important role in global agricultural production and environmental politics, and thus a national spectral library can bring light to new initiatives on soil monitoring. The middle infrared spectral range (MIR, 4000–600 cm−1) includes the fundamental reflectance of soil organic and mineral components and thus can bring important information on soil characterization. This work aimed to build a national soil spectral library from the MIR, relate its descriptive and quantitative potential to soil assessment. We characterized up to 4309 soil samples from different depths (0–20, 40–60, 80–100, and 100–120 cm) including particle size distribution and chemical analyses (2963–4309 samples), and mineralogical analyses (278–861 samples). Unsupervised classification distinguished five soil spectra classes with distinct absorption shapes and features. The modeling results showed that MIR can accurately predict soil physicochemical attributes and revealed a strong association with environmental and geographical variables. There were no significant differences between raw and preprocessed MIR spectral data in predicting soil attributes. In general, local spectral models presented better results than national ones, as expected. Consistent results were achieved for several soil attributes, such as mineralogy (R2 = 0.68–0.87), clay fraction (R2 = 0.55–0.91), organic carbon (R2 = 0.77–0.94), and base saturation (R2 = 0.68–0.87). It was possible to create a MIR spectral classification based only on the spectra and assess its relation with environmental and geographical variables. The information generated in this work may be the basis for future research as MIR spectra contain fundamental soil signatures that can be practically used for agronomic and environmental decisions.

Prevalence of pulmonary arterial hypertension in severe chronic obstructive pulmonary disease patients attending tertiary care centre Ernakulam

Background: Chronic obstructive pulmonary disease (COPD) is an irreversible bronchial inflammation of lung airways and parenchyma. Various factors play an important role in occurrence and severity of pulmonary arterial hypertension (PAH), a common in severe COPD. The objective of the study is to know the proportion of PAH in patients with severe COPD and to find the association between various factors.Methods: 180 cases of severe COPD patients admitted in Government Medical College Ernakulum from January 2019-December 2019, were enrolled into this cross-sectional descriptive study. Subject’s history, clinical examination, anthropometric measurements, vitals, Arterial Blood Gas (ABG) analysis were done.Results: Among 180 subjects, 148 (82.22%) had mild PAH, 22 (12.22%) subjects had moderate PAH and 10 (5.56%) had severe PAH. Use of accessory muscle was the most elicited sign in the study with 174 (96.67%). 170 (94.44%) had cough and 169 (93.89%) had breathlessness which were the most reported symptoms. Demographic variables and clinical features had no significant mean pulmonary artery pressure (mPAP) association. Grade 3 PAH groups were elder than others, which was statistically significant (p<0.047). FEV1, Oxygen Saturation and ejection fraction were lowest in grade 3 PAH subjects. Respiratory rate, hemoglobin, PCV, tricuspid velocity, PaCO2 were highest in grade 3 PAH subjects being statistically significant (p<0.0001).Conclusions: In our study, majority of severe COPD patients had mild PAH. There was an independent correlation between respiratory rate, hemoglobin, PCV, tricuspid regurgitant velocity and PaCO2 with severity of PAH.

Maturity and depositional controls on compound-specific sulfur isotope values of saline lacustrine source rocks in the north Dongpu Depression, Bohai Bay Basin

Source rocks and oil sands from the northern Dongpu Depression have been analyzed by gas chromatography multicollector inductively coupled plasma mass spectrometry (GC-MC-ICP MS) to investigate the compound-specific sulfur isotope (δ34S) values of saline lacustrine source rocks. The samples were also subject to more traditional organic geochemical analyses including hydrocarbon biomarker detection by gas chromatography/mass spectrometry (GC/MS), carbon and oxygen isotopic analysis by isotope ratio mass spectrometer, and major and trace inorganic element analysis. δ34SOSCs values measured for a limited number of organic sulfur compounds (OSCs) showed a quite large range (5.16‰–44.73‰). The source rocks and oil sands could be separated into two groups with δ34S values above or below 25.00‰. The first group with δ34S > 25.00‰, were primarily the Weicheng source rocks, which also typically showed an increase in δ34S values with increasing alkylation. The second group had δ34S < 25.00, the δ34S of dibenzothiophenes showed a positive correlation with the concentration of the saturated hydrocarbon fraction of rocks, and a negative correlation with the polar (resin + asphaltene) fraction. The δ34SOSCs show obvious positive correlation with gammacerane/C31 hopane and C35/C34 hopanes and excellent correlation with contents of minerals and ratios of trace elements, reflecting a 34S enrichment in closed evaporative environment (conducive to the sulfurisation of organic matter) and relative 34S depletion in terrestrial environments. These trends identify the depositional environment of the source rocks as one of controls on δ34SOSCs values. Thermal maturity was also observed to influence δ34SOSCs values, becoming heavier with increasing maturity. There was a good result of oil-source rock correlation by δ34SOSC in this study. This study demonstrates the contribution δ34SOSCs data can make to oil-oil and oil-source rock correlations as well as providing further evidence of their sensitivity to depositional environments and thermal maturity.

Vorticity and Thermodynamics in a Gulf of Mexico Atmospheric River

This paper examines the interaction of tropical moisture with an atmospheric river. The analysis of this paper is focused mainly on dropsonde data collected during the fifth day of the Convective Processes Experiment (CPEX). An area of interest is chosen over the central Gulf of Mexico, where the remnant moisture of the tropical system Beatriz penetrated from the Eastern Pacific after making landfall in the western coast of Mexi-co. Results in this study show an eastward-tilting pattern of enhanced mid-level vorticity, coupled with high saturation fraction and low instability index in the predominantly stratiform regime present in the region. An inverse relation between saturation fraction and instability index, as indicated by moisture quasi-equilibrium (MQE), is found in a previously-dominant convective regime. Strong vertical shear signals that the vorticity pattern within this stratiform system is being advected poleward into mid-latitudes. Poleward-moving moisture plumes in narrow channels called atmospheric rivers (ARs) are observed during the mission. We provide insights into vorticity and MQE as conceptual tools to characterize the moisture mechanism of atmospheric rivers near the tropics, where the physical processes behind these river-like structures are less well-understood.

Serum sex hormone-binding globulin levels are reduced and inversely associated with intrahepatic lipid content and saturated fatty acid fraction in adult patients with glycogen storage disease type 1a

PurposeDe novo lipogenesis has been inversely associated with serum sex hormone-binding globulin (SHBG) levels. However, the directionality of this association has remained uncertain. We, therefore, studied individuals with glycogen storage disease type 1a (GSD1a), who are characterized by a genetic defect in glucose-6-phosphatase resulting in increased rates of de novo lipogenesis, to assess the downstream effect on serum SHBG levels.MethodsA case–control study comparing serum SHBG levels in patients with GSD1a (n = 10) and controls matched for age, sex, and BMI (n = 10). Intrahepatic lipid content and saturated fatty acid fraction were quantified by proton magnetic resonance spectroscopy.ResultsSerum SHBG levels were statistically significantly lower in patients with GSD1a compared to the controls (p = 0.041), while intrahepatic lipid content and intrahepatic saturated fatty acid fraction—a marker of de novo lipogenesis—were significantly higher in patients with GSD1a (p = 0.001 and p = 0.019, respectively). In addition, there was a statistically significant, inverse association of intrahepatic lipid content and saturated fatty acid fraction with serum SHBG levels in patients and controls combined (β: − 0.28, 95% CI: − 0.47;− 0.09 and β: − 0.02, 95% CI: − 0.04;− 0.01, respectively).ConclusionPatients with GSD1a, who are characterized by genetically determined higher rates of de novo lipogenesis, have lower serum SHBG levels than controls.

Validation of Respiratory Rate-Oxygenation Index in Patients With COVID-19-Related Respiratory Failure.

OBJECTIVES:The respiratory rate-oxygenation (ROX) index is a fraction of oxygen saturation, Fio2, and respiratory rate that has been validated to predict receipt of invasive mechanical ventilation in patients receiving high-flow nasal cannula (HFNC). This study aimed to validate ROX in a cohort of inpatients with COVID-19–related respiratory failure.DESIGN:Retrospective validation of the ROX index. We calculated sensitivity, specificity, positive predictive value, negative predictive value, and 95% CIs of ROX for invasive mechanical ventilation any time during hospitalization.SETTING:Twenty-one hospitals of Kaiser Permanente Northern California, an integrated healthcare delivery system.PATIENTS:We identified adults with positive severe acute respiratory syndrome coronavirus 2 polymerase chain reaction test within 3 weeks of, or during, hospitalization between February 1, 2020, and December 31, 2020. We calculated ROX at 12 hours after HFNC initiation. We grouped patients as low (≥ 4.88), intermediate (< 4.88 and ≥ 3.85), or high (< 3.85) risk using previously published thresholds.INTERVENTIONS:None.MEASUREMENTS AND MAIN RESULTS:We identified 1,847 patients who had no limitation of life support. Of these, 525 (31.7%) received invasive mechanical ventilation any time during hospitalization and 511 died (27.7%). The sensitivity, specificity, positive predictive value, and negative predictive value of 12-hour ROX threshold (< 3.85) predicting invasive mechanical ventilation were 32.3% (95% CI, 28.5–36.3%), 89.8% (95% CI, 88.0–91.4%), 59.4% (95% CI, 53.8–64.9%), and 74.1% (95% CI, 71.8–76.3%), respectively.CONCLUSIONS:The 12-hour ROX index has a positive predictive value (59.4%) using threshold of less than 3.85 for COVID-19 patients needing invasive mechanical ventilation. Our health system has embedded ROX into the electronic health record to prioritize rounding during periods of inpatient surge.

A New Scoring Model to Diagnose COVID-19 Using Lung Ultrasound in the Emergency Department

BackgroundSeveral studies have reported the predictors of the prognosis in COVID-19 patients; however, smoking, X-ray findings of pulmonary congestion, and A-profile and areas of consolidation in LUS are independent predictors for COVID-19 infection. The new score had a sensitivity of 93.8% and a specificity of 58% for the prediction of COVID-19. Mortality in COVID-19 patients is significantly correlated with age, fever duration, cardiac history, and B-profile and areas of consolidation in LUS. However, it is negatively correlated with initial O2 saturation and ejection fraction. This study aimed to design a new scoring model to diagnose COVID-19 using bedside lung ultrasound (LUS) in the emergency department (ED).ResultsEighty-two patients were recruited. Fifty patients (61%) were negative for COVID-19, and 32 (39%) were positive. Sixty-four patients (78%) recovered while 18 patients (22%) died. COVID-19 patients had more AB-profile and more areas of consolidation than the non-COVID-19 group (p<0.001). Smoking, congestion in X-ray, A-profile, and abnormal A line in LUS are independent predictors for COVID-19 infection. The score had a sensitivity of 93.8% and a specificity of 58% for the prediction of COVID-19. Mortality in COVID-19 patients is significantly correlated with age, fever duration, cardiac history, and B-profile and areas of consolidation in LUS. However, it is negatively correlated with initial O2 saturation and ejection fraction.ConclusionsIn conclusion, the application of our new score can stratify patients presented to ED with suspected COVID-19 pneumonia, considering that it is a good negative test. Moreover, this score may have a good impact on the safety of medical personnel.Trial registrationClinicalTrials.gov Identifier: NCT05077202. Registered October 14, 2021 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT05077202

A model to characterize soil moisture and organic matter profiles in the permafrost active layer in support of radar remote sensing in Alaskan Arctic tundra

Organic matter (OM) content and a shallow water table are two key variables that govern the physical properties of the subsurface within the active layer of arctic soils underlain by permafrost, where the majority of biogeochemical activities take place. A detailed understanding of the soil moisture and OM profile behavior over short vertical distances through the active layer is needed to adequately model the subsurface physical processes. To observe and characterize the profiles of soil properties in the active layer, we conducted detailed soil sampling at five sites along Dalton Highway on Alaska’s North Slope. These data were used to derive a generalized logistics function to characterize the total OM and water saturation fraction behavior through the profile. Furthermore, a new pedotransfer function was developed to estimate the soil bulk density and porosity—information that is largely missing from existing soil datasets—within each layer, solely from the soil texture (organic and mineral properties). Given the currently sparse soil database of the Alaskan Arctic, these profile models can be highly beneficial for radar remote sensing models to study active layer dynamics.

Light hydrocarbons and diamondoids in deep oil from Tabei of Tarim Basin: Implications on petroleum alteration and mixing

The Tuofutai Bulge in central Tabei of northern Tarim Basin provides insights into the complex geochemical processes of deep oil accumulations. Fifteen crude oil samples collected from deep Ordovician reservoirs were tested and analyzed with light hydrocarbons (LHs) and diamondoids to evaluate the oil family, secondary alteration, and mixing processes. Results show that the oil samples share similar distribution characteristics of LHs and diamondoids and contain low concentrations of methyldiamantanes, suggesting that they belong to one group and have not been significantly altered by thermal cracking. Geochemistry of LHs and diamondoids indicate that the thermochemical sulfate reduction is limited and negligible, whereas some samples are severely altered by biodegradation. The phase fractionation is mainly related to the leakage of light hydrocarbon caused by geological activities such as tectonic uplift and fault activity, and some samples show weak evaporative fractionation. The biodegradation causes the increase in the values of methyladamantane to adamantane (MAs/A) and the concentrations of (1 + 2)-methyladamantane and (3 + 4)-methyldiamantane. The thermal maturity of oil calculated on the basis of LHs and diamondoids is generally higher than that calculated using saturated and aromatic fractions. The difference of various maturity parameters related to saturated hydrocarbon, aromatic hydrocarbon, LHs and diamondoids records multiple oil charging and mixing processes.

Distribution Characteristics of Long-Chain Branched Alkanes With Quaternary Carbon Atoms in the Carboniferous Shales of the Wuwei Basin, China

The branched alkanes with quaternary carbon atoms (BAQCs) and monomethylakanes (MMAs), cycloalkanes, monoethylalkanes (MEAs) have been detected by GC-MS in the saturated hydrocarbons fractions of Carboniferous black shale from the Wuwei Basin in northwest China. Nine series of BAQCs (series A-I) are present in Carboniferous black shale, which are concomitant with two series of long-chain cycloalkanes, two series of MMAs and one series of MEAs. All of these series are expressed as exclusively odd or exclusively even carbon numbers with consistent changes of abundance in the samples, meanwhile, based on the analysis of basic geochemical characteristics and other biomarkers of the samples, we presume that it possessed a similar parent materials or evolutionary process and weak oxidation-reduction sedimentation environments. In addition, the results show that the abundance of the long-chain branched alkanes is highly correlated with the odd-even predominances (OEP (15–19)) of the short-chain n-alkane. The lower the OEP (15–19) values of the short-chain n-alkane are (more significant the even-carbon dominance), the higher the abundance of the long-chain branched alkanes. The significant even-carbon dominance of the short-chain n-alkanes indicates the strong input of archaea or algal organic matter. The relatively wide occurrence and high abundance of these alkanes suggests a relationship with specific paleoenvironment and paleoclimate conditions.

Domain structures induced by tensile thermal strain in epitaxial PbTiO3 films on silicon substrates

The fabrication of epitaxial ferroelectric materials on Si substrates is key to the design of superior ferroelectric devices for applications involving microelectromechanical systems (MEMS). The domain structures of epitaxial PbTiO3 films grown on Si substrates with an epitaxial SrTiO3 buffer layer were investigated, especially in terms of film thickness dependence. The low thermal expansion coefficient of Si was found to affect the volume fraction of (001)-oriented domains not only in relatively thick film regions but also in the thinner ones. Compared with the PbTiO3 films deposited on SrTiO3 substrates, (100)-oriented domains were observed in films as thin as 18 nm, notwithstanding the strong misfit strain induced by the substrate. Moreover, the saturated volume fraction of the (001)-oriented domain was smaller than that of PbTiO3 on SrTiO3. Thermal strain plays a critical role in determining domain structures and is, therefore, expected to govern the electric properties of films useful in MEMS devices.

Hemodynamic response to positive end-expiratory pressure and prone position in COVID-19 ARDS

BackgroundUse of high positive end-expiratory pressure (PEEP) and prone positioning is common in patients with COVID-19-induced acute respiratory failure. Few data clarify the hemodynamic effects of these interventions in this specific condition. We performed a physiologic study to assess the hemodynamic effects of PEEP and prone position during COVID-19 respiratory failure. MethodsNine adult patients mechanically ventilated due to COVID-19 infection and fulfilling moderate-to-severe ARDS criteria were studied. Respiratory mechanics, gas exchange, cardiac output, oxygen consumption, systemic and pulmonary pressures were recorded through pulmonary arterial catheterization at PEEP of 15 and 5 cmH2O, and after prone positioning. Recruitability was assessed through the recruitment-to-inflation ratio. ResultsHigh PEEP improved PaO2/FiO2 ratio in all patients (p = 0.004), and significantly decreased pulmonary shunt fraction (p = 0.012), regardless of lung recruitability. PEEP-induced increases in PaO2/FiO2 changes were strictly correlated with shunt fraction reduction (rho=-0.82, p = 0.01). From low to high PEEP, cardiac output decreased by 18 % (p = 0.05) and central venous pressure increased by 17 % (p = 0.015).As compared to supine position with low PEEP, prone positioning significantly decreased pulmonary shunt fraction (p = 0.03), increased PaO2/FiO2 (p = 0.03) and mixed venous oxygen saturation (p = 0.016), without affecting cardiac output. PaO2/FiO2 was improved by prone position also when compared to high PEEP (p = 0.03). ConclusionsIn patients with moderate-to-severe ARDS due to COVID-19, PEEP and prone position improve arterial oxygenation. Changes in cardiac output contribute to the effects of PEEP but not of prone position, which appears the most effective intervention to improve oxygenation with no hemodynamic side effects.