Variable Component Research Articles

Endogenous plasma resuspension of peripheral blood mononuclear cells prevents preparative-associated stress that modifies polyA-enriched RNA responses to subsequent acute stressors.

Human peripheral blood mononuclear cells (PBMCs) are used to examine biological processes and disease, when basal variability in cellular activation and splicing is described and unexplained. Using isolation systems that maintained buffy coat cells (PBMCs, platelets) in their own plasma, poly-A enriched RNA-sequencing (RNASeq) detected 42,720 Ensembl gene IDs, including >95% of the top 100 Genotype Tissue Expression Project (GTEx)-expressed genes in lung, colon, heart, skeletal muscle and liver, and 10/17 clinically-actionable genes listed by the Pharmacogenomics Knowledgebase. Transcriptome changes were defined after 1h treatment with 32°C hypothermia (hsp70 family member change), 10 μmol/L ferric citrate that had no discernible effect, and 100 μg/mL cycloheximide leading to induction of primary response (immediate early) genes including IL1B and TNF. Same-donor PBMCs prepared conventionally using washes then resuspension in serum-supplemented media demonstrated basal upregulation of stress signalling pathway genes that masked and overlapped differential gene expression profiles after 100 µg/L cycloheximide. Plasma-resuspended PBMCs demonstrated minor transcriptome changes after 40 μmol/L ferric citrate, whereas consistent and greater magnitude changes were observed for washed/media-resuspended PBMCs. We conclude that endogenous plasma-maintained PBMCs provide a more robust platform to interrogate acute cellular perturbations triggering innate immunity, and that varying susceptibility of PBMCs to preparative stresses is an important component of experimental variability.

Technical Efficiency of Smallholder Dairy Farms in Rural Assam: A Double Bootstrap Data Envelopment Analysis Approach

Analysing a sample of 245 smallholder rural dairy farms in Assam, it is found that most dairy farms operate at technically inefficient level. The analysis of input-oriented conventional and bias-corrected data envelopment analysis (DEA) procedure entails that most farms produce milk below the production frontier with underlying scope of reducing variable input component up to 50% to retain the same level of output. Further, exploring the bias-corrected efficiency score determinants, it is found that input use decision is superior for male-headed households, farms that are involved in fodder cultivation, farms with proximity to markets and resource poor farmers whose dairy farming is mostly a principal source of income. The findings of the study indicate presence of ample scope and potential to leverage the technical efficiency (TE) and thereby increase the socio-economic wellbeing of the smallholder dairy farm households in the state. The study also points towards the need for sensitising farmers about the improved dairy farm technologies such as artificial insemination to produce more crossbred cattle along with building a strong network of extension machineries.

Effects of different postures on the hemodynamics and cardiovascular autonomic control responses to exercise in postural orthostatic tachycardia syndrome.

To assess the effects of two different body positions on the cardiovascular autonomic profile during a single bout of exercise in patients with postural orthostatic tachycardia syndrome (POTS). Thirteen patients with POTS and thirteen healthy controls (C) participated in the study. ECG, respiration, beat-by-beat arterial pressure and O2 consumption (VO2) were continuously recorded while on a cycle ergometer in supine and upright positions, before and during exercise (6min, 50 Watts). Spectral analysis of RR intervals and systolic arterial pressure (SAP) variability provided indexes of cardiac sympathovagal interaction (LF/HF ratio), cardiac vagal modulation (HFRR, high-frequency component of RR variability, ~ 0.25Hz), sympathetic vasomotor control (LFSAP, low-frequency component of SAP variability, 0.1Hz) and baroreflex sensitivity (BRS, αLF). While supine, patients with POTS showed lower HFRR and αLF, greater heart rate (HR), LF/HF and LFSAP, compared with C, suggesting cardiovascular sympathetic over-activity and reduced BRS. While sitting upright, POTS showed greater HR and reduced HFRR and αLF compared with C. During supine exercise, SAP, HR, LF/HF increased and HFRR and αLF decreased similarly in POTS and C. In POTS, upright sitting exercise was associated with slightly higher , a greater increase in HR whereas LFSAP was lower than in C. Upright exercise was associated with excessive enhancement of HR and a blunted increase of the sympathetic vasomotor control in POTS. Conversely, supine exercise-induced hemodynamic and autonomic changes similar in POTS and C, thus making supine exercise potentially more suitable for physical rehabilitation in POTS.

A review of optimization and decision models of prescribed burning for wildfire management.

Prescribed burning is an essential forest management tool that requires strategic planning to effectively address its multidimensional impacts, particularly given the influence of global climate change on fire behavior. Despite the inherent complexity in planning prescribed burns, limited efforts have been made to comprehensively identify the critical elements necessary for formulating effective models. In this work, we present a systematic review of the literature on optimization and decision models for prescribed burning, analyzing 471 academic papers published in the last 25 years. Our study identifies four main types of models: spatial-allocation, spatial-extent, temporal-only, and spatial-temporal. We observe a growing number of studies on modeling prescribed burning, primarily due to the expansion in spatial-allocation and spatial-temporal models. There is also an increase in complexity as the models consider more elements affecting prescribed burning effectiveness. We identify the essential components for optimization models, including stakeholders, decision variables, objectives, and influential factors, to enhance model practicality. The review also examines solution techniques, such as integer programming in spatial allocation, stochastic dynamic programming in probabilistic models, and multiobjective programming in balancing trade-offs. These techniques' strengths and limitations are discussed to help researchers adapt methods to specific challenges in prescribed burning optimization. In addition, we investigate general assumptions in the models and challenges in relaxation to enhance practicality. Lastly, we propose future research to develop more comprehensive models incorporating dynamic fire behaviors, stakeholder preferences, and long-term impacts. Enhancing these models' accuracy and applicability will enable decision-makers to better manage wildfire treatmentoutcomes.

Influence of DC/DC Converter Control on Source Current Ripple of the Switched Reluctance Motor

This paper presents a solution to reduce source current ripple in the electrical power supplying a switched reluctance motor (SRM) drive. Source current ripple negatively affects the power source by introducing a variable frequency component and increasing losses in the power source. Reducing the source current ripple is important, especially in battery electric vehicles (BEVs). The solution proposed in this paper for reducing source current ripple is to use a classic DC/DC boost converter connected in series with the SRM power supply system. The key to reducing source current ripple is the DC/DC converter control method proposed and described in this article. This method involves controlling the DC/DC converter synchronized with the speed of the SRM motor DC/DC. To verify the correct operation of the proposed solution, simulation and laboratory tests of an SRM drive were performed, the results of which are shown in this paper.

Circadian rhythm of blood pressure and its correlations with short-term variability

Background. Arterial hypertension (AH) is the main risk factor for cardiovascular (CV) and cerebrovascular diseases. To effectively prevent damage to target organs and reduce morbidity and mortality, adequate control of blood pressure (BP), including its variability (VAR), is important. The latter includes circadian, short-term, and long-term components, and VAR is best documented with out-of-office BP monitoring methods such as ambulatory BP monitoring (ABPM). The morning rise (MR) of BP is one of the components of variability, its disturbances are associated with an increased risk of stroke and CV events, regardless of the level of BP. Purpose – the aim of the study was to study the relationship between the morning rise in blood pressure and the short-term blood pressure variability in patients with arterial hypertension. Materials and Methods. The study included 169 patients with hypertension aged 43 to 78 years. Based on the results of ABPM, an assessment of the morning dynamics and short-term BP VAR were carried out. To assess the morning dynamics of blood pressure, the speed and amplitude of MR of systolic BP (SBP) and diastolic BP (DBP) were studied. SBP and DBP VAR were evaluated separately for day, night, and 24-hour periods using the SD, SDcorr, and ARV indices. Results. In this open, non-randomized, cross-sectional study of patients with hypertension, a direct relationship between BP VAR and its morning dynamics was revealed – the increase in VAR was associated with greater amplitude and speed of BP MR. The established correlations were closer for MR amplitude than for MR speed, which allows to draw a conclusion about different pathogenesis mechanisms of their disorders and requires further study of this phenomenon. An increase in VAR SBP was associated not only with changes in the morning dynamics of SBP, but also with changes in the morning dynamics of DBP, and vice versa Conclusions. ABPM should be an essential part of the management of hypertensive patients with an individualized approach to pharmacotherapy to achieve not only optimal 24-hour BP control, but also correction of elevated BP and excessive morning rise for the best cardiovascular and cerebrovascular protection.

A machine learning model for predicting worsening renal function using one-year time series data in patients with type 2 diabetes.

To prevent end-stage renal disease caused by diabetic kidney disease, we created a predictive model for high-risk patients using machine learning. The reference point was the time at which each patient's estimated glomerular filtration rate (eGFR) first fell below 60 mL/min/1.73 m2. The input period spanned the reference point to 1 year prior. The primary endpoint was a 50% decrease in eGFR from the mean of the input period over the 3 year evaluation period. We created predictive models for patients' primary endpoints using time series data of various variables over the input period. Among 2,533 total patients, 1,409 had reference points, 31 had records for their input and evaluation periods and had reached their primary endpoints, and 317 patients had not. The area under the curve (AUC) of the predictive model peaked (0.81) when the minimum eGFR, the difference between maximum and minimum eGFR, and both maximum and minimum urinary protein values were included in the features. The accuracy of prognosis prediction can be improved by considering the variable components of urinary protein and eGFR levels. This model will allow us to identify patients whose renal functions are relatively preserved with eGFR of more than 60 mL/min/1.73 m2 and are likely to benefit clinically from immediate treatment intensification.

ОБУЧЕНИЕ КАК ВАРИАТИВНАЯ СОСТАВЛЯЮЩАЯ ПРОФЕССИОНАЛЬНОЙ СОЦИАЛИЗАЦИИ БУДУЩИХ СПЕЦИАЛИСТОВ СОЦИАЛЬНОЙ СФЕРЫ В РАЗЛИЧНЫХ ТИПАХ УЧРЕЖДЕНИЙ ВЫСШЕГО ОБРАЗОВАНИЯ

In the social sphere of modern Russia against the background of rapid transformation socio-economic and political processes, the phenomenon of professional socialisation has become an urgent social problem. Society's expectations from education as a key component of the social sphere are largely related to the capabilities and readiness of higher education to find the most effective ways to solve the problems of training and professional socialisation of social sphere specialists. The purpose of the article is to focus the attention of subjects of professional socialisation and scientific and pedagogical community on the necessity to comprehend the role of one of the variable components of professional socialisation of future social sphere specialists in different types of higher education institutions, namely the form of organisation of the pedagogical process - training, which determines the content of professional socialisation of future social sphere specialists. The materials presented in the article significantly expand the subject field of humanitarian knowledge and are a stimulus to conceptual understanding of the problems of professional socialisation of a person. The article is addressed to specialists, professionally interested in solving actual problems of professional socialisation, as well as adjuncts, cadets, listeners, teachers of educational organisations of the Ministry of Internal Affairs of Russia, teachers and students of educational institutions of psychological, pedagogical and confession-oriented profiles

Spectral Analysis of the Morphology of Fresh Lunar Craters I: Rim Crest, Floor, and Rim Flank Outlines

AbstractThe morphology of fresh lunar craters contains information about the physical properties of both the impactors and the lunar surface, and is therefore crucial to our knowledge of the impact cratering process. Spectral analysis is a powerful tool to study crater morphology, as it can reveal the topographic variation on different scales. In this study, we calculate the power spectral densities of the radial distance and elevation of the rim crest, floor, and rim flank outlines of fresh lunar craters. The resulting power spectral density can be decomposed into an average component and a natural variability component. For the average component, we derive the classic morphometric parameter‐crater diameter relations that are consistent with previous studies. For the natural variability component, we find that in general the spectral power increases with wavelength, which can be fitted by a piecewise function with four breakpoints. Among the four breakpoints, the power of the third breakpoint (i.e., the degree‐2 power) is of particular interest, as it determines the ellipticity of the outline. The power of the third breakpoint is found to have a diameter dependence with a peak at 20 km, which indicates that transitional craters are more elliptical than simple and complex craters. The diameter dependence of the power spectral density enables us to generate the synthetic outlines of a crater of a particular size, which can be used to develop a preliminary 3‐dimensional shape model for fresh lunar craters that is useful for improving Monte Carlo modeling of cratered surfaces on the Moon.

Adaptive Free-Form Deformation Parameterization Based on Spring Analogy Method for Aerodynamic Shape Optimization

An adaptive Free-Form Deformation parameterization method based on a spring analogy is presented for aerodynamic shape optimization problems. The proposed method effectively incorporates the gradients of the objective and constraint functions, achieving automatic control point adjustment based on variances in design variable components. To evaluate the performance of the adaptive FFD parameterization method, two 2D airfoil optimization design problems are examined. The optimization of the RAE2822 airfoil with 12, 18 and 24 design variables demonstrates superior results for the adaptive method compared to uniform parameterization. The adaptive method requires fewer iterations and achieves lower objective function values. Additionally, the optimization design from NACA0012 to RAE2822 airfoil with 18 design variables shows that the adaptive parameterization method achieves a lower drag coefficient while satisfying the optimization objective. This validates the method’s capability to finely adjust airfoil shapes and capture more optimal design points by exerting stronger control over local shapes. The proposed adaptive FFD parameterization method proves highly effective for optimizing aerodynamic shapes, offering stability and efficiency in the early stages of optimization, even with a limited number of design variables.

Understanding the evolution of engagement with brand posts on social media using agent-based models

PurposeThis paper aims to delineate the nature of the costs associated with the diffusion of brand posts. Since cost is an essential component of customer lifetime value, this research also aims to identify factors that impact consumer engagement (CE) with brand posts.Design/methodology/approachThis study conceptualize marginal cost of CE as the ratio of a unit change in cost for a unit change in CE – this ratio is conceptualized for a paid brand post compared to an organic brand post. The authors present a theoretically grounded simulation method that analyzes the relative impact of several factors that influence CE with brand posts. By using an agent-based simulation model, the method presented in this paper helps explain the relative impact of four factors on CE with brand posts on social media.FindingsThe authors explain four factors that influence the diffusion of CE with a brand post – promotion-related (i.e. whether it is paid vs organic), network-related, user-related and active periods. The authors also show that the effectiveness of paid posts vs organic posts attributed to a better audience assembled by the seeding algorithms dissipates after the initial stages of diffusion. These findings indicate that paid posts are effective vs organic posts in large part due to higher exposure than due to the efficiency of the algorithms to assemble nodes that are likely to engage with the post.Research limitations/implicationsAn agent-based model details the impact of several factors that influence the effectiveness of paid and organic posts and presents methods to analyze the impact of these factors that have implications for theory.Practical implicationsThe authors address the difficulty in ascertaining the effectiveness of paid posts by proposing a metric – marginal cost of engagement, defined as the incremental cost incurred by the marketer in earning one additional unit of CE. Since the costs incurred on paid and organic posts differ only on variable components, the marginal cost of engagement presents a way to benchmark paid posts against organic posts, which is very useful for managers in ascertaining the amount to spend on paid posts on social media.Originality/valueThere is little prior research on the costs involved in the diffusion of brand posts on social media. Identifying specific factors that impact costs is valuable for theory and practice.

Characterization of high-yielding aman rice genotypes through genetic and agronomic analysis

ABSTRACT Rice (Oryza sativa L.) holds immense global significance, serving as a staple food crop that sustains billions of people and supports livelihoods across diverse cultures and economies, including Bangladesh. For food security in Bangladesh, there is a significant demand for high-yielding Aman rice varieties. We assessed genetic variability of 16 Aman rice genotypes, including 11 promising Aman lines and 5 established Aman cultivars in Bangladesh, with the aim of identifying high-yielding genotypes through a three-year field experiment. The examined genotypes displayed notable variations in both yield and agronomic traits contributing to yield, as evidenced by their greater range of coefficients of variance and genetic variability components. Traits such as effective tillers per hill (ET), filled grains per panicle (FG), plant height (PH) at 80 days after transplanting, and panicle length (PL) demonstrated notable correlations with grain yield (GY) throughout the three-year evaluation. Moreover, the higher broad-sense heritability (H 2) observed in ET, FG, PH, and PL traits suggested a substantial influence of genetic factors on the variability of the Aman rice genotypes. Principal component analysis based biplot and heatmap analyses revealed that the advanced lines BU acc4 and BU acc5 had higher harvest index and relatively greater GY compared to the other Aman rice varieties. These promising Aman lines could prove to be valuable materials for future multi-location yield trials or ongoing and forthcoming breeding programs aimed at enhancing high-yielding Aman rice cultivars.

Multiple “spaces”: Using wildlife surveillance, climatic variables, and spatial statistics to identify and map a climatic niche for endemic plague in California, U.S.A.

Regional climatic features in endemic areas can help inform surveillance for plague, a bacterial disease typically transmitted by fleas and maintained in mammals. We use 7,954 coyotes (Canis latrans), a sentinel species for plague, screened for plague exposure by the California Department of Public Health - Vector-Borne Disease Section (CDPH-VBDS; 1983-2015) to identify and map plague-suitable local climates within California to empirically inform ongoing sampling and surveillance plans. Using spatial point processes, we compare the distributions of seropositive and seronegative coyotes within the “space” defined by the first two principal components of PRISM Climate Group 30-year average climate variables (primarily temperature and moisture). The approach identifies both regions consistent with CDPH-VBDS mapping of plague-positive rodent and other carnivore samples over the same period and additional plague-suitable areas with climate profiles similar to seropositive samples elsewhere but little or no historical sampling, providing new data-informed insight for prioritizing limited surveillance resources.

Unveiling the genetic variability, character association and principal component analysis for yield and yield contributing traits in brinjal (Solanum melongena) genotypes

The experiment was conducted during rainy (kharif) and winter (rabi) seasons of 2023 and 2024 at Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu to assess 45 brinjal (Solanum melongena L.) genotypes for growth and yield related parameters. The experiment was laid out in randomized block design (RBD) with three replications. The result showed high genotypic coefficient of variance (GCV) and phenotypic coefficient of variance (PCV) values for plant height, number of primary branches/plant, length of fruit and weight of fruit and yield/plant. Whereas, the traits such as days to first flowering, days to 50% flowering, fruit girth, fruit borer infestation and number of fruits/ plant exhibited medium GCV and PCV values. The registered high heritability values ranged from 94.29–99.49% and genetic advance as a percentage of the mean ranged from 19.25–70.25%. Correlation analysis on number of fruits/ plant showed positive and significant association with fruit yield/plant. Principal component analysis showed four principal components with eigen values of unity and accounted for 75.81% of total variance.

Material-Sparing Approach to Predict Tablet Capping Under Processing Compression Conditions Based on Mechanical and Molecular Properties Derived from Compaction Simulation and Crystal Structural Analysis.

Present study evaluates the usability of compaction simulation-based mechanical models as a material-sparing approach to predict tablet capping under processing compression conditions using Acetaminophen (APAP) and Ibuprofen (IBU). Measured mechanical properties were evaluated using principal component analysis (PCA) and principal component regression (PCR) models. PCR models were then utilized to predict the capping score (CS) from compression pressure (CP). APAP formulations displayed a quadratic correlation between CS and CP, with CS rank order following CP of 200MPa < 300MPa < 100MPa, indicating threshold compression pressure (TCP) limit between 200 and 300 MPa, resulting in higher CS at 300 than 200 MPa regardless of increased CP. IBU formulations displayed a linear correlation between CS and CP, with CS rank order following CP of 100MPa < 200MPa < 300MPa, indicating TCP limit between 100 and 200 MPa, resulting in higher CS at 200 and 300 than 100 MPa regardless of increased CP. Molecular models were developed as validation methods to predict capping from CP. Measured XRPD patterns of compressed tablets were linked with calculated Eatt and d-spacing of slip planes and analyzed using variable component least square methods to predict TCP triggering cleavage in slip planes and leading to capping. In APAP and IBU, TCP values were predicted at 245 and 175 MPa, meaning capped tablets above these TCP limits regardless of increased CP. A similar trend was observed in CS predictions from mechanical assessment, confirming that compaction simulation-based mechanical models can predict capping risk under desired compression conditions rapidly and accurately.

Civil liability of the sole executive body of a business company: correlation with labor and tax law institutions

In modern conditions of business turnover, characterized by the desire of business entities to achieve the benefits and goals of social corporate responsibility, the issues of preserving the balance of interests of parties that have a diversified status are of particular relevance. Such subjects include the general director, who is simultaneously a management body, an employee and a taxpayer, being in relations with a business company regulated by both corporate, labor and tax law norms, which allows to qualify his status as a diversified one. The issue of correlation of the norms of three branches of law in relation to the status of the chief executive officer (CEO) through the prism of the institute of civil liability in the form of compensation for losses caused to the company by incentive (bonus) payments to the CEO is considered. The article assesses the law enforcement practice in disputes concerning the recovery of this category of losses from the director, where the courts give priority to the norms of corporate law without taking into account the explanations of the Constitutional Court of the Russian Federation on the unconditional right of an employee to receive bonuses, which are a variable component of salary. The court approaches are analyzed and their justifications are given with regard to the inclusion of the amounts of personal income tax paid by the company to the budget of the Russian Federation into the damages recovered from the CEO. The conclusions are made about the priority importance of labor and tax legislation norms in correlation with corporate law norms when applying the institute of directors’ indemnification for losses. The results of the study can be used for the development by the Supreme Court of the Russian Federation of appropriate explanations to the courts of lower instances on consideration of disputes on the recovery of losses from the sole executive body of a business company.

Relationship Between High Frequency Component of Heart Rate Variability and Delta EEG Power During Sleep in Women With Irritable Bowel Syndrome Compared to Healthy Women.

To explore the relationship between the high frequency (HF) heart rate variability (HRV) and electroencephalogram (EEG) delta band power in women with irritable bowel syndrome (IBS) versus healthy control women. Twenty women with IBS and twenty healthy controls were studied over three consecutive nights using polysomnography in a sleep laboratory. To avoid the first night effect, only second-night data were analyzed. Power spectral analysis was applied to HRV and EEG recordings. The linear system coherence/phase analysis assessed the relationship between normalized HF power of HRV and normalized delta band power of EEG during the first four NREM-REM sleep cycles. Women with IBS exhibited a significantly higher percentage of NREM sleep, higher normalized HF, lower normalized low frequency (LF) and decreased LF/HF ratio of HRV in the first four NREM-REM sleep cycles compared to controls. Additionally, their normalized delta band power was significantly lower in these sleep cycles and over the whole night. The phase shift between HF and delta band power was significantly longer in the IBS group. While the coherence between normalized HF and normalized delta band power was lower in the IBS group, the difference was not statistically significant. The coherence/phase analysis showed a dysregulated interaction between autonomic and central nervous systems in women with IBS, manifested by increased lag time between cardiac and EEG delta band power compared to healthy controls. Whether this dysregulation contributes to the pathophysiology of IBS remains to be determined.

Microjet Flow Control on an Airfoil Flap: Particle Image Velocimetry Characterization

Normal-blowing microjets near the trailing edge of a flap can improve the aerodynamic performance of high-lift systems, potentially without some of the system-integration drawbacks of traditional systems. Previous two-dimensional simulations and a preliminary wind-tunnel test demonstrated the effectiveness of the microjet concept on a deployed flap. To further validate microjet effectiveness, this study uses a specially developed particle image velocimetry technique to estimate the momentum injected by a microjet on a deployed Fowler flap of a two-element NLR7301 airfoil while simultaneously measuring the lift enhancement provided by the microjet via surface pressure taps. The test results are broadly consistent with numerical simulations that predict lift increases proportionally to the square root of momentum injection. Within the experimental uncertainties, the test results show slightly less lift benefit for a given level of estimated momentum injection compared to the simulations, possibly due to three-dimensional effects such as spanwise variability and spanwise velocity components of the injected air, which could not be measured with the current instrumentation.

Genetic variability, diversity and principal component analysis in B and R lines of rabi sorghum [Sorghum bicolor (L.) Moench

Hybrid technology is exploited in kharif (rainy) sorghum while the same is not the scenario in Rabi sorghum which is still dominated by landraces and varieties which have poor yield potentiality. Considering the necessity of development of heterotic hybrids, an attempt was made to screen hybrid parents (B and R lines) to assess variability and genetic diversity, for productivity traits. The study was conducted with 32 B and R lines at Regional Agricultural Research Station, Vijayapur during 2021-22. PCV was observed to surpass GCV across all traits. The traits grain yield per plant, fodder yield per plant, grain number per plant, and harvest index exhibited notably high PCV and GCV. Plant height, panicle length, panicle harvest index, and harvest index recorded high heritability and genetic advance, suggesting their control by additive gene action and potential for improvement via selection. Cluster analysis classified the 32 genotypes into four groups. PCA condensed 14 traits into five principal components, capturing 81.50% of total variation. The genotypes remained scattered in all four quadrants in PCA- Biplot, showing large genetic variability in quantitative traits studied. Keywords: Genetic variability, heritability, diversity, clusters, PCA and rabi sorghum

Disentangling seasonal and annual precipitation signals in the tropics over the Holocene: Insights from δD, alkanes and GDGTs

Rainfall seasonality in the tropics has a substantial impact on both ecosystems and human livelihoods. Yet, reconstructions of past rainfall variability have so far generally been unable to differentiate between annual and seasonal precipitation changes. Past variations in seasonality are therefore largely unknown. Here, we disentangle hydrogen isotopic (δD) signals from terrestrial leaf waxes and algae in an 8000-year peat core from Sumatra, which reflect annual versus wet season rainfall signals, respectively. We validate these results using lipid biomarkers by reconstructing vegetation dynamics via n-alkane distributions and peatland hydrological conditions using glycerol dialkyl glycerol tetraethers (GDGTs), as well as biomass burning using levoglucosan concentrations in the core. Finally, we compare our proxy results to a transient climate model simulation (MPI-ESM1.2) to identify the mechanism for seasonality changes. We find that algal δD indicates stronger Indonesian-Australian Summer Monsoon (IASM) precipitation in the Mid-Holocene, between 8 and 4.2 cal ka BP. A period of alternating flooding, droughts and wildfires is reconstructed between 6 and 4.2 cal ka BP, implicating very strong monsoonal precipitation and drying out and burning during a longer and intensified dry season. We attribute this strong rainfall seasonality in the Mid-Holocene mainly to orbitally forced insolation seasonality and a strengthened IASM, consistent with the modeling results. In terms of annual rainfall, terrestrial plant δD, vegetation composition and GDGTs all indicate wetter conditions peaking between 3 and 4.5 cal ka BP, preceded by drier conditions, followed by drastic and rapid drying in the late Holocene from around 2.8 cal ka BP. Our multiproxy annual precipitation reconstruction thereby indicates the wettest overall conditions approximately 1500–2000 years later than a nearby speleothem δ18O record, which instead follows the seasonally biased algal δD in our record. We, therefore, hypothesize that speleothem reconstructions over the Holocene in parts of the tropics with low but significant seasonality may carry a stronger seasonal component than previously suggested. The data presented here contribute with new insights on how isotopic rainfall proxies in the tropics can be interpreted. Our findings resolve the seasonal versus annual components of Holocene rainfall variability in the Indo-Pacific Warm Pool region, highlighting the importance of considering seasonality in rainfall reconstructions.