Natural Variation Research Articles

Exploring the Factors Controlling the Annual Range of Amazon Precipitation

Abstract The annual range (AR) of precipitation in the Amazon River basin has increased steadily since 1979. This increase may have resulted from natural variability and/or anthropogenic forcing, such as local land-use changes and global warming, which has yet to be explored. In this study, climate model experiments using the Community Earth System Model, version 2 (CESM2), were conducted to examine the relative contributions of sea surface temperatures (SSTs) variability and anthropogenic forcings to the AR changes in the Amazon rainfall. With CESM2, we design several factorial simulations, instead of actual model projection. We found that the North Atlantic SSTs fluctuation dominantly decreases the precipitation AR trend over the Amazon by −85%. In contrast, other factors, including deforestation and carbon dioxide, contributed to the trend changes, ranging from 25% to 35%. The dynamic component, specifically the tendency of vertical motion, made negative contributions, along with the vertical profiles of moist static energy (MSE) tendency. Seasonal-dependent changes in atmospheric stability could be associated with variations in precipitation. It is concluded that surface ocean warming associated with the North Atlantic natural variability and global warming is the key factor in the increased precipitation AR over the Amazon from 1979 to 2014. The continuous local land-use changes may potentially influence the precipitation AR in the future. Significance Statement The annual range (AR) in precipitation, the difference between wet- and dry-season precipitation, has increased from 1979 to 2014 in the Amazon. This increase may have resulted from global warming, deforestation, and sea surface temperature variability in North Atlantic and Pacific. To explore the role of each of these factors in altering the Amazon precipitation AR, five experiments were designed in the climate model (CESM). Among these experiment results, the effect of North Atlantic SSTs was the strongest. In the future, deforestation, global warming, and different ocean temperature states in the North Atlantic and Pacific may become increasingly influential on the changes in precipitation. Further investigation is needed to ascertain how the AR of precipitation in the Amazon will change.

Arabidopsis transcriptome responses to low water potential using high-throughput plate assays.

Soil-free assays that induce water stress are routinely used to investigate drought responses in the plant Arabidopsis thaliana. Due to their ease of use, the research community often relies on polyethylene glycol (PEG), mannitol, and salt (NaCl) treatments to reduce the water potential of agar media, and thus induce drought conditions in the laboratory. However, while these types of stress can create phenotypes that resemble those of water deficit experienced by soil-grown plants, it remains unclear how these treatments compare at the transcriptional level. Here, we demonstrate that these different methods of lowering water potential elicit both shared and distinct transcriptional responses in Arabidopsis shoot and root tissue. When we compared these transcriptional responses to those found in Arabidopsis roots subject to vermiculite drying, we discovered many genes induced by vermiculite drying were repressed by low water potential treatments on agar plates (and vice versa). Additionally, we also tested another method for lowering water potential of agar media. By increasing the nutrient content and tensile strength of agar, we show the 'hard agar' (HA) treatment can be leveraged as a high-throughput assay to investigate natural variation in Arabidopsis growth responses to low water potential.

Comparative genomic analysis of Bradyrhizobium strains with natural variability in the efficiency of nitrogen fixation, competitiveness, and adaptation to stressful edaphoclimatic conditions.

Bradyrhizobium is known for fixing atmospheric nitrogen in symbiosis with agronomically important crops. This study focused on two groups of strains, each containing eight natural variants of the parental strains, Bradyrhizobium japonicum SEMIA 586 (=CNPSo 17) or Bradyrhizobium diazoefficiens SEMIA 566 (=CNPSo 10). CNPSo 17 and CNPSo 10 were used as commercial inoculants for soybean crops in Brazil at the beginning of the crop expansion in the southern region in the 1960s-1970s. Variants derived from these parental strains were obtained in the late 1980s through a strain selection program aimed at identifying elite strains adapted to a new cropping frontier in the central-western Cerrado region, with a higher capacity of biological nitrogen fixation (BNF) and competitiveness. Here, we aimed to detect genetic variations possibly related to BNF, competitiveness for nodule occupancy, and adaptation to the stressful conditions of the Brazilian Cerrado soils. High-quality genome assemblies were produced for all strains. The core genome phylogeny revealed that strains of each group are closely related, as confirmed by high average nucleotide identity values. However, variants accumulated divergences resulting from horizontal gene transfer, genomic rearrangements, and nucleotide polymorphisms. The B. japonicum group presented a larger pangenome and a higher number of nucleotide polymorphisms than the B. diazoefficiens group, possibly due to its longer adaptation time to the Cerrado soil. Interestingly, five strains of the B. japonicum group carry two plasmids. The genetic variability found in both groups is discussed considering the observed differences in their BNF capacity, competitiveness for nodule occupancy, and environmental adaptation.IMPORTANCEToday, Brazil is a global leader in the study and use of biological nitrogen fixation with soybean crops. As Brazilian soils are naturally void of soybean-compatible bradyrhizobia, strain selection programs were established, starting with foreign isolates. Selection searched for adaptation to the local edaphoclimatic conditions, higher efficiency of nitrogen fixation, and strong competitiveness for nodule occupancy. We analyzed the genomes of two parental strains of Bradyrhizobium japonicum and Bradyrhizobium diazoefficiens and eight variant strains derived from each parental strain. We detected two plasmids in five strains and several genetic differences that might be related to adaptation to the stressful conditions of the soils of the Brazilian Cerrado biome. We also detected genetic variations in specific regions that may impact symbiotic nitrogen fixation. Our analysis contributes to new insights into the evolution of Bradyrhizobium, and some of the identified differences may be applied as genetic markers to assist strain selection programs.

Human cytomegalovirus glycoprotein variants governing viral tropism and syncytium formation in epithelial cells and macrophages.

Human cytomegalovirus (HCMV) displays a broad cell tropism, and the infection of biologically relevant cells such as epithelial, endothelial, and hematopoietic cells supports viral transmission, systemic spread, and pathogenesis in the human host. HCMV strains differ in their ability to infect and replicate in these cell types, but the genetic basis of these differences has remained incompletely understood. In this study, we investigated HCMV strain VR1814, which is highly infectious for epithelial cells and macrophages and induces cell-cell fusion in both cell types. A VR1814-derived bacterial artificial chromosome (BAC) clone, FIX-BAC, was generated many years ago but has fallen out of favor because of its modest infectivity. By sequence comparison and genetic engineering of FIX, we demonstrate that the high infectivity of VR1814 and its ability to induce syncytium formation in epithelial cells and macrophages depends on VR1814-specific variants of the envelope glycoproteins gB, UL128, and UL130. We also show that UL130-neutralizing antibodies inhibit syncytium formation, and a FIX-specific mutation in UL130 is responsible for its low infectivity by reducing the amount of the pentameric glycoprotein complex in viral particles. Moreover, we found that a VR1814-specific mutation in US28 further increases viral infectivity in macrophages, possibly by promoting lytic rather than latent infection of these cells. Our findings show that variants of gB and the pentameric complex are major determinants of infectivity and syncytium formation in epithelial cells and macrophages. Furthermore, the VR1814-adjusted FIX strains can serve as valuable tools to study HCMV infection of myeloid cells.IMPORTANCEHuman cytomegalovirus (HCMV) is a major cause of morbidity and mortality in transplant patients and the leading cause of congenital infections. HCMV infects various cell types, including epithelial cells and macrophages, and some strains induce the fusion of neighboring cells, leading to the formation of large multinucleated cells called syncytia. This process may limit the exposure of the virus to host immune factors and affect pathogenicity. However, the reason why some HCMV strains exhibit a broader cell tropism and why some induce cell fusion more than others is not well understood. We compared two closely related HCMV strains and provided evidence that small differences in viral envelope glycoproteins can massively increase or decrease the virus infectivity and its ability to induce syncytium formation. The results of the study suggest that natural strain variations may influence HCMV infection and pathogenesis in humans.

High-resolution methylome analysis uncovers stress-responsive genomic hotspots and drought-sensitive TE superfamilies in the clonal Lombardy poplar.

DNA methylation is environment-sensitive and can mediate stress responses. In long-lived trees, changing environments might cumulatively shape the methylome landscape over their lifetime. However, because high-resolution methylome studies usually focus on single environmental cues, it remains unclear to what extent the methylation responses are generic or stress-specific, and how this relates to their long-term stability. Here, we studied the methylome plasticity of a Populus nigra cv. 'Italica' clone that is widespread across Europe. Adult trees from a variety of geographic locations were clonally propagated in a common garden experiment, and the ramets were exposed to cold, heat, drought, herbivory, rust infection, and salicylic acid treatments. Through comprehensive whole-genome bisulfite sequencing, we analyzed stress-induced and naturally occurring DNA methylation variants. Stress-induced methylation changes predominantly targeted transposable elements. When occurring in CG/CHG contexts, the same regions were often affected by multiple stresses, suggesting a generic response of the methylome. Drought stress caused a distinct CHH hypermethylation response in transposable elements, affecting entire TE superfamilies near drought-responsive genes. Methylation differences in CG/CHG contexts that were induced by stress treatments showed striking overlap with methylation differences observed between trees from distinct geographical locations. Thus, we revealed genomic hotspots of methylation change that are not stress-specific and that contribute to natural DNA methylation variation, and we identified specific transposable element superfamilies that respond to a specific stress with possible functional consequences. Our results underscore the importance of studying the effects of multiple stressors in a single experiment for recognizing general versus stress-specific methylome responses.

A non-linear stress–strain relationship for soil and rock

While many employ a hyperbolic stress–strain relationship for soils, it is known that such a relationship is accurate over the small-strain range as encountered in earthquake and soil dynamics problems. For large strains, a relationship with different input parameters is needed, as is required for finite-element analyses of large-deformation behaviour. These separate characterisations do not carry over into the other application. Here, a proposed power relationship is presented that was developed to characterise the triaxial test stress–strain behaviour of cohesionless material from lubricated or ‘frictionless’ cap and base tests (144 tests) covering a range in the natural variation in particle size, particle shape and surface roughness, over low to high confining pressure. This relationship covers the strain range from 10−6 to soil failure. To date, it has been successfully used in laterally loaded pile response characterisation (the strain wedge model) and shallow-foundation load–settlement–bearing capacity response. Most recently, it has been extended to assess the behaviour of rock-like material (caliche). The relationship and its comparison with the hyperbolic relationship for large strain and the shear modulus reduction curve for seismic behaviour are presented.

Transcription factor binding site divergence across maize inbred lines drives transcriptional and phenotypic variation.

Regulatory elements are important constituents of plant genomes that have shaped ancient and modern crops. Their identification, function, and diversity in crop genomes however are poorly characterized, thus limiting our ability to harness their power for further agricultural advances using induced or natural variation. Here, we use DNA affinity purification-sequencing (DAP-seq) to map transcription factor (TF) binding events for 200 maize TFs belonging to 30 distinct families and heterodimer pairs in two distinct inbred lines historically used for maize hybrid plant production, providing empirical binding site annotation for 5.3% of the maize genome. TF binding site comparison in B73 and Mo17 inbreds reveals widespread differences, driven largely by structural variation, that correlate with gene expression changes. TF binding site presence-absence variation helps clarify complex QTL such as vgt1, an important determinant of maize flowering time, and DICE, a distal enhancer involved in herbivore resistance. Modification of TF binding regions via CRISPR-Cas9 mediated editing alters target gene expression and phenotype. Our functional catalog of maize TF binding events enables collective and comparative TF binding analysis, and highlights its value for agricultural improvement.

Influence of global teleconnections on long-term variability in flood seasonality across peninsular India

Climate change and natural climate variability impact not only the frequency and magnitude of floods but also flood seasonality. However, limited to no study has investigated the seasonality in flood occurrence in peninsular Indian rivers. The Central Water Commission opening its long-term records of river stage and discharge gathered from many monitoring stations offers a unique opportunity to analyse flood seasonality. The primary aims of this study are to identify the time of the year when floods are most likely, investigate whether the occurrence of floods has changed over time due to the influence of climate change and natural climate variability, and determine the most significant large-scale and local climate drivers of flood seasonality. Stage and discharge data from 281 gauging stations across ten peninsular river basins are considered to identify the annual maximum gauge level for a gauging point while retaining the corresponding Julian day (also known as the date of occurrence or DO) for further analysis. Several attributes related to circular statistics are calculated from the DO series to find that 68% of the gauging stations experience floods during August, indicating the dominance of the monsoon system on DO. Preliminary analysis confirms that while most stations experience a non-stationarity in the DO series, a few stations exhibit a non-linear trend. Furthermore, our study develops a machine learning model with DO as predictand and 36 local and large-scale predictors to identify the dominant predictors of DO. The predictor importance metric shows that the Pacific Decadal Oscillation (PDO) and the El Niño and Southern Oscillation (ENSO) explain DO variability better than other drivers. Moreover, since ENSO and PDO are teleconnected with the onset of monsoon and annual maximum rainfall (Pradhan et al 2017 Sci. Rep. 7 14229; Choudhury et al 2021a Q. J. R. Meteorol. Soc. 147 3111–23), flood seasonality demonstrates a connection with both PDO and ENSO.

Recent progress and potential future directions to enhance biological nitrogen fixation in faba bean (Vicia faba L.).

The necessity for sustainable agricultural practices has propelled a renewed interest in legumes such as faba bean (Vicia faba L.) as agents to help deliver increased diversity to cropped systems and provide an organic source of nitrogen (N). However, the increased cultivation of faba beans has proven recalcitrant worldwide as a result of low yields. So, it is hoped that increased and more stable yields would improve the commercial success of the crop and so the likelihood of cultivation. Enhancing biological N fixation (BNF) in faba beans holds promise not only to enhance and stabilize yields but also to increase residual N available to subsequent cereal crops grown on the same field. In this review, we cover recent progress in enhancing BNF in faba beans. Specifically, rhizobial inoculation and the optimization of fertilizer input and cropping systems have received the greatest attention in the literature. We also suggest directions for future research on the subject. In the short term, modification of crop management practices such as fertilizer and biochar input may offer the benefits of enhanced BNF. In the long term, natural variation in rhizobial strains and faba bean genotypes can be harnessed. Strategies must be optimized on a local scale to realize the greatest benefits. Future research must measure the most useful parameters and consider the economic cost of strategies alongside the advantages of enhanced BNF.

On the state principle of classical thermodynamics

We discuss the state principle of classical thermodynamics, namely that the thermodynamic state of a simple compressible system can be uniquely determined by specifying two independent properties. We show that for certain combinations of properties, one is not guaranteed to arrive at a unique state. This caveat to the state principle is illustrated with three examples, two involving liquid water and a third using real gases. Finally, we show that to guarantee a unique state for a simple compressible system, the required two independent properties must be chosen from the trio consisting of a thermodynamic potential and its two natural variables.

The impact of aragonite saturation variability on shelled pteropods: An attribution study in the California Current System.

Observations from the California Current System (CalCS) indicate that the long-term trend in ocean acidification (OA) and the naturally occurring corrosive conditions for the CaCO3 mineral aragonite (saturation state Ω < 1) have a damaging effect on shelled pteropods, a keystone group of calcifying organisms in the CalCS. Concern is heightened by recent findings suggesting that shell formation and developmental progress are already impacted when Ω falls below 1.5. Here, we quantify the impact of low Ω conditions on pteropods using an individual-based model (IBM) with life-stage-specific mortality, growth, and behavior in a high-resolution regional hindcast simulation of the CalCS between 1984 and 2019. Special attention is paid to attributing this impact to different processes that lead to such low Ω conditions, namely natural variability, long-term trend, and extreme events. We find that much of the observed damage in the CalCS, and specifically >70% of the shell CaCO3 loss, is due to the pteropods' exposure to naturally occurring low Ω conditions as a result of their diel vertical migration (DVM). Over the hindcast period, their exposure to damaging waters (Ω < 1.5) increases from 9% to 49%, doubling their shell CaCO3 loss, and increasing their mortality by ~40%. Most of this increased exposure is due to the shoaling of low Ω waters driven by the long-term trend in OA. Extreme OA events amplify this increase by ~40%. Our approach can quantify the health of pteropod populations under shifting environmental conditions, and attribute changes in fitness or population structure to changes in the stressor landscape across hierarchical time scales.

Thiosulfinate Tolerance Gene Clusters Are Common Features of Burkholderia Onion Pathogens.

Burkholderia gladioli pv. alliicola, B. cepacia, and B. orbicola are common bacterial pathogens of onion. Onions produce organosulfur thiosulfinate defensive compounds after cellular decompartmentalization. Using whole-genome sequencing and in silico analysis, we identified putative thiosulfinate tolerance gene (TTG) clusters in multiple onion-associated Burkholderia species similar to those characterized in other Allium-associated bacterial endophytes and pathogens. Sequence analysis revealed the presence of three Burkholderia TTG cluster types, with both Type A and Type B being broadly distributed in B. gladioli, B. cepacia, and B. orbicola in both the chromosome and plasmids. Based on isolate natural variation and generation of isogenic strains, we determined the in vitro and in vivo contribution of TTG clusters in B. gladioli, B. cepacia, and B. orbicola. The Burkholderia TTG clusters contributed to enhanced allicin tolerance and improved growth in filtered onion extracts by all three species. TTG clusters also made clear contributions to B. gladioli foliar necrosis symptoms and bacterial populations. Surprisingly, the TTG cluster did not contribute to bacterial populations in onion bulb scales by these three species. Based on our findings, we hypothesize onion-associated Burkholderia may evade or inhibit the production of thiosulfinates in onion bulb tissues. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Decadal Thermal Variability of the Upper Southern Ocean: Zonal Asymmetry

Abstract As the major sink of anthropogenic heat, the Southern Ocean has shown quasi-symmetric, deep-reaching warming since the mid-twentieth century. In comparison, the shorter-term heat storage pattern of the Southern Ocean is more complex and has notable impacts on regional climate and marine ecosystems. By analyzing observational datasets and climate model simulations, this study reveals that the Southern Ocean exhibits prominent decadal (&gt;8 years) variability extending to ∼700-m depth and is characterized by out-of-phase changes in the Pacific and Atlantic–Indian Ocean sectors. Changes in the Pacific sector are larger in magnitude than those in the Atlantic–Indian Ocean sectors and dominate the total heat storage of the Southern Ocean on decadal time scales. Instead of heat uptake through surface heat fluxes, these asymmetric variations arise primarily from wind-driven heat redistribution. Pacemaker and preindustrial simulations of the Community Earth System Model version 1 (CESM1) suggest that these variations in Southern Ocean winds arise primarily from natural variability of the tropical Pacific, as represented by the interdecadal Pacific oscillation (IPO). Through atmospheric teleconnection, the positive phase of the IPO gives rise to higher-than-normal sea level pressure and anticyclonic wind anomalies in the 50°–70°S band of the Pacific sector. These winds lead to warming of 0–700 m by driving the convergence of warm water. The opposite processes, involving cyclonic winds and upper-layer divergence, occur in the Atlantic–Indian Ocean sector. These findings aid our understanding of the time-varying heat storage of the Southern Ocean and provide useful implications on initialized decadal climate prediction.

Morpho-physiological traits and tissue burdens of Ecklonia radiata linked to environmental variation in an urban estuary

Organisms respond to their environment in various ways, including moving, adapting, acclimatising or a combination of responses. Within estuarine habitats, organisms are exposed to naturally variable environmental conditions. In urbanised estuaries, these natural variations can interact with human stressors such as habitat modification and pollution. Here, we investigated trait variation in the golden kelp Ecklonia radiata across an urban estuary - Sydney Harbour, Australia. We found that kelp morphology differed significantly between the more human-modified inner and the less modified outer harbour. Kelp individuals were smaller, had fewer laminae, and lacked spines in the inner harbour where it was warmer, more contaminated and less light was available. Inner harbour populations were characterised by lower tissue nitrogen and higher lead concentrations. These findings provide insights into how environmental variation could affect kelp morphology and physiology, and the high trait variation suggests adaptive capacity in E. radiata.

Circulating biomarker profile changes in obese patients undergoing bariatric surgery

Bariatric surgery (BS) remains the most effective treatment for morbid obesity (MO). It`s relevant to identify biomarkers for predicting the outcome of BS in patients with MO. The aim of the study was to determine the dynamical change in the biomarker levels in patients undergoing BS and apparently healthy donors. Serum and plasma samples were obtained from 66 patients, of which 26 patients with MO (aged 26–72 years) underwent BS, and 40 healthy donors, at the age of 56 ± 10.3 years. Patient samples were obtained the day before BS (first group), 3–7 months after BS (second group), and 7 or more months after BS (third group). Analyte concentrations were determined by multiplex immunoassay on the xMAP platform (Luminex). Spearman’s rank correlation was used. The nature of analyte variability was described by building multiple regression models. In the patients compared with healthy controls, differences in the levels of resistin, PAI1, MCP1, GLP1, leptin, FGF23, adiponectin, adipsin were observed. In patients after BS, the levels of resistin, ANGPTL6, FGF21, and leptin changed. In patients over 55 years old compared with younger patients, differences for total ANGPTL4, amylin, and pancreatic polypeptide were observed. Differences in levels of glucagon, resistin, GLP1 and leptin were noted between men and women. The dynamics of the levels of adipokines and incretins indicates biochemical changes in patients after BS compared with healthy persons.

Plant regeneration in the new era: from molecular mechanisms to biotechnology applications.

Plants or tissues can be regenerated through various pathways. Like animal regeneration, cell totipotency and pluripotency are the molecular basis of plant regeneration. Detailed systematic studies on Arabidopsis thaliana gradually unravel the fundamental mechanisms and principles underlying plant regeneration. Specifically, plant hormones, cell division, epigenetic remodeling, and transcription factors play crucial roles in reprogramming somatic cells and reestablishing meristematic cells. Recent research on basal non-vascular plants and monocot crops has revealed that plant regeneration differs among species, with various plant species using distinct mechanisms and displaying significant differences in regenerative capacity. Conducting multi-omics studies at the single-cell level, tracking plant regeneration processes in real-time, and deciphering the natural variation in regenerative capacity will ultimately help understand the essence of plant regeneration, improve crop regeneration efficiency, and contribute to future crop design.

Natural variation of immune epitopes reveals intrabacterial antagonism

Plants and animals detect biomolecules termed microbe-associated molecular patterns (MAMPs) and induce immunity. Agricultural production is severely impacted by pathogens which can be controlled by transferring immune receptors. However, most studies use a single MAMP epitope and the impact of diverse multicopy MAMPs on immune induction is unknown. Here, we characterized the epitope landscape from five proteinaceous MAMPs across 4,228 plant-associated bacterial genomes. Despite the diversity sampled, natural variation was constrained and experimentally testable. Immune perception in both Arabidopsis and tomato depended on both epitope sequence and copy number variation. For example, Elongation Factor Tu is predominantly single copy, and 92% of its epitopes are immunogenic. Conversely, 99.9% of bacterial genomes contain multiple cold shock proteins, and 46% carry a nonimmunogenic form. We uncovered a mechanism for immune evasion, intrabacterial antagonism, where a nonimmunogenic cold shock protein blocks perception of immunogenic forms encoded in the same genome. These data will lay the foundation for immune receptor deployment and engineering based on natural variation.

Natural Variation in the Promoter of GmSPL9d Affects Branch Number in Soybean.

The branch number is a crucial factor that influences density tolerance and is closely associated with the yield of soybean. However, its molecular regulation mechanisms remain poorly understood. This study cloned a candidate gene GmSPL9d for regulating the soybean branch number based on the rice OsSPL14 homologous gene. Meanwhile, the genetic diversity of the GmSPL9d was analyzed using 3599 resequencing data and identified 55 SNP/InDel variations, which were categorized into seven haplotypes. Evolutionary analysis classified these haplotypes into two groups: GmSPL9d H-I and GmSPL9d H-II. Soybean varieties carrying the GmSPL9d H-II haplotype exhibited a significantly lower branch number compared with those carrying the GmSPL9d H-I haplotype. Association analysis between the variation sites and branch number phenotypes revealed a significant correlation between the promoter variations and the branch number. Promoter activity assays demonstrated that the GmSPL9d H-II promoter displayed significantly higher activity than the GmSPL9d H-I promoter. Transgenic experiments confirmed that the plants that carried the GmSPL9d H-II promoter exhibited a significantly lower branch number compared with those that carried the GmSPL9d H-I promoter. These findings indicate that the variation in the GmSPL9d promoter affected its transcription level, leading to differences in the soybean branch number. This study provides valuable molecular targets for improving the soybean plant structure.

Primary Drivers of the Recent Changes Observed in Global Ocean Circulation Patterns in Mozambique

Purpose: The aim of the study was to examine the primary drivers of the recent changes observed in global ocean circulation patterns in Mozambique Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The study revealed that primary drivers of the recent changes observed in global ocean circulation patterns are involving a combination of natural variability and anthropogenic influences. Key factors identified include global warming, alterations in wind patterns, sea surface temperature anomalies, and increased freshwater input from melting ice caps and glaciers. These elements interact in intricate ways to influence the dynamics of ocean currents, which are critical for regulating Earth's climate and supporting marine ecosystems. Unique Contribution to Theory, Practice and Policy: Bronfenbrenner's Ecological Systems Theory &amp; Abraham Maslow's Hierarchy of Needs may be used to anchor future studies on primary drivers of the recent changes observed in global ocean circulation patterns in Mozambique. Increase investment in global ocean monitoring systems, such as Argo floats, satellite missions, and autonomous underwater vehicles, to collect high-resolution data on temperature, salinity, and currents. This data is crucial for validating models and understanding the current state and trends of ocean circulation. Strengthen international cooperation to address global warming, a primary driver of changes in ocean circulation. This includes adhering to and expanding commitments under the Paris Agreement to reduce greenhouse gas emissions.

Growth and pinch-off of sidearm necks: a model of dendrite fragmentation

Dendrite fragmentation commonly occurs by pinch-off of sidearms at the narrow neck with the parent stem. Comprehensive measurements of the local neck dynamics are performed using in-situ synchrotron radiography experiments in which a flat sample of a Ga–35wt%. In alloy is solidified under both steady and transient growth conditions with minimal effects of melt convection. The measurements reveal two characteristic limits where the neck radius follows universal self-similar t1/3 power laws, with a positive rate constant in the limit of steady growth and a negative rate constant in the isothermal pinch-off limit. The temporal power law for steady growth found here relates the sidearm neck radii to the tip radius of the primary dendrite stem, and the neck radius probability density distribution is shown to be symmetric. For the more general case of decelerated growth, it is observed that the neck initially widens along the steady growth limit, is then increasingly limited by the pinching tendency, and for sufficiently large decelerations converges ultimately to the pinch-off limit. A dynamical model is derived that predicts the behavior of the sidearm neck radius under arbitrary decelerating growth conditions. The highly variable nature of dendrite fragmentation is explained by the stochastic properties of the initial sidebranch development process. The model can be used to estimate the number of dendrite fragments forming during a certain time interval at any location behind the primary tips.