Separation Strategy Research Articles

A View on technology and controls for epidemic preparedness and the growth of COVID-19 disease in Saudi Arabia

This work emphasizes that the best chance of ending the pandemic lies in the Measures that can help us respond to these epidemic threats more effectively than before in the scope of protection from epidemic risks that we were not aware of before the outbreak of the disease, which is to benefit from the study of previous experiences. The work show the importance of technology about how to prepare for and handle any pandemic by discussing a successful case from the past. We examine Saudi Arabia's COVID-19 pandemic response experiences. We proposed a case evolution study from the southern region of Jazan to demonstrate the consequences of these techniques. Data on the daily Jazan COVID-19 infection curve collected from July 1st to September 30th, 2020, was processed using multiple Python software modules, such as encoder-decoder LSTM, 1D-CNN, and Complex network analysis of time series to identify changes within the infection curve's structure. A Gaussian modeling study was performed to compare the data movement with the protection from epidemic risks computed by stratification based on the data group.The network analysis shows that hubs are stable while medium and low-degree nodes are unstable. Also, from the perspective of Gaussian modeling, the COVID-19 infection curve parts indicate that the pandemic in Saudi Arabia is about to peak and move into the second (declining) half of the bell-shaped distribution.Technology in many areas and internet access make Saudi Arabia's social separation strategies a pandemic-eradication success story

Membrane hydrophobicity enhanced by non-solvent induced separation strategy for improving membrane distillation performance

Development of high-performance hydrophobic layer using green and economic method is still urgently on demand for wide applications of membrane distillation (MD). In this study, a novel Janus membrane was prepared by electrospinning polystyrene with the water addition on the surface of hydrophilic electrospun nanofiber substrate. With increasing water content to 3 wt%, the hydrophobic layer is completely converted to be nanofiber-dominate morphology that could be beneficial for water vapor permeation during MD process. The surface roughness, water contact angle value and porosity of the hydrophobic layer are enhanced by the water addition, and the optimized Janus membrane with the hydrophobic layer prepared at the water content of 2 wt% could achieve a high water flux of 33.1 L/m2h and superior salt rejection of >99.9 % when 3.5 wt% NaCl solution was used as the feed solution. The as-prepared Janus membrane shows better performance stability and reusability than the control membrane (without the water addition) within the 24-h continuous operation duration. Our work demonstrates that the proper water addition could be used as a green strategy for fabricating efficient electrospun nanofiber membranes for the direct contact membrane distillation (DCMD) processes.

Tough and stretchable copolymer eutectogels constructed via in situ phase separation for flexible strain sensors

AbstractDeep eutectic solvent (DES)‐based eutectogels, known for their superior ionic conductivity, non‐volatility, biocompatibility, and cost‐effectiveness, have emerged as promising materials for flexible devices. However, the development of tough and stretchable eutectogels remains a significant challenge. Herein, we introduce a one‐step in‐situ phase separation strategy to fabricate tough and stretchable P(MAA‐co‐AAm)/TEAC‐EG copolymer eutectogels through random copolymerization of methacrylic acid (MAA) and acrylamide (AAm) in a tetraethylammonium chloride‐ethylene glycol (TEAC‐EG) DES. The poor compatibility of PAAm segments with TEAC‐EG DES results in the formation of a polymer‐rich phase, leading to energy dissipation during loading. Simultaneously, PMAA segments exhibiting good compatibility with DES, form a solvent‐rich phase that distributes stress and facilitates ion migration. The synergy between these two phases imparts ultratoughness and excellent conductivity to the copolymer eutectogel. The resultant copolymer eutectogel exhibits high strength (2.40 MPa), toughness (22.90 MJ m−3), and remarkable stretchability of 1340%, while demonstrating excellent self‐recovery, self‐healing abilities, and adhesive performance. Notably, its ionic conductivity reaches 1.07 mS cm−1 at 20°C, rendering these eutectogels well‐suited for applications as strain sensors in human motion detection. This study presents a facile approach to tune eutectogel microstructure and properties, thereby expanding their potential applications in high‐performance flexible electronics.

Thermoplastic elastomer obtained by photopolymerization‐induced concomitant macrophase and microphase separations

AbstractWe report on concomitant photoinitiated polymerization‐induced macrophase and microphase separation strategies to produce hierarchically structured recyclable poly(n‐butyl acrylate) based elastomeric materials. The investigated crosslinker‐free formulations are composed of n‐butyl acrylate monomer and a UV photo‐initiator mixed with poly(methyl methacrylate)‐b‐poly(n‐butyl acrylate)‐poly(methyl methacrylate) ABA triblock copolymers. Two different pre‐synthesized copolymers are used to control the macrophase separation. One synthesized by nitroxide‐mediated radical polymerization (NMRP), and a second by anionic polymerization (AP). Essentially, NMRP route leads to copolymer with unsaturated chain ends, activated during UV photopolymerization. On the other hand, the copolymer synthesized by AP are chemically inert. That dissimilarity is also highlighted by time‐resolved FTIR and SAXS, performed to monitor respectively monomer conversion and nanostructure evolution during photopolymerization. The experimental data demonstrate that the reactivity of the triblock copolymer impacts drastically the polymerization kinetics and the self‐assembly processes. Finally, the rheological analysis shows that the produced materials present a solid‐like behavior at low frequencies despite a large PnBA content (i.e., 85 wt%). This property is associated to the phase segregation and to the sample hierarchical morphology.

Synergy of Post-Crosslinked imprinting strategy and silanol chemistry for the anisotropic construction of molecularly imprinted polymers onto Halloysite nanotubes

Searching for alternative porous substrates which can realize anisotropic preparation of “tailor-made” complementary binding sites is an important way to improve the identification efficiency and interfacial stability of the surface molecularly imprinted polymers (SMIPs). In this work, a functional polymer (FP) with multi-functional properties was firstly synthesized using 3-(isobutenyloxy) propyltrimethoxysilane, 1-(vinylbenzyl) thymidine and cinnamoyloxyethyl methacrylate (CEMA) as monomers, and then FP with post-crosslinking property was covalently deposited onto theoutersurfaceof halloysite nanotubes (HNTs) using silanol chemistry to prepare 2′-deoxyadenosine (dA) imprinted sorbents (HNTs-SMIPs). More than 65 % of dA molecules was captured within the first 2.0 h. The number of high affinity site from the total binding sites of HNTs-SMIPs is estimated to be as high as 73.25 %, and the maximum adsorption amount of HNTs-SMIPs is 48.78 μmol g -1 at 25 °C. The imprinting factor (IF) of HNTs-SMIPs towards dA is 1.89, and 79.49 % the adsorption capacity is remained after five adsorption–desorption cycles. In addition, 70.2 % of the dA from spiked human urine samples can be selectively extracted by HNTs-SMIPs. HNTs-SMIPs have excellent interfacial stability and strong affinity for the template molecule dA, and this work provides a new strategy for the specific separation and enrichment of dA.

An End-to-end Deep Clustering Method with Consistency and Complementarity Attention Mechanism for Multisensor Fault Diagnosis

Deep clustering methods have found successful applications in single-sensor data fault diagnosis. However, most of these methods employ separate optimization strategies that overlook the interaction between feature learning and clustering. Moreover, conventional deep learning methods for fault diagnosis often disregard the consistent and complementary information inherent in the multisensor data, resulting in unsatisfactory multisensor fault diagnosis performance. In this study, we introduce a novel End-to-end Deep Clustering Method with Consistency and Complementarity Attention Mechanism, termed EDCM-CCAM, tailored for multisensor fault diagnosis. Firstly, multiple deep autoencoder networks are utilized to concurrently extract the deep representation features from various sensor inputs. Secondly, we introduce a Consistency and Complementarity Attention Mechanism (CCAM) to facilitate multisensor feature fusion, accompanied by the design of two distinct loss functions to fully exploit the consistent and complementary information within multisensor data. Finally, fault pattern recognition in multisensor data is accomplished through Kullback-Leibler (KL) divergence-based clustering, while a joint optimization strategy is employed to simultaneously optimize all components of the EDCM-CCAM. The efficacy of the proposed method is validated on a gearbox dataset, demonstrating superior performance in multisensor fault diagnosis compared to alternative methods.

Efficient recovery of Al foil and regeneration of cathode materials from spent lithium-ion batteries with methanol-citric acid

Efficient separation of cathode materials from current collectors is an important step to simplify the recycling process of spent lithium-ion batteries (LIBs). However, traditional methods have the shortcomings of incomplete separation, release of toxic substances and high cost. Here, the methanol-citric acid solvent (MeOH-CA), prepared from green and low-cost reagents methanol (MeOH) and citric acid (CA), can separate above 99.5 wt% of spent nickel-manganese-cobalt (NCM) cathode materials in 15 min with negligible metal loss at an ultralow temperature of 45 °C. The separated NCM has high purity and no structure changes, and the recovered Al foil is intact and non-corrosive. The mechanism analysis indicates that the reaction between MeOH-CA and Al foil and the inactivation of PVDF by the abundant hydrogen bonds in the MeOH-CA solvent cause the separation. Meanwhile, the formation of AlF3 passivation layer and the ester film on the surface of Al foil prevent further corrosion of Al foil. Through hydrothermal treatment combined with a short thermal annealing, the regenerated NCM delivers a reversible capacity of 151 mAh g−1 at 1C and 117 mAh g−1 after 100 cycles. The facile separation strategy provides a sustainable and economic solution for the recovery of spent LIBs.

Linking and Delinking Aspects of Economic Growth and Employment in the Indian Economy: Granger Causality Approach

The purpose of this paper is to provide an overview of various economic growth and employment approaches that have been popular throughout economic history, with a focus on linking and delinking aspects of GDP and employment in the Indian economy. The semi-log quadratic model was used for the trends of GDP and employment across the selected countries. For the determination of the linkages between the variables, the Granger causality test promulgated by Engel and Granger (1987), and the maximum likelihood-based technique of Johansen and Julius (1990) and Johansen (1992) were used in the study. The results found that employment and GDP are two different aspects of an economy not only in the Indian economy but across the majority of the world economies. The results of model specification proved the presence of both long-run and short-run relationships between GDP and employment by the Johansen co-integration test in the Indian economy over the period. It has been found that the increase in GDP is negatively influencing the employment level by the VECM model as a 1 per cent increase in GDP results in 0.28 per cent of job losses in the Indian economy. This study aims to provide an overview of several approaches to economic growth and employment that have been popular throughout economic history up to the present, with an emphasis on linking and delinking aspects of economic growth and employment. In the context of an economy, economic growth and employment are two distinct aspects that should be tackled with separate economic strategies.

Earnings quality and national IPO: AEM practices of Central Asia

Once the key insights of corporate finance quality in Kazakhstani listed state SOEs are obtained, it is time to turn to separate strategies of corporate reporting manipulations. The purpose of this research is to look at accrual-based AEM strategies that adjust real activity REM practices at year-end. We follow Kasznik cash flow model for accrual-based earnings management as a best practice methodology and apply it to 572 unbalanced panel firm-year non-financial observations over 13-year time horizon. To strengthen our analysis, we compare main results with another popular measurement of accrual-based Earnings management based on the Shivakumar 1996 model. We also winsorised key investment indicators to reduce the impact of outliers on the main results. The results answer major questions: 1) what AEM strategies state SOEs prefer; 2) how accrual-based manipulations affect the choice of investment indicators; and 3) whether partially-privatized state SOEs under/over perform private POEs in Kazakhstan. In terms of theoretical and practical implications, our research findings could be useful to analysts of various strategies in the AEM/REM dimensions, academic scientists and advocates of partial privatization of state companies. We assure that theoretical gaps of corporate data manipulations in Central Asian context are to be reduced with increasing number of publications in the field of AEM practices.

Histidine tag modified magnetic beads for analysis of arsenic binding proteins

BackgroundMany proteins with thiol groups can bind with trivalent arsenic which are termed as arsenic binding proteins, thus change their physiological functions. Therefore, it is vital to analyze the arsenic binding proteins in cells. The Pull-Down strategy based on biotinylated phenylarsenic acid (Bio-PAO(III)) probes is an effective way for analysis of arsenic binding proteins. In this strategy, streptavidin magnetic beads (SA-MBs) was applied to capture the arsenic binding proteins conjugating with Bio-PAO(III) probe. However, strong interaction between SA and biotin makes the elution of arsenic binding proteins not easy. ResultsWe developed a novel affinity separation strategy to address the challenge of eluting arsenic binding proteins, a key issue with the existing Bio-PAO(III) Pull-Down method. By employing magnetic beads modified with Nα-Bis(carboxymethyl)-l-lysine (NTA-Lys), polyhistidine-tag (His6-Tag), and SA (MB-NTA(Ni)-His6-SA), we established a more efficient purification process. This innovative approach enables selective capture of arsenic binding proteins in HepG2 cells labeled by Bio-PAO(III) probes, facilitating gentle digestion by trypsin for precise identification through capillary high performance liquid chromatography (Cap HPLC)-electrospray ionization (ESI)-tandem mass spectrometry (MS/MS). What is more, the magnetic beads can be regenerated by using imidazole as the eluent, and the obtained MB-NTA(Ni) can be reloaded with His6-SA for next use. Our method successfully identified 41 arsenic binding proteins, including those involved in cytoskeletal structure, heat shock response, transcriptional regulation, DNA damage repair, redox state regulation, mitochondrial dehydrogenase function, and protein synthesis and structure. SignificanceThis work contributes to a more comprehensive understanding of the toxic mechanisms of arsenic, potentially providing valuable insights for the prevention or treatment of arsenic-related diseases.

Single proxy control.

Negative control variables are sometimes used in nonexperimental studies to detect the presence of confounding by hidden factors. A negative control outcome (NCO) is an outcome that is influenced by unobserved confounders of the exposure effects on the outcome in view, but is not causally impacted by the exposure. Tchetgen Tchetgen (2013) introduced the Control Outcome Calibration Approach (COCA) as a formal NCO counterfactual method to detect and correct for residual confounding bias. For identification, COCA treats the NCO as an error-prone proxy of the treatment-free counterfactual outcome of interest, and involves regressing the NCO on the treatment-free counterfactual, together with a rank-preserving structural model, which assumes a constant individual-level causal effect. In this work, we establish nonparametric COCA identification for the average causal effect for the treated, without requiring rank-preservation, therefore accommodating unrestricted effect heterogeneity across units. This nonparametric identification result has important practical implications, as it provides single-proxy confounding control, in contrast to recently proposed proximal causal inference, which relies for identification on a pair of confounding proxies. For COCA estimation we propose 3 separate strategies: (i) an extended propensity score approach, (ii) an outcome bridge function approach, and (iii) a doubly-robust approach. Finally, we illustrate the proposed methods in an application evaluating the causal impact of a Zika virus outbreak on birth rate in Brazil.

Electricity generation from carbon dioxide adsorption by spatially nanoconfined ion separation

Selective ion transport underpins fundamental biological processes for efficient energy conversion and signal propagation. Mimicking these ‘ionics’ in synthetic nanofluidic channels has been increasingly promising for realizing self-sustained systems by harvesting clean energy from diverse environments, such as light, moisture, salinity gradient, etc. Here, we report a spatially nanoconfined ion separation strategy that enables harvesting electricity from CO2 adsorption. This breakthrough relies on the development of Nanosheet-Agarose Hydrogel (NAH) composite-based generators, wherein the oppositely charged ions are released in water-filled hydrogel channels upon adsorbing CO2. By tuning the ion size and ion-channel interactions, the released cations at the hundred-nanometer scale are spatially confined within the hydrogel network, while ångström-scale anions pass through unhindered. This leads to near-perfect anion/cation separation across the generator with a selectivity (D-/D+) of up to 1.8 × 106, allowing conversion into external electricity. With amplification by connecting multiple as-designed generators, the ion separation-induced electricity reaching 5 V is used to power electronic devices. This study introduces an effective spatial nanoconfinement strategy for widely demanded high-precision ion separation, encouraging a carbon-negative technique with simultaneous CO2 adsorption and energy generation.

Isomers-oriented separation of forty-five plasma bile acids with liquid chromatography-tandem mass spectrometry

Some bile acids (BAs) were considered as biomarkers or have therapeutical effect on metabolic diseases. However, due to the existence of isomers and limitations in sensitivity, simultaneous quantification of multiple BAs remains a challenge. The aim of this study is to establish an accurate and sensitive method for the determination of multiple BAs with similar polarity. A LC-MS/MS analytical method capable of quantifying forty-five BAs simultaneously using nine stable isotope internal standards was developed and fully validated based on key isomers-oriented separation strategy. The method was further applied to analyze plasma samples to describe the dynamic profile of BAs after high glucose intake. The chromatography and mass spectrum conditions were optimized to enable the accurate quantification of forty-five BAs, while ensuring the lower limit of quantification between 0.05–10 ng/mL. The results of system suitability, linearity, dilution integrity, accuracy and precision demonstrated the good quantitative capacity and robustness of the method. A total of thirty-five BAs were quantified in plasma samples from twelve healthy Chinese individuals. The established method featured superior sensitivity and better separation efficiency compared to previous studies. Meanwhile, BAs exhibited correlations with glucose and insulin, suggesting their potential as biomarkers for metabolic disorders.

Inhibition strategies for phase separation of iron-based oxygen carriers in chemical looping gasification- enhanced oxygen transport efficiency through oxide-support interactions

Chemical looping gasification partially oxidizes biomass to obtain high-quality syngas using oxygen carriers, emerging as a potential method to cope with energy shortages. However, the oxygen carriers were susceptible to deactivation due to phase separation caused by different migration rates between atoms. In this work, the phase deviation of the oxygen carrier is inhibited by enhancing the lattice oxygen activity. Typically, the NiFe-based oxygen carriers were used as active sites and Ce atoms were introduced to change the lattice structure of the oxygen carriers. Calculated by density functional theory (DFT), Ce atoms formed a strong bonding interaction (Ni-O-Ce) with Ni atoms, causing lattice distortion of NiFe oxygen carriers that promote the formation of oxygen vacancies. Therefore, the syngas yields were increased from 537 ml/g (NF) to 633 ml/g (NF@0.5Ce) and 615 ml/g (NF@1.5Ce) in the N2 atmosphere. The syngas yields were increased from 895 to 1101 ml/g (NF@0.5Ce) and 1186 ml/g (NF@1.5Ce) with steam atmosphere. During the 20-cycle experiments, the phase separation of NiFe-based oxygen carriers was effectively suppressed by the intervention of Ce atoms. Therefore, it is a feasible option to induce lattice distortion of active grains by introducing inert elements to suppress phase separation.

A novel, low-cost, and efficient separation strategy based on S-doped C3N4 for the analysis of PCDD/Fs and dioxin-like PCBs

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) are widespread and highly toxic persistent organic pollutants with similar chemical structure. The popular process for the separation of PCDD/Fs and dl-PCBs in one sample often relies on imported and expensive activated carbon, giving rise to an urgent need of inexpensive and efficient separation method. Herein, a novel, simple, and low-cost separation strategy based on sulfur-doped carbon nitride (S-C3N4) is reported. The S-C3N4 material was synthesized through simple thermal annealing with precursor of thiocyanuric acid. After recovery experiments, the optimal addition ratio of S-C3N4 was determined to be 40% mixed with silica gel. The recoveries for PCDD/Fs and dl-PCBs congeners are 32% - 105% and 60% - 70% respectively, which not only meets USEPA and Chinese standards but also shows comparable performance to activated carbon. Moreover, the proposed S-C3N4 strategy exhibits excellent performance for the analysis of PCDD/Fs and dl-PCBs in real complex samples (sediment and fish liver) in terms of detected concentrations and toxic equivalents. Overall, this study puts forward a new and low-cost avenue for the separation of PCDD/Fs and dl-PCBs, which is of remarkable meaning for motivating the development of detection techniques and domestic equipment for dioxins and other pollutants in the environment.

Atomic-level charge separation boosting the photocatalytic hydrogen evolution

The synergistic implementation of atomic-level charge separation strategies for bulk–surfaces is a meaningful study that fundamentally addresses the shortcomings of single materials. Here, we report for the first time the atomic-level engineering of atomic doping in combination with surface ion grafting, which can be coordinated to significantly facilitate photocatalytic H2 evolution. More impressively, the study systematically investigated the atomic doping effects of Fe, Co, Ni and Cu atoms, and analyzed the conditions for optimal doping with experimental and theoretical calculations. The doping of variable valence Cu atoms leads to the emergence of newly occupied electronic states at the Fermi energy level, which effectively improves the carrier separation. The X-ray absorption spectroscopy (XAS) results verified the precise coordination environments of the doped Cu atoms, as well as confirmed the solid grafting of Ni ions on the catalyst surface. Furthermore, the hydrogen production rate of 1.2 % Cu–Zn0.67Cd0.33S–0.5 wt% Ni reached 38.17 mmol/g/h, corresponding to an apparent quantum efficiency of 35.5 %, which is 82.8 times higher than that of pure ZCS. Besides, the H2 production rate can reached 118.73 mmol/g/h without cooling. Meanwhile, the synergistic strategy of manipulating the bulk and surface photo-charges of Zn0.67Cd0.33S also effectively enhances the photothermal effect and further improves its photocatalytic performance. This work provides different inspirations for bottom-up design of efficient photocatalysts to achieve synergistic facilitation strategies.

Reversibly Cross-Linked Isoporous Membranes Fabricated by the Recyclable Block Copolymer with Pendent Dithiolane Groups.

The reversible formation and cleavage of disulfide bonds under physical/chemical stimuli make it a valuable motif in constructing dynamically cross-linked materials. In the present work, the block copolymer bearing pendent dithiolanes was synthesized and fabricated into isoporous membranes by the combination of self-assembly and nonsolvent-induced phase separation strategy. The cross-linking within the membrane was realized by the thiol-initiated ring-opening cascades of cyclic disulfides. Successful formation of disulfide bond networks within the isoporous membranes was proved by the Raman spectra, UV-vis diffuse reflectance spectroscopy, differential scanning calorimetry, and rheological analysis. The cross-linking in membranes was further demonstrated by the notably improved toughness and obviously enhanced swelling resistance to acid/alkaline solution as well as organic solvents. Importantly, the cross-linked isoporous membranes were fully dissolvable in solution containing dithiothreitol, which enabled the complete cleavage of disulfide bonds and successful recovery of the block copolymer that was able to be repeatedly fabricated into isoporous membranes with pore sizes identical to membranes prepared from the freshly synthesized copolymer. Our results indicate that dynamically cross-linked isoporous membranes with improved durability and good recyclability can be custom-made by simply incorporating active dithiolane moieties into self-assembling block copolymers.

The role of university–industry partnership in innovative curriculum development: A case study of South African universities in the fourth industrial revolution

This study was motivated by the need to strategically implement changes propelled by the advent of the fourth industrial revolution (4IR) to meet the increasing demand for theoretical skills required by industries for regional and global competitiveness through a university–industry partnership among South African universities. A total of 22 out of 26 South African Universities were purposefully selected for the study. A survey design was adopted in which a structured online interview was conducted with 70 out of 188 Deans/Executive Deans of faculties through the Microsoft Teams and Zoom platforms. The results show that most of the academic faculties had implemented the specific guidance provided by industry partners and relevant associations into the curriculum for teaching and learning at the faculty level. However, only 18% of the Deans/Executive Deans had the 4IR as a separate strategy formulated in their institutions, while about 30% of faculty Deans/Executive Deans had 4IR strategies integrated into the existing institutional strategy. Further findings revealed the unwillingness of the faculties of Engineering and the Built Environment and the faculty of science to embrace any form of institutional guidelines for responding to evolutionary change and for implementing the 4IR in their activities. They preferred to remain open to innovation and respond in the best way possible rather than being stiffened by organizational policy.

Preparation of highly elastic superhydrophobic CNF/Fe3O4 based materials modified in aqueous phase for oil-water separation

Magnetic superhydrophobic materials have broad application prospect in oil-water separation. In this study, a magnetic and superhydrophobic aerogel with lamellar structure was successfully prepared using cellulose nanofibrils (CNF) as the skeleton, Fe3O4 as the magnetic ion, 1H, 1H, 2H, 2H trialkylfluorooctane triethoxysilane (FS) and 3-(2-aminoethyl amino)-propyl trimethoxysilane (AS) as the combined modifier. The prepared aerogel shows lower density (38.63 mg/cm3), excellent magnetic (15.13 emu/g), high elasticity and good oil sorption properties (21 g/g). In addition, FS/AS also exhibits excellent mechanical properties and superhydrophobic ability (water contact angle (WCA) of 151.9 ± 1.4°), as it provides sufficient toughness and low surface energy for the layer-branch structure. It should be noted that the entire preparation process is carried out in the aqueous phase, without the use of any organic solvents, providing a green oil-water separation strategy.

Giraffe lineages are shaped by major ancient admixture events

Strong genetic structure has prompted discussion regarding giraffe taxonomy,1,2,3 including a suggestion to split the giraffe into four species: Northern (Giraffa c. camelopardalis), Reticulated (G.c. reticulata), Masai (G.c. tippelskirchi), and Southern giraffes (G.c. giraffa).4,5,6 However, their evolutionary history is not yet fully resolved, as previous studies used a simple bifurcating model and did not explore the presence or extent of gene flow between lineages. We therefore inferred a model that incorporates various evolutionary processes to assess the drivers of contemporary giraffe diversity. We analyzed whole-genome sequencing data from 90 wild giraffes from 29 localities across their current distribution. The most basal divergence was dated to 280 kya. Genetic differentiation, FST, among major lineages ranged between 0.28 and 0.62, and we found significant levels of ancient gene flow between them. In particular, several analyses suggested that the Reticulated lineage evolved through admixture, with almost equal contribution from the Northern lineage and an ancestral lineage related to Masai and Southern giraffes. These new results highlight a scenario of strong differentiation despite gene flow, providing further context for the interpretation of giraffe diversity and the process of speciation in general. They also illustrate that conservation measures need to target various lineages and sublineages and that separate management strategies are needed to conserve giraffe diversity effectively. Given local extinctions and recent dramatic declines in many giraffe populations, this improved understanding of giraffe evolutionary history is relevant for conservation interventions, including reintroductions and reinforcements of existing populations.