Diameter Distribution Research Articles

Diameter-Controlled Synthesis of Carbon Nanotubes Using [2n]Collarenes as Rigid Organic Templates.

An effective route to diameter-controlled single-walled carbon nanotubes (SWCNTs) remains elusive. The use of organic templates to precisely control the diameter of the resulting nanotubes holds great promise in this regard but has hitherto had very limited practical success. A main obstacle is the limited availability of suitable organic templates. Here, we report the diameter-controlled bottom-up synthesis of SWCNTs with elaborately designed [2n]collarenes, hydrocarbon belts consisting of alternating phenylene and 1,4-cyclohexadiene rings, as rigid organic templates. A new approach has been developed to construct these collarenes, which are then used as templates in the bottom-up growth of SWCNTs. The resulting SWCNTs exhibit narrow diameter distributions, matching the diameters of the employed collarene templates. This work greatly propels the synthesis of diameter-controlled SWCNTs.

Effects of low temperature on near-nozzle breakup and droplet size distribution in airblast kerosene spray

Atomization of low-temperature fuel is encountered in extreme operating conditions of liquid propulsion systems such as cold start and high-altitude relight for aeroengines. Fuel temperature has a great impact on airblast spray characteristics by influencing fuel viscosity and thus the gas–liquid interaction, which raises the demand to clarify the temperature-dependent transition in near-nozzle breakup behavior and the corresponding droplet size distribution. A liquid-centered swirl coaxial injector is tested on the low-temperature swirl spray and combustion test rig at Zhejiang University, using 25 kHz high-speed digital off-axis holography. RP-3 aviation kerosene is atomized under ignition conditions at temperatures of 233, 253, and 301 K, fuel pressures of 0.03 and 0.69 MPa, and air pressure ranging from 0 to 4.0 kPa. Time-resolved near-nozzle dynamics suggest four types of elementary breakup processes: wavy-sheet breakup, pulsating breakup, membrane-type breakup, and nonaxisymmetric Rayleigh breakup. Each process alternately dominates the near field as fuel Reynolds number (Ref) and aerodynamic Weber number (Weg) decrease, corresponding to four primary breakup modes. A mode classification plot is summarized. Spray structures show an extended breakup length and reduced spray cone angle as fuel temperature (Tf) decreases. Increasing air pressure (Pg) promotes spray expansion at 0.03 MPa, but contracts spray cone at 0.69 MPa. Cross-sectional Sauter mean diameter (SMD) distribution indicates a solid-cone spray at 0.03 MPa and a hollow cone spray at 0.69 MPa. Lowering Tf will rise the SMD in the spray center at 0.03 MPa and transform the toroidal SMD distribution at 0.69 MPa into a solid one. Finally, a temperature-related SMD model is derived considering the exponential viscosity–temperature relationship, and a good fit with R2 > 0.95 is achieved. This research aims to deepen the understanding of the effects of low temperature on the transition of near-nozzle atomization characteristics for airblast sprays. Both spray visualization and SMD results provide reference for numerical simulations and near-nozzle spray modeling.

Electrospun hydrophilic PAN/CO/TA composite nanofibrous membrane for adsorbing Cu(II) in water

In this paper, a novel polyacrylonitrile (PAN)/collagen (CO)/tannic acid (TA) composite nanofiber membrane for the adsorption of Cu(II) in water was prepared. The nanofibrous membranes were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), thermogravimetric (TG), and water contact angle (WCA) techniques, and their adsorption performance on Cu(II) in water was tested. The results showed that incorporating CO improved the hydrophilic performance of the membranes, and the contact angle of PAN/CO decreased from 60.57° to 39.16° with the increase of CO content, which exhibited good hydrophilicity. Moreover, CO effectively crosslinked TA, so that TA was well fixed on the surface of the fiber membrane, and the resulting PAN/CO/TA composite nanofiber membrane had good fiber morphology, uniform fiber diameter distribution, with an average diameter of 292.22 nm, and good adsorption performance for Cu(II), up to 133.26 mg/g. The adsorption kinetics fitting showed that the adsorption mechanism was mainly electrostatic adsorption and chelation of Cu(II) by phenoxy anion. PAN/CO/TA and PAN/CO/TA/Cu nanofiber membranes showed bacteriostatic effects on E. coli and S. aureus, with PAN/CO/TA/Cu nanofiber membranes being particularly effective, with the average inhibition bands for E. coli and S. aureus being 7.50 mm and 10.05 mm, respectively. The distribution of the electric field during the spinning process was also simulated by finite element analysis in this study. Since TA is a natural polymer of plant origin and CO is of animal origin, it provides an environmentally friendly and cost-effective method to remove Cu(II) from water.

Detailed analysis on primary and secondary break up characteristics of liquid fuel jet in crossflow using homogeneous mixture model and large eddy simulation

The detailed breakup characteristics of the liquid jet fuel, Jet-A, in crossflow to various ranges of momentum flux ratios and Weber numbers have been investigated using a high-fidelity compressible multi-phase numerical technique. Multi-phase large eddy simulation with adaptive mesh refinement and Eulerian to Lagrangian transformation are applied to the homogeneous mixture model. The liquid surface instabilities and their frequencies inside the injector orifice are observed and analyzed. Interactions between liquid jet and crossflow result in phenomena such as horse-shoe vortex formation, boundary separation, liquid trailing, and counter-rotating vortex pair. Liquid column breakup characteristics and wave structures are analyzed from both temporal and spatial viewpoints. The Sauter mean diameter distribution and cumulative distributions of droplets resulting from secondary breakup are presented, along with the droplet size distribution derived from the momentum flux ratio and Weber number. Several engineering models, including the instability frequencies, the breakup length, and the penetration depth, are proposed in terms of the momentum flux ratio and Weber number, providing valuable insights for injector and combustor design.

Efficient Growth of 1D Van der Waals Heterostructures on Zeolite-Supported SWCNTs.

The controlled synthesis of 1D van der Waals (1D vdW) heterostructures, specifically single-walled carbon nanotubes encapsulated within boron nitride nanotubes (SWCNT@BNNT), presents a challenge due to an incomplete understanding of the factors influencing BNNT growth. This study investigates the growth yield of SWCNT@BNNT heterostructures produced using zeolite-supported SWCNT templates on SiO2-coated Transmission Electron Microscopy (TEM) grids, which enable in situ synthesis and thorough evaluation of each step without compromising the nanotube structure. The high-resolution TEM analysis reveals a significant improvement in BNNT coverage on individual nanotubes, increasing from 9% to 42%, through optimization of the ammonia borane precursor amount. A thorough comparison of BNNT growth efficiency is performed using zeolite-supported SWCNT templates against the current benchmark of free-standing SWCNT films, highlighting comparable synthesis yields despite different morphologies and SWCNT diameter distributions. By integrating all Raman and TEM data from the studied SWCNT@BNNT samples, a correlation between BNNT coverage and the intensity of the buckling R-mode of BNNTs is established, providing a reliable criterion for evaluating BNNT growth efficiency in 1D vdW heterostructures. This work advances the understanding and characterization of 1D vdW heterostructures, offering insights into synthesizing hetero-nanotubes using other types of SWCNT templates and paving the way for their diverse applications.

Energy-economic analysis and optimization of a shell and tube heat exchanger using a multi-objective heat transfer search algorithm

This study presents the energy-economic analysis and optimization of a shell and tube heat exchanger. A water-water, segmental baffled shell and tube heat exchanger was designed using the Kern method and analysed by performing energy and economic modelling. The analysis is carried out considering the design variables on the shell side i.e. baffle cut, baffle spacing, shell diameter and tube side variables i.e. tube layout, tube outside diameter, number of tube passes and number of tubes. The multi-objective heat transfer search algorithm was used to optimize the heat exchanger for minimum total cost and maximum heat exchanger efficiency. Multiple optimal solutions were presented using the Pareto optimal curve. TOPSIS selection criteria was used to identify the optimum operating condition. Within the given bounds of the variables, the shell and tube heat exchanger can be operated at a minimum cost of 72,000 $/year resulting in 16.4 % efficiency, or, it can be operated at a maximum efficiency of 81.6 % with a total cost of 275,000 $/year. The scattered distribution of shell diameter, baffle spacing, number of tube passes and number of tubes between the lower and upper bound represent their substantial role in optimizing the heat exchanger performance. The number of tubes and tube passes showed the maximum variation in efficiency, while significantly less impact was observed when the tube layout was altered.

Light-demanding canopy tree species do not indicate past human disturbance in the Yangambi rainforest (Democratic Republic of the Congo)

Key messageIn a former paper, we investigated whether the presence of light-demanding tree species in the forest canopy of the Yangambi Biosphere Reserve (central Congo basin) might be a result of past human disturbances (Luambua et al., Ecol Evol 11:18691–18707, 2021). We focussed on the spatial distribution of the most abundant light demanders, but this approach did not yield conclusive results. In the present study, we focus on all species in the forest and conclude that light demanders are not a transient feature of successional tropical forests but an intrinsic component of old-growth forests in Yangambi.ContextCentral African rainforests are characterised by an abundance of light-demanding tree species, which are aggregated in the canopy but underrepresented in the understorey. A popular explanation is that these forests are recovering from slash-and-burn farming activities preceding the relocation of settlements during the colonial era. In a former paper, we showed that the abundance of light-demanding tree species in the Yangambi Biosphere Reserve (central Congo basin) cannot be unambiguously attributed to past human disturbances, using an approach that focused on the spatial distribution of the most abundant light demanders (Luambua et al., Ecol Evol 11:18691–18707, 2021).AimsAs the former study was inconclusive, the present study aims to further test the assumptions behind the ‘recovery from human disturbance hypothesis’, by considering all species in the forest of Yangambi. We addressed four specific research questions: (i) do light demanders occur in large ‘pockets’ occupying large areas of forest? (ii) Are light demanders abundant? (iii) Do they exhibit a regeneration deficit? (iv) Is species composition in pockets of light demanders different from the surrounding forests?MethodsWe identified the location and size of pockets of light demanders in several transects cumulating to 50 km. We installed permanent inventory plots within and outside these pockets and calculated the diameter and age distributions of light demanders within each pocket. We assessed whether pockets of light demanders are different from surrounding forests, using plot clustering analysis.ResultsOur results showed that light demanders were aggregated, but the pockets were small, scarce, and represent a minor fraction of the total forest area. Furthermore, light demanders were not abundant, even in pockets where they were aggregated. Their age distributions did not show a regeneration deficit. Finally, species composition in pockets of light demanders did not differ substantially from surrounding forests where they were scarce or absent.ConclusionsWe conclude that light-demanding canopy species do not indicate past human disturbance in Yangambi and that they are an intrinsic component of old-growth forests rather than a transient feature of successional forests. Our insights show that the large carbon sink observed in mature forests in this region is not driven by successional forest dynamics.

Impact of Carbon Source on Bacterial Cellulose Network Architecture and Prolonged Lidocaine Release.

The biosynthesis of bacterial cellulose (BC) is significantly influenced by the type of carbon source available in the growth medium, which in turn dictates the material's final properties. This study systematically investigates the effects of five carbon sources-raffinose (C18H32O16), sucrose (C12H22O11), glucose (C6H12O6), arabinose (C5H10O5), and glycerol (C3H8O3)-on BC production by Komagataeibacter hansenii. The varying molecular weights and structural characteristics of these carbon sources provide a framework for examining their influence on BC yield, fiber morphology, and network properties. BC production was monitored through daily measurements of optical density and pH levels in the fermentation media from day 1 to day 14, providing valuable insights into bacterial growth kinetics and cellulose synthesis rates. Scanning electron microscopy (SEM) was used to elucidate fibril diameter and pore size distribution. Wide-angle X-ray scattering (WAXS) provided a detailed assessment of crystallinity. Selected BC pellicles were further processed via freeze-drying to produce a foam-like material that maximally preserves the natural three-dimensional structure of BC, facilitating the incorporation and release of lidocaine hydrochloride (5%), a widely used local anesthetic. The lidocaine-loaded BC foams exhibited a sustained and controlled release profile over 14 days in simulated body fluid, highlighting the importance of the role of carbon source selection in shaping the BC network architecture and its impact on drug release profile. These results highlight the versatility and sustainability of BC as a platform for wound healing and drug delivery applications. The tunable properties of BC networks provide opportunities for optimizing therapeutic delivery and improving wound care outcomes, positioning BC as an effective material for enhanced wound management strategies.

Fabrication of gallic acid containing poly(vinyl alcohol)/chitosan electrospun nanofibers with antioxidant and drug delivery properties

Chitosan-based nanofibers with excellent properties are attractive materials for specific industrial applications of contemporary interest. This work aims to fabricate functional nanofibers based on poly(vinyl alcohol)/chitosan (CS) with an antioxidant and model drug molecule, gallic acid (GA), by electrospinning, followed by cross-linking through glutaraldehyde (PVA-CS-GAs). PVA-CS-GAs were electrospun at two different concentrations by the adjustment of the CS feeding ratio. The detailed characteristics of the as-prepared electrospun nanofibers were elucidated by Fourier Transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), water contact angle (WCA) measurements, thermogravimetric and differential scanning calorimetry (TGA and DSC) analyses. SEM images indicated that the average fiber diameter distribution was in the range of 90–110 nm. The results show that morphology, mean diameter, wettability, and thermal characteristics of the composite nanofibers were affected by the CS feeding ratio. Although the increase in the amount of polar -OH groups with the addition of GA caused an improvement in the hydrophilicity and thermal stability of the electrospun nanofibers, it also caused a decrease in the thermal transition temperatures. Furthermore, antioxidant tests based on DPPH radical scavenging ability and in vitro release studies demonstrated that the cross-linked PVA-CS-GA composite nanofibers have good antioxidant activity and a pH-dependent drug release rate, indicating their potential for implementation in wound healing and drug delivery applications.

Selenium Dioxide Catalyzed Polymerization of N‐doped Poly(benzodifurandione) (n‐PBDF) and Its Derivatives

The recent discovery of highly conductive, solution‐processable, n‐doped poly(benzodifurandione) (n‐PBDF) marks a milestone in the development of conducting polymers. Currently, n‐PBDF is prepared by either duroquinone‐mediated or copper‐catalyzed polymerizations, where scalability and cost‐effectiveness may present challenges. Here, we report a general, scalable, and cost‐effective method for n‐PBDF and its derivatives, namely selenium dioxide (SeO2) catalyzed polymerization. We discovered that a catalytic amount of selenium dioxide leads to high monomer conversions (>99% by NMR). The obtained n‐PBDF exhibits a consistently narrow hydrodynamic diameter distribution and its thin films show high conductivities. Furthermore, we revealed that this polymerization involves a mechanism distinct from the previously reported radical pathway. It involves successive Riley oxidation and aldol polycondensation processes. It was also found that the reduced selenium precipitates from dimethyl sulfoxide (DMSO) when the catalytic cycle is terminated, allowing for a straightforward purification process through centrifugation and filtration. This method thus eliminates the need for the costly and slow dialysis process. Finally, we demonstrated that SeO2 catalyzed polymerization is applicable to n‐PBDF derivatives, proving the generality of this method.

Selenium Dioxide Catalyzed Polymerization of N-doped Poly(benzodifurandione) (n-PBDF) and Its Derivatives.

The recent discovery of highly conductive, solution-processable, n-doped poly(benzodifurandione) (n-PBDF) marks a milestone in the development ofconducting polymers. Currently, n-PBDF is prepared by either duroquinone-mediated or copper-catalyzed polymerizations, where scalability and cost-effectiveness may present challenges. Here, we report a general, scalable, and cost-effective method for n-PBDF and its derivatives, namely selenium dioxide (SeO2) catalyzed polymerization. We discovered that a catalytic amount of selenium dioxide leads to high monomer conversions (>99% by NMR). The obtained n-PBDF exhibits a consistently narrow hydrodynamic diameter distribution and its thin films show high conductivities. Furthermore, we revealed that this polymerization involves a mechanism distinct from the previously reported radical pathway. It involves successive Riley oxidation and aldol polycondensation processes. It was also found that the reduced selenium precipitates from dimethyl sulfoxide (DMSO) when the catalytic cycle is terminated, allowing for a straightforward purification process through centrifugation and filtration. This method thus eliminates the need for the costly and slow dialysis process. Finally, we demonstrated that SeO2 catalyzed polymerization is applicable to n-PBDF derivatives, proving the generality of this method.

Preparation and properties of bio-based PA56/SiO2–NH2 composite nanofiber membranes for high efficiency oil-water separation

With the continuous development of environmental protection and resource recycling demands, the development of bio-based separation membrane materials has increasingly attracted attention. Bio-based polyamide 56 (PA56), exhibiting excellent hydrophilicity, spinnability, and mechanical properties, is expected to complement and replace traditional separation membrane materials. In this study, the electrospinning preparation and structural control of PA56 nanofiber membranes were achieved through the optimization of PA56 content and mixed solvent ratios. The study found that when the PA56 content was 16 wt% and the formic acid to acetone ratio in the mixed solvent was 8:2, the nanofiber diameter distribution was the most uniform. Building on this, amino-functionalized modified silica (SiO2–NH2) nanoparticles were introduced to prepare PA56/SiO2–NH2 composite nanofiber membranes featuring a cobweb-like nanofiber network and micro-nodule structure. The effects of the addition of SiO2–NH2 nanoparticles on the morphology, structure, and properties of the fiber membranes were studied. The results indicate that the control of the mixed solvent ratio and the addition of SiO2–NH2 nanoparticles led to the formation of a cobweb-like nanofiber network and micro-nano nodular structure on the nanofiber surface, enhancing the hydrophilicity of PA56 nanofiber membranes. The M − 3 membrane with a nanoparticle addition amount of 0.8 wt% exhibited high hydrophilicity and underwater superoleophobic properties, achieving efficient separation of stable oil-in-water emulsions with a separation efficiency of 99.8 %. This work provides a new bio-based membrane material and its preparation method for treating oily wastewater using the membrane separation method.

Electric field simulation, structure and properties of nanofiber- coated yarn prepared by multi-needle water bath electrospinning.

To address the issue of low yield in the preparation of nanofiber materials using single-needle electrospinning technology, multi-needle electrospinning technology has emerged as a crucial solution for mass production. However, the mutual interference of multiple electric fields between the needles can cause significant randomness in the morphology of the produced nanofibers. To better predict the influence of electric field distribution on nanofiber morphology, simulation analysis of the multi-needle arrangement was conducted using finite element analysis software. Nanofiber-coated yarn was produced continuously with the core yarn rotating. The water bath was utilized as the receiver of nanofibers on self-made water bath electrospinning equipment. The electric field distribution and mutual interference under seven different needle arrangements was simulated and analyzed by finite element analysis software ANSYS Maxwell. The results indicated that when the needles were arranged diagonally in a staggered pattern and directly above the core yarn, the simulated electric field distribution was relatively uniform, with less mutual interference. The produced nanofibers exhibited a finer diameter and the diameter distribution was more concentrated. In addition, the nanofiber coating showed higher crystallinity and better mechanical properties.&#xD.

Electrospun gelatin/tea polyphenol@pullulan nanofibers for fast-dissolving antibacterial and antioxidant applications.

Bio-based active food packaging materials have a high market demand. We use coaxial electrospinning technology to prepare core-shell structured nanofibers with sustained antibacterial and antioxidant properties. The fiber core layer was composed of gelatin and tea polyphenols, whereas tea polyphenols provide antibacterial and antioxidant properties; the fiber sheath was composed of pullulan polysaccharides with antioxidant properties. By using a scanning electron microscope, it can be seen that the diameter distribution of the prepared nanofibers was uniform and the surface is smooth; using a transmission electron microscope, it can be clearly seen that the nanofibers have a core-shell structure; Fourier Transform Infrared and X-ray diffraction analysis indicate that the nanofibers have an amorphous structure; the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging shows that nanofibers have higher antioxidant properties with the addition of tea polyphenols; antibacterial test showed that nanofibers had obvious inhibitory effect on the growth of Staphylococcus aureus and Escherichia coli; and the nanofiber film dissolution test shows that nanofibers can be used as fast soluble active packaging. Finally, core-sheath-structured nanofibers can serve as active packaging for instant food, possessing both rapid water solubility and excellent antibacterial and antioxidant activity, making water-soluble nanofibers interesting applications in the field of food packaging.

Utilizing polydispersity in three-dimensional random fibrous based sound absorbing materials

The distribution of fiber diameters plays a crucial role in the transport and sound absorbing properties of a three-dimensional random fibrous (3D-RF) medium. Conventionally, volume-weighted averaging of fiber diameters has been utilized as an appropriate microstructural descriptor to predict the static viscous permeability of 3D-RF media. However, the long wavelength acoustical properties of a 3D-RF medium are also sensitive to the smallest fibers, this is particularly true in the high-frequency regime. In our recent research, we demonstrated that an inverse volume-weighted averaging of fiber diameters can effectively serve as a complementary microstructural descriptor to capture the high-frequency behavior of polydisperse fibrous media. In the present work, we reexamine the identification of two representative volume elements (RVEs) which relies on the reconstruction of 3D-RF microstructures having volume-weighted and inverse-volume weighted averaged fiber diameters, respectively in the low-frequency and high frequency regimes. We investigate the implication of such a weighting procedure on the transport and sound absorbing properties of polydisperse fibrous media, highlighting their potential advantages. Furthermore, we discuss the challenges associated with this research field. Finally, we provide a brief perspective of the future directions and opportunities for advancing this area of study.

Supernova Remnants in Clumpy Medium: A Model of Hydrodynamic and Radio Synchrotron Evolution

We present an analytical model of the Σ–D relation for supernova remnants (SNRs) evolving in a clumpy medium. The model and its approximations were developed using the hydrodynamic simulations of SNRs in environments of low-density bubbles and clumpy media with different densities and volume filling factors. For calculation of SNR luminosities we developed the synchrotron emission model, implying the test-particle approximation. The goal of this work is to explain the flattened part of the Σ–D relation for Galactic SNRs at D ≈ 14–50 pc. Our model shows that the shock collision with the clumpy medium initially enhances the brightness of individual SNRs, which is followed by a steeper fall of their Σ–D curve. We used the analytical model to generate large SNR samples on the Σ–D plane, within a span of different densities and distances to the clumpy medium, keeping the observed distribution of diameters. After comparison with the Galactic sample, we conclude that the observed Σ–D flattening and scatter originate in sporadic emission jumps of individual SNRs while colliding with the dense clumps. Statistically, the significant impact of the clumps starts at diameters of ≈14 pc, up to ∼70 pc, with the average density jump at the clumpy medium of ∼220 times, roughly depending on the low density of the circumstellar region. However, additional analysis considering the selection effects is needed, as well as improvement of the model, considering radiation losses and thermal conduction.

Fundamental studies of liquid fuel fraction and droplet diameter distribution of diethyl ether using a double injection strategy

Fundamental studies of liquid fuel fraction and droplet diameter distribution of diethyl ether using a double injection strategy

Impact of deep eutectic solvent pre-treatment on the extraction of cellulose nanofibers

Deep Eutectic Solvents (DESs) have emerged as promising eco-friendly pre-treatment agents for lignocellulosic biomass, offering considerable advantages for the nanofibrillation process. This study investigates the impact of DESs on cellulose fibers morphology, focusing on solubilization phenomena in the amorphous regions that may facilitate cellulose nanofiber production. The pre-treatment process combining a DES (triethylmethylammonium chloride and imidazole, TEMA:IMD) with microwave (MW) energy was optimized to enhance the solubility of cellulosic fibers. A response surface methodology (RSM) was employed to optimize the DES-MW-assisted pre-treatment. Results show that the reaction time and the temperature significantly influence the solubility of cellulosic fibers. The optimized conditions resulted in cellulose fibers with low content of hemicellulose and lignin, high crystallinity index, and improved thermal stability. The effectiveness of DES-MW pre-treatment in producing cellulose nanofibers (CNFs) from native and pre-treated fibers was investigated. Cellulose fibers pre-treated with a DES yielded CNFs with a narrower diameter distribution. Overall, optimized DES-MW pre-treatment offers a promising strategy for the efficient and sustainable extraction of CNFs.

Impact of climate, land management and harvesting patterns on the ecological traits and the population structure of Pterocarpus lucens in West African semi-arid areas

Multipurpose woody plant species experience severe pressure owing to human overexploitation, land management and climate change. In response to their inability to cope with environmental disturbances in their natural range, some species such as Pterocarpus lucens migrate to more suitable areas. To better conserve P. lucens, this study examined the impacts of climate, land management and harvesting practices on its natural populations.This study was conducted in Burkina Faso using a combined gradient approach involving two climatic zones and two land management types. Data on the biological age classes, structural traits and intensities of harvesting were collected on each individual of the species. Linear models were used to assess the effects of the investigated gradients on structural traits of the species. The diameter and height class size distributions were evaluated using the least squares method.The results showed that the species’ pre-reproductive individuals increased significantly (p < 0.05) with climatic and the protection gradient, resulting in an invasive trend of P. lucens in the Sudano-Sahelian protected areas. The species is overexploited in unprotected areas, with the majority of individuals undergoing all pruning intensities. However, while in the Sahelian climatic zone, decreasing pruning rates were observed according to the severity gradient (low intensity 36.02 %, moderate intensity 27.47 %, and severe intensity 19.73 %), an increasing pruning rate was observed in the Sudan-Sahelian climatic zone (low intensity 16.49 %, moderate intensity 17.38 %, severe intensity 24.48 %, and very severe intensity 35.79 %). Linear regression analysis showed a significant effect (p < 0.05) of climate, land management, pruning, and debarking on the structural traits of the species. The diameter class structure revealed unstable populations of the adult stratum in the Sahelian climatic zone, regardless of the land management types. The juvenile stratum of this species exhibited an unstable structure in unprotected areas, regardless of climatic zone.This study highlights the urgent need to implement effective management strategies to mitigate the decline of P. lucens populations in the Sahelian climatic zone and in unprotected areas through its integration in reforestation programmes.

Nomogram based on lymphocyte-associated inflammatory indexes predicts portal vein thrombosis after splenectomy with esophagogastric devascularization

ObjectiveThe relationship between lymphocyte-associated inflammatory indices and portal vein thrombosis (PVT) following splenectomy combined with esophagogastric devascularization (SED) is currently unclear. This study aims to investigate the association between these inflammatory indices and PVT, and to develop a nomogram based on these indices to predict the risk of PVT after SED, providing an early warning tool for clinical practice.MethodsWe conducted a retrospective analysis of clinical data from 131 cirrhotic patients who underwent SED at Lanzhou University’s Second Hospital between January 2014 and January 2024. Independent risk factors for PVT were identified through univariate and multivariate logistic regression analyses, and the best variables were selected using the Akaike Information Criterion (AIC) to construct the nomogram. The model’s predictive performance was assessed through receiver operating characteristic (ROC), calibration, decision, and clinical impact curves, with bootstrap resampling used for internal validation.ResultsThe final model incorporated five variables: splenic vein diameter (SVD), D-Dimer, platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), and red cell distribution width-to-lymphocyte ratio (RLR), achieving an area under the curve (AUC) of 0.807, demonstrating high predictive accuracy. Calibration and decision curves demonstrated good calibration and significant clinical benefits. The model exhibited good stability through internal validation.ConclusionThe nomogram model based on lymphocyte-associated inflammatory indices effectively predicts the risk of portal vein thrombosis after SED, demonstrating high accuracy and clinical utility. Further validation in larger, multicenter studies is needed.