Actual Density Research Articles

Geospatial Data Analysis of School Distribution in Baghdad City

Education and lifelong learning are necessary components of daily city life for urban communities to encourage sustainable and positive communities. The study attempts to analyze the actual school distribution patterns and densities in Baghdad, the Iraqi capital. The significance of this study is that it is associated with one of the essential aspects of humanity: the improvement and affluence of schooling; it impacts school attendance limitations and educational evolution. The education process has been inextricably tied to students' timely and orderly entrance to their schools. Hence the decision maker and planner are concerned by this. The statistics examined elementary and high schools, and the investigated data are related to the Ministry of Education that was available in 2004. Regarding spatial analysis and results assessment, this work employs Microsoft Excel techniques, ArcGIS, C# simulator, and the buffer methodology. It has depicted the school densities and assessed the distances between them using spatial analytic techniques. The study reveals that the school distribution is uneven, and there is a disparity among neighbors in the spatial distribution. Also, the in-between distances of observed schools formulate four significant patterns. At the same time, this study offers important information about the spatial distribution of schools as a significant influencing indicator. In the future, it will be beneficial to investigate the student's geographical accessibility to their residence and the transportation to/from these schools.

High-entropy alloy reinforcement in aerospace-grade aluminum 7075: A study of yield strength and elastic modulus

This research aims to identify an appropriate theoretical model for assessing the yield strength and elastic modulus of a composite material consisting of aerospace-grade aluminum 7075 base matrix reinforced with nanocrystalline high-entropy alloy particle (HEAp) composed of CrCuFeMnNi. To fabricate the aluminum composite with a high-entropy alloy base, an innovative casting method was utilized. This method involved the use of a modified bottom-pouring stir casting furnace, integrated with a mechanical supersonic vibrator and a squeeze infiltration setup. The measured theoretical density was higher than the actual density, while the cast specimen exhibited porosity below 6.6%. Scanning electron microscopy (SEM) images revealed the presence of strengthening precipitates and a uniform dispersion of HEAp in the composite. Comparing the developed HEAp composites (CH2, CH3, and CH4) with the base AA7075 cast CH1 (AA7075 + 0 wt.% CrCuFeMnNi-HEAp), the ultimate tensile strength increased by 4% for CH2 (5 wt.% CrCuFeMnNi-HEAp), 21% for CH3 (10 wt.% CrCuFeMnNi-HEAp), and decreased by 9% for CH4 (15 wt.% CrCuFeMnNi-HEAp). Similarly, the yield strength increased by 10% for CH2, 24% for CH3, and decreased by 5% for CH4. The elongation showed an increasing trend of 5% for CH2, 12% for CH3, and 2% for CH4. The flexural strength of the HEAp composites (CH2, CH3, and CH4) increased by 2%, 5%, and 10%, respectively. The proposed model yielded similar yield strength values that closely aligned and were consistent with the experimental value within a deviation of 3.32%. The modified Halpin-Tsai models agreed with experimental value up to a reinforcement volume fraction of 4.89% when calculating the elastic modulus. The proposed model and the Hashin-Shtrikman upper bound also agreed on values up to a 3.32% reinforcement volume fraction.

Sarcomere level mechanics of the fast skeletal muscle of the medaka fish larva.

The medaka fish (Oryzias latipes) is a vertebrate model used in developmental biology and genetics. Here we explore its suitability as a model for investigating the molecular mechanisms of human myopathies caused by mutations in sarcomeric proteins. To this end, the relevant mechanical parameters of the intact skeletal muscle of wild-type medaka are determined using the transparent tail at larval stage 40. Tails were mounted at sarcomere length of 2.1 μm in a thermoregulated trough containing physiological solution. Tetanic contractions were elicited at physiological temperature (10°C-30°C) by electrical stimulation, and sarcomere length changes were recorded with nanometer-microsecond resolution during both isometric and isotonic contractions with a striation follower. The force output has been normalized for the actual fraction of the cross section of the tail occupied by the myofilament lattice, as established with transmission electron microscopy (TEM), and then for the actual density of myofilaments, as established with X-ray diffraction. Under these conditions, the mechanical performance of the contracting muscle of the wild-type larva can be defined at the level of the half-thick filament, where ∼300 myosin motors work in parallel as a collective motor, allowing a detailed comparison with the established performance of the skeletal muscle of different vertebrates. The results of this study point out that the medaka fish larva is a suitable model for the investigation of the genotype/phenotype correlations and therapeutic possibilities in skeletal muscle diseases caused by mutations in sarcomeric proteins.NEW & NOTEWORTHY The suitability of the medaka fish as a model for investigating the molecular mechanisms of human myopathies caused by mutations of sarcomeric proteins is tested by combining structural analysis and sarcomere-level mechanics of the skeletal muscle of the tail of medaka larva. The mechanical performance of the medaka muscle, scaled at the level of the myosin-containing thick filament, together with its reduced genome duplication makes this model unique for investigations of the genotype/phenotype correlations in human myopathies.

An Ultrafast, Durable, and High-Loading Polymer Anode for Aqueous Zinc-Ion Batteries and Supercapacitors

With high theoretical capacities (820 mAh g−1 and 5855 mAh cm−3), suitable electrochemical potential (−0.763 V vs standard hydrogen electrode), low cost, and rich abundance of component materials, aqueous zinc-ion batteries (ZIBs) and capacitors (ZICs) have exhibited great promise for grid-level energy storage and other stationary applications. Zn metal as excessive Zn are often used to compensate for the uncontrollable dendritic growth, corrosion behaviour, and low Coulombic efficiency (CE) of the Zn metal. As such, most of the ZIBs and ZICs developed using these electrode materials exhibited actual device energy and power densities that were significantly lower than the corresponding theoretical values. Another key performance metric that needs to be improved in ZIBs is their high-rate charge and discharge. In addition to the dendrite-derived problems commonly experienced in batteries based on other metal anodes, ZIBs are disadvantaged by hydrogen gas evolution from water decomposition especially under high-rate charge/discharge, leading to poor cycle life.Herein, an ultrafast, stable, and high-loading polymer anode for aqueous Zn-ion batteries and capacitors (ZIBs and ZICs) is developed by engineering both the electrode and electrolyte. The anode polymer is rationally prepared to have a suitable electronic structure and a large π-conjugated structure, whereas the electrolyte is manufactured based on the superiority of trif late anions over sulfate anions, as analyzed and confirmed via experiments and simulations. This dual engineering results in an optimal polymer anode with a low discharge potential, near-theoretical capacity, ultrahigh-loading capability (≈50 mg cm−2), ultrafast rate (100 A g−1), and ultralong lifespan (one million cycles). Its mechanism involves reversible Zn2+/proton co-storage at the carbonyl site. When the polymer anode is coupled with cathodes for both ZIB and ZIC applications, the devices demonstrate ultrahigh power densities and ultralong lifespans, far surpassing those of corresponding Zn-metal-based devices. Figure 1

Toward Stimulating the Chemistry Process for Garnet Electrolyte-Based Molten Li-S Batteries: Modulation of the End-Product in the Cathode with High Loading.

Due to their low self-discharge rate, no intermediate product dissolution in the cathode, and easy recycle of electrode materials, solid electrolyte-based molten lithium sulfur batteries can be one of the highly anticipated advanced electrochemical chemistry technologies for grid-scale energy storage. However, the actual energy density and reversibility of them still face severe challenges for low active materials loading and the inherent low conductivity of sulfur and its end-products. In this work, with the iodide modulation effect, small size (∼5 nm for the primary particles) and low relative crystallinity discharge end-products in the sulfur cathode can be formed, contributing to the immense specific capacity and reversibility. As validated by theoretical calculations, iodide ions in the homogeneous molten composite cathode display a profound comprehensive effect on the chemical reaction and cycling stability. As a result, high sulfur loading (over 80 mg cm-2) with a significant utilization rate can be achieved, corresponding to a single Li-S cell of 1.39 Ah and a volumetric energy density of 528.5 Wh L-1 based on the overall cell volume; simultaneously, a prominent cycling stability during 300 cycles along with an impressive reversibility is obtained.

Gravimetric analysis of lithium-air batteries during discharge/charge cycles

Because the mass of lithium-air battery (LAB) changes due to oxygen reduction/evolution reactions (ORR/OER), weighing of the battery is an indispensable method for determining its actual energy density and analyzing the battery reactions. To this end, we have newly developed a weight monitoring system which can trace the semi-permanent weight change of air-batteries (∼11 g including a holder) with a precision of 7.87 μg. The system reveals the weight decrease of LAB in each cycle before finally losing its capacity. The in-situ weighing during battery operation also provides first-hand evidence of double layer capacitance and electrolyte evaporation of LABs. Specifically, the e−/O2 ratio during discharge is determined to be 1.954 ± 0.004 based on the weight increase of an LAB cell using tetraethylene glycol-based electrolyte at a current density of 100 μA cm−2, confirming the slightly lower e−/O2 ratio than the ideal two electron ORR. During charge, the initial weight decrease is 5.4% less than the 2e−/O2 OER process, and the weight decreases sharply at the end of charge due to CO2 evolution. The main rates of weight increase/decrease remain the same throughout the cycle life, but side reactions are accelerated with cycling, causing the deterioration of LABs.

The Effects of the Al and Zr Contents on the Microstructure Evolution of Light-Weight AlxNbTiVZry High Entropy Alloy.

To investigate the comprehensive effects of the Al and Zr element contents on the microstructure evolution of the AlNbTiVZr series light-weight refractory high entropy alloys (HEAs), five samples were studied. Samples with different compositions were designated Al1.5NbTiVZr, Al1.5NbTiVZr0.5, AlNbTiVZr, AlNbTiVZr0.5, and Al0.5NbTiVZr0.5. The results demonstrated that the actual density of the studied HEA samples ranged from 5.291 to 5.826 g·cm-3. The microstructure of these HEAs contains a solid solution phase with a BCC structure and a Laves phase. The Laves phase was further identified as the ZrAlV intermetallic compound by TEM observations. The microstructure of the AlNbTiVZr series HEAs was affected by both the Al and Zr element contents, whereas the Zr element showed a more dominant effect due to Zr atoms occupying the core position of the ZrAlV Laves phase (C14 structure). Therefore, the as-cast Al0.5NbTiVZr0.5 sample exhibits the best room temperature compression property with a compression strength (σp) of 1783 MPa and an engineering strain of 28.8% due to having the lowest ZrAlV intermetallic compound area fraction (0.7%), as characterized by the EBSD technique.

Wear Characteristics of (Al/B4C and Al/TiC) Nanocomposites Synthesized via Powder Metallurgy Method

Objective: The aim of the present work is to study the microstructure, wear behavior, physical properties, and micro-hardness of the aluminum matrix AA6061 reinforced with TiC and B4C nanoparticles with different concentrations of 2.5, 5, 7.5, 10, and 12.5 wt.%. Methodology: Al/B4C and Al/TiC nanocomposites were fabricated with a powder metallurgy route. A dry sliding wear test was performed with a pin-on-disc machine. The wear test was performed at the applied loads of 3, 6, 9, 12, and 15 N at a constant time for about 10 min. The microstructural analysis of the fabricated nanocomposites was examined via field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) analysis. The obtained data: The results of this work show that increasing the applied load leads to a decrease in the wear rate of the aluminum matrix and its nanocomposites. The wear rate of the aluminum matrix without any additives is about 7.25 × 10−7 (g/cm), while for Al/TiC and Al/B4C, it is 5.1 × 10−7 (g/cm) and 4.21 × 10−7 (g/cm), respectively. An increment in B4C percent increases the actual density, while an increment in TiC percent minimizes the actual density at 2.90 g/cm3 and 2.51 g/cm3, respectively. An increment in B4C percent decreases by 4.61%, while the porosity slightly increases with increases in TiC percent of 6.2%. Finally, the micro-hardness for Al/B4C is about 92 (HRC), and for Al/TiC, it is about 87.4 (HRC). Originality: In the present work, nanocomposites were fabricated using a powder metallurgy route. Fabricated nanocomposites are important in engineering industries owing to their excellent wear resistance, low thermal distortion, and light weight compared with other nanocomposites. On the other hand, Al/B4C and Al/TiC nanocomposites fabricated with a powder metallurgy route have not previously been investigated in a comparative study. Therefore, an investigation into these nanocomposites was performed.

Hopf bifurcation control of macroscopic traffic flow model considering vehicle braking effect.

Traffic congestion not only has a great impact on people's travel, but also increases energy consumption and air pollution. The control analysis of the macroscopic traffic flow model considering the vehicle braking effect is particularly important, reflecting the impact on the actual traffic flow density wave, so as to better solve the actual traffic problems. In this paper, based on a speed difference optimization speed model, the micro-macro-variables are transformed into a high-order continuous traffic flow model. Then, a random function considering the physical correlation of random components is added to the high-order continuous traffic flow model to establish a random traffic flow model that can reflect the uncertain behavior of traffic flow acceleration or deceleration. Based on this stochastic traffic model, the existence of Hopf bifurcation and bifurcation control of the traffic flow system model considering stochastic characteristics are derived by using Hopf bifurcation theorem. By Chebyshev polynomial approximation method, the stochastic problem of the system is transformed into the bifurcation control problem of its equivalent deterministic system. A feedback controller is designed to delay the occurrence of Hopf bifurcation and control the amplitude of the limit cycle. Without changing the equilibrium point of the system, the complete elimination of Hopf bifurcation can be achieved by controlling the amplitude of the limit cycle. That is, the feedback controller is used to modify the bifurcation characteristics of the system, such as the bifurcation appearing at the equilibrium point in the control system moves forward, moves backward or disappears, so as to achieve the effect of preventing or alleviating traffic congestion.

Wheat Quantity Monitoring Methods Based on Inventory Measurement and SVR Prediction Model

Due to the influences of the storage environment, water content change, particle settlement, natural loss, and other factors, the distribution density of wheat and the volume of grain pile in the storage process are gradually changed so that the single weight calculation method cannot objectively evaluate the storage quantity of wheat and also causes difficulties to the regular inspection of the quantity of wheat stock. To meet the practical needs of wheat inventory monitoring, a wheat inventory monitoring method based on inventory measurement and the support vector machine regression (SVR) prediction model is proposed. By collecting the working papers for the physical inspection of wheat in grain warehouses in Shanxi province, Hebei province, Henan province, Jiangsu province, and other places, the storage time, storage weight, storage moisture content, measured moisture content, measured volume weight, measured net volume, and measured weight for inspection were selected as training samples for the SVR prediction model, and kernel function selection and parameter optimization were carried out. We developed an optimal prediction model for the amount of wheat in the grain depots. In the actual grain store measurement process, the net volume of wheat in the current grain store was obtained by a laser volumetric measuring apparatus, the actual bulk density of wheat was sampled, and the actual moisture content of wheat was measured by sampling. The three samples, their storage time, their storage moisture content, and their storage weight were fed into the trained SVR prediction model as new samples, and the predicted weight of the wheat in the current grain store was obtained from the output. The error rate calculation procedure was introduced to achieve an anomalous judgment error rate for grain depots. The experimental results showed that the SVR prediction model based on the linear kernel function had a very low mean squared error and high determination coefficient, and the average prediction accuracy of the grain stock error rate reached 93.2 percent, which can meet the requirements of wheat quantity monitoring in grain warehouses.

Pembuatan Komposit dari Serat Sabut Kelapa dan Resin Polyester sebagai Material untuk Helm

A composite is a material made from a combination of two or more materials. The purpose of this study was to determine the feasibility of a reinforced configuration of coco fiber. The method of making this composite used the hand lay-up method or an open mold process. The test results of the coir fiber composite had an actual density value of 60% fiber and 40% resin composition of 1.19 g/cm3 and the lowest porosity value of 0.58% in the random arrangement fiber impact test specimen. The best value of impact toughness was found in the composition of 50% fiber and 50% resin of 271,311.29 J/m2 in straight fiber specimens with ductile mechanical properties. This value was much higher than the impact toughness of SNI 18111-2007 helmet material of 9,720 J/m2. Based on these results, the composite material, polyester resin reinforced with coconut fiber, is suitable as an alternative material in the manufacture of SNI helmets when viewed from the value of impact toughness and tensile strength.

Exploring the potential of a novel alternating current stimulated iron‑carbon anammox process: A new horizon for nitrogen removal

This study explored a novel alternating current (AC) stimulation approach to enhance the nitrogen removal efficiency of an iron‑carbon based anammox (FeC anammox) system. In the preliminary experiment, the TN removal efficiency of the AC stimulated system was 8.06 % higher than that of a DC simulated system in same current densities of 0.25 mA/cm2. Gene expression analysis revealed that the AC-stimulated system, where, compared with the anammox system alone, the expression of HZS, HDH, NarG, NirS, NorB and NosZ increased by 1.81, 2.50, 1.64, 0.23, 1.15 and 1.27 times, respectively. In the continuous experiment, the TN removal rate increased from 60.13 % to 84.34 % after AC stimulation, and the working time of the FeC materials increased to 20 days. An analysis of the mechanism revealed that the parallel connection between the capacitive reactance and filler resistance in AC might reduce the internal resistance of the system, thereby improving the actual current density received by local microorganisms, and achieving a better strengthening effect.

Determining nitrogen topdressing rates in accordance with actual seedling density and crop nitrogen status in direct-seeded rice.

Adjusting nitrogen (N) input based on actual seedling density (ASD) and plant N status is a practical approach for improving the yield stability of direct-seeded rice. However, the adjustment of topdressing N rates has been empirical in the past. This study aimed to establish a quantitative approach for determining N topdressing rates during tillering (Ntil ) and panicle development (NPI ) based on ASD and crop N status in direct-seeded rice. Field experiments were conducted involving 12 treatments, consisting of four Ntil and three seeding rates in 2017, and eight treatments combining seeding rate, Ntil , and NPI in 2020. Linear regression analysis revealed that the tiller number at panicle initiation (TILPI ) was predominantly influenced by ASD and Ntil . The determination coefficients (R2 ) of the regression models ranged from 0.887 to 0.936 across the four-season experiments. The results indicated that Ntil could be determined accurately using ASD and the target maximum tiller number. Similarly, grain yield was influenced significantly by the N uptake at panicle initiation (NUPPI ) and NPI , with R2 of 0.814 and 0.783 in the early and late seasons of 2020, respectively. This suggested that NPI could be calculated based on NUPPI and the target grain yield. The findings offer a quantitative method for establishing N topdressing rates for tillering and panicle development, relying on the monitoring of actual seedling density and plant N status in direct-seeded rice production. © 2023 Society of Chemical Industry.

MD simulation study on the microstructural evolution of single-crystal Fe with pre-existing defects by Cr ion implantation

In this study, we present the molecular dynamics simulation of metal ion implantation, investigating the strengthening mechanism from a microstructural perspective. A single crystal Fe with pre-existing defects is constructed based on actual dislocation density and the effects of Cr ion implantation are investigated. Additionally, nanoindentation simulations are conducted to analyze the mechanical properties of workpieces with and without ion implantation. Effects of implantation energy and dose on the microstructure and hardness of workpieces are analyzed. The results indicate that (i) ion implantation introduces FeCr bonds with higher bond energy while reducing the original FeFe bond energy, (ii) increasing implantation energy and dose corresponds to a greater number of point defects and a higher amorphous structures proportion, (iii) the microstructure transformed by ion implantation promotes dislocation nucleation during nanoindentation, (iv) ion implantation enhances workpiece hardness due to the dual effects of interstitials impeding dislocation motion and the heightened mutual obstruction attributed to a higher dislocation density. Notably, the hardness initially enhances with increasing implantation energy and dose, followed by a slight decrease. The computational approach in this paper can serve as a valuable tool for studying the microstructural evolution of metal ion implantation by molecular dynamics simulations.

Structural Performance of Ti6Al4V Tibial Tray in Total Knee Arthroplasty (TKA) by Functionally Graded Lattice Structures using Numerical Analysis

The medical industry benefits greatly from the additive manufacturing (AM) technology used on customized products. Total knee arthroplasty (TKA) has been widely used however it has drawbacks of stress shielding and loosening due to the excessive daily routine of patients. The problem could be minimized by applying lattice structures to the implant and mimicking the actual density of human bone. This study aims to investigate the optimal design of a Ti6Al4V alloy tibial tray by applying different types of lattice structure designs. A finite element analysis was used to investigate the mechanical behavior of uniform and non-uniform lattice structures in a walking position. Functional gradation structure was optimized on selected regions of the tibial tray with weight reduction and adaptation to the near actual density of the human bone without compromising its mechanical performance. The results indicated that the Voronoi structure has improved stress behavior and the capability to withstand the loads exerted, based on the Von Mises stress result of the Voronoi structure at 35.83 MPa as compared to the gyroid and diamond structures at 61.65 MPa and 49.74 MPa, respectively. The optimal design of the tibial implant was achieved by functionally graded lattice structures, replacing the solid tibial implant.

A New Hybrid Concentrated-Winding Concept With Improved Power Factor for Permanent Magnet Vernier Machine

This paper investigates a high power-factor permanent magnet vernier machine (PMVM) equipped with low-coupling hybrid concentrated-winding (CW). The proposed hybrid-CW, carrying both star- and delta-winding sets, exhibits a good filtering property to both sub- and super-order harmonics. Through the meticulous design of the short coil pitch, the ratio of inductance to magnet flux linkage is decreased, leading to a great improvement in power factor. The proposed low-coupling winding design contributes to further power factor improvement by reducing the inductance while retaining the magnet flux linkage. It is revealed that the mutual coupling between different coils of single phase and that between different windings of three phases are suppressed significantly in the hybrid-CW, thus leading to high power factor and potentially high fault tolerance. Finite element results show that the proposed hybrid-CW PMVM exhibits a significantly improved power factor up to 0.96 from 0.83 and 0.75, as compared with two counterpart PMVMs with open-slot and split-tooth structures, respectively. Benefiting from the magnetic gearing effect, the proposed PMVM has a promising active torque density of 40 Nm/L. Taking end-winding volume into consideration, the proposed PMVM exhibits an actual torque density of 21.98 Nm/L, which is 22.52% and 52.43% higher than the investigated open-slot and split-tooth counterpart PMVMs. Finally, a prototype is fabricated and tested to validate the high-power-factor and high-torque-density features of the proposed hybrid-CW PMVM.

Evaluating quasi-static and fatigue performance of IN718 gyroid lattice structures fabricated via LPBF: Exploring relative densities

Additive manufacturing (AM) technology has unlocked the possibilities of fabricating complex structures of components such as lattice structures. Based on the literature review, the significance of the thickness effect on lattice structures has not been completely investigated yet. Therefore, this research aims to study the wall thickness effect on the mechanical performance of sheet-based lattice structures under quasi-static compression and fatigue loading conditions. For this aim, four geometries of lattice structures with designed relative densities of 12.5%, 25.0%, 37.5%, and 50.0% were fabricated via Laser Powder Bed Fusion (LPBF) process using Inconel alloy 718. The specimens were heat-treated to eliminate residual stresses and then tested under monotonic and cyclic compressive loading conditions to obtain the mechanical responses for each respective relative density. The experimental results from the quasi-static and fatigue compression tests on different geometries were compared and analyzed with the use of Scanning Electron Microscopy (SEM) to observe the fatigue failure locations and their dependency on the surface morphology of those failure locations. In addition, the actual relative densities were also calculated to evaluate the geometrical deviations and correct the experimental results. Overall, the experimental data revealed that there are strong associations between the lattices with various wall thicknesses and corresponding quasi-static and fatigue performance.

Influence of Water Absorption on Mechanical and Morphological Behaviour of Roystonea-Regia/Banana Hybrid Polyester Composites

This study investigated the properties of hybrid composites made from Roystonea-Regia and banana fibers for potential applications in industries requiring lightweight, environmentally favorable, and mechanically strong materials. The analysis of density and void fraction revealed that the addition of banana fibers increased the composite's density, despite the fact that the actual density was slightly lower than the theoretical density due to confined gases during fabrication. The results of tensile tests revealed that water absorption negatively affected tensile strength, whereas alkali treatment and hybridization enhanced performance. The composition of 10 wt % Roystonea-Regia and 5 wt % banana had the highest tensile strength of 64.76MPa, which was attributable to the hydrophilicity and hydration content of the banana fiber. Further flexural and impact experiments confirmed that the influence of water absorption of composites showed a decrement in mechanical properties. The highest impact strength of 45.28 J/m and flexural strength of 75.6MPa were noted for 10 wt % Roystonea-Regia and 5 wt % banana. In addition, Scanning Electron Microscopy (SEM) analysis revealed that alkali treatment improved fiber-matrix interface bonding and roughened fiber surfaces, thereby enhancing the composites' overall performance. The study provides precious insights into the potential of Roystonea-Regia and banana hybrid composites for industrial applications as lightweight, environmentally friendly, and mechanically robust materials.

Know When You Are Too Many: Density-Dependent Release of Pheromones During Host Colonisation by the European Spruce Bark Beetle, Ips typographus (L.)

Individuals across various animal species communicate their presence to conspecifics. Especially phytophagous and parasitoid insects with their brood developing on limited resources rely on chemical cues, such as host-marking pheromones, to reduce intraspecific competition. Bark beetles are phytophagous insects with some species being economically and ecologically relevant forest pests. Several of them use the volatile compound verbenone to inhibit attraction and reduce intraspecific competition. However, in the Eurasian spruce bark beetle, Ips typographus (L.), temporal emission patterns did so far not quite support the putative function of verbenone as an indicator of densely colonised host trees. More importantly, it is currently unclear how well verbenone emission is actually related to colonisation density and thus intraspecific competition. Here, we inoculated Norway spruce logs with I. typographus at two defined colonisation densities in the greenhouse and measured the emission of verbenone and its precursors α-pinene and verbenol over time. Verbenone emission was 3–7 times greater from colonised logs compared to decaying logs without beetles during the major part of larval development. Furthermore, our data supports the quantitative hypothesis, that the termination of attack on a tree is mediated by a cessation of the release of verbenol and continuous emission of verbenone. The latter is most likely a passively produced host-marking cue reflecting the actual density of conspecifics since per-beetle emission was unaffected by colonisation density. These findings shed new light on the regulation of bark beetle mass aggregations, which are currently causing previously unseen economic damages in temperate forests.

Modelling of deuterium diffusion and thermal desorption in tungsten exposed to high-flux deuterium plasma

In nuclear fusion, hydrogen isotopes transportation in tungsten has been identified as a crucial process which could affect various key processes in the operation of a fusion device, such as tritium self-sustaining and operational safety. To enhance the understanding of deuterium diffusion and trapping in millimeter-thick tungsten under high-flux plasma conditions, we carried out a systematic simulation investigation on the deuterium plasma exposure and subsequent thermal desorption using the TMAP7 code based on experimental results. The simulation reveals that the defect concentration with a low de-trapping energy , as estimated solely from simulating thermal desorption, is lower than its actual density due to the temperature history of plasma exposure and subsequent cooling processes. Moreover, the growth rate of deuterium mobile concentration exhibits nonmonotonic behavior over time during plasma exposure, which strongly depends on the ratio of defect concentration with a high de-trapping energy to that with a low de-trapping energy. Additionally, we observed that the maximum deuterium diffusion depth does not follow a proportional relationship with the square root of exposure time, which is attributed to the growing number of plasma-induced defects and the reducing injection coefficient with increasing fluences. This work provides valuable insights into the understanding of deuterium transportation in tungsten during high-flux plasma exposure which could contribute to understanding and modelling of hydrogen isotopes recycling in future fusion devices.