Delay-tolerant networking (DTN) enables communication in disruptive scenarios where issues such as sparse and intermittent connectivity, long and variable delays, high latency, high error rates, or ...no end-to-end connectivity exist. Internet of Vehicles (IoV) is a network of the future in which integration between devices, vehicles, and users will be unlimited and universal, overcoming the heterogeneity of systems, services, applications, and devices. Delay-tolerant internet of vehicles (DT-IoV) is emerging and becoming a popular research topic due to the critical applications that can be realized, such as software or map update dissemination. For an IoV to work efficiently, a degree of cooperation between nodes is necessary to deliver messages to their destinations. However, nodes might misbehave and silently drop messages, also known as a black-hole attack, degrading network performance. Various solutions have been proposed to deal with black-hole nodes, but most are centralized or require each node to meet every other node. This paper proposes a decentralized reputation scheme called BiRep that identifies and punishes black-hole nodes in DT-IoV. BiRep is tested on the Prophet routing protocol. Simulation results show excellent performance in all scenarios, comparable or better to other reputation schemes, significantly increasing the delivery ratio of messages.
Centrioles are structurally conserved organelles, composing both centrosomes and cilia. In animal cycling cells, centrioles often form through a highly characterized process termed canonical ...duplication. However, a large diversity of eukaryotes assemble centrioles de novo through uncharacterized pathways. This unexplored diversity is key to understanding centriole assembly mechanisms and how they evolved to assist specific cellular functions. Here, we show that, during spermatogenesis of the bryophyte Physcomitrium patens, centrioles are born as a co-axially oriented centriole pair united by a cartwheel. Interestingly, we observe that these centrioles are twisted in opposite orientations. Microtubules emanate from the bicentrioles, which localize to the spindle poles during cell division. After their separation, the two resulting sister centrioles mature asymmetrically, elongating specific microtubule triplets and a naked cartwheel. Subsequently, two motile cilia are assembled that appear to alternate between different motility patterns. We further show that centriolar components SAS6, Bld10, and POC1, which are conserved across eukaryotes, are expressed during spermatogenesis and required for this de novo biogenesis pathway. Our work supports a scenario where centriole biogenesis, while driven by conserved molecular modules, is more diverse than previously thought.
•Centrioles assemble de novo via bicentrioles in P. patens•Bicentrioles have two inversely twisted centrioles connected by the cartwheel•Sister centrioles mature asymmetrically and contain long naked cartwheels•SAS6, Bld10, and POC1 are required for cartwheel and centriole assembly, respectively
Gomes Pereira et al. show that centriole biogenesis in P. patens occurs via bicentrioles—two sister centrioles inversely twisted, relying on a conserved pathway involving SAS6, Bld10, and POC1. Sister centrioles mature asymmetrically, assembling long naked cartwheels, microtubules of variable lengths, and seemingly individually regulated cilia.
► XPS and ToF-SIMS study of solid electrolyte interphase layer on Si thin film and Si nanowires electrodes is presented. ► Modification of Si electrode surface morphology is evidenced by SEM ...micrographs. ► Organic part of solid electrolyte interphase is present at the outer- and inorganic part in the innermost surface. ► Different thickness of solid electrolyte interphase is observed in a function of type of electrolytes.
The effect of the Si electrode morphology (amorphous hydrogenated silicon thin films – a-Si:H as a model electrode and Si nanowires – SiNWs electrode) on the interphase chemistry was thoroughly investigated by the surface science techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). XPS analysis shows a strong attenuation and positive shift of the Si 2p peaks after a complete charge/discharge performed in PC- and EC:DMC-based electrolytes for both electrodes (a-Si:H and SiNW), confirming a formation of a passive film (called solid electrolyte interphase – SEI layer). As evidenced from the XPS analysis performed on the model electrode, the thicker SEI layer was formed after cycling in PC-based electrolyte as compared to EC:DMC electrolyte. XPS and ToF-SIMS investigations reveal the presence of organic carbonate species on the outer surface and inorganic salt decomposition species in the inner part of the SEI layer. Significant modification of the surface morphology for the both electrodes and a full surface coverage by the SEI layer was confirmed by the scanning electron microscopy (SEM) analysis.
Si thin films obtained by plasma enhanced chemical vapor deposition (PECVD) were used to investigate chemical and morphological modifications induced by lithiation potential and cycling. These ...modifications were thoughtfully analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling, which allows to distinguish the surface and bulk processes related to the formation of the solid electrolyte interphase (SEI) layer, and Li–Si alloying, respectively. The main results are a volume expansion/shrinkage and a dynamic behavior of the SEI layer during the single lithiation/delithiation process and multicycling. Trapping of lithium and other ions corresponding to products of electrolyte decomposition are the major reasons of electrode modifications. It is shown that the SEI layer contributes to 60% of the total volume variation of Si electrodes (100 nm). The apparent diffusion coefficient of lithium (D Li) calculated from the Fick’s second law directly from Li-ion ToF-SIMS profiles is of the order of ∼5.9 × 10–15 cm2.s–1. This quite low value can be explained by Li trapping in the bulk of electrode material, at the interfaces, continuous growth of the SEI layer and increase of SiO2 quantity. These modifications can result in limitation the ionic transport of Li.
In this study, the description of the karyotypes of the endangered chubs Squalius aradensis (Coelho, Bogutskaya, Rodrigues and Collares-Pereira, 1998) and Squalius torgalensis (Coelho, Bogutskaya, ...Rodrigues and Collares-Pereira, 1998) is presented by means of conventional (Giemsa-staining, Chromomycin A3 (CMA3)-fluorescence, Silver-impregnation (Ag-NORs)) and molecular (fluorescence in situ hybridization (FISH) with 18S rDNA probe) protocols. These endemic sister-species have an allopatric but adjacent distribution in the most southwestern part of the Iberian Peninsula. Diploid chromosome number was invariably 2n = 50 and karyotypes of both species were grossly similar, composed of metacentric and submetacentric elements with a reduced number of acrocentric pairs. Sequential staining using FISH with an 18S rDNA probe, CMA3 and Ag-NORs treatments revealed consistent positive signals located at the end of the short arms of a submetacentric chromosome pair, likely homologous in both species. While providing useful cytogenetic comparative data against other members of the genus Squalius Bonaparte, 1837, the work aimed to draw attention towards the conservation of two narrow-range and highly confined fish species.
► Electro-precipitation of ceria on graphite. ► Graphite modification by ceria thin film for negative electrodes. ► Reversible insertion and deinsertion of lithium in graphite through ceria layer. ► ...Formation of solid electrolyte interphase (SEI) layer.
Thin ceria layer deposited by electro-precipitation onto graphite was synthesised and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electro-precipitated ceria has a cubic structure with nanocrystallites of about 6
nm. The SEM analyses shows that the ceria layer reflects the morphology of the graphite electrode, exhibits small cracks usually found on the electro-precipitated films but covers almost completely the surface of the graphite. The ceria layer is composed of 75% Ce(IV) and 25% Ce(III) oxides as indicated by the XPS analyses. Cyclic voltammetry and galvanostatic charge–discharge tests in ethylene carbonate/dimethyl carbonate (1/1) (wt/wt) in the presence of 1
M LiPF
6 show that reversible lithium insertion and deinsertion occurs in the graphite/ceria electrode and that the ceria layer on the graphite electrode prevents from the loss of capacity during the first four cycles. The reduction of the electrolyte occurs at about 0.7
V
vs Li/Li
+ on both electrodes but XPS and SEM analyses show that the SEI layer is thin and not as homogenous on the graphite as on the graphite/ceria electrode. The composition of the SEI layer on the graphite/ceria electrode, mainly composed of Li
2CO
3, ROCO
2Li, R–CH
2OLi and LiF, is different than those obtained on the graphite.
In situ electrochemical (by electrochemical impedance spectroscopy, EIS) and ex situ surface (by time-of-flight secondary ions mass spectrometry, ToF-SIMS) analysis were applied to investigate ...solid-state diffusion coefficient (D Li) into conversion-type α-Fe2O3 negative electrode for Li-ion batteries. D Li values obtained from EIS were in the range of 10–16 to 10–15 cm2 s–1 for electrodes partially and fully lithiated, respectively, showing that pulverization of the converted material promotes Li-ion migration. ToF-SIMS ion depth profiling performed after partial lithiation enabled discriminating the surface solid electrolyte interphase (SEI) region, a converted electrode region (Li2O/Fe0 matrix) of slow diffusion (D Li = 6 × 10–16 cm2 s–1) and an unconverted region (intercalated Fe2O3 matrix) of faster diffusion (D Li = 2 × 10–13 cm2 s–1) ahead of the conversion front. Comparison of the ex situ and in situ results indicates that the electrode conversion kinetics is limited by Li-ion diffusion in the converted matrix and suggests a hindering effect of the passivating SEI layer. ToF-SIMS depth profile analysis appears as a most appropriate and direct methodology to measure Li-ion diffusion solely in electrode materials, excluding SEI layer effects.
The effect of lithiation–delithiation rate and of the number of cycles on the properties of Si nanowires (SiNWs) and electrolyte interface is presented in this paper. The surface and bulk ...modifications of SiNW electrode induced by electrochemical process of lithiation–delithiation were investigated by combined electrochemical tests (galvanostatic cycling), field emission gun scanning electron microscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. Low lithiation–delithiation rate improves electrochemical performance due to a better penetration depth of lithium into the SiNW electrode and the formation of a homogeneous solid electrolyte interphase (SEI) layer on the SiNWs after the first cycle. However, after repeated cycling, SiNWs suffered strong mechanical stress leading to a rough or porous SiNW structure covered by a porous SEI layer. This study highlights the SEI modifications caused by the lithiation–delithiation rate and the modifications of the Si electrode upon cycling.
Epoxy-amines are used as structural adhesives deposited on Ti. The amine adhesion to a Ti surface depends highly on the surface state (oxidation, hydroxylation). Amines may adsorb above preadsorbed ...water molecules or substitute them to bind directly to surface Ti(4+) Lewis acid sites. The adsorption of a model amine molecule, diaminoethane (DAE), on a model surface, hydrated TiO2-anatase (101) surface, is investigated using Density Functional Theory including Dispersive forces (DFT-D) calculations. DAE adsorption and water substitution by DAE are exothermic processes and turn nearly isoenergetic at high coverage with adsorption-substitution energies around -0.3 eV (including dispersion forces and ZPE). Complementary ab initio molecular dynamics studies also suggest that the formation of an amine-water interaction induces water desorption from the surface at room temperature, a preliminary step towards the amine-Ti bond formation. An atomistic thermodynamic approach is developed to evaluate the interfacial free energy balance of both processes (adsorption and substitution). The main contributions to the energetic balance are dispersive interactions between molecules and the surface on the exergonic side, translational and rotational entropic contributions on the endergonic one. The substitution process is stabilized by 0.55 eV versus the adsorption one when free solvation, rotational and vibrational energies are considered. The main contribution to this free energy gain is due to water solvation. The calculations suggest that in toluene solvent with a water concentration of 10(-4) M or less, a full DAE layer replaces a preadsorbed water layer for a threshold concentration of DAE ≥ 0.1 M.
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