Hotspot Mechanism Research Articles

Characteristic Times for Gap Relaxation and Heat Escape in Nanothin NbTi Superconducting Filaments: Thickness Dependence and Effect of Substrate.

We measured the temporal voltage response of NbTi superconducting filaments with varied nanoscale thicknesses to step current pulses that induce non-equilibrium superconducting states governed by a hot spot mechanism. Such detected voltage emerges after a delay time td, which is intimately connected to the gap relaxation and heat escape times. By employing time-dependent Ginzburg-Landau theory to link the delay time to the applied current, we determined that the gap relaxation time depends linearly on film thickness, aligning with the acoustic mismatch theory for phonon transmission at the superconductor-substrate interface. We thereby find a gap relaxation time of 104 ps per nm of thickness for NbTi films on polished sapphire. We further show that interfacial interaction with the substrate significantly impacts the gap relaxation time, with observed values of 9 ns on SiOx, 6.8 ns on fused silica, and 5.2 ns on sapphire for a 50 nm thick NbTi strip at T=5.75 K. These insights are valuable for optimizing superconducting sensing technologies, particularly the single-photon detectors that operate in the transient regime of nanothin superconducting bridges and filaments.

Acoustic shock wave processing on amorphous carbon quantum dots – correlation between spectroscopic-morphological–magnetic and electrical conductivity properties

In this context, we report the acoustic shock wave processing on amorphous Carbon quantum dots (a-CQD) such that its degree of graphitization and magnetic properties are analyzed. Analytical techniques such as the Raman spectrometer, high resonation–transmission electron microscopy (HR-TEM) and vibrating sample magnetometer (VSM) are utilized to understand the structural, morphological and magnetic properties changes under shocked conditions. The Raman spectroscopic data reveal that the ID/IG ratio is slightly reduced under shocked conditions and the observed values are 0.78, 0.77 and 0.75 for the respective 0, 150 and 300 shocked conditions. The formation of ultra-short-range graphitic nanostructures is confirmed by HR-TEM results at the 300-shocked condition. The most convincing and supporting results for the enhancement of the degree of graphitization are found by the outcome of the magnetic properties such that the saturation magnetization (Ms) is found to be linearly reduced with respect to the number of shock pulses and the observed values are 0.869, 0.757 and 0.710 emu/g for the 0, 150 and 300 shocked conditions, respectively. The electrical resistance of the a-CQD is found to be linearly reduced with respect to the number of shock pulses due to the reduction of sp3 carbon networks. The formation of crystalline graphitic nanostructures in amorphous CQD is explained on the basis of the hot-spot nucleation mechanism. Based on the obtained Raman, HR-TEM and VSM results, during the shocked conditions, slight enhancement of the graphitization is observed; however, from the structural stability point of view, the Carbon dots have high shock resistance than that of the amorphous carbon nanoparticles, multi-wall carbon nanotubes, and reduced graphene oxide nanoparticles. Hence, the title quantum dots can be strongly considered for the applications of device fabrication.

Ignition response of NEPE-based propellants under drop weight through experiments and numerical simulation

ABSTRACT Experimental and numerical studies were conducted to investigate the effects of drop height on the ignition mechanism of NEPE nitrate ester plasticized polyether-based propellants. A modified drop-weight system was equipped with a high-speed camera to capture the ignition response images during the whole impact process. A macro-mesoscopic thermomechanical model considering the microcrack and viscous shear flow hotspot formation mechanism was established. The experimental results showed that the ignition responses of the propellants heavily depended on drop height, and the main ignition mechanism was viscous shear flow. The whole loading process could be summarized into three stages: radial extension (viscous shear flow), macroscopic crack initiation and ultimate failure (multiple macroscopic cracks or ignition). The ignition threshold was 35 cm. The posttest scanning electron microscopy (SEM) images further revealed that viscous shear flow played an important role in the ignition of propellants. The numerical simulation results indicated that viscous shear flow was the dominant ignition mechanism compared with the microcrack hotspot mechanism. Point A (along L1) was the most dangerous location under the drop-weight experiment. The predicted features of ignition evolution were consistent with the experimental results and prove that the critical drop height of ignition was 35 cm.

Reduction of amorphous carbon clusters from the highly disordered and reduced graphene oxide NPs by acoustical shock waves — Towards the formation of highly ordered graphene

The journey of exploring the acoustical shock wave-induced solid state phase transitions on polymorphic and allotropy materials have gained enormous momentum in recent years after the invention of the tabletop Reddy tube, but, the knowledge of shock wave-induced phase transitions on allotropy materials is very limited in comparison to the polymorphic materials. Hence, in this framework, we report the shock wave-induced transitions based on the reduction of the amorphous carbon clusters in the highly disordered and reduced graphene oxide nanoparticles (rGO NPs) [rGO — is also called as modified graphene]. The reduction of the disordered carbon in the rGO NPs under shocked conditions is examined by the techniques such as X-ray diffractometry and Raman spectrometer. X-ray crystallographic studies clearly present that as the shock pulses are increased, the intensity of the (002) peak is increased for which the authentication is observed by the Raman spectral analyses wherein it is clearly indicated the decrement and increment of the D and G bands against the exposure of the shock pulses thereby the ID/IG ratios are found to be 1.24, 1.17, 1 and 0.927 for 0, 100, 200 and 400 shocks, respectively. According to the Raman spectral results, the area of the amorphous Raman peak is reduced against the shock pulses such that the values are 98, 82, 81 and 48 for the 0, 100, 200 and 400 shocks, respectively. The removal of amorphous carbon clusters in the rGO NPs can be explained on the basis of the conversion of sp3 to sp2 hybridizations based on the shock wave induced hot-spot nucleation mechanism.

Adaptive simulations of flame acceleration and detonation transition in subsonic and supersonic mixtures

Two-dimensional simulations were carried out to investigate the flame acceleration and deflagration-to-detonation transition (DDT) in a combustion chamber filled with a subsonic or supersonic mixture by employing Navier-Stokes equations together with a detailed chemistry reaction mechanism of 11 species and 27 steps under adaptive mesh refinement. The effects of the initial mixture Mach number and mesh resolution on the flame acceleration and DDT were studied in detail, and the entire processes of the flame acceleration, DDT and detonation propagation were revealed. Two DDT mechanisms are obtained in a chamber having the same low blockage ratio but with different initial velocities of the mixture. Regime I: multiple shock wave collisions, shock focusing and shock reflection result in a rapid energy deposition in a small region; a direct detonation subsequently occurs in the boundary wall for the subsonic mixture. Regime II: the classic hot-spot mechanism due to the reactive gradient mechanism is responsible for the detonation transition in the supersonic mixture when the intense leading shock wave impacts and reflects on the solid surface. By increasing the initial mixture Mach number, the run-up time and distance to DDT are dramatically reduced. The flame front structure and propagation in the supersonic flow demonstrate that the detonation cell size rapidly increases when propagating into the smooth region due to detonation attenuation and resulting pressure decrease. Additionally, a much higher combustion temperature occurs in the upper and lower walls because of the Mach stem. In comparison, the results show that the detonation overdrive degree and pressure gain ratio in the subsonic mixture are higher than in the supersonic mixture. Moreover, flame propagation upstream also suggests that increased pressure and temperature occur in the inlet isolation section, even forming a localized explosion point.

Enhanced microwave absorption capacity of iron-based catalysts by introducing Co and Ni for microwave pyrolysis of waste COVID-19 Masks

Inexpensive iron-based catalysts are the most promising catalysts for microwave-assisted deconstruction of waste plastics. However, the microwave heating efficiency of most of the synthesized iron-based catalysts is very low, in particular, the FeAl catalyst was prepared by microwave combustion method, and its mixture with disposable medical masks (DMMs) was only heated to about 150℃ within 10 min. Here, we introduce the second-phase metals (Co or Ni) into the FeAl catalyst, resulting in the rearrangement of the catalyst structure and electrons to give the catalyst good microwave absorption ability. The mixture of the catalyst and DMMs can be quickly heated to above 900℃ in 10 min, especially after reaching the melting point of plastic, the instantaneous heating rate reaches 350 ℃·min−1. under the unique microwave hot-spot pyrolysis mechanism, DMMs can be rapidly pyrolyzed into carbon nanotubes (19.65 wt%) and gas (77.65 wt%) within 14 min due to the efficient dehydrogenation efficiency and activity of Co. The corresponding H2 yield is up to 38.66 mmolH2·g−1DMMs, and the percentage of CO and H2 in the gas is as high as 90 wt%. This work improves the microwave conversion efficiency of iron-based catalysts by introducing second phase metals, and waste DMMs were efficiently converted into CO, H2 and CNTs, which can also be extended to other polymer or biomass chemical cycles.

Multidisciplinary green approaches (ultrasonic, co-precipitation, hydrothermal, and microwave) for fabrication and characterization of Erbium-promoted Ni-Al2O3 catalyst for CO2 methanation

The dispersion of nickel catalysts is crucial for the catalytic ability of CO2 methanation, which can be influenced by the fabrication method and the operation process of the catalysts. Therefore, a series of fabrication methods, including ultrasonic, hydrothermal, microwave, and co-precipitation, have been applied to prepare 25Ni-5Er-Al2O3 catalysts. The fabrication method can partially influence the structural and catalytic activity of the nickel aluminate catalysts. Among the catalysts modified by Erbium prepared with various methods, the catalyst fabricated by ultrasonic pathway exhibited better catalytic performance and CH4 selectivity especially, at a temperature (400 ℃). The impact of the temperature of the reaction (200–500 °C) was examined under a stoichiometric precursor ratio of (H2:CO2) = 4: 1, atmospheric pressure, and space velocity (GHSV) of 25000 mL/gcath. The results demonstrate that the ultrasonic method is strongly efficient for fabricating Ni-based catalysts with a high BET surface area of about 190.33 m2g−1. The catalyst composed via the ultrasonic technique has 69.38 % carbon dioxide conversion and 100 % methane selectivity at 400 °C for excellent catalytic performance in CO2 methanation reactions. The fabrication effect can be associated with its high surface area, which is achieved via the hot spot mechanism. Besides, the addition of Erbium promotes the Ni dispersion on the supports and stimulates the positive reaction because of the erbium oxygen vacancies.

Effect of the Rare Earth Metals (Tb, Nd, Dy) addition for the modification of nickel catalysts supported on alumina in CO2 Methanation

In the current research, a group of rare-earth metals functionalized mesoporous Ni-M/Al2O3 (M = Tb, Dy, Nd) composite oxides were prepared by the one-pot sonochemical pathway and applied in the CO2 methanation procedure. Promoters can partially influence the textural and catalytic characteristics of Ni–Al2O3 catalysts. Physicochemical characteristics of the as-fabricated catalysts were identified utilizing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Energy-dispersive X-ray spectroscopy (EDS), Temperature Programmed Reduction (H2-TPR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analyses. Among the specimens, the catalyst modified by Terbium (Tb) manifested better catalytic performance and CH4 selectivity, particularly at low temperatures (350–400 °C). The influence of reaction temperature (200–500 °C) was scrutinized below space velocity (GHSV) of 25,000 ml/gcath, atmospheric pressure, and stoichiometric ratio of CO2 to H2 (1: 4). The impact of the desired content of nickel and terbium was examined. The 25Ni–5Tb–Al2O3 operates the best function for CO2 methanation, which can attain the highest CO2 conversion of 66.93% at 400 °C at atmospheric pressure. The superior catalytic performance of 25Ni–5Tb–Al2O3 could be assigned to the appropriate fabrication method and the promotion effect of Terbium. The synthesis effect could be assigned to its large surface area, obtaining by the hot spot mechanism. The addition of Terbium promotes the Ni distribution on the supports as well as accelerates the positive reaction due to the oxygen vacancies of Terbium. Besides, these outcomes could be defined with the maximum distribution of active nickel sites on the catalyst and improvement in the catalyst reduction ability at low temperatures.

Morphostructure, emplacement and duration of the Abrolhos Magmatic Province: A geophysical analysis of the largest post-breakup magmatism of the South-Eastern Brazilian margin

The Abrolhos Magmatic Province (AMP), located in the Ocean Continent Transition (OCT) of the Brazilian South Atlantic rifted margin, is spatially extensive covering an area larger than 63,000 km2 and was emplaced in the Early Cenozoic, approximately 40 Ma after rifted margin formation in Early Cretaceous. The explanation for the origin of the AMP is that it forms part of a hotspot track that initiated at ~85 Ma in the Poxoréu region, an igneous province located ~1500 km to the west of the AMP, within Brazilian continental lithosphere and is presently located under Trindade and Martin Vaz Islands at the Vitoria-Trindade seamount chain (VTC). The aim of this work is to investigate the morphostructure, duration and spatial distribution of the AMP, exploring its significance for the margin evolution and possible origins. The magnetic, reflexion seismic and well data analysis show that the AMP consists of an assembly of large volcanic edifices formed during the Paleogene, each with individual diameters in excess of 50 km, sizes varying from 280 to 2100 km2, and formed by multiple volcanic events. The igneous bodies are mainly buried at different depths (from ~2 Km to 8 km below seafloor), while some emerge to form the Abrolhos Archipelago. The spatial arrangement of the igneous edifices of the AMP suggest that in its central part are the main feeders for the outer and shallower bodies at the borders which have a radial distribution. Their distribution seems to partially follow preexisting structural trends like Precambrian and Mesozoic weakness zones, represented by the onshore Paramirin Aulacogen, the Araçuaí and Ribeira belts, and the offshore rifting structures. These observations suggest an influence of lithosphere inheritance on the emplacement of the AMP. The tectono-stratigraphic architecture indicate margin uplift at Early Cenozoic related to the emplacement of the AMP, creating an elevated area. Mapped hydrothermal vents indicate AMP magmatic activity continued into the Neogene, and connect Abrolhos volcanism with that in the VTC located 650 km to the east. This and reported low S-wave velocity from tomographic model and anomalous dynamic topography suggest a distinct mantle thermal structure under the AMC and VTC. However, the spatial extent and duration of the AMP are inconsistent with a fixed hotspot mechanism and linear trail.

Outsourcing Hotspot Governance within the EU: Cultural Mediators as Humanitarian–Border Workers in Greece

Abstract Responding to the self-declared “Mediterranean migration crisis” in 2015, the European Commission launched a Hotspot Approach to speed up the handling of incoming migrants in the “frontline states” of Greece and Italy. A key element in this operation is the identification of those eligible for asylum, which requires effective communication across cultural and linguistic difference between the asylum system and the migrants, facilitated by officially designated “cultural mediators.” We assess the hotspot governance as a form of outsourcing border control within the EU territory. Beyond sorting out and separating migrants into the categories of deservingness and undeservingness, we propose that the hotspot mechanism represents “governing by communication,” with cultural mediators as key players in this humanitarian–bordering strategy. A focus on how cultural mediators provide the precarious human labor for this governance, offers, we argue, a productive inroad into the ways in which the hotspot economies of deterrence, containment, and care sustain inequalities embedded in race, socioeconomic status, and citizenship.

A melt-cast Duan-Zhang-Kim mesoscopic reaction rate model and experiment for shock initiation of melt-cast explosives

A melt-cast Duan-Zhang-Kim (DZK) mesoscopic reaction rate model is developed for the shock initiation of melt-cast explosives based on the pore collapse hot-spot ignition mechanism. A series of shock initiation experiments was performed for the Comp B melt-cast explosive to estimate effects of the loading pressure and the particle size of granular explosive component, and the mesoscopic model is validated against the experimental data. Further numerical simulations indicate that the initial density and formula proportion greatly affect the hot-spot ignition of melt-cast explosives.

Size effect of explosive particle on shock initiation of aluminized 2,4-dinitroanisole (DNAN)-based melt-cast explosive

An aluminized melt-cast Duan–Zhang–Kim mesoscopic reaction rate model based on the pore collapse hot-spot ignition mechanism is proposed to characterize the shock initiation behavior as well as size effects of explosive particles on the shock initiation of aluminized melt-cast explosives. For aluminized 2,4-dinitroanisole (DNAN)-based melt-cast R1 explosives [containing 60 wt. % HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazoncine), 30 wt. % DNAN, and 10 wt. % aluminium] with different particle sizes of HMX, both shock initiation experiments and corresponding numerical simulations were performed. The numerical results are found to be in good agreement with the experimental data, by which the mesoscopic reaction rate model is verified and the model parameters for the R1 explosive are determined. It is also found that the smaller the particle size of the granular explosive component, the faster the leading shock wave propagates, and the faster the detonation growth inside the aluminized melt-cast explosive.

Binding Hotspot and Activation Mechanism of Maltitol and Lactitol toward the Human Sweet Taste Receptor.

Human sweet taste receptor (hSTR) recognizes a wide array of sweeteners, resulting in sweet taste perception. Maltitol and lactitol have been extensively used in place of sucrose due to their capability to prevent dental caries. Herein, several molecular modeling approaches were applied to investigate the structural and energetic properties of these two polyols/hSTR complexes. Triplicate 500 ns molecular dynamics (MD) simulations and molecular mechanics/generalized Born surface area (MM/GBSA)-based free energy calculations revealed that the TAS1R2 monomer is the preferential binding site for maltitol and lactitol rather than the TAS1R3 region. Several polar residues (D142, S144, Y215, D278, E302, R383, and especially N143) were involved in polyols binding through electrostatic attractions and H-bond formations. The molecular complexation process not only induced the stable form of ligands but also stimulated the conformational adaptation of the TAS1R2 monomer to become a close-packed structure through an induced-fit mechanism. Notably, the binding affinity of the maltitol/TAS1R2 complex (ΔGbind of -17.93 ± 1.49 kcal/mol) was significantly higher than that of the lactitol/TAS1R2 system (-8.53 ± 1.78 kcal/mol), in line with the experimental relative sweetness. These findings provide an in-depth understanding of the differences in the sweetness response between maltitol and lactitol, which could be helpful to design novel polyol derivatives with higher sweet taste perception.

Energy Efficient Decision based Routing Technique using Fog Computing Paradigm

In the era of new technologies, Fog computing becomes very popular in today’s scenario. Fog computing paradigm brings a concept that extends cloud computing to the edge and close proximity to the Internet of Things (IoT) network. The fundamental components of fog computing are fog nodes. Additionally, fog nodes are energy efficient nodes. Numerous fog nodes are deployed in the associated fields that will handle the Internet of Things (IoT) sensors computation. Meanwhile, the Internet of Things (IoT) faces challenges, among which energy efficiency is one of the most prominent or critical challenges in the current scenario. However, sensor devices are an energy constraintthatcreateshotspotduringtheroutingprocess.Forthis reason,tohandlesuchconstraints,thispaperpresentsaneffective hotspot mechanism using fog nodes that demonstrate the routing process and directed the sensors to choose the routing path as selected by the fog node. Moreover, fog node will act as a decision maker node and maintain the energy efficiency of sensors during the routing as fog nodes are energy efficient nodes. As it moves towards the emergency situation, the most appropriate and effective routing approach has been designed who maintain the energy level of sensors will be high during the routing process. The proposed routing technique could be better performance for the sake of efficient routing in terms of energy consumption and prolonging networklifetime.

A Constitutive Model for the Shock Ignition of Polymer Bonded Explosives

ABSTRACTThe ignition behavior of polymer bonded explosives (PBXs) is critical to the safety assessments of weapons systems. The shock initiation experiment was designed to study this behavior. This article develops the constitutive model for the shock initiation of the PBX that includes viscoelastic response, statistical fracture mechanics, and an ignition hot spot mechanism. Friction heating on slip planes during plastic flow of explosives is considered as the main mechanism for the formation of hotspots and their ignition. Major results are the use of the ignition model for the PBX. The model was implemented in ABAQUS to predict the ignition of experiments. Computational results were verified by the experiments.

Pembangunan Class Library untuk Domain Product Management di Aplikasi M-Commerce pada Android

Criteo reports that the use of M-Commerce in 2015 has increased about 15% - 26%, compared to 2014. In 2015, users access M-Commerce using mobile phone more often than other devices. Around 54% of those users use mobile app while 46% use mobile browser. In addition, there is an increase in conversion value of the number of users switching from mobile browser to mobile app by 120%. In all these activities, 286% of users focus on product viewing activities. This phenomenon requires software developers to develop M-Commerce in a short time. On the other hand, the developers need time to develop MCommerce. One of the time-consuming activities is the development of functions for product management. Based on the software development, there is one concept that can be used, which is class library. A class library is a collection of classes and methods that provide functionality as basis for building a system within a case domain. The first step in this research is to do domain analysis to acquire frozenspot, hotspot, and function mechanism that will be provided in class library. The result of the hotspot will be analyzed to obtain the nine basic functions in the domain of product catalog case in M-Commerce. These functions will be mapped into ten classes in a class library which will be tested using unit testing and integration testing that can be used by M-Commerce developers to accelerate the development of product management on M-Commerce.

Multiscale damage evolution in polymer bonded sugar under dynamic loading

Ultra-high-speed and high spatial resolution digital image correlation based experiments are performed to understand the sub grain level local failure mechanisms in polymer bonded explosives under dynamic loading. Polymer bonded sugar that mimics the mechanical properties of polymer bonded explosives is used in this study. The experiments are conducted in a split Hopkinson pressure bar setup at an intermediate strain rate. From the digital image correlation analyses, high strain localization was observed predominantly in the regions filled by the polymer binder surrounding the sugar crystals. The damage evolution was quantified by calculating the Poisson's ratio and volumetric strain as a function of loading. It was observed that the damage incubation is started at a very small global strain and causes mechanical softening in the material that leads to shear band formation. Also, the possible hotspot mechanism in the material was seen to be frictional heating of crystals and de-bonding of the polymer binder.

Superconducting thermal neutron detectors

A neutron detection concept is presented that is based on superconductive niobium nitride (NbN) strips coated by a boron (B) layer. The working principle is well described by a hot spot mechanism: upon the occurrence of the nuclear reactions n + 10B → α + 7Li + 2.8 MeV, the energy released by the secondary particles into the strip induces a superconducting-normal state transition. The latter is recognized as a voltage signal which is the evidence of the incident neutron. The above described detection principle has been experimentally assessed and verified by irradiating the samples with a pulsed neutron beam at the ISIS spallation neutron source (UK). It is found that the boron coated superconducting strips, kept at a temperature T below 11K and current-biased below the critical current IC, are driven into the normal state upon thermal neutron irradiation. Measurements on the counting rate of the device are presented and the basic physical features of the detector are discussed and compared to those of a borated Nb superconducting strip.

Magnetic-Responsive Release Controlled by Hot Spot Effect.

Magnetically triggered drug delivery nanodevices have attracted great attention in nanomedicine, as they can feature as smart carriers releasing their payload at clinician's will. The key principle of these devices is based on the properties of magnetic cores to generate thermal energy in the presence of an alternating magnetic field. Then, the temperature increase triggers the drug release. Despite this potential, the rapid heat dissipation in living tissues is a serious hindrance for their clinical application. It is hypothesized that magnetic cores could act as hot spots, this is, produce enough heat to trigger the release without the necessity to increase the global temperature. Herein, a nanocarrier has been designed to respond when the temperature reaches 43 °C. This material has been able to release its payload under an alternating magnetic field without the need of increasing the global temperature of the environment, proving the efficacy of the hot spot mechanism in magnetic-responsive drug delivery devices.

Non-conservative evolution in Algols: where is the matter?

There is gathering indirect evidence suggesting non-conservative evolutions in Algols. However, the systemic mass-loss rate is poorly constrained by observations and generally set as a free parameter in binary-star evolution simulations. Moreover, systemic mass loss may lead to observational signatures that are still to be found. We investigate the impact of the outflowing gas and the possible presence of dust grains on the spectral energy distribution (SED). We used the 1D plasma code Cloudy and compared the results with the 3D Monte-Carlo radiative transfer code Skirt for dusty simulations. The circumbinary mass-distribution and binary parameters are computed with state-of-the-art binary calculations done with the Binstar evolution code. The outflowing material reduces the continuum flux-level of the stellar SED in the optical and UV. Due to the time-dependence of this effect, it may help to distinguish between different ejection mechanisms. Dust, if present, leads to observable infrared excesses even with low dust-to-gas ratios and traces the cold material at large distances from the star. By searching for such dust emission in the WISE catalogue, we found a small number of Algols showing infrared excesses, among which the two rather surprising objects SX Aur and CZ Vel. We find that some binary B[e] stars show the same strong Balmer continuum as we predict with our models. However, direct evidence of systemic mass loss is probably not observable in genuine Algols, since these systems no longer eject mass through the hotspot mechanism. Furthermore, owing to its high velocity, the outflowing material dissipates in a few hundred years. If hot enough, the hotspot may produce highly ionised species such as SiIV and observable characteristics that are typical of W Ser systems.