Initial Trapping Research Articles

Endovascular stent-coiling of a giant basilar artery aneurysm through a previous radial artery bypass

Giant, partially-thrombosed basilar artery (BA) aneurysms are extraordinarily difficult to treat. Due to the high risk of rupture exclusion of these aneurysms from the circulation is imperative. In certain instances, direct clipping is unsuitable, and high-flow bypass and proximal parent vessel clip occlusion is required. We report a case of a recurrent partially-thrombosed giant BA apex aneurysm treated with endovascular stent-coiling through a previous radial artery bypass graft. Following the initial bypass and aneurysm trapping six years prior, the patient was neurologically stable until three months prior to admission when he developed new diplopia and left third nerve palsy. Imaging studies demonstrated interval enlargement of the thrombosed portion of the aneurysm and increased size in the filling portion of the aneurysm. In the present case, the existing radial artery bypass graft between left VA and left PCA permitted successful stent-assisted embolization of the recurrent BA aneurysm. To our knowledge, this is the first published case of endovascular stent-coiling of a BA aneurysm through a radial artery bypass graft. This novel technique can be a useful alternative for endovascular aneurysm treatment in these challenging lesions.

3D seismic analysis investigating the relationship between stratigraphic architecture and structural activity in the intra-cratonic Cooper and Eromanga basins, Australia

This research uses four three-dimensional (3D) seismic surveys located in Australia's largest onshore hydrocarbon province, the intra-cratonic Cooper and Eromanga basins, to present an approach that extracts important structural and stratigraphic information from geophysical data that can then be used to define the tectonostratigraphic evolution of subsurface provinces. The methodology consists of: (1) analysing isopach maps; (2) cross-section interpretation of stratigraphic features, erosional surfaces, and faults; and (3) constraining the evolution of fault activity. Most faults within this province are basement-involved with high dip angles. The primary fault set is NE-SW striking, with secondary sets striking N-S, E-W and NW-SE. These high angle faults most likely developed as normal faults before being reactivated by five of the six major tectonic events. Field scale NW-SE strike-slip faults are prolific and can often be overlooked due to the low seismic resolution. A close relationship between on-lapping features and present-day structural highs was found during each of the major structural events, particularly within hydrocarbon-rich Permian stratigraphy, inferring that present-day structures were present throughout basin development and intermittently reactivated. Significant stratal-package thinning, and a high presence of on-lapping features, were associated with regional basement-involved faults, particularly along the Gidgealpa-Merrimelia-Innamincka and Murteree-Nappacoongee ridges. Initial structural trap development occurred during the early Permian, but was most significant during the Late Triassic. Hydrocarbon accumulations were unaffected by structural growth after the critical moment in the petroleum system (90 Ma), as the final period of fault activity was during the Late Cretaceous. This research constrains the tectonostratigraphic evolution of the intra-cratonic Cooper and Eromanga basins, while detailing an approach that extracts and analyses important structural and stratigraphic information from geophysical data, where outcrop is not accessible.

Characterization of Low-Frequency Excess Noise in CH3NH3PbI3-Based Solar Cells Grown by Solution and Hybrid Chemical Vapor Deposition Techniques.

In this study, detailed investigations of low-frequency noise (LFN) characteristics of hybrid chemical vapor deposition (HCVD)- and solution-grown CH3NH3PbI3 (MAPI) solar cells are reported. It has been shown that LFN is a ubiquitous phenomenon observed in all semiconductor devices. It is the smallest signal that can be measured from the device; hence, systematic characterization of the LFN properties can be utilized as a highly sensitive nondestructive tool for the characterization of material defects in the device. It has been demonstrated that the noise power spectral densities of the devices are critically dependent on the parameters of the fabrication process, including the growth ambient of the perovskite layer and the incorporation of the mesoscopic structures in the devices. Our experimental results indicated that the LFN arises from a thermally activated trapping and detrapping process, resulting in the corresponding fluctuations in the conductance of the device. The results show that the presence of oxygen in the growth ambient of the HCVD process and the inclusion of an mp-TiO2 layer in the device structure are two important factors contributing to the substantial reduction in the density of the localized states in the MAPI devices. Furthermore, the lifetimes of the MAPI perovskite-based solar cells are strongly dependent on the material defect concentration. The degradation process is substantially more rapid for the devices with higher initial defect density compared to the devices prepared under optimized conditions and structure that exhibit substantially lower initial trap density.

One-dimensional Bose gas driven by a slow time-dependent harmonic trap

We consider the unitary time evolution of a one-dimensional cloud of hard-core bosons loaded on a harmonic trap potential which is slowly released in time with a general ramp . After the identification of a typical length scale , related to the time ramp, we focus our attention on the dynamics of the density profile within a first order time-dependent perturbation scheme. In the special case of a linear ramp, we compare the first order predictions to the exact solution obtained through Ermakov–Lewis dynamical invariants. We also obtain an exact analytical solution for a cloud released from a harmonic trap with an amplitude that varies as the inverse of time. In such situations, the typical size of the cloud grows with a power law governed by an exponent that depends continuously on the initial trap frequency. At a high enough initial trap amplitude, the exponent acquires an imaginary part that leads to the emergence of a log-periodic modulation of the cloud expansion.

(Invited) Charge Traps, Temperature- and Bias-Stress Stability of Alumina Dielectric / Indium Gallium Arsenide Gate Stacks

Both interface defects and border traps - charge traps in the gate oxide - influence the behavior of InGaAs metal-oxide-semiconductor (MOS) devices. This presentation will summarize the different effects of interface and border traps on the temperature- and bias-stress behavior of aluminum oxide/InGaAs MOS gate stacks, with particular emphasis on threshold voltage stability. The influence of local interface chemistry and the complex role of hydrogen as a defect passivant are highlighted. In one set of experiments, a temperature dependent border trap response for Al2O3 gate dielectrics is investigated. This behavior is unexpected for defects that have typically been reported to charge and discharge through direct tunneling of electrons from the n-type substrate. Temperature dependent border trap frequency dispersion of the accumulation capacitance and conductance is found to be correlated with the presence of a defective interfacial layer, which can be intentionally produced either by excessive exposure to hydrating or oxidizing species during atomic layer deposition of Al2O3 or by use of a previously-reported aqueous HCl wet clean of the InGaAs surface prior to ALD. These results point out the sensitivity of the temperature dependence of the border trap response in metal oxide/III-V MOS gate stacks to the presence of processing-induced interface oxide layers, which alter the dynamics of carrier trapping at defects that are not located at the semiconductor interface. We also report on the effects of pre- and post-atomic layer deposition (ALD) defect passivation with hydrogen on the trap density and reliability of Al2O3/InGaAs gate stacks. Reliability is characterized by capacitance-voltage hysteresis measurements on samples prepared using different fabrication procedures and having different initial trap densities. Despite its beneficial ability to passivate both interface and border traps, a final forming gas (H2/N2) anneal (FGA) step is found to induce a significant hysteresis. This is caused by hydrogen depassivation of defects in the gate stack under bias stress, supported by the observed bias stress-induced increase of interface trap density, and strong hydrogen isotope effects on the measured hysteresis. Additional strategies, beyond hydrogen annealing, for more stable interface defect passivation on InGaAs will be discussed briefly.

Enhanced red afterglow in Sr2SnO4:Sm3+ by co-doping Na+/K+

Red afterglow phosphors, Sr2SnO4:Sm3+ co-activated with alkali ions (K+, Na+) were prepared via solid-state reaction. The phase identification and photoluminescence were characterized and analyzed by X-ray diffraction (XRD), photoluminescence spectroscope, afterglow measurement and thermal luminescence spectroscope. XRD results confirmed an orthorhombic structure for all the samples prepared in the experiment, showing the doping ions had negligible influence on the crystal structure. The photoluminescent spectra of the Sm-doped phosphors revealed a group of reddish orange emission lines originating from 4G5/2 → 6HJ transition of Sm3+. The optimal doping concentration of Sm3+ was determined as 1 mol% and concentration quenching was observed afterwards. For the alkaline ion co-doped samples, Na+ and K+ ions were found profitable to improve both the photoluminescence and the afterglow behavior. Thermal simulated luminescence study indicated that the persistent afterglow of Sr2SnO4:Sm3+ phosphor and alkali ions (K+, Na+) co-doped Sm3+:Sr2SnO4 phosphors were generated by the recombination of the electrons released from the electron traps with the holes in the valence band. The co-doping of alkaline ions (K+, Na+) increased not only the initial trap concentration, but also increased the depth of electron traps, which can be regarded as the main reasons for the enhanced afterglow. Based on such results, possible mechanisms for the afterglow of Sr2SnO4:Sm3+ and alkaline ions (K+, Na+) co-doped phosphors were proposed.

The Co-60 gamma-ray irradiation effects on the Al/HfSiO4/p-Si/Al MOS capacitors

In this work, the initial interface trap density (Nit) to examine device compability for microelectronics and then the Co-60 gamma irradiation responses of Al/HfSiO4/p-Si/Al (MOS) capacitors were investigated in various dose ranges up to 70Gy. Pre-irradiation response of the devices was evaluated from high frequency (HF) and low frequency (LF) capacitance method and the Nit was calculated as 9.91 × 1011cm−2 which shows that the HfSiO4/p-Si interface quality is convenient for microelectronics applications. The irradiation responses of the devices were carried out from flat-band and mid-gap voltage shifts obtained from stretch of capacitance characteristics prior to and after irradiation. The results show that the flat band voltages very slightly shifted to positive voltage values demonstrating the enhancement of negative charge trapping in device structure. The sensitivity of the Al/HfSiO4/p-Si/Al MOS capacitors was found to be 4.41mV/Gy for 300nm-thick HfSiO4 gate dielectrics. This value approximately 6.5 times smaller compared to the same thickness conventional SiO2 based MOS devices. Therefore, HfSiO4 exhibits crucial irradiation tolerance in gamma irradiation environment. Consequently, HfSiO4 dielectrics may have significant usage for microelectronic technology as a radiation hard material where radiation field exists such as in space applications.

Time-dependent dielectric breakdown characterizations of interlayer dielectric damage induced during plasma processing

We proposed an electrical evaluation method on the basis of leakage current–stress time (I–t) measurement for plasma-induced damage (PID) in interlayer dielectric films. The I–t measurement, which is widely used for the time-dependent dielectric breakdown (TDDB) test is applied to the evaluation of PID in thick SiO2 films. We focus on the electron trapping process during the TDDB test. The initial stage of time evolution of leakage current is monitored, and compared among the samples damaged under various plasma conditions. It was found that the initial electron trapping rate depends on the amount of damage, i.e., the rate increases with increasing in process time (tpr) and dc self-bias voltage (Vdc). The proposed technique can be used to assess the reliability degradation of interlayer dielectric films caused by PID.

Interface Defect Hydrogen Depassivation and Capacitance-Voltage Hysteresis of Al2O3/InGaAs Gate Stacks.

We investigate the effects of pre- and postatomic layer deposition (ALD) defect passivation with hydrogen on the trap density and reliability of Al2O3/InGaAs gate stacks. Reliability is characterized by capacitance-voltage hysteresis measurements on samples prepared using different fabrication procedures and having different initial trap densities. Despite its beneficial capability to passivate both interface and border traps, a final forming gas (H2/N2) anneal (FGA) step is correlated with a significant hysteresis. This appears to be caused by hydrogen depassivation of defects in the gate stack under bias stress, supported by the observed bias stress-induced increase of interface trap density, and strong hydrogen isotope effects on the measured hysteresis. On the other hand, intentional air exposure of the InGaAs surface prior to Al2O3 ALD increases the initial interface trap density (Dit) but considerably lowers the hysteresis.

Inhibiting effect of carbonate on the photoinduced flatband potential shifts during water photooxidation at TiO2/solution interface

The TiO2/solution interfacial junction is of scientific and practical importance in the field of photoelectrochemical water splitting. Illumination of this interface usually induces unwanted positive shifts in the flatband potential of TiO2 photoelectrode. In this paper, the inhibiting effect of carbonate on the flatband potential shifts during water oxidation at the illuminated TiO2/solution interface was investigated in pH 6–14 solutions by using Mott-Schottky measurement technique. The footprints of the photohole trapping at the TiO2 surface were traced. Most significant effects of the carbonate additive on the flatband potential shifts and on the interfacial charge densities of surface-trapped holes (STHs) were observed in pH < 12 near-neutral and weak-basic solutions. Based on a generalized surface-OH oxidation mechanism of water photooxidation, the experimental results were interpreted. Some novel features and/or properties for the photohole transport kinetics, such as the preferential surface-OH sites for initial hole trapping into TiO2 surface, pH- and carbonate-dependent charge density of STHs, and the kinetic rate determining step (RDS), were revealed and discussed by correlating the differentiated long-lived and short-lived STHs with photogenerated surface intermediate species of water oxidation. The results and discussion reported in this work provide new physical insights for understanding the mechanisms of water photooxidation.

Ex vacuo atom chip Bose-Einstein condensate

Ex vacuo atom chips, used in conjunction with a custom thin walled vacuum chamber, have enabled the rapid replacement of atom chips for magnetically trapped cold atom experiments. Atoms were trapped in &amp;gt;2 kHz magnetic traps created using high power atom chips. A thin walled vacuum chamber allowed the atoms to be trapped ≲1 mm from the atom chip conductors which were located outside of the vacuum system. Placing the atom chip outside of the vacuum simplified the electrical connections and improved the thermal management. Using a multi-lead Z-wire chip design, a Bose-Einstein condensate was produced with an external atom chip. Vacuum and optical conditions were maintained while replacing the Z-wire chip with an atom chip with a cross-wire design. The atom chips were exchanged and an initial magnetic trap was achieved in less than 3 h.

Direct Time-Resolved Observation of Carrier Trapping and Polaron Conductivity in BiVO4

BiVO4 is a promising photoanode candidate for water splitting applications, but its microscopic charge carrier transport properties are not yet fully understood. We investigated the photoinduced carrier mobility for undoped and 1% tungsten-doped BiVO4 thin films in an early time window from 1 ps to 1 ns using THz spectroscopy. The combined electron–hole effective mobility gradually decreases with time by 1 order of magnitude starting at an upper limit of ∼0.4 cm2 V–1 s–1. The loss is attributed to carrier localization. We provide for the first time direct time-resolved evidence of hole polaron formation accompanied by the temporal buildup of a polaron population in parallel to initial carrier trapping. A mobility of 0.02 cm2 V–1 s–1 is found for the self-trapped carriers, which leads to a thermal hopping activation energy of ∼90 meV.

Uranium Mineralisation in Carbonate Rocks from the Upper Part of Krol Formation in Nainital Syncline and its Significance for Uranium Exploration in Lesser Himalaya

Abstract: Low grade uranium mineralisation associated with phosphorites/phosphatic sediments and carbonaceous shale has been well established at and/or close to Krol-Tal contact in some of sub-basins of inner Krol belt such as Nigalidhar, Mussoorie and Garhwal synclines in the realm of lesser Himalaya. Unlike the other sub-basins of the belt, though the Nainital syncline is sparsely phosphatic and carbonaceous, carbonate hosted uranium occurrence is reported for the first time from the syncline. The carbonate-hosted uranium occurrences in Krol D of Nainital syncline are of limited extent with values ranging from 200 ppm to 840 ppm eU3O8. Radioactivity is associated with fractured dolostone/dolomitic limestone and pelloidal limestone. Uranium phases mostly occur in association with carbonaceous, ferruginous matters and clays. However, ultrafine pitchblende grains do occur associated with idiotopic pyrite aggregates suggesting initial trapping of uranium by organic matters present in sediments which later remobilised and precipitated as fine pitchblende. Subsequently, second phase of remobilisation of uranium under oxidising condition gave rise uraniferous goethite, limonite and other iron oxyhydoxides. In contrast to other sub-basins, the Krol-Tal contact in Nainital syncline does not appear to hold any promising phosphate and uranium mineralisation due to less suitable basinal morphology and low Ca/Mg ratio.

A Wigner Function Approach to Coherence in a Talbot-Lau Interferometer

Using a thermal gas, we model the signal of a trapped interferometer. This interferometer uses two short laser pulses, separated by time T, which act as a phase grating for the matter waves. Near time 2 T , there is an echo in the cloud’s density due to the Talbot-Lau effect. Our model uses the Wigner function approach and includes a weak residual harmonic trap. The analysis shows that the residual potential limits the interferometer’s visibility, shifts the echo time of the interferometer, and alters its time dependence. Loss of visibility can be mitigated by optimizing the initial trap frequency just before the interferometer cycle begins.

NMR study comparing capillary trapping in Berea sandstone of air, carbon dioxide, and supercritical carbon dioxide after imbibition of water

AbstractNuclear magnetic resonance (NMR) techniques were used to study the capillary trapping mechanisms relevant to carbon sequestration. Capillary trapping is an important mechanism in the initial trapping of supercritical CO2 in the pore structures of deep underground rock formations during the sequestration process. Capillary trapping is considered the most promising trapping option for carbon sequestration. NMR techniques noninvasively monitor the drainage and imbibition of air, CO2, and supercritical CO2 with DI H2O at low capillary numbers in a Berea sandstone rock core under conditions representative of a deep underground saline aquifer. Supercritical CO2 was found to have a lower residual nonwetting (NW) phase saturation than that of air and CO2. Supercritical CO2 behaves differently than gas phase air or CO2 and leads to a reduction in capillary trapping. NMR relaxometry data suggest that the NW phase, i.e., air, CO2, or supercritical CO2, is preferentially trapped in larger pores. This is consistent with snap‐off conditions being more favorable in macroscale pores, as NW fluids minimize their contact area with the solid and hence prefer larger pores.

Role of quantum statistics in multi-particle decay dynamics

The role of quantum statistics in the decay dynamics of a multi-particle state, which is suddenly released from a confining potential, is investigated. For an initially confined double particle state, the exact dynamics is presented for both bosons and fermions. The time-evolution of the probability to measure two-particle is evaluated and some counterintuitive features are discussed. For instance, it is shown that although there is a higher chance of finding the two bosons (as oppose to fermions, and even distinguishable particles) at the initial trap region, there is a higher chance (higher than fermions) of finding them on two opposite sides of the trap as if the repulsion between bosons is higher than the repulsion between fermions. The results are demonstrated by numerical simulations and are calculated analytically in the short-time approximation. Furthermore, experimental validation is suggested.

Efficiently engineering pore-scale processes: The role of force dominance and topology during nonwetting phase trapping in porous media

We investigate trapping of a nonwetting (NW) phase, air, within Bentheimer sandstone cores during drainage–imbibition flow experiments, as quantified on a three dimensional (3D) pore-scale basis via x-ray computed microtomography (X-ray CMT). The wetting (W) fluid in these experiments was deionized water doped with potassium iodide (1:6 by weight). We interpret these experiments based on the capillary–viscosity–gravity force dominance exhibited by the Bentheimer–air–brine system and compare to a wide range of previous drainage–imbibition experiments in different media and with different fluids. From this analysis, we conclude that viscous and capillary forces dominate in the Bentheimer–air–brine system as well as in the Bentheimer–supercritical CO2–brine system. In addition, we further develop the relationship between initial (post-drainage) NW phase connectivity and residual (post-imbibition) trapped NW phase saturation, while also taking into account initial NW phase saturation and imbibition capillary number. We quantify NW phase connectivity via a topological measure as well as by a statistical percolation metric. These metrics are evaluated for their utility and appropriateness in quantifying NW phase connectivity within porous media. Here, we find that there is a linear relationship between initial NW phase connectivity (as quantified by the normalized Euler number, χˆ) and capillary trapping efficiency; for a given imbibition capillary number, capillary trapping efficiency (residual NW phase saturation normalized by initial NW phase saturation) can decrease by up to 60% as initial NW phase connectivity increases from low connectivity (χˆ≈0) to very high connectivity (χˆ≈1). We propose that multiphase fluid-porous medium systems can be efficiently engineered to achieve a desired residual state (optimal NW phase saturation) by considering the dominant forces at play in the system along with the impacts of NW phase topology within the porous media, and we illustrate these concepts by considering supercritical CO2 sequestration scenarios.

Negative bias temperature instability threshold voltage shift turnaround in SiGe channel MOSFETs

Negative bias temperature instability (NBTI) has been measured at various temperatures in high-k gate insulator MOSFETs with buried Si0.65Ge0.35 channels and with regular Si surface channels. Previous studies on both surface channel Si devices and Si1−xGex buried channel devices provide evidence for net positive charge trapping as a function of electrical stressing time albeit reduced for the case of Si1−xGex compared to the Si case. In our case, for buried Si0.65Ge0.35, the authors find initial negative charge trapping followed by positive charge trapping at longer times, typically &amp;gt;10−1 s. The effect is accentuated at higher temperatures and yields a turnaround in the measured threshold voltage shift as a function of stress time. Closer examination of NBTI in high-k gate, Si surface devices stressed at room temperature and 90 °C suggests both electron and hole trapping may be present there although the majority effect is hole trapping.

Search-based QoS ranking prediction for web services in cloud environments

Unlike traditional quality of service (QoS) value prediction, QoS ranking prediction examines the order of services under consideration for a particular user. To address this NP-Complete problem, greedy strategy-based solutions, such as CloudRank algorithm, have been widely adopted. However, they can only produce locally approximate solutions. In this paper, we propose a search-based prediction framework to address the QoS ranking problem. The traditional particle swarm optimization (PSO) algorithm has been adapted to optimize the order of services according to their QoS records. In real situations, QoS records for a given consumer are often incomplete, so the related data from close neighbour users is often used to determine preference relations among services. In order to filter the neighbours for a specific user, we present an improved method for measuring the similarity between two users by considering the occurrence probability of service pairs. Based on the similarity computation, the top-k neighbours are selected to provide QoS information support for evaluation of the service ranking. A fitness function for an ordered service sequence is defined to guide search algorithm to find high-quality ranking results, and some additional strategies, such as initial solution selection and trap escaping, are also presented. To validate the effectiveness of our proposed solution, experimental studies have been performed on real-world QoS data, the results from which show that our PSO-based approach has a better ranking for services than that computed by the existing CloudRank algorithm, and that the improvement is statistically significant, in most cases.

Monte Carlo simulations of TL and OSL in nanodosimetric materials and feldspars

The study of luminescent materials consisting of nanoclusters is an increasingly active research area. It has been shown that the physical properties of such nanodosimetric materials can be very different from those of similar conventional microcrystalline phosphors. In addition, it has been suggested that traditional energy band models may not be applicable for some of these nanodosimetric materials, because of the existence of strong spatial correlations between traps and recombination centers. The properties of such spatially correlated materials have been previously simulated by using Monte Carlo techniques and by considering the allowed transitions of charge carriers between the conduction band, electron traps and recombination centers. This previous research demonstrated successfully the effect of trap clustering on the kinetics of charge carriers in a solid, and showed that trap clustering can significantly change the observed luminescence properties. This paper presents a simplified method of carrying out Monte Carlo simulations for thermoluminescence (TL) and optically stimulated luminescence (OSL) phenomena, based on a recently published model for feldspar. This model is based on tunneling recombination processes involving localized near-neighbor transitions. The simulations show that the presence of small clusters consisting of a few traps can lead to multiple peaks in both the TL and linearly modulated OSL signals. The effects of donor charge density, initial trap filling and cluster size are simulated for such multi-peak luminescence signals, and insight is obtained into the mechanism producing these peaks.