Initial Trapping Research Articles

Electron trapping in HfO2 layer deposited over a HF last treated silicon substrate

Electron trapping in HfO2-based MOS structures was studied through pulsed capacitance-voltage (C-V) technique. 10 nm HfO2 layer was deposited by atomic layer deposition over a HF last treated Si substrate. The C-V curves were observed to shift to positive voltages driven by the positive applied voltage along the pulses, consistent with electron trapping due to tunneling transitions between the substrate and pre-existing defects within the oxide and the subsequent lattice relaxation through electron-phonon interaction. The dependences of the voltage shift for a given capacitance value (ΔVC) with stress bias and time, allowed to distinguish two mechanisms. An initial trapping process occurs for times shorter than the microsecond, probably associated with a thin non-stoichiometric SiOx interfacial layer, which is followed by a trapping process that starts after tens of μs and progressively slowed down, associated with traps within the HfO2 layer. Numerical simulations yield for the HfO2 traps an energy of 1.3 eV below the conduction band edge, decreasing exponentially with the distance from the Si interface with a characteristic length of 1.7 nm; and phonon and relaxation energies of 50 meV and 1 eV, respectively. These physical parameters are consistent with previous reports of electron trapping in HfO2 layers deposited on a controlled interfacial layer, suggesting that trapping properties of defects inside the HfO2 layer are insensitive to the treatment of the Si surface before HfO2 deposition. On the other hand, the observed large initial trapping suggests that the non-controlled SiOx interfacial region is more defective than a controlled one.

Measurement of the optical stiffness of photophoretic force tweezers in air

We report on a method of measuring the stiffness in photophoretic force tweezers in air by using an experimental configuration with two counter-propagating hollow beams. By setting the optical traps of both beams in the same focal plane of the camera, we are able to record the flight procedure of a trapped particle into the other trap after the initial trapping beam is switched off. Then, the stiffness of optical trap can be obtained by fitting the relationship of particle position vs time during the flight procedure. It is found that the measurement is tolerant to the distance between the traps and laser power variation. In addition, the measured stiffness is demonstrated applicable in determining the size of aerosol particles. The reliable method provided in this work is not only useful in studying the physical behavior of signal particle under atmosphere condition but also meaningful in the applications of aerosol studies, such as in situ aerosol characterization and the local surrounding environment sensing.

Surface ocean warming near the core of hurricane Sam and its representation in forecast models

On September 30, 2021, a saildrone uncrewed surface vehicle intercepted Hurricane Sam in the northwestern tropical Atlantic and provided continuous observations near the eyewall. Measured surface ocean temperature unexpectedly increased during the first half of the storm. Saildrone current shear and upper-ocean structure from the nearest Argo profiles show an initial trapping of wind momentum by a strong halocline in the upper 30 m, followed by deeper mixing and entrainment of warmer subsurface water into the mixed layer. The ocean initial conditions provided to operational forecast models failed to capture the observed upper-ocean structure. The forecast models failed to simulate the warming and developed a surface cold bias of ~0.5°C by the time peak winds were observed, resulting in a 12-17% underestimation of surface enthalpy flux near the eyewall. Results imply that enhanced upper-ocean observations and, critically, improved assimilation into the hurricane forecast systems, could directly benefit hurricane intensity forecasts.

Negative diffusion of excitons in quasi-two-dimensional systems.

We show how two different mobile-immobile type models explain the observation of negative diffusion of excitons reported in experimental studies in quasi-two-dimensional semiconductor systems. The main reason for the effect is the initial trapping and a delayed release of free excitons in the area close to the original excitation spot. The density of trapped excitons is not registered experimentally. Hence, the signal from the free excitons alone includes the delayed release of not diffusing trapped particles. This is seen as the narrowing of the exciton density profile or decrease of mean-squared displacement which is then interpreted as a negative diffusion. The effect is enhanced with the increase of recombination intensity as well as the rate of the exciton-exciton binary interactions.

Unraveling the Mechanism of Epichaperome Modulation by Zelavespib: Biochemical Insights on Target Occupancy and Extended Residence Time at the Site of Action.

Drugs with a long residence time at their target sites are often more efficacious in disease treatment. The mechanism, however, behind prolonged retention at the site of action is often difficult to understand for non-covalent agents. In this context, we focus on epichaperome agents, such as zelavespib and icapamespib, which maintain target binding for days despite rapid plasma clearance, minimal retention in non-diseased tissues, and rapid metabolism. They have shown significant therapeutic value in cancer and neurodegenerative diseases by disassembling epichaperomes, which are assemblies of tightly bound chaperones and other factors that serve as scaffolding platforms to pathologically rewire protein-protein interactions. To investigate their impact on epichaperomes in vivo, we conducted pharmacokinetic and target occupancy measurements for zelavespib and monitored epichaperome assemblies biochemically in a mouse model. Our findings provide evidence of the intricate mechanism through which zelavespib modulates epichaperomes in vivo. Initially, zelavespib becomes trapped when epichaperomes bound, a mechanism that results in epichaperome disassembly, with no change in the expression level of epichaperome constituents. We propose that the initial trapping stage of epichaperomes is a main contributing factor to the extended on-target residence time observed for this agent in clinical settings. Zelavespib's residence time in tumors seems to be dictated by target disassembly kinetics rather than by frank drug-target unbinding kinetics. The off-rate of zelavespib from epichaperomes is, therefore, much slower than anticipated from the recorded tumor pharmacokinetic profile or as determined in vitro using diluted systems. This research sheds light on the underlying processes that make epichaperome agents effective in the treatment of certain diseases.

Brighten strontium aluminate long-persistence materials via optimizing defect energy level distribution

Afterglow brightness of inorganic persistent luminescent (PersL) materials upon ceasing light excitation represents an important parameter for various glow-in-the-dark applications. Although the emission wavelength of PersL materials is developed to cover over the whole spectral range from ultraviolet to near infrared light, and light emission is sufficiently long-lasting with a fractional number of rare-earth doped PersL materials commercially available, PersL materials with high initial afterglow brightness at room-temperature condition remain rarely reported. Employing trap-controlled temperature dependency of persistent luminescence mechanism, defect energy level distribution, and microwave-assisted solid-state reaction, here a highly bright green-emitting strontium aluminate phosphor is reported. Higher initial afterglow brightness (a photometric luminance of 99.8 cd/m2, enhanced 1.7 times than that of the commercial one) is achieved due to the massive aggregation of charge carriers at shallow-trap energy levels. The relation between initial afterglow brightness and trap energy level distribution is investigated. The glowing-in-the-dark composite panel composed of Sr4Al14O25:Eu2+, Dy3+ and Polydimethylsiloxane can light up the safety sign and the map of fire evacuation route. These findings may provide a major step forward to developing high-brightness PersL materials and are expected to further benefit a wide range of PersL material systems for practical glow-in-the-dark applications.

Advanced Digital-SCAL Measurements of Gas Trapped in Sandstone

Trapped gas saturation (Sgr) plays an important role in subsurface engineering, such as carbon capture and storage, H2 storage efficiency as well as the production of natural gas. Unfortunately, Sgr is notoriously difficult to measure in the laboratory or field. The conventional method of measurement—low-rate unsteady-state coreflooding—is often impacted by gas dissolution effects, resulting in large uncertainties of the measured Sgr. Moreover, it is not understood why this effect occurs, even for brines carefully pre-equilibrated with gas. To address this question, we used high-resolution X-ray computed tomography (micro-CT) imaging techniques to directly visualize the pore-scale processes during gas trapping. Consistent with previous studies, we find that for pre-equilibrated brine, the remaining gas saturation continually decreased with more (pre-equilibrated) brine injected and even after the brine injection was stopped, resulting in very low Sgr values (possibly even zero) at the pore-scale level. Furthermore, we were able to clearly observe the initial trapping of gas by the snap-off effect, followed by a further shrinkage of the gas clusters that had no connected pathway to the outside. Our experimental insights suggest that the effect is related to the effective phase behavior of gas inside the porous medium, which due to the geometric confinement, could be different from the phase behavior of bulk fluids. The underlying mechanism is likely linked to ripening dynamics, which involves a coupling between phase equilibrium and dissolution/partitioning of components, diffusive transport, and capillarity in the geometric confinement of the pore space.

Engineering the electronic structure of platinum single-atom sites via tailored porous carbon nanofibers for large-scale hydrogen production

Pt single-atom catalysts are promising for efficient hydrogen evolution reactions (HER) due to their ultra-high catalytic activity and atomic utilization. However, developing a scalable preparation method of binder-free Pt single-atom catalysts with optimal electronic structures for large-scale hydrogen production is still a serious challenge. In this work, we fabricated tailored nitrogen-doped porous carbon nanofibers as a support for engineering the electronic structure of Pt single-atom sites via initial micropore trapping and subsequent optimized nitrogen/carbon anchoring. The as-prepared Pt single-atom catalysts exhibited impressively enhanced HER activity and satisfactory stability, superior to the state-of-the-art single-atom catalysts. X-ray absorption structure analysis combined with theoretical simulation demonstrated the mechanisms for HER performance improvement. In particular, the free-standing Pt single-atom catalysts for a binder-free electrode showed a low overpotential of 64 mV even at 500 mA cm−2, indicating promising application for the large-scale hydrogen production.

A Flexible, Modular Platform for Multidimensional Ion Mobility of Native-like Ions.

Native ion mobility (IM) mass spectrometry (MS) is used to probe the size, shape, and assembly of biomolecular complexes. IM-IM-MS can increase the amount of information available in structural studies by isolating subpopulations of structures for further analysis. Previously, IM-IM-MS has been implemented using the Structures for Lossless Ion Manipulations (SLIM) architecture to probe the structural stability of gas-phase protein ions. Here, a new multidimensional IM instrument constructed from SLIM devices is characterized using multiple operational modes. In this new design, modular devices are used to perform all ion manipulations, including initial accumulation, injection, separation, selection, and trapping. Using single-dimension IM, collision cross section (Ω) values are determined for a set of native-like ions. These Ω values are within 3% of those reported previously based on measurements using RF-confining drift cells. Tandem IM experiments are performed on a sample of ubiquitin ions that contains both compact and partially unfolded structures, demonstrating that this platform can isolate subpopulations of structures. Finally, additional modes of analysis, including multiplexed IM and inverse IM, are demonstrated using this platform. The ability of this platform to quickly switch between different modes of IM analysis makes it a highly flexible tool for studying protein structures and dynamics.

Dynamical Fermionization in One-Dimensional Spinor Gases at Finite Temperature.

Following the removal of axial confinement the momentum distribution of a Tonks-Girardeau gas approaches that of a system of noninteracting spinless fermions in the initial harmonic trap. This phenomenon, called dynamical fermionization, has been experimentally confirmed in the case of the Lieb-Liniger model and theoretically predicted in the case of multicomponent systems at zero temperature. We prove analytically that for all spinor gases with strong repulsive contact interactions at finite temperature the momentum distribution after release from the trap asymptotically approaches that of a system of spinless fermions at the same temperature but with a renormalized chemical potential which depends on the number of components of the spinor system. In the case of the Gaudin-Yang model we check numerically our analytical predictions using the results obtained from a nonequilibrium generalization of Lenard's formula describing the time evolution of the field-field correlators.

Электризация поверхности кварцевых стекол электронными пучками

To establish the effect of subthreshold defect formation on the charge accumulation in quartz glasses, a comprehensive study of the process of their electrization by electron beams was carried out. Earlier it was shown that the process of radiative electrization of quartz glasses consists of two stages. The short-term stage of charging can be explained by the accumulation of charge on the initial trap centers, and the long-term component can be caused by the generation of deep trap centers capable of capturing electrons. In the studied quartz samples, the trapping centers can be three-coordinated silicon atoms (E'-centers). The presence of two stages of the charging process is confirmed by two different methods for determining the surface potential. Despite the increase in the surface potential during irradiation and the resulting decrease in the energy of the incident electrons, an increase in the intensity of the cathodoluminescent signal is observed. Such an increase in intensity can be caused by an increase in the number of luminescent defects in quartz, a two-coordinated silicon atom or a non-bridging oxygen atom, as well as by charge accumulation at competing nonradiative trap centers.

Trap Generation in Whole Gate Stacks of FeFET With TiN/Hf0.5Zr0.5O2/SiOx/Si (MFIS) Gate Structure During Endurance Fatigue

This work investigates trap generation in gate stacks of ferroelectric field-effect transistor (FeFET) with TiN/Hf0.5Zr0.5O2/SiOx/Si gate structure during endurance fatigue by using the low-frequency noise method. We find that the traps are generated not only at Hf0.5Zr0.5O2/SiOx interface but also in both the Hf0.5Zr0.5O2 and SiOx. Our work provides evidence of defect generation inside the ferroelectric layer of FeFET during cycling. Furthermore, the traps in the SiOx are more detrimental to endurance fatigue. And the trap generation in the SiOx is more important than its initial trap density for endurance fatigue. Our work is helpful in deeply understanding the endurance of FeFET.

Impact of Floods on Sediment Trap Efficiency of a Small Shallow Reservoir—A Case Study

Silting is the main factor limiting the ability to perform the tasks that small reservoirs are intended for. Therefore, the change in sediment trap efficiency was studied for a small shallow reservoir, Krempna, which, due to high silting intensity, was desilted twice (2005, 2018). Siltation measurements were performed in two periods (1987–2005, 2006–2018) after the reservoir was desludged. It was found that the sediments were composed of fine-fraction sediment; therefore, a series of measurements of suspended sediment transport were performed. These data allowed us to calculate the daily sediment transport flowing into and out of the reservoir and water-level measurements. Then, the sediment trap efficiency was calculated. The aim of this study was: (1) to determine the impact of flood flows on the sediment trap efficiency (STE) of a small shallow reservoir, (2) to determine changes in the value of the sediment trap efficiency of a small shallow reservoir in two different periods of its operation, and (3) to demonstrate whether it is possible to determine the value of the initial sediment trap efficiency and changes in the STE values during operation using empirical formulas. Finally, during flood flows, the amount of sediment retained in the studied reservoir was several times lower than during freshets with a much smaller flow. It is these small freshets that reduce the capacity of the reservoir. A correlation relationship was developed for 18 data—flood flows (Q) and sediment trap efficiency (STE).

Inverse engineering of fast state transfer among coupled oscillators

We design faster-than-adiabatic state transfers (switching of quantum numbers) in time-dependent coupled-oscillator Hamiltonians. The manipulation to drive the process is found using a two-dimensional invariant recently proposed in S. Simsek and F. Mintert, Quantum 5 (2021) 409, and involves both rotation and transient scaling of the principal axes of the potential in a Cartesian representation. Importantly, this invariant is degenerate except for the subspace spanned by its ground state. Such degeneracy, in general, allows for infidelities of the final states with respect to ideal target eigenstates. However, the value of a single control parameter can be chosen so that the state switching is perfect for arbitrary (not necessarily known) initial eigenstates. Additional 2D linear invariants are used to find easily the parameter values needed and to provide generic expressions for the final states and final energies. In particular we find time-dependent transformations of a two-dimensional harmonic trap for a particle (such as an ion or neutral atom) so that the final trap is rotated with respect to the initial one, and eigenstates of the initial trap are converted into rotated replicas at final time, in some chosen time and rotation angle.

Dynamical fermionization in a one-dimensional Bose-Fermi mixture

After release from the trap the momentum distribution of an impenetrable gas asymptotically approaches that of a spinless noninteracting Fermi gas in the initial trap. This phenomenon is called dynamical fermionization and, very recently, has been experimentally confirmed in the case of the Lieb-Liniger model in the Tonks-Girardeau regime. We prove analytically and confirm numerically that following the removal of axial confinement the strongly interacting Bose-Fermi mixture exhibits dynamical fermionization and the asymptotical momentum distribution of each component has the same shape as its density profile at $t=0$. Under a sudden change of the trap frequency to a new nonzero value the dynamics of both fermionic and bosonic momentum distributions presents characteristics which are similar to the case of single component bosons experiencing a similar quench. Our results are derived using a product representation for the correlation functions which, in addition to analytical considerations, can be implemented numerically very easily with complexity which scales polynomially in the number of particles.

Initial and residual trapping of hydrogen and nitrogen in Fontainebleau sandstone using nuclear magnetic resonance core flooding

Hydrogen is among a few promising energy carriers of the future mainly due to its zero-emission combustion nature. It also plays an important role in the transition from fossil fuel to renewable. Hydrogen technology is relatively immature and serious knowledge gaps do exist in its production, transport, storage, and utilization. Although the economical generation of hydrogen to the scale required for such transition is still the biggest technical and environmental challenge, unlocking the large-scale but safe storage is similarly important. It is difficult to store hydrogen in solid and liquid states and storing it in the gaseous phase requires a huge volume which is just available in subsurface porous media. Sandstone is the most abundant and favourable medium for such storage as carbonate rock might not be suitable due to potential geochemical reactions.It is well established in the literature that interaction of the host rock-fluid and injected gas plays a crucial role in fluid flow, residual trapping, withdrawal, and more generally storing capacity. Such data for the hydrogen system is extremely rare and are generally limited to contact angle measurements, while being not representative of the reality of rock-brine-hydrogen interaction(s). Therefore, we have conducted, for the first time, a series of core flooding experiments using Nuclear Magnetic Resonance (NMR) to monitor hydrogen (H2) and Nitrogen (N2) gas saturations during the drainage and imbibition stages under pressure and temperature that represent shallow reservoirs. To avoid any geochemical reaction during the test, we selected a clean sandstone core plug of 99.8% quartz (Fontainebleau with a gas porosity of 9.7% and a permeability of 190 mD).Results show significantly low initial and residual H2 saturations in comparison with N2, regardless of whether the injection flow rate or capillary number were the same or not. For instance, when the same injection flow rate was used, H2 saturation during primary drainage was 4% and it was <2% after imbibition. On other hand, N2 saturation during the primary drainage was 26% and it was 17% after imbibition. However, when the same capillary number of H2 was utilised for the N2 experiment, the N2 saturation values were ∼15% for initial gas saturation and 8% for residual gas saturation. Our results promisingly support the idea of hydrogen underground storage; however, we should emphasise that more sandstone rocks of different clay mineralogy should be investigated before reaching a conclusive outcome.

Attraction of Choristoneura rosaceana to pheromone blends in ratios produced in glands or emitted by females

AbstractTrap captures of obliquebanded leafroller, Choristoneura rosaceana (Harris), to pheromone blends in ratios approximating those reported in pheromone glands and a novel blend based on a volatile headspace collection from live virgin females were evaluated in field experiments in Michigan apple orchards. In an initial field trapping study, pheromone lures composed of either a three‐ or four‐component blend approximation of the blend present in female pheromone glands at doses ranging from 0.1 to 20 mg/lure were compared. The four‐component blend was a combination of (Z)‐11‐tetradecenyl acetate (Z11‐14:Ac), (E)‐11‐tetradecenyl acetate (E11‐14:Ac), (Z)‐11‐tetradecenol (Z11‐14:OH) and (Z)‐11‐tetradecenal (Z11‐14:Al) in a ratio of 96.5:1.8:1.4:0.2, respectively, while the three‐component blend lacked Z11‐14:Al. Pheromone emissions by groups of virgin females and commercial lures were collected in the laboratory and analysed by gas chromatography. These data were used to formulate a new pheromone lure that was compared to a commercial lure in a second trapping study. In the first field study, traps baited with 10 mg pheromones or above captured significantly more moths than traps baited with 1 mg or less, regardless of the blend. Surprisingly, groups of virgin females only emitted two detectable pheromone components, Z11‐14:Ac and Z11‐14:OH in a ratio of 37:63, which was substantially different from the blends detected in pheromone glands in the literature. The newly formulated pheromone lure based on females’ emission was more than twice as attractive as the commercial lure which emitted a 74:5:21 three‐component blend of Z11‐14:Ac, E11‐14:Ac and Z11‐14:OH. Our results suggested that the actual pheromones released by females may not translate directly to the content of pheromone glands.

Photorefractive Response Enhancement in Poly(triarylamine)-Based Polymer Composites by a Second Electron Trap Chromophore.

Photorefractive (PR) performances are affected by the components of the photoconductor, sensitizer, nonlinear optical dye, and plasticizer. A photoconductor with high hole mobility promises a faster response time, whereas it induces higher photoconductivity, which leads to easy dielectric breakdown. Adding a second electron trap is effective in controlling photoconductivity. In this study, the role of a second electron trap 1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene (TmPyPB) was investigated in a PR composite consisting of a photoconductor of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] with a high hole mobility, a nonlinear optical chromophore of piperidinodicyanostyrene, a plasticizer of (2,4,6-trimethylphenyl)diphenylamine, and a sensitizer of [6,6]-phenyl C61 butyric acid-methyl ester. The minimum time response with the maximum optical diffraction efficiency and sensitivity was measured at a 1 wt % content of TmPyPB. These results were consistent with the number of charge carriers trapped per unit volume and per unit time Nc (cm–3 s–1), which is defined as the ratio between the initial trap density Ti (cm–3) and response time τ (s), at a 1 wt % content of TmPyPB. A faster response time of 149 μs, optical diffraction of 24.1% (external diffraction of 4.8%), and a sensitivity of 2746 cm2 J–1 were measured at 50 V μm–1 for the sample with 1 wt % TmPyPB. High loading of 5 wt % TmPyPB led to a large decrease in photoconductivity and effectively suppressed the dielectric breakdown under a stronger electric field, whereas a slower response time with lower diffraction efficiency was observed for optical diffraction.

A high-throughput microfluidic diploid yeast long-term culturing (DYLC) chip capable of bud reorientation and concerted daughter dissection for replicative lifespan determination

BackgroundBudding yeast, Saccharomyces cerevisiae, has been extensively favored as a model organism in aging and age-related studies, thanks to versatile microfluidic chips for cell dynamics assay and replicative lifespan (RLS) determination at single-cell resolution. However, previous microfluidic structures aiming to immobilize haploid yeast may impose excessive spatial constraint and mechanical stress on cells, especially for larger diploid cells that sprout in a bipolar pattern.ResultsWe developed a high-throughput microfluidic chip for diploid yeast long-term culturing (DYLC), optical inspection and cell-aging analysis. The DYLC chip features 1100 “leaky bowl”-shaped traps formatted in an array to dock single cells under laminar-perfused medium and effectively remove daughter cells by hydraulic shear forces. The delicate microstructures of cell traps enable hydrodynamic rotation of newborn buds, so as to ensure bud reorientation towards downstream and concerted daughter dissection thereafter. The traps provide sufficient space for cell-volume enlargement during aging, and thus properly alleviate structural compression and external stress on budding yeast. Trapping efficiency and long-term maintenance of single cells were optimized according to computational fluid dynamics simulations and experimental characterization in terms of critical parameters of the trap and array geometries. Owing to the self-filling of daughter cells dissected from traps upstream, an initial trapping efficiency of about 70% can rapidly reach a high value of over 92% after 4-hour cell culturing. During yeast proliferation and aging, cellular processes of growth, budding and daughter dissection were continuously tracked for over 60 h by time-lapse imaging. Yeast RLS and budding time interval (BTI) were directly calculated by the sequential two-digit codes indicating the budding status in images. With the employed diploid yeast strain, we obtained an RLS of 24.29 ± 3.65 generations, and verified the extension of BTI in the first couple of generations after birth and the last several generations approaching death, as well as cell de-synchronization along diploid yeast aging.ConclusionsThe DYLC chip offers a promising platform for reliable capture and culturing of diploid yeast cells and for life-long tracking of cell dynamics and replicative aging processes so that grasping comprehensive insights of aging mechanism in complex eukaryotic cells.Graphical

Biologically active cuticular compounds of female Sirex noctilio

AbstractThe Eurasian woodwasp Sirex noctilio Fabricius (Hymenoptera: Siricidae) is a major invasive pest in pine plantations of the Southern Hemisphere. In this study, we aimed to identify pheromone compounds in S. noctilio females, for potential use in lures for pest monitoring and control. An examination of S. noctilio body washes resulted in the identification of a behaviorally active compound, 10‐oxo‐decanoic acid (10‐ODA), that is derived from cuticular hydrocarbons of females. This oxocarboxylic acid is likely produced through oxidative reactions at the cleavage of double bonds of certain female‐produced cuticular dienes. Gas chromatography‐electroantennogram detection (GC‐EAD) analyses showed that only male antennae consistently responded to natural and synthetic 10‐ODA. In olfactometer assays, 10‐ODA alone was attractive to S. noctilio males, although males marginally preferred the combination of 10‐ODA and nonanal, compared with 10‐ODA alone. This suggests pheromonal activity of this compound. However, no wasps were captured in initial field trapping experiments with 10‐ODA and further work is required.