Pa Range Research Articles

Ultra-low dark current and high sensitivity lead-free perovskite–like photodetector realized by anti-solvent optimization Cs3Bi2I9 amorphous film

Compared with lead halide perovskite, bismuth-based perovskite has lower toxicity and air stability, demonstrating enormous potential for application, among them, Cs3Bi2I9 materials has been researched as an alternative to lead-based perovskite for application of optoelectronic devices. It is crucial for the realization of high-performance photodetectors which need high-quality perovskite thin films. Here, we prepared a lead-free, all-inorganic, Cs3Bi2I9 perovskite-like amorphous films by spin coating method, and diethyl ether was added as an anti-solvent at different times of spin-coating. The results show that the homogeneous and dense Cs3Bi2I9 amorphous films can be obtained by adding anti-solvent at 14seconds. Furthermore, Cs3Bi2I9 perovskite-like UV photodetector achieved extremely low dark current around ~pA range, high sensitivity of 1.10×104 was fabricated. Our research shows that the preparation of Cs3Bi2I9 amorphous films by the simple antisolvent-assisted spin-coating method are very promising for optoelectronic device.

Association of cognitive performance with overall, dosage, intensity, and domain physical activity in aging: NHANES 2011–2014

BackgroundThe specific relationship between PA in detailed types and cognition is still unclear due to limited evidence. Our study aimed to investigate the relationship between cognitive performance and various aspects of physical activity, including overall activity, dosage, intensity levels [moderate physical activity (MPA), vigorous PA], and different domains of activity [occupational PA (OPA), transportation PA (TPA), and leisure-time PA (LTPA)] in older adults using data from the NHANES database.MethodsThis cross-sectional analysis used data from 2 cycles of NHANES (2011–2014). PA was determined through participants' self-reports using the Global Physical Activity Questionnaire (GPAQ). Cognitive performance was evaluated by the presence of psychometric mild cognitive impairment (p-MCI), identified based on a composite measure derived from three cognitive tests including the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), the Animal Fluency test, and the Digit Symbol Substitution test (DSST). Logistic regression models were used to evaluate the association.ResultsA total of 2588 participants aged 60 years or older were included, with an average age of 69.4 years and 48% being male. In the fully adjusted model, compared to no PA, performing 300 min of PA, and MPA were associated with 44%, and 33% reductions in the prevalence of p-MCI, respectively. Additionally, engaging in 1–149 min/week [OR 0.56, 95% CI (0.33–0.92)] and ≥ 300 min/week [OR 0.66, 95% CI (0.44–0.96)] of OPA, as well as ≥ 300 min/week [OR 0.56, 95% CI (0.36–0.86)] of LTPA, were also associated with a lower prevalence of p-MCI. Additionally, engaging in a diverse range of PA had better outcomes.ConclusionsOur results suggested a positive association between higher levels of PA and enhanced cognitive performance. Different intensities and domains of PA have varying impacts on cognition. Future exploration, such as objectively measured PA and longitudinal studies were needed to validate our conclusion.

A Comparative Study on Picoammeter Designs as Alternatives for Nuclear Reactor Power Measurement Systems

Abstract The study investigates the picoammeter, a highly sensitive current measurement device capable of measuring currents in the picoampere (pA) range. It discusses the typical amplification technique in picoammeters, utilizing an Op-Amp in a trans-impedance amplifier (TIA) circuit to convert the current into a voltage signal. The paper explores the impact of different IC Op-Amps on the picoammeter’s performance, evaluating AD549, MAX4230, LMC662, TLV272, and MCP6001. The result reveals that AD549 Op-Amp ICs are more suitable for picoammeter design due to their low noise performance and low input bias current. Noise output and AC stability are assessed through numerical analysis and simulations using a circuit simulator. The resulting picoammeter exhibits low noise, high sensitivity, and precise measurement accuracy, making it an optimal choice for precise low-current measurements in CIC detectors.

Encapsulation of crystalline and amorphous Sb2S3 within carbon and boron nitride nanotubes.

The recent rediscovery of 1D and quasi-1D (q-1D) van der Waals (vdW) crystals has laid foundation for the realization of emergent electronic, optical, and quantum-confined physical phenomena in both bulk and at the nanoscale. Of these, the highly anisotropic q-1D vdW crystal structure and the visible-light optical/optoelectronic properties of antimony trisulfide (Sb2S3) have led to its widespread consideration as a promising building block for photovoltaic and non-volatile phase change devices. However, while these applications will greatly benefit from well-defined and sub-nanometer-thick q-1D structures, little has been known about feasible synthetic routes that can access single covalent chains of Sb2S3. In this work, we explore how encapsulation in single or multi-walled carbon nanotubes (SWCNTs or MWCNTs) and visible-range transparent boron nitride nanotubes (BNNTs) influences the growth and phase of Sb2S3 nanostructures. We demonstrate that nanotubes with smaller diameters had a more pronounced effect in the crystallographic growth direction and orientation of Sb2S3 nanostructures, promoting the crystallization of the guest structures along the long-axis [010]-direction. As such, we were able to reliably access well-ordered few to single covalent chains of Sb2S3 when synthesized within defect-free SWCNTs with sub-2 nm inner diameters. Intriguingly, we found that the degree of crystalline order of Sb2S3 nanostructures was strongly influenced by the presence of defects and discontinuities along the Sb2S3-nanotube interface. We show that amorphous nanowire domains of Sb2S3 form around defect sites in larger, multi-walled nanotubes that manifest inner wall defects and discontinuities, suggesting a means to manipulate the crystallization dynamics of confined sub-10 nm-thick Sb2S3 nanostructures within nanotubes. Lastly, we show that ultranarrow amorphous Sb2S3 can impart functionality onto isolable BNNTs with photocurrent generation in the pA range which, alongside the dispersibility of the Sb2S3@BNNTs, could be leveraged to easily fabricate photoresistors only a few nm in width. Altogether, our results serve to solidify the understanding of how q-1D vdW pnictogen chalcogenides crystallize within confined synthetic platforms and are a step towards realizing functional materials from ensembles of encapsulated heterostructures.

Flexible pressure sensors based on reduced graphene oxide @ porous silicone elastomers with good resolution and wide working range

Current flexible piezoresistive pressure sensors still face challenges, such as poor stability and a limited detection range, making it difficult to accurately discern small-scale pressures in the Pa or MPa range when meeting sudden pressure events. To tackle the above issues, this study presents the development of a competent sensor composed of porous conductive elastomer and laser-induced graphene electrodes. The substrate of the composite elastomer is a porous silicone elastomer obtained by the additive reaction using template methods, and the conductive filler consisting of reduced graphene oxide is synthesized through an eco-friendly approach. We demonstrated that the sensors fabricated here have the ability to precisely resolve pressures from 542 Pa to 1.5 MPa with long-term stability, as well as the detection of subtle signals, such as pulse pulsation and throat vibrations. Above all, such sensors have great potential in the application of human-machine interaction.

Studying the impacts of deep uncertainties on water resources system in Ba River Basin through the combined use of a climate stress-test and land use change

Study regionBa River Basin, Viet Nam. Study focusThe impacts of deep uncertainties on the water resources system in the Ba River Basin are explored through the combined use of a climate stress-test and land use change. The performance of the water resources system is assessed using water supply reliability under various climate conditions and land use. A MIKE HYDRO Basin model is developed with 7 irrigation regions, 45 irrigation users, 8 regular users, 48 reservoirs, and 10 hydropower plants. 40 different combinations of climate conditions and land use change were simulated. New hydrological insights for the regionClimatic and land use change is expected to reduce water supply reliability in the river basin by between 2.1% and 5.2%. The most significant reliability decrease is in Nam Bac An Khe (−29.4%), while the most increase is in Upper Ayun (+10.9%). The spatial variation of climatic change impact is high and is reflected in the reliability range. The reliability range of Upper Ayun and Ayun Pa is narrow (1.2% in Upper Ayun and 0.7% in Ayun Pa). In contrast, the reliability range of Nam Bac An Khe, Krong Pa, Krong Hnang, and Upper Dong Cam is wide (14.3% in Nam Bac An Khe, 12.7% in Krong Pa, 12.4% in Krong Hnang, 11.7% in Upper Dong Cam, and 3.4% in Lower Dong Cam).

Integrating shear flow and trypsin treatment to assess cell adhesion strength.

Cell adhesion is of fundamental importance in cell and tissue organization and for designing cell-laden constructs for tissue engineering. Prior methods to assess cell adhesion strength for strongly adherent cells using hydrodynamic shear flow either involved the use of specialized flow devices to generate high shear stress or used simpler implementations like larger height parallel plate chambers that enable multihour cell culture but generate low wall shear stress and are, hence, more applicable for weakly adherent cells. Here, we propose a shear flow assay for adhesion strength assessment of strongly adherent cells that employs off-the-shelf parallel plate chambers for shear flow as well as simultaneous trypsin treatment to tune down the adhesion strength of cells. We implement the assay with a strongly adherent cell type and show that wall shear stress in the 0.07-7 Pa range is sufficient to dislodge the cells with simultaneous trypsin treatment. Imaging of cells over a square centimeter area allows cell morphological analysis of hundreds of cells. We show that the cell area of cells that are dislodged, on average, does not monotonically increase with wall shear stress at the higher end of wall shear stresses used and suggest that this can be explained by the likely higher resistance of high circularity cells to trypsin digestion. The adhesion strength assay proposed can be used to assess the adhesion strength of both weakly and strongly adherent cell types and has the potential to be adapted for substrate stiffness-dependent adhesion strength assessment in mechanobiology studies.

Fluorescent biosensor based on MB-APT combined with Pt NPs for the detection of infectious bacteria in mouse and human wounds

Bacterial infection of wounds is one of great concern to patients, and rapid and correct detection of bacterial infection is crucial to ensure accurate diagnosis and early intervention. Based on the principle that glucose can only be consumed by live bacteria, a fluorescent biosensor was constructed to detect four kinds of common infectious bacteria (Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus) in skin wounds, taking advantage of magnetic bead-aptamer for recognizing, sorting and enrichment, platinum nanoparticles for signal amplification. The linear detection range of AB, EC, PA and SA were 27– 8 × 106 CFU/mL, 10– 2.5 × 107 CFU/mL, 34– 2.5 × 107 CFU/mL and 10– 1.0 × 107 CFU/mL, respectively, and the limits of detection were 27 CFU/mL, 10 CFU/mL, 34 CFU/mL and 2 CFU/mL. Furthermore, all target bacteria in samples containing 8 × 108 CFU/mL of other interfering bacteria have been successfully identified and quantified. The proposed method was also successfully applied to the detection of bacterial infection in skin wounds of mouse and human, including the detection of separate bacterial infection as well as a coinfection. The recovery of this method was in the range of 90.161– 109.961%. Thus, this proposed method can be a promising candidate for rapid and convenient evaluation of infectious bacteria in point-of-care settings.

Preliminary study of laser-induced breakdown spectroscopy for non-destructive pressure measurement in confined vacuum interlayers

The pressure measurement within a closed vacuum chamber is a crucial indicator for evaluating vacuum performance. The commonly used puncture and sampling method is destructive to the device. This paper presents a new method based on laser-induced breakdown spectroscopy (LIBS) to evaluate the pressure inside a confined, transparent vacuum sandwich. The intensity of the emission spectra of copper sheets inside the sandwich was tested at different pressures, and three cylindrical cavities of different heights were subjected to experiments. The results show that the Cu and O intensity ratio varies linearly with gas pressure in the 1–103 Pa range, which can be used to predict the pressure inside the interlayer. It is fast, non-destructive, and remotely detectable. This work extends the application of LIBS for spatial confinement effects to enhance the spectral intensity and provides a new idea for pressure measurement in confined devices.

Graphene woven fabric-polydimethylsiloxane piezoresistive films for smart multi-stimuli responses

The outstanding properties of graphene, including its electromechanical property, could be engineered for wearable electronic sensor platforms. The tubular graphene weaved into a mesh or graphene woven fabrics (GWF) has been reported as one of the most sensitive materials for deformation detection, as well as a promising temperature sensor. Herein, we present the performance of our developed flexible, stretchable, and multiple sensitive sensors fabricated from GWF embedded in polydimethylsiloxane (PDMS) film substrate. The GWF/PDMS sensor shows a pressure sensitivity of 0.0142 kPa−1 in a wide linearity range of 0–20 kPa, an outstanding Gauge factor (GF) of 582 at a strain of 6.2 %, and a very high positive sensitivity of 0.0238 °C−1 in the temperature range of 25–80 °C. A practical application as a high sensitivity air pressure sensor able to measure low pressures (in the range of Pa to kPa) was also demonstrated. This sensor platform having desirable performance characteristics is an excellent candidate for wearable devices in the healthcare sector.

Community-based physical activity and/or nutrition interventions to promote mobility in older adults: An umbrella review.

Background: Physical activity and a healthy diet are important in helping to maintain mobility and quality of life with aging. Delivery of physical activity and nutrition interventions in a group setting adds the benefits of social participation. Several published systematic reviews have explored a broad range of PA and/or nutrition interventions for older adults, making it challenging to bring together the best scientific evidence to inform program design and to inform multicomponent intervention development. This umbrella review aims to identify group-based physical activity and nutrition interventions for community-dwelling older adults that improve mobility. Methods: Five electronic databases (MEDLINE, Embase, CINAHL, Cochrane CENTRAL, Sociological Abstracts) were searched from inception to April 28, 2020. Eligibility criteria included systematic reviews exploring the effectiveness of physical activity and/or nutrition interventions, delivered in a group setting for community-dwelling older adults. Two reviewers independently performed eligibility screening, critical appraisal (using AMSTAR 2) and data extraction. The GRADE approach was used to assess the overall certainty of the evidence. Older adult/provider research partners informed data synthesis and results presentation. Results: In total, 54 systematic reviews (1 high, 21 moderate, 32 low/critically low quality) were identified; 46 included physical activity only, and eight included both physical activity and nutritional supplements. No reviews included nutrition interventions alone. Combined aerobic/resistance, general physical activity, and mind-body exercise all improved physical function and balance (moderate-high certainty). Aerobic/resistance training improved aerobic capacity (high certainty). Resistance training and general physical activity improved muscle strength (moderate certainty). Aerobic/resistance training and general physical activity are likely to reduce falls among older adults (moderate certainty). There was no evidence of benefit for nutritional supplementation with physical activity. Conclusions: Multicomponent group-based physical activity interventions can improve measures of mobility in community-dwelling older adults. We found no reviews focused on nutrition only, highlighting a gap in the literature.

Physical Activity and Fundamental Motor Skill Outcome: A Quasi-Experimental Study Among Rural Pre-schoolers in Kuching, Sarawak

Fundamental movement skills (FMS)-oriented school-based intervention allows children to be more competent and interested to participate in a wider range of physical activities. This study aimed to determine the physical activity and fundamental motor skills outcome from a school-based intervention programme among rural pre-schoolers in Kuching. It used a quasi-experimental non-randomised design with a total of 153 children from 9 government kindergartens. For physical activity level, there was a significant difference between the intervention and control group at the 3 months, F (1, 151) = 3.90, p = 0.05, with a ŋ2 = 0.025 and 6 months-time duration, F (1, 151) = 55.70, p < 0.001, with a ŋ2 = 0.27. The same pattern of interaction effect (time * group) was also found in gross motor skill, F (2, 150) = 80.9, p < 0.001, ŋ2 = 0.52, where the mean score in intervention group was greater than in control group. It is important to understand in depth each of the skills components involved in locomotor and object control and also its differences between the boys and girls, as it can help in planning of the module of an intervention programme. Object control skills have higher predictive value in engaging in wider range of PA which could be the possible reason why boys are more active than girls.

Iron oxide thin films grown on (00l) sapphire substrate by pulsed-laser deposition

Magnetite (Fe3O4) and wustite (FeO) are well-known oxides for their promising magnetic properties. However, growing stable FeOx thin films with controlled iron oxidation states could be of interest for further applications. In this work, we highlight the formation of different FeOx-based thin films grown by pulsed-laser deposition (PLD) from Fe or α-Fe2O3 targets onto sapphire substrates. Based on X-ray diffraction and Rutherford backscattering spectroscopy analyses, we report on films with various O/Fe ratios obtained by controlling both the substrate temperature and the oxygen pressure in the 10−5 – 10 Pa range during the PLD growth. Thus, the different crystalline phases of the Fe-O system can be grown: metallic iron, α-Fe2O3, Fe3O4, and the thermodynamically metastable phase FeO. On one hand, we demonstrate that at low pressures (< 10−4 Pa) metal-oxide composite thin films with both metallic Fe and Fe3O4 phase are epitaxially grown on the sapphire substrates even at room temperature. On the other hand, we highlight that using a α-Fe2O3 target, films composed with a mixture of wustite and spinel phases have been obtained at room temperature. The precise growth conditions leading to the formation of FeO-based films or metal-oxide composite films are discussed.

Development of Inspired Therapeutics Pediatric VAD: Computational Analysis and Characterization of VAD V3

Pediatric heart failure patients remain in critical need of a dedicated mechanical circulatory support (MCS) solution as development efforts for specific pediatric devices continue to fall behind those for the adult population. The Inspired Pediatric VAD is being developed as a pediatric specific MCS solution to provide up to 30-days of circulatory or respiratory support in a compact modular package that could allow for patient ambulation during treatment. Hydrodynamic performance (flows, pressures), impeller/rotor mechanical properties (torques, forces), and flow shear stress and residence time distributions of the latest design version, Inspired Pediatric VAD V3, were numerically predicted and investigated using computational fluid dynamics (CFD) software (SolidWorks Flow Simulator). Hydrodynamic performance was numerically predicted, indicating no change in flow and pressure head compared to the previous device design (V2), while displaying increased impeller/rotor torques and translation forces enabled by improved geometry. Shear stress and flow residence time volumetric distributions are presented over a range of pump rotational speeds and flow rates. At the lowest pump operating point (3000 RPM, 0.50 L/min, 75 mmHg), 79% of the pump volume was in the shear stress range of 0-10 Pa with < 1% of the volume in the critical range of 150-1000 Pa for blood damage. At higher speed and flow (5000 RPM, 3.50 L/min, 176 mmHg), 65% of the volume resided in the 0-10 Pa range compared to 2.3% at 150-1000 Pa. The initial computational characterization of the Inspired Pediatric VAD V3 is encouraging and future work will include device prototype testing in a mock circulatory loop and acute large animal model.

Evaluating the methods for predicting permeability of unsaturated soils

The unsaturated permeability (kuns) is one of the key parameters in geotechnical and geo-environmental engineering involving unsaturated soils. To measured kuns in a matrix suction range of few Pa to thousands of kPa is time consuming and sometimes not practical. Thus, various methods for predicting the values of kuns were established, and their performances are quite different. The performance of two commonly used methods, i.e. Mualem’s method adopting Van Genuchten’s soil water characteristic curve (SWCC) (designated as MVG), and Fredlund et al.’s method (designated as FXM), have been evaluated comparing the predicted values with the measured data, which are test data from this study and the data from literature. The analysis results indicate that MVG method yielded a better prediction.

Identification of DNA nucleotides by conductance and tunnelling current variation through borophene nanogaps.

Rapid and inexpensive DNA sequencing is critical to biomedical research and healthcare for the accomplishment of personalized medicine. Solid-state nanopores and nanogaps have marshalled themselves in the fascinating paradigm of nano-research since the advent of its application in DNA sequencing by analyzing the quantum conductance and electric current signals. In this study, the feasibility of the considered borophene nanogaps for DNA sequencing purposes via the electronic tunnelling current approach was investigated by utilizing combined density functional theory with non-equilibrium Green's function (DFT-NEGF) techniques. The interaction energy (Ei) and the charge density difference (CDD) plots exploit the charge modulation around the nanogap edges due to the presence of each nucleotide. Our results revealed a distinct variation in the tunnelling conductance, as a characteristic fingerprint of each nucleotide at the Fermi level. The calculated tunnelling current variation across the nanogap under an applied bias voltage was also significant due to the effective coupling of nucleotides with the electrode edges. The current was in the picoampere (pA) range, which was fairly higher than the electrical background noise and also experimentally detectable by the canning tunnelling microscopy (STM) technique. Our findings demonstrated that in the borophene nanopore vs. nanogap scenario, the nanogap has several advantages and is a more promising nanobiosensor. Moreover, we also compared our results with various previous experimental and theoretical reports on nanogaps as well as nanopores for gaining better insights.

2D van der Waals Heterojunction of Organic and Inorganic Monolayers for High Responsivity Phototransistors

AbstractVan der Waals (vdW) heterostructures composing of organic molecules with inorganic 2D crystals open the door to fabricate various promising hybrid devices. Here, a fully ordered organic self‐assembled monolayer (SAM) to construct hybrid organic–inorganic vdW heterojunction phototransistors for highly sensitive light detection is used. The heterojunctions, formed by layering MoS2 monolayer crystals onto organic [12‐(benzo[b]benzo[4,5]thieno[2,3‐d]thiophen‐2‐yl)dodecyl)]phosphonic acid SAM, are characterized by Raman and photoluminescence spectroscopy as well as Kelvin probe force microscopy. Remarkably, this vdW heterojunction transistor exhibits a superior photoresponsivity of 475 A W−1 and enhanced external quantum efficiency of 1.45 × 105%, as well as an extremely low dark photocurrent in the pA range. This work demonstrates that hybridizing SAM with 2D materials can be a promising strategy for fabricating diversified optoelectronic devices with unique properties.

Nitrogen species in a thermal plasma under very low pressure (150 Pa): Application to reactive plasma spraying

Very Low-Pressure Plasma Spraying (VLPPS) is an emerging process allowing the manufacturing of metallic or ceramic coatings under reduced pressure conditions (i.e., in the 150 Pa range). It aims at vaporizing primary feedstock precursors in the warm core of the plasma flow and at carrying them, through the expanded plasma column, towards the surface to be coated, where they condense to form a deposit. This process also can be operated in a reactive mode. In such a case, a secondary reactive gaseous precursor is injected in the plasma flow where it can react with the primary vaporized precursors. In this work, nitrogen is considered as the secondary gaseous precursor. Thereby, nitriding reactions occur between this secondary precursor and the primary one, titanium in the considered case. Optical emission spectroscopy is implemented to identify the reactive nitrogen species in an Ar-H2-N2 plasma gas ternary mixture together with the reaction mechanisms giving rise to the nitriding processes. Two mechanisms have been identified. At first, a gas-gas reactions occur between titanium vapors and N2, N2+ and N species leading to the formation of TiN nitrides; At second, a solid-gas reactions occur between flattened titanium lamellae and N2 species, leading to the formation of Ti2N nitrides, which as evidenced by XRD analyses. Nevertheless, the number of nitrides is rather low, very likely due to the limited fraction of titanium vapors in the system: this is a consequence of a rather limited plasma energy (i.e., net power of about 26 kW, corresponding to an average plasma mass enthalpy of 15.21 kJ kg−1).

Hemodynamic Comparison of Stent-Grafts for the Treatment of Aortoiliac Occlusive Disease

Purpose: To compare the flow patterns and hemodynamics of the AFX stent-graft and the covered endovascular reconstruction of aortic bifurcation (CERAB) configuration using laser particle image velocimetry (PIV) experiments. Materials and Methods: Two anatomically realistic aortoiliac phantoms were constructed using polydimethylsiloxane polymer. An AFX stent-graft with a transparent cover made with a new method was inserted into one phantom. A CERAB configuration using Atrium’s Avanta V12 with transparent covers made with a previously established method was inserted into the other phantom, both modified stent-grafts were suitable for laser PIV, enabling visualization of the flow fields and quantification of time average wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT). Results: Disturbed flow was observed at the bifurcation region of the AFX, especially at the end systolic velocity (ESV) time-point where recirculation was noticeable due to vortical flow. In contrast, predominantly unidirectional flow was observed at the CERAB bifurcation. These observations were confirmed by the quantified hemodynamic results from PIV analysis where mean TAWSS of 0.078 Pa (range: 0.009–0.242 Pa) was significantly lower in AFX as compared with 0.229 Pa (range: 0.013–0.906 Pa) for CERAB (p<0.001). Mean OSI of 0.318 (range: 0.123–0.496) in AFX was significantly higher than 0.252 (range: 0.055–0.472) in CERAB (p<0.001). Likewise, mean RRT of 180 Pa−1 (range: 9–3603 Pa−1) in AFX was also significantly higher than 88 Pa−1 (range: 2–840 Pa−1) in CERAB (p=0.0086). Conclusion: In this in vitro study, the flow pattern of a modified AFX stent-graft was found to be more disturbed especially at the end systolic phase, its hemodynamic outcomes less desirable than CERAB configuration. Clinical Relevance: While the AFX stent-graft has an advantage over the CERAB configuration in eliminating radial mismatch, and maintaining the anatomical bifurcation for future endovascular intervention, this in vitro study revealed that the associated lower TAWSS, higher OSI and RRT may predispose to thrombosis and are, thus, less desirable as compared to a CERAB configuration. Further investigation is warranted to confirm whether these findings translate into the clinical setting.

Pyroelectric lithium niobate electron emission-based ion-pump

This work presents a compact ion-pump that utilizes pyroelectricity for ionization of ambient molecules. The pyroelectric ionization is realized by heating a lithium niobate (LiNbO3) crystal with low voltage resistive heating (10 V drive voltage, 0.5 W Joule heating) to generate a high voltage across the poled surface of the crystal. Pyroelectrically generated electrons from the polarized surface of the crystal are accelerated using an electric field generated by both the crystal and external titanium (Ti) electrodes biased at ±300 V, which results in the ionization of molecules in the chamber. The low collector current in the pA range ensures that the power consumed due to ionization current is lower than the LiNbO3 heating power. The ionized gas molecules are accelerated toward the Ti collector electrodes where they are implanted owing to large acceleration produced by the collector electrodes. The system is configured as a sputter pump for gettering ions to reduce chamber pressure from the baseline value of 1.4 μTorr with just the external pump to 1.1 μTorr by incorporating the LiNbO3 pump. The proof-of-concept of the pyroelectric pumping mechanism is demonstrated using a 140 cm3 stainless steel vacuum chamber, with supplementary turbomolecular and diaphragm pumps and demonstrates that a 50 s thermal cycling of the crystal is optimal for the ion-pump. Pumping action was measured with a Pirani gauge and a hot cathode ion gauge. Analytical modeling and experimental results for pumping speed calculations showed a good match during high-pressure pumping.