Half Tube Research Articles

Effect of enhanced quenching on properties of melt spun multifilament poly[3-hydroxybutyrate] yarns

Bacterial poly-3-hydroxybutyrate is a thermoplastic biopolyester that is considered a potential alternative to traditional fossil-based plastics due to its rapid biodegradation performance in both soil and marine environments and its compostability. Due to problems in thermal and crystallization behaviors of the bacterial poly-3-hydroxybutyrate polymer, an improvement has been made in the cooling channel of the conventional fiber spinning process. Using an enhanced quench channel, named as a half tube on a conventional melt spinning line, melt spinning of the bacterial poly-3-hydroxybutyrate multifilament fibers is successfully carried out. The maximum crystallization temperature of polymers was taken into account while adjusting the quenching process. The study examined the impact of varying drawing ratios and the designed quenching apparatus on the thermal (differential scanning calorimetry), mechanical (tensile and drawing force tests), morphological, and crystal structure characteristics of fibers. The quenching apparatus has visibly created a homogeneous melt flow under the spinnerets. While it has a negative impact on fiber cross-sectional formation, raising the draw ratio greatly enhances mechanical properties.

Exploring Ethnomathematics at South Kalimantan NU University's As-Su'ada Campus Mosque, based on Geometry Perspective and Its Relationship to Learning Activity

This research aims to explore the cultural site of the Masjid Kampus As-Su’ada Universitas NU Kalimantan Selatan in terms of geometric aspects and its relationship to mathematics learning, especially geometry. The research method used was qualitative with a realist ethnographic approach. The data collection technique is exploration through observation and interviews. The analysis technique in this research is through source collation, namely clarifying the results of observations by interviewing informants. The research results show that the Masjid Kampus As-Su'ada has many geometric shapes on the exterior and interior of the mosque. The geometric shapes contained in it include plane geometry (circle, square, rectangle, triangle and ellipse), solid geometry (pyramid, block, prism) and modified geometry (half tube, truncated pyramid and elliptical approach). Lessons that can be carried out include case studies of mosque roofs, study tours identifying mosque geometric shapes, and determining the area of the building.

Thermal performance of a novel high-temperature sensible heat thermal storage steam generation system using solid graphite as material

In this paper, a prototype of high-temperature sensible heat thermal storage system for direct steam generation was presented. The structure of solid graphite blocks with embed tube was applied to improve the efficient density of thermal storage. And a net thermal storage capacity of 1.038 GJ was achieved for the module with a total mass of 1480 kg solid graphite under the working temperature range of 250–600 °C. Meanwhile, a novel series-parallel tube structure was applied for discharging power regulation. A two-stage working strategy was found to be efficient for confining discharging power fluctuated in a certain range instead of monotonously decreasing. Further, three mass flow rates from 106 kg/h to 175 kg/h were performed to investigate thermal performance of the thermal storage system. The results show that the effect of mass flow rate on discharging power and heat transfer coefficient seems to be tiny due to the major thermal resistance is resulted from contact thermal resistance. The extension of working tube in stage II has improve the development of two-phase flow, which finally results in a higher heat transfer coefficient. The flow distribution in parallel tube has a significant effect on the local discharging characteristics and the two-phase flow development in tube. The manifold header for stage transition has not only enhanced the heat transfer in the second half tube by mixing effect but also redistributed the flow rate in parallel tubes.

Optimizing impedance matching by a dual-carbon Co-regulation strategy of Co3O4@rGO/celery stalks derived carbon composites for excellent microwave absorption

• Co 3 O 4 @rGO/CDC composites with different mass ratios of rGO:CDC were prepared. • S13 (weight ratio for rGO:CDC is 1:3) composite showed best microwave absorption performance. • It showed RL min value of -84.3dB and the widest effective bandwidth of 4.5 GHz. • Better impedance matching can be obtained by tuning the CDC ratio. Both macroscopic composition and microstructure should be considered for reasonable microwave absorbent designing. In this study, Co 3 O 4 @reduced graphene oxide (rGO)/Celery stalks derived carbon (CDC) was prepared by loading Co 3 O 4 particles into rGO and biomass-derived carbon mixture through oxidation precipitation. By changing the mass ratio of rGO to CDC, the dielectric and impedance matching properties of the composites can be easily regulated. The RL min value of Co 3 O 4 @rGO/CDC 13 composite (weight ratio for rGO: CDC is 1:3) reaches –84.3 dB with a thickness of 4.6 mm, and the widest effective bandwidth can be obtained at 4.5 GHz with a matching thickness of 2.8 mm. The Co 3 O 4 @rGO/CDC 13 composite with multiple components (Co 3 O 4 , CDC, rGO) and 3D net structure produces magnetic/dielectric loss combinations, interfacial polarization, and multiple reflections and scattering, and the CDC with half tube and half sheet structure is conducive to the optimization of impedance matching. The strategy of co-regulating dielectric properties of materials with double carbon provides a novel pathway for the preparation of lightweight, low-cost, and high-performance absorbers.

Preparation of crack-free, non-notched, flattened bamboo board and its physical and mechanical properties

Bamboo flattening technology can increase the utilization of bamboo, flattening half or third bamboo tube sections into flattened bamboo strips through steam softening, roller flattening and drying. Compared with earlier notched flattening technology, newer non-notched flattening technology does not incise or damage the culm inner surface. In this paper, we introduce a non-notched flattening method and assess the macro-and micro-mechanical properties of the flattened bamboo. Results showed that the parenchyma cells shrank and distorted and the hygroscopicity of bamboo decreased and the hygroscopicity of bamboo decreased due to the decomposition of hemicelluloses. The modulus of elasticity (MOE) and hardness were increased as a function of treatment temperature and time. The MOE increased by 25% and the hardness significantly increased by 34% after the flattening process due to the tissue densification and increased crystallinity index. The improved micromechanical properties of cell walls and increased density positively contributed to the macro-mechanical properties.

Parametric CFD Thermal Performance Analysis of Full, Medium, Half and Short Length Dimple Solar Air Tube

In the present decade, research regarding solar thermal air heaters (SAHs) has noticed a continuous progression in thermo-hydraulic performance augmentation approaches. There now exists a wide variety of thermo-hydraulic performance augmentation approaches and researchers have designated various structures. Nevertheless, there seems to be no generalization to any of the approaches employed. The present numerical investigation reports on the thermo-hydraulic characteristics and thermal performance for flow through a varied length (full, medium, half, and short length) dimple solar air heater (SAH) tube. The study highlights recent developments on enhanced tubes to augment heat transfer in SAH. The influence of different length ratio, dimple height ratio (H), and pitch ratio (s) on thermo-hydraulic characteristics have been investigated in the Reynolds number (Re) range from 5000 to 25,000. Air is used as the working fluid. The commercial software ANSYS Fluent is used for simulation. The shear stress transport (SST) model is used as the turbulence model. Thermal energy transport coefficient is increased in the full-length dimple tube (FLDT), compared to the medium-length dimple tube (MLDT), half-length dimple tube (HLDT) and short-length dimple tube (SLDT). Similarly, the pitch ratio (s) has more influence on Nusselt number (Nu) compared to the dimple height ratio (H). The friction factor decreases with an increase in pitch ratio. Nu increases and f decreases with increasing Re for all combinations of H and s. Low s and higher H yields high enhancement of HT and PD. Integration of artificial roughness on the tube increases the values of Nu and f by 5.12 times and 77.23 times for H = 0.07, s = 1.0 at Re value of 5000 and 25,000, respectively, in regard to the plain tube. For all the tested cases, the thermo-hydraulic performances (η) are greater than unity.

Highly efficient water desalination through hourglass shaped carbon nanopores

Biological nanopores such as aquaporins combine the opposing functions of high water permeation and total ion exclusion in part by the virtue of their hourglass shape. Here, we perform molecular dynamics simulations to examine water and ion conduction through hourglass shaped nanopores created from carbon nanotubes (CNTs) of chirality (6,6), (8,8), and (10,10) in combination with carbon nanocones of half cone angles 41.8°, 30.0°, 19.45°, 9.6° and 0.0°. We observe large variations in flow through the nanopores with change in half cone angles and tube diameters. By computing the pore-water interactions we find a correlated change between the flux and the density profiles of water inside the nanopores. Further, from the orientation, and the hydrogen bonding characteristics of water, we uncover some unexplored facets of flow through hourglass shaped nanopores. The results are insightful for devising novel separation membranes based on nanopores that mimic the shape of biological nanochannels.

Creating a cross-sectional, CT and MR atlas of the Pannon minipig.

The purpose of this study was to create a detailed cross-sectional anatomical reference atlas of the Pannon minipig by correlating good resolution CT and MR images with high quality cross-sectional anatomical images. According to the authors knowledge, no detailed anatomical atlas is available for the minipig. An adult female minipig was utilized for this purpose. The animal was placed in a PVC half tube, and CT generated images of 0.6mm slice thickness and MR images of 1.41mm slice thickness were obtained. The images covered the whole body from the most rostral portion of the snout to the tip of the tail. The CT and MR scans were aligned with frozen anatomical sections prepared with an anatomical band saw from the same animal and significant structures were identified and labelled. The terminology employed has been referenced from the Nomina Anatomica Veterinaria 6th edition-2017. The resulting atlas consists of 109 anatomical slices and the corresponding 109 CT and 109 MR scans (altogether 327 images) and the nomenclature list for each image. Although this publication contains limited images of the resulted atlas, it is a reference source for anatomy education and clinical sciences. We are of the opinion that more comprehensive and especially online available interactive atlases should be prepared using similar methodology.

A Simple and Convenient Method to Isolate and Culture Rat Aorta Endothelial Cells

Aim: Endothelial injury results in vascular disorders. Culture of endothelial cells (ECs) is important to investigate the pathogenesis of vascular diseases. ECs of rat aorta are widely applied in these researches. However, there are many problems to isolate them, which make it hard to culture primary ECs. In the present study, we established a simple and convenient method to isolate and culture rat aorta ECs. Methods: Two 5ml centrifuge tubes were prepared. An opening (3 mm × 25 mm) was made in one tube wall while the other was cut in half longitudinally. After the rat aorta was dissected along one side and attached to the wall of the half tube, the tube with an opening and the half tube with aorta were mated and secured by a rotund metal clip. Then, ECs were digested via the opening by 0.2% collagenase I at 37℃ for 1 h and identified by immunofluorescence of von Willebrand factor (vWF) and smooth muscle actin (SMA). Results: A simple method for isolating ECs were established. Cultured ECs exhibited typical “cobblestone” morphology at confluence. vWF was positively expressed in the ECs, and neither the negative stain of vWF nor the positive stain of SMA was found. Conclusion: This simple and convenient method to isolate and culture ECs of rat aorta can be implemented with readily available 5ml centrifuge tubes and will greatly benefit the research of vascular diseases.

Performance analyses in parabolic trough collectors by inserting novel inclined curved-twisted baffles

The operation stability demands for low and uniform wall temperature in the parabolic trough collector which acts as an energy conversion component in concentrating thermal conversion technology. In order to reduce the local high temperature with moderate pump power consumption, this paper proposed longitudinal swirls impinging cooling method. Three types of novel inclined curved-twisted baffles (A1, A2, and A3) were devised to realize this method. With selecting the absorber tube as research model, this paper numerically compared the impinging cooling characteristics, wall temperature uniformity performance, and efficiency performance by inserting the three types of baffles. The A1 and A2 types each generated a pair of longitudinal swirls while the A3 type generated two pairs of longitudinal swirls. The impinging cooling always appeared near the front edge of inclined baffles. The A1 type was the best in wall temperature uniformity and efficiencies among three baffles. Furthermore, as the inlet temperature increased from 400 K to 600 K at a mass flow rate of 1.13 kg/s in the A1 type tube, the average wall temperature difference between bottom half tube and top half tube was decreased by 55.1%. Meanwhile, the average overall efficiency and exergy efficiency were increased by 0.52% and 0.22%, respectively.

Letter to the Editor Regarding “Ossification of the Ligamentum Flavum at the Thoracic and Lumbar Region in an Achondroplastic Patient”

To evaluate the image quality and diagnostic confidence of reduced-dose computed tomography (CT) of the lumbar spine (L-spine) reconstructed with knowledge-based iterative model reconstruction (IMR).Prospectively, group A consisted of 55 patients imaged with standard acquisition reconstructed with filtered back-projection. Group B consisted of 58 patients imaged with half tube current, reconstructed with hybrid iterative reconstruction (iDose4) in Group B1 and knowledge-based IMR in Group B2. Signal-to-noise ratio (SNR) of different regions, the contrast-to-noise ratio between the intervetebral disc (IVD) and dural sac (D-D CNR), and subjective image quality of different regions were compared. Higher strength IMR was also compared in spinal stenosis cases.The SNR of the psoas muscle and D-D CNR were significantly higher in the IMR group. Except for the facet joint, subjective image quality of other regions including IVD, intervertebral foramen (IVF), dural sac, peridural fat, ligmentum flavum, and overall diagnostic acceptability were best for the IMR group. Diagnostic confidence of narrowing IVF and IVD was good (kappa = 0.58–0.85). Higher strength IMR delineated IVD better in spinal stenosis cases.Lower dose CT of L-spine reconstructed with IMR demonstrates better tissue differentiation than iDose4 and standard dose CT with FBP.

Performance of a photovoltaic-thermal solar collector using two types of working fluids at different fluid channels geometry

The purpose of this paper is to investigate theoretically the performances of a photovoltaic-thermal solar collector by applying three different geometrical shapes of fluid circulation channels (circular tube, half tube and square tube) and using pure water and Ethylene glycol-water (EG-W) mixture as heat transfer fluids. The computational model developed is based on thermal balance equations. Predicted results show that half tube design provides best photovoltaic cooling effect and highest efficiency compared to others geometries. At 0.04kg/s mass flow rate, the use of half tube increases thermal efficiency by 1.17% and 2.6% compared to circular and square tubes respectively. Moreover, for the same comparison, an enhancement of 0.53% and 1.16% is obtained for electrical efficiency. It is found that the use of pure water as working fluid improves the thermal and electrical yields by 4.5% and 1.85% respectively referred to EG-W mixture. The thermal effect of using the both working fluids is investigated at different flow rate. It is found that EG-W mixture causes higher energy losses due to the pressure drop in comparison with water especially for high flow rate. Furthermore, the impact of photovoltaic/thermal collector design parameters on the electrical and thermal performances has been analyzed and discussed.

Slope retreat rates estimated from chronology of tufa deposits sheltered by inland notches on Mt. Carmel, Israel

Inland notches are elongated half tube indentations that develop on the carbonate rocky cliffs of mountainous zones. Occasionally tufa accumulates within notches as stalactites, drapes and crusts, covering the cavity backwall or floors. In attempt to determine the age of the latest stage of notch formation and calculate the relative rate of slope retreat, UTh dating was used on 16 tufa samples from 2 notches, providing 28 ages. Tufa grow during the time interval between the backwall erosion and visor collapse, and therefore tufa age is an approximation of the timing of the formation of the surface it developed on, i.e. the age of the notch.The oldest known tufa sample is 39.0 ± 10.4 ky (2σ), and the ages of other tufa samples range from 2.1 to 23.3 ky. At the Nahal Oren notch, the present-day backwall formed by the end of the last glacial period (14 to18 ky), whereas the visor in its present form is from the early Holocene (7 to10 ky). The oldest sample was found ~1 m from the backwall, suggesting that backwall retreat rate ranges from 20 to 35 mm/ky. Other samples were deposited 50 to 200 cm from the visor edge, suggesting that slope retreat order of magnitude ranges from 101 to 102 mm/ky. The backwall of the Nesher notch formed between 10 and 14 ky. Our results correspond with the rates of tens of meters per million years, similar to the magnitude of denudation found by previous studies in the Mediterranean zone of Israel.Dating tufa deposits is a good proxy to estimate the rate of erosion in carbonate slope retreat; however, a precautionary approach should be taken, as rock particles from the eroded bedrock might embed within the tufa, affecting the age results. Questionable samples can be identified using Cathodoluminescence (CL) microscopy.

Performance of semiconductor dosimeters with a range of radiation qualities used for mammography: A calibration laboratory study.

PurposeTo investigate the radiation quality dependence of the response of commercial semiconductor‐based dosimeters, and to estimate potential errors and uncertainties related to different measurement and calibration scenarios.MethodsAll measurement results were compared to reference values measured at the IAEA dosimetry laboratory which is traceable to the international system of units (SI). Energy dependence of the response of eight semiconductor dosimeters were determined for five different anode‐filter combinations and tube voltages from 25 to 35 kV. For systems capable of deriving half value layer (HVL) and tube voltage from measurements, calibration coefficients for these measurements were calculated.ResultsFor six dosimeters, the maximum deviations from the reference value of the air kerma measurement were within ±5% as required by IEC 61674. Calibration coefficients for radiation qualities (anode‐filter and tube voltage combinations) relative to reference radiation quality Mo‐Mo 28 kV deviate up to 12%. HVL and tube voltage measurements exhibited deviations up to 11% and 10%, respectively.ConclusionsThe air kerma responses of modern semiconductor dosimeters have a small energy dependence. However, no dosimeter tested complied with the accuracy limits stated by the manufacturer for tube voltage measurements, and only two dosimeters complied with the limits for HVL measurements. Absolute measurement of HVL and tube voltage with semiconductor dosimeters have to be verified for actual clinical radiation conditions on clinical mammography systems. Semiconductor dosimeters can be used for quality control measurements if individual calibration coefficients are available for the radiation condition applied. If other conditions are applied, additional uncertainty needs to be considered, particularly in the case of HVL and tube voltage measurements.

Investigation on influence of mandrel shape on shear stress in pure shearing test of thin-walled aluminum alloy tubes

A novel testing method of pure shear loading for tubes is proposed in this paper. A special designed tubular sample and two semicircle mandrels are used in this test. The interface between the two half tube on the whole tube zone of the sample is under shearing deformation with relative movement of the two mandrels, and the middle point of the shearing zone is under a pure shearing stress state. The influence of friction condition between the two mandrels caused by the relative movement of the mandrels was analyzed. Three different friction conditions of semi-circle mandrels were used in the simulation and the relation between the loading force and mandrel displacement was obtained. It is shown the friction force has very small influence on the loading force. This shearing test can be used to get the shearing property of tubes, also, it is a testing method of tubes except the axial and circumferential direction.

Pig tracheal patchy xenotransplantation in the dog

A long-segmental tracheal lesion is difficult to repair by tracheal allotransplantation due to the lack of a well-defined blood supply for blood vessel anastomosis. The donor trachea needs to be revascularized within a well-vascularized soft tissue flap for several months to allow successful trachea allotransplantation. To date, xenotransplantation using the wild-type or genetically modified pig has been widely studied. The object of this study was to evaluate the feasibility of a small-sized (2×2cm) wild-type pig tracheal patchy in a dog tracheal defect model before trying a long-segment tracheal defect model and using a genetically modified pig as a donor in dog xenotransplantation. Three healthy beagle dogs (8-9kg) were used as recipients, and one pig (20kg) was used as the donor. A pig cartilaginous tracheal patchy (2×2cm half tube) was sutured to the tracheal resected site in each dog. Antithymocyte globulin (2.5mg/kg infusion, D0 and 1), tacrolimus (4.5mg/kg, twice a day for 2months), and methylprednisolone sodium succinate (1mg/kg, IV, for 2days and tapering) were administered for immunosuppression. The levels IL-2 and IFN-γ in the serum were measured at D0, 7, and 28. Tracheoscopy was performed at D28, 60, and 90. The recipients were sacrificed at D90, and the expression of dog and pig genes in the graft was evaluated by PCR. Histopathological examination of the graft was conducted. All of the dogs survived without complications during the experimental period. Their IL-2 and IFN-γ levels were significantly increased at D7 after transplantation compared to D0 and D28 (P<0.05). The pig tracheal patchy site was open, and no stenosis was observed until D90 on tracheoscopy, when pale mucosa erosion was observed; there was also remnant suture material at D28. However, the tracheal patchy sites gradually became similar to normal mucosa at D60 and 90. The expression of pig genes was detected in the graft by PCR. Normal epithelium and CD3 cells were observed in the histological examination at D90. In this study, our data suggest that the pig tracheal patchy can be successfully engrafted into the trachea of dog, although erosion of mucosa on the graft was seen at D30, in spite of the discordant species.

Knowledge-based iterative model reconstruction technique in computed tomography of lumbar spine lowers radiation dose and improves tissue differentiation for patients with lower back pain

PurposeTo evaluate the image quality and diagnostic confidence of reduced-dose computed tomography (CT) of the lumbar spine (L-spine) reconstructed with knowledge-based iterative model reconstruction (IMR). Materials and methodsProspectively, group A consisted of 55 patients imaged with standard acquisition reconstructed with filtered back-projection. Group B consisted of 58 patients imaged with half tube current, reconstructed with hybrid iterative reconstruction (iDose4) in Group B1 and knowledge-based IMR in Group B2. Signal-to-noise ratio (SNR) of different regions, the contrast-to-noise ratio between the intervetebral disc (IVD) and dural sac (D-D CNR), and subjective image quality of different regions were compared. Higher strength IMR was also compared in spinal stenosis cases. ResultsThe SNR of the psoas muscle and D-D CNR were significantly higher in the IMR group. Except for the facet joint, subjective image quality of other regions including IVD, intervertebral foramen (IVF), dural sac, peridural fat, ligmentum flavum, and overall diagnostic acceptability were best for the IMR group. Diagnostic confidence of narrowing IVF and IVD was good (kappa=0.58–0.85). Higher strength IMR delineated IVD better in spinal stenosis cases. ConclusionLower dose CT of L-spine reconstructed with IMR demonstrates better tissue differentiation than iDose4 and standard dose CT with FBP.

Сравнительный анализ приближенного аналитического и конечно-элементного решений для несоосной трубы

The boundary value problem of steady-state creep for thick-walled misaligned tube under internal pressure was considered. The approximate analytical solution of this problem by method of small parameter including the second approach is under construction. The solution for the state of plane deformation is constructed. The hypothesis of incompressibility of material for creep strain is used. As a small parameter the misalignment of the centers of the inner and outer radii of the tube is used. The main attention to the convergence of the resulting analytical solution considering the second approximation and assessment of its error is paid. It is noted that the convergence problem is solved only for boundary value problems in the theory of elasticity. Therefore the error assessment in the problem is solved on the basis of a comparison of the approximate analytical solution with the numerical solution constructed on the finite element method, for some special cases. Considering the symmetry of the problem, the finite element model was built for the half tube. The number of finite elements is about 18,000. Considering the symmetry of the problem the second half of the tube is replaced by boundary conditions. Analysis of analytical and numerical solutions is executed depending on the steady-state creep nonlinearity parameter and misaligned parameter that is ratio of the misalignment of the centers of the outer and inner diameter to the outer radius. It is shown that the error of deviation of the approximate analytical solution in the second approximation from numerical solution until the misalignment value of the centers of the inner and outer diameters of 0.1 for the tubes with small exponent of the steady-state creep (3 to 8) is not more than 9 %, and error to 8 % for the tubes with a large exponent of the steady-state creep nonlinearity is observed in the misaligned parameter to 0.06. Results of computations are presented in tabular form and in the form of graphs. Recommendations for the use of the constructed approximate analytical solution in applied problems are given.

Image quality of ultra-low-dose dual-source CT angiography using high-pitch spiral acquisition and iterative reconstruction in young children with congenital heart disease

BackgroundObtaining diagnostic CT image quality with ultra-low radiation dose in young children with congenital heart disease remains challenging. ObjectiveWe evaluated the feasibility and image quality of prospectively electrocardiogram (ECG)-triggered high-pitch spiral acquisition with iterative reconstruction for pediatric cardiovascular CT angiography. MethodsSixty-two consecutive pediatric patients younger than 2 years with congenital heart disease underwent prospectively ECG-triggered high-pitch spiral dual-source CT acquisition. Patients were randomly assigned into 2 groups: full tube current (40–70 mAs) scans with filtered back projection reconstruction (group A) and half tube current (20–35 mAs) scans with sinogram-affirmed iterative reconstruction (group B). Attenuation, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and subjective image quality were compared between the 2 groups. Effective radiation dose was also estimated for both groups. ResultsNo significant difference was found in the attenuation, image noise, SNR, and CNR between the 2 groups in the same evaluated anatomic regions, whereas the attenuation and image noise were slightly lower, and the SNR and CNR were slightly higher in group B. No significant difference was found in subjective image quality between the 2 groups (4.27 ± 0.73 vs. 4.34 ± 0.42; P = .813). Effective dose was 0.06 ± 0.03 mSv in group B and 0.13 ± 0.04 mSv in group A, reflecting dose savings of 53.8% by using iterative reconstruction. ConclusionsA combination of prospectively ECG-triggered high-pitch spiral acquisition, low tube current, and iterative reconstruction may offer diagnostic image quality in pediatric cardiovascular CT angiography with effective radiation dose < 0.1 mSv.

Electric-field-direction dependent spatial distribution of electron emission along electrically biased carbon nanotubes

The spatial distribution of lateral electron emission from individual electrically biased carbon nanotubes (CNTs) along the tube axis is resolved for the first time by combining multiprobe simultaneous emission current collection and electron trajectory simulations. The spatial distribution is found to be asymmetric along the tube axis and depends on the direction of the electric field in CNTs. The average emission density of the half tube with a higher electric potential is higher than that of the other half with a lower electric potential. The electric-field-direction dependent asymmetric spatial distribution of the electron emission is absent in all pre-existing well-established mechanisms but is well explained in terms of the recently proposed phonon-assisted electron emission (PAEE). This, together with a quantitative description of experimentally measured emission currents, provides solid evidence for the validity of the PAEE mechanism. PAEE from CNTs is predicted to take place near room temperature; thus, it opens up a new and promising route for fabricating cold electron emitters with a high emission density and a low working voltage.