Microscopy analysis and production rate data for needleless vertical rods electrospinning parameters

AbstractA multiple vertical rod setup for needless electrospinning was used to fabricate submicron polymer fibers. The design with multiple vertical rods is a new concept for increased production of electrospun fibers. Different geometries and operating conditions are possible. The effects of varying the number of rods in the array have been studied and reported [1]. The goal of this work was a proof of concept of the threaded rod design by exploring the effects of variations in applied voltage and gap distance for a fixed array of rods. Effects on fiber diameter and production rate of fibers are reported. More extensive experiments are needed to quantify the interrelations between parameters and to guide the design and operation of the method. No attempt was made to optimize the operating parameters or the geometry in terms of production rates or fiber diameters

VALIDATION OF OPTIMALLY DESIGNED STATOR-PROPELLER SYSTEM BY EFD AND CFD

The development of energy-saving devices to lower the energy efficiency design index (EEDI) of ships has been actively researched worldwide. One such device is an asymmetric pre-swirl stator, which helps to improve the propulsion efficiency by recovering the rotational energy generated during propeller rotation. Determining the pitch angle is the most important factor in the design of an efficient asymmetric pre-swirl stator. To optimize the pitch angle of an asymmetric pre-swirl stator, this study deals with potential-flow, computational fluid dynamics, and model tests. The model delivered power at a design speed of 24 kt was compared by changing the pitch angle by ±2° with respect to the reference angle designed using a potential-flow program. The commercial code Star-CCM+ was used for the numerical analysis, and the model was also tested in a towing tank at Pusan National University. This study proposes an effective method for determining and verifying the optimal pitch angle of an asymmetric pre-swirl stator

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Comparative Dissolution of Electrospun Al2o3 Nanofibres in Artificial Human Lung Fluids

Sub-micron sized alumina fibres were fabricated by electrospinning and calcination of a polymer template fibre. In the calcination step, different controlled temperature heating cycles were conducted to obtain fibres of different crystalline structures. Their biodurabilities were tested at pH 7.4 with lung airway epithelial lining fluid or serum ultrafiltrate (SUF) and at pH 4.5 with macrophage phagolysosomal simulant fluid (PSF). Potential to generate free radicals was tested in vitro. Through the variation in the soak temperature from 650 °C to 950 °C (experiments S650–S950), the heating protocol affected the morphological characteristics, crystal structure, surface area, and density of the alumina fibres while their dissolution half-times were not significantly affected in SUF or PSF. Fibre samples formed at different heating ramp rates (experiments R93–R600) showed significant variation in the dissolution rates with the highest ramp rate corresponding to the highest dissolution rate. Thus, by increasing the calcination temperature ramp rate the alumina fibres may be produced that have reduced biodurability and lower inflammogenic potential. The fibres with the highest dissolution rated had the least aluminium content. The solubility half-times of the alumina fibres were shortest for fibres calcined at the fastest temperature ramp rate (though soak temperature did not have an effect). The ramp rates also affected the aluminium content of the fibres suggesting that the content may affect the structural strength of the fibres and control the dissolution

Vertical Rod Method for Electrospinning Polymer Fibers

Electrospinning is often used to produce sub-micron size fibers. Most electrospinning applications employ charged needles or nozzles but have low production rates. For higher production rates several needleless systems have been developed. This work reports on a simple unique needleless method that employs charged vertically oriented threaded rods for holding multiple drops to launch many simultaneous jets. Experiments were conducted with a single rod or multiple rods arranged in a linear array. The direction of the launched jets was controlled using a secondary electrode to direct the jets towards the grounded collector. Results show a single rod of about 50 cm in length can produce PVP fibers at a rate of 4.5 g/hr and 200–400 nm size range

Microscopy analysis and production rate data for needleless vertical rods electrospinning parameters

A multiple vertical rod setup for needless electrospinning was used to fabricate submicron polymer fibers. The design with multiple vertical rods is a new concept for increased production of electrospun fibers. Different geometries and operating conditions are possible. The effects of varying the number of rods in the array have been studied and reported [1]. The goal of this work was a proof of concept of the threaded rod design by exploring the effects of variations in applied voltage and gap distance for a fixed array of rods. Effects on fiber diameter and production rate of fibers are reported. More extensive experiments are needed to quantify the interrelations between parameters and to guide the design and operation of the method. No attempt was made to optimize the operating parameters or the geometry in terms of production rates or fiber diameters

Liquid Phase Selective Hydrogenation of Phenol to Cyclohexanone over Electrospun Pd/PVDF-HFP Catalyst

Cyclohexanone is an important industrial intermediate in the synthesis of materials such as nylons, but preparing it efficiently through one-step hydrogenation of phenol is hindered by over-reduction to cyclohexanol. Using an efficient catalyst can enhance the selectivity of cyclohexanone at high phenol conversion. In this study, catalysts comprised of palladium nanoparticles supported on electrospun PVDF-HFP (polyvinylidene fluoride-co-hexafluoropropylene) nanofibers were prepared using the electrospinning technique. The catalysts were characterized using thermogravimetric analyzer (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM), and drop shape analyzer (DSA). The prepared catalysts were used to hydrogenate phenol into cyclohexanone in a batch reactor. The Pd/PVDF-HFP catalyst showed a very high product selectivity and high phenol conversion. The conversion of phenol achieved was 98% with 97% cyclohexanone selectivity in 7 h using 15 wt% of palladium (0.0021 moles) relative to phenol (0.0159 moles). The turnover number (TON) and turnover frequency (TOF) values calculated were 7.38 and 1.05 h−1, respectively. This paper presents original research in heterogeneous catalysis using novel electrospun nanofibers. Multiphase hydrogenation of phenol to cyclohexanone over electrospun Pd/PVDF-HFP catalyst has not been reported by any researcher in the literature. This work will also provide a research window for the application of electrospun polymeric nanofibers in multiphase reactions

Probing Evolution of Twist-Angle-Dependent Interlayer Excitons in MoSe2/WSe2 van der Waals Heterostructures

Interlayer excitons were observed at the heterojunctions in van der Waals heterostructures (vdW HSs). However, it is not known how the excitonic phenomena are affected by the stacking order. Here, we report twist-angle-dependent interlayer excitons in MoSe2/WSe2 vdW HSs based on photoluminescence (PL) and vdW-corrected density functional theory calculations. The PL intensity of the interlayer excitons depends primarily on the twist angle: It is enhanced at coherently stacked angles of 0 degrees and 60 degrees (owing to strong interlayer coupling) but disappears at incoherent intermediate angles. The calculations confirm twist-angle-dependent interlayer coupling: The states at the edges of the valence band exhibit a long tail that stretches over the other layer for coherently stacked angles; however, the states are largely confined in the respective layers for intermediate angles. This interlayer hybridization of the band edge states also correlates with the interlayer separation between MoSe2 and WSe2 layers. Furthermore, the interlayer coupling becomes insignificant, irrespective of twist angles, by the incorporation of a hexagonal boron nitride monolayer between MoSe2 and WSe2

Probing Evolution of Twist-Angle-Dependent Interlayer Excitons in MoSe₂/WSe₂ van der Waals Heterostructures

Interlayer excitons were observed at the heterojunctions in van der Waals heterostructures (vdW HSs). However, it is not known how the excitonic phenomena are affected by the stacking order. Here, we report twist-angle-dependent interlayer excitons in MoSe₂/WSe₂ vdW HSs based on photoluminescence (PL) and vdW-corrected density functional theory calculations. The PL intensity of the interlayer excitons depends primarily on the twist angle: It is enhanced at coherently stacked angles of 0° and 60° (owing to strong interlayer coupling) but disappears at incoherent intermediate angles. The calculations confirm twist-angle-dependent interlayer coupling: The states at the edges of the valence band exhibit a long tail that stretches over the other layer for coherently stacked angles; however, the states are largely confined in the respective layers for intermediate angles. This interlayer hybridization of the band edge states also correlates with the interlayer separation between MoSe₂ and WSe₂ layers. Furthermore, the interlayer coupling becomes insignificant, irrespective of twist angles, by the incorporation of a hexagonal boron nitride monolayer between MoSe₂ and WSe₂