Filtration properties of staple fibre thermo-bonded nonwoven fabrics

Thermal bonded polyester staple fibre nonwoven fabrics have been produced, considering different proportions of binder fibres, directions of web laid as variables, and bonding time and bonding temperature as constant. The influence of process variables on fabric properties, such as bursting strength, air permeability, bubble point diameter, mean flow pore diameter and filtration efficiency with three different particle (1, 0.5, and 0.3µ) along with the overall filtration efficiency have been tested and the results are compared with spun laced nonwoven fabrics. The fibres are oriented in cross and parallel directions, this arrangement of fibres leads to increase in bursting strength. The trend in air permeability of cross-laid web fabrics is found similar to spunlaced fabrics. The pore sizes of the thermal bonded fabrics have been minimized by laying the web in cross direction and increasing the binder fibre proportion; it has minimum variation with spunlaced fabrics. Aerosols of different particles are fed to the upstream of the filters with the face velocity of 16.6 cm/s which is then maintained as constant. The maximum filtration efficiency achieved is found to be 93.13% which is around 13% higher than that of the spunlaced fabric. For 80g/m2 fabrics with 0.3µ particles, the filtration efficiency of spun laced fabric is only 38% which is around one and a half time lesser than 80 g/m2 of thermal bonded fabric; 90g/m2 fabrics show equal and better properties than 100g/m2 fabrics

On the flow unsteadiness and operational characteristics of a novel supersonic fluidic oscillator

A novel supersonic jet oscillating method is investigated both experimentally and numerically. A rectangular primary supersonic jet is issued into a confined chamber with sudden enlargement. Secondary control jets are issued from the top, and bottom backwards-facing step regions formed due to sudden enlargement. The secondary jet also expands in the confined chamber shrouding the primary jet from the top and bottom sides. The primary jet is oscillated in the transverse direction by blowing the secondary jets in the streamwise direction in a pulsating manner with a phase shift. The out-of-phase secondary jet blowing causes the primary jet to periodically adhere to the upper and lower part of the confined chamber, causing flapping of the primary jet and acting as a supersonic fluidic oscillator. The supersonic jet oscillation characteristics are experimentally investigated using shadowgraph type flow visualization technique and steady and unsteady pressure measurements. Quantitative analysis of the shadowgraph images using the construction of $y-t$ and $y-f$ plots reveals the presence of periodic jet oscillation with a discrete dominant frequency similar to the secondary jet excitation frequency. The existence of linearity between the excitation frequency and the flapping jet frequency on the low-frequency ($0.66-6.6$ Hz) side is first proven experimentally. Later, the high-frequency ($16.67-5000$ Hz) operation extent of the supersonic fluidic oscillator is further demonstrated using unsteady computational studies owing to the existing experimental facility's limitations. It is found from the computational studies that there exists a limiting oscillation frequency for the present fluidic oscillator (nearly $4.486$ kHz with the particular geometric size and the injection momentum considered in the present study).Comment: 11 Figures. Relevant multimedia views and supplementary videos are embedded in the pdf itself. The article is prepared for submission to Phys. Fluid

Preparation and Characterization of Silver Nanoparticle/Aloe Vera Incorporated PCL/PEO matrix for wound dressing application

Polymeric wound dressing materials have remarkable mechanical, structural, and biocompatible behavior. In this work, a polymer matrix of Polycaprolactone (PCL)/Polyethylene Oxide (PEO) incorporated with Aloe Vera (AV) extract and silver nanoparticles were prepared for wound dressing application. Initially, the phytochemicals from AV were extracted by Soxhlet apparatus, and then the aloe extract was used as a reducing agent to synthesize silver nanoparticles (Ag NP). Ag NP's formation was confirmed by the presence of a characteristic UV absorbance peak at 420 nm. Ag NP's average diameter and shape were found to be between 10-50 nm and spherical, respectively. AV extract and Ag NP were incorporated into PCL/PEO polymer solution to prepare the polymer matrix by solution casting method. Box-Behnken design (BBD) was used to study the effect of Ag NP concentration, AV extract percentage, and PEO weight percentage concerning PCL on wound dressing application. Water Vapor Transmission Rate (WVTR) and swelling properties of all the sample were tested and found that the PEO and AV extract plays a major role in both swelling and WVTR irrespective of Ag NP concentration. The antimicrobial property of synthesized Ag NP was studied against gram-negative bacteria Escherichia coli with control samples (PCL and PCL/PEO), Ag NP with 150 mg concentration showed a higher zone of inhibition than the other concentrations. Thus, the prepared PCL/PEO polymer matrix incorporated with AV extract and Ag NP can be used as an effective wound dressing material

Comprehensive survey of VUV induced dissociative photoionization of aniline: Role of H migration assisted isomerization

A complete dissociation progression of aniline under VUV irradiation over the entire relevant internal energy range and inclusive of all decay channels is presented. The onset energy and breakdown curve was found to be instrumental in selecting relevant pathways out of multiple possibilities predicted by computation for all significant decay channels. The relevance of the ring contraction in the formation of the intermediate five-member ring structure and its consequences for the important channels such as HNC, H and HNCH losses are highlighted. In addition, a potential route for the formation of previously unexplored and astronomically important fragments HNCH and HCCN has been found. It could be deduced that aniline differs from its bicyclic nitrogenated counterpart, naphthalamine, as ring contraction in aniline is found to be favourable over ring expansion. Moreover, the role of H migration-assisted isomerization is highlighted in the context of the formation of astronomically important species

Preparation and Characterization of Silver Nanoparticle/Aloe Vera Incorporated PCL/PEO matrix for wound dressing application

35-44Polymeric wound dressing materials have remarkable mechanical, structural, and biocompatible behavior. In this work, a polymer matrix of Polycaprolactone (PCL)/Polyethylene Oxide (PEO) incorporated with Aloe Vera (AV) extract and silver nanoparticles were prepared for wound dressing application. Initially, the phytochemicals from AV were extracted by Soxhlet apparatus, and then the aloe extract was used as a reducing agent to synthesize silver nanoparticles (Ag NP). Ag NP's formation was confirmed by the presence of a characteristic UV absorbance peak at 420 nm. Ag NP's average diameter and shape were found to be between 10-50 nm and spherical, respectively. AV extract and Ag NP were incorporated into PCL/PEO polymer solution to prepare the polymer matrix by solution casting method. Box-Behnken design (BBD) was used to study the effect of Ag NP concentration, AV extract percentage, and PEO weight percentage concerning PCL on wound dressing application. Water Vapor Transmission Rate (WVTR) and swelling properties of all the sample were tested and found that the PEO and AV extract plays a major role in both swelling and WVTR irrespective of Ag NP concentration. The antimicrobial property of synthesized Ag NP was studied against gram-negative bacteria Escherichia coli with control samples (PCL and PCL/PEO), Ag NP with 150 mg concentration showed a higher zone of inhibition than the other concentrations. Thus, the prepared PCL/PEO polymer matrix incorporated with AV extract and Ag NP can be used as an effective wound dressing material

In search of universalities in the dissociative photoionization of PANHs via isomerizations

In search of the cause behind the similarities often seen in the fragmentation of PANHs, vacuum ultraviolet (VUV) photodissociation of two pairs of isomers quinoline-isoquinoline and 2-naphthylamine-3-methyl-quinoline are studied using the velocity map imaging technique. The internal energy dependence of all primary fragmentation channels is obtained for all four target molecules. The decay dynamics of the four molecules is studied by comparing their various experimental signatures. The dominant channel for the first pair of isomers is found to be hydrogen cyanide (HCN) neutral loss, while the second pair of isomers lose HCNH neutral as its dominant channel. Despite this difference in their primary decay products and the differences in the structures of the four targets, various similarities in their experimental signatures are found, which could be explained by isomerization mechanisms to common structures. The fundamental role of these isomerization in controlling different dissociative channels is explored via a detailed analysis of the experimental photoelectron-photoion coincidences and the investigation of the theoretical potential energy surface. These results add to the notion of a universal PANH fragmentation mechanism and suggests the seven member isomerization as a key candidate for this universal mechanism. The balance between isomerization, dissociation, and other key mechanistic processes in the reaction pathways, such as hydrogen migrations, is also highlighted for the four molecules

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Filtration properties of staple fibre thermo-bonded nonwoven fabrics

62-66Thermal bonded polyester staple fibre nonwoven fabrics have been produced, considering different proportions of binder fibres, directions of web laid as variables, and bonding time and bonding temperature as constant. The influence of process variables on fabric properties, such as bursting strength, air permeability, bubble point diameter, mean flow pore diameter and filtration efficiency with three different particle (1, 0.5, and 0.3µ) along with the overall filtration efficiency have been tested and the results are compared with spun laced nonwoven fabrics. The fibres are oriented in cross and parallel directions, this arrangement of fibres leads to increase in bursting strength. The trend in air permeability of cross-laid web fabrics is found similar to spunlaced fabrics. The pore sizes of the thermal bonded fabrics have been minimized by laying the web in cross direction and increasing the binder fibre proportion; it has minimum variation with spunlaced fabrics. Aerosols of different particles are fed to the upstream of the filters with the face velocity of 16.6 cm/s which is then maintained as constant. The maximum filtration efficiency achieved is found to be 93.13% which is around 13% higher than that of the spunlaced fabric. For 80g/m2 fabrics with 0.3µ particles, the filtration efficiency of spun laced fabric is only 38% which is around one and a half time lesser than 80 g/m2 of thermal bonded fabric; 90g/m2 fabrics show equal and better properties than 100g/m2 fabrics

Biocompatible and bioactive PVA/Sericin/Chitosan nanofibrous wound dressing matrix

This work focuses on preparation of electrospun matrix for wound dressing application by utilizing sericin, chitosan and silver nanoparticles in PVA nanofibers. Sericin (SS) is extracted from silk cocoon (Bombyx Mori) by alkali degumming method. The extracted sericin is characterised by UV-visible Spectroscopy and FT-IR. Then, individual stock solutions of 2% (w/v) Chitosan (CH) in acetic acid, 10% (w/v) of PVA in deionised water were prepared. To enhance the antimicrobial property to the wound dressing, silver nanoparticles (Ag NP) was prepared using Cynodan dactylon (Bermuda grass) leaves extract and characterised using UV-visible Spectroscopy. The prepared Ag NP was incorporated in the nanofibers at constant proportion. Furthermore, three blended PVA/SS/CH solutions were prepared in the following ratios 8:1:1, 5:2.5:2.5, and 2:4:4 and electrospun to create nanofibrous dressing material. The structural and physical characteristics of the prepared nanofibrous dressing material were studied using SEM and Universal Testing Machine. Based upon mechanical strength and SEM analysis PVA/SS/CH in the ratio 8:1:1 was chosen for In-vitro studies. From the studies it concludes that the prepared PVA/SS/CH electrospun nanofiber will be a promising material for wound dressing

A Review on Dead-Time Effects in PWM Inverters and Various Elimination Techniques

Abstract-- Dead-time is necessary to prevent the short circuit of the power supply in PWM Inverters or converters. But, it will result in output voltage deviations and in case of lower values of current, lower order harmonics will be taken into account. So, dead-time elimination is required in all PWM Inverters or converters. This paper is dealing with a summary of dead-time effects in PWM inverters and various methodologies proposed for eliminating the dead-time and improving the R.M.S value of the output voltage and removing the harmonics concurrently. In case of three phase inverters, the dead-time effect is similar to that of single phase VSI.The waveforms for the analysis of the dead time effect are based on the leg of an inverter, using IGBT'S as switching device (Fig. 2)