Probing the Structural and Antimicrobial Study on a Sol–Gel Derived Velosef-Loaded Bioactive Calcium Magneso-Silicate Xerogel

Silicon - The nature of the opening silicate- based surface affects the chemical interaction, spectroscopic and antimicrobial efficiency. The aim of this approach was to evaluate the spectroscopic...     

Styrene N-vinylpyrrolidone metal-nanocomposites as antibacterial coatings against Sulfate Reducing Bacteria

Copolymer of styrene, and vinylpyrrolidone was prepared by various techniques. Different nanometals and nanometal oxides were added into the copolymer as antimicrobial agents against Sulfate Reducing Bacteria (SRB). The nanocomposite chemical structure was confirmed by using FTIR, ¹H NMR spectroscopy and thermogravimetric analysis (TGA). The biocidal action of these nanocomposites against the SRB was detected using sulfide determination method in Postgate medium B. The data indicated that the nanocomposites had an inhibitory effect on the growth of SRB and reduced the bacterial corrosion rate of mild steel coupons. The prepared nanocomposites have high inhibition efficiency when applied as coatings and show less efficiency when applied as solids or solution into SRB medium. The copolymer and its nanocomposites effectively reduced the total corrosion rate as determined by total weight loss method.     

The Thermal Protective Performance of Firefighters' Clothing: The Air Gap Between the Clothing and the Body

The air gaps entrapped in firefighters' clothing play a crucial role in determining the protective performance of the clothing. Nevertheless, most of the models in the literature ignored the air gaps between the clothing layers and dealt with the air gap between the clothing and the body in an approximate way. In addition, none of these studies addressed the influence of these air gaps on the protective performance of the clothing. This paper introduces a finite-volume model that employs a more realistic analysis for the air gaps entrapped in firefighters' clothing as compared to the typical model in the literature. The paper further investigates the influence of different clothing parameters on the heat release from the clothing to the skin and their corresponding influence on the clothing protective performance. Skin burns predictions made by the present model were compared to those made by the typical model in the literature. The paper demonstrates the influence of the air gap between firefighters' protective clothing and the body on the protection provided by the clothing. The paper also illustrates that inappropriate modeling of the air gaps entrapped in firefighters' clothing would underestimate the protective performance of the clothing.     

Thermal conductivity enhancement in a latent heat storage system

Latent heat storage systems especially those employing organic materials have been reported to exhibit a rather slow thermal response. This is mainly due to the relatively low thermal conductivity of organic latent heat materials. In this study, experiments were carried out to investigate a method of enhancing the thermal conductivity of paraffin wax by embedding aluminum powder in it. The size of the aluminum powder particles was 80 μm. The tested mass fractions in the PCM-aluminum composite material were 0.1, 0.3, 0.4, and 0.5 of aluminum. The used mass fraction in the experimental work was 0.5.The experiments were conducted by using a compact PCM solar collector. In this collector, the absorber-container unit performed the function of absorbing the solar energy and storing the phase change material (PCM). The solar energy was stored in the PCM and was discharged to cold water flowing in pipes located inside the PCM. Charging and discharging processes were carried out. The propagation of the melting and freezing fronts was studied during the charging and the discharging processes. The time wise temperatures of the PCM were recorded during the processes of charging and discharging. The solar intensity was recorded for the charging process. It was found that the charging time was reduced by approximately 60% by adding aluminum powder in the wax. In the discharging process, experiments were conducted for different water flow rates of 9-20.4 kg/h. It was found that the useful heat gained increased when adding aluminum powder in the wax as compared to the case of pure paraffin wax. The heat transfer characteristics were studied.     

On the Protective Performance of Firefighters’ Garments: Air Gaps Between Fabric Layers

Municipal firefighters count on their protective garments to avoid skin burns caused by thermal and flame exposures. Typical firefighting garment consists of three layers of different fire-resistant fabrics named as outer shell, moisture barrier and thermal liner. This paper employed a numerical heat transfer model for firefighters’ garments, which paid more attention to modeling air gaps bounded between garment’s layers. The paper explored and compared the influences of air gaps bounded between garment’s layers on its protective performance. Specifically, the paper investigated the effect of a variation in the air gaps between the garment layers from 1 mm to 6 mm, a variation in the backside emissivity of the outer shell and moisture barrier layers from 0.9 to 0.1 and a variation in their typical thicknesses from 50% to 200% on the protective performance of garment. The results showed that increasing the width of the gap between the moisture barrier and the thermal liner, reducing the outer shell backside emissivity and increasing the moisture barrier thickness improves the protective performance of firefighters’ garments more than does increasing the width of the gap between the moisture barrier and outer shell, reducing the moisture barrier backside emissivity and increasing the outer shell thickness, respectively.     

Synthesis and characterization of Ag nanoparticles embedded in PVA via UV-photoreduction technique for synthesis of Prussian blue pigment

Silver nanoparticles doped in polyvinyl alcohol (AgNps/PVA) were synthesized via polymer-promoted reductive reaction of AgNO₃ and PVA under time-dependent exposure to UV radiation. The AgNps/PVA composites were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction, UV–Vis spectroscopy, and transmission electron microscopy to describe the structure, nuclearity, and distribution of Ag Nps within the PVA matrix. The UV–Vis spectrum of AgNps/PVA exhibited a broad surface plasmon absorption around 425–443 nm which originated from the formation of Ag NPs. Surface analysis by XPS indicated that the Ag NPs were grown solely on the PVA surface at UV exposure time of 2 h (2.0AgNPs/PVA). Increasing the UV exposure time to 4 h will cause the transformation of metallic nanosilver to oxidized nanosilver. UV–Vis absorption spectra were in situ recorded to follow the synthesis of Prussian blue (PB) on 2.0AgNPs/PVA (PB@2.0AgNPs/PVA). The colloidal dispersion of 2.0AgNPs/PVA in an acidic medium containing free Fe(III) ions and potassium hexacyanoferrate(III) revealed an additional band centered at 720 nm due to the intermetal charge-transfer absorbance of the polymeric Fe(II)-C-N-Fe(III) of the PB@2.0AgNPs/PVA nanocomposite. Control experiments were shown to involve a spontaneous electron transfer reaction between 2.0AgNPs/PVA and Fe(III) ions, with a concomitant decomposition of hexacyanoferrate(III) and formation of PB was observed. Moreover, IR gave clear cut evidence for the synthesis of PB@2.0AgNPs/PVA from the appearance of a band for the cyano group at 2090 cm^?1.     

Electropolishing of AISI-304 stainless steel for protection against SRB biofilm

Electropolishing treatment (EP) can be used to remove the biofilm formed on AISI-304 stainless steel surface and protect it against bacterial colonization. High levels of both smoothness and brightness of AISI-304 stainless steel surfaces can be attained by using electropolishing technique, where the sample was fixed as anode and a suitable current was applied into electrolytic cell containing H₃PO₄. AISI-304 stainless steel was exposed to stabilized mixed culture of sulfate reducing bacteria (SMC-SRB) under different conditions as, temperature, pH, salinity, incubation time and inoculum size. The present study recorded the main indicators of bacterial activity such as S⁻⁻, Fe⁺⁺, most probable number (MPN) of SRB and weight loss (corrosion rate) by milinches per year (mpy). The results revealed that the bacterial counts were obviously decreased under all conditions of bacterial biofilm formation after electropolishing treatment.     

Numerical Simulation of Transient Heat Transfer in a Protective Clothing System during a Flash Fire Exposure

A finite volume model was developed to simulate the transient heat transfer in a protective clothing system. The model domain consists of a fire-resistant fabric, the human skin, and the air gap between the fabric and the skin. The model uses a more sophisticated treatment of the air gap compared to previous models: it accounts for transient combined conduction-radiation heat transfer within the air gap and includes the variation in the air gap properties with temperature. Predictions were obtained for the temperature and heat flux distributions in the fabric, skin, and air gap as a function of time, as well as the time to receive skin burn injuries. The numerical model was used to explore the physics of heat transfer in protective clothing, which could potentially be used to improve the performance of this clothing. This study illustrates the dependence of the temporal behavior of the heat fluxes on the specific model assumptions, as well as the associated sensitivity of skin burn predictions to these assumptions.     

Electroencephalography and computerized transaxial tomography in epilepsy diagnosis

Over a 6-month period 89 patients with epileptic seizures were systematically examined by EEGs and CT. Forty-two percent of all cases showed pathological findings in CT compared to 89% with abnormal EEGs. CT is very useful in identifying organic lesions in the epileptic patient. CT identified 11 cases of supratentorial tumour which were correctly localized by EEG. In patients with seizures after trauma or encephalitis the EEG abnormalities were more than could be detected by CT. The EEG and CT findings in cerebrovascular disorders, alcoholism and other diseases are discussed. A remarkable result is the relatively high percentage of hydrocephalus (23%) in the group of cryptogenic epilepsy. Positive EEG findings as to epilepsy could be seen in 62% of the cases.     

Synthesis and characterization of new modified anti-corrosive polyesteramide resins incorporated pyromellitimide ring for surface coating

In this paper new modified anti-corrosive polyesteramide resins were obtained by means of a condensation polymerization reaction between N,N-bis (2-hydroxyethyl) linseed oil fatty acid amide (HELA) and phthalic anhydride (PA), which was partially replaced with pyromellitimide acetic acid (PAA) as a new dibasic acid source. The structure of the resin was confirmed by FT-IR and ¹H NMR spectral studies. The coatings of 50 ± 5 μm thickness were applied to the surface of glass panels and mild steel strips by means of a brush. The coating performance of the resins was evaluated using international standard test methods and involved the measurement of phyisco-mechanical properties such as viscosity, drying time, specular gloss, pencil hardness, adhesion, flexibility and impact resistance. Chemical resistance of the resins to water, acid, alkali and solvent was also evaluated to ascertain their suitability as a surface coatings vehicle. The results show that the modification enhances both phyisco-mechanical and chemical properties. The resins were incorporated within primer formulations and evaluated as anti-corrosive single coatings. The results illustrate that the introduction of pyromellitimide acetic acid, containing a pyromellitimide ring, within the resin structure, enhances the corrosion resistance performance of polyesteramide resins.