Toxic effect of high concentration of sonochemically synthesized polyvinylpyrrolidone-coated silver nanoparticles on Citrobacter sp. A1 and Enterococcus sp. C1

Background/Purpose Currently, silver nanoparticles (AgNPs) have gained importance in various industrial applications. However, their impact upon release into the environment on microorganisms remains unclear. The aim of this study was to analyze the effect of polyvinylpyrrolidone-capped AgNPs synthesized in this laboratory on two bacterial strains isolated from the environment, Gram-negative Citrobacter sp. A1 and Gram-positive Enterococcus sp. C1. Methods Polyvinylpyrrolidone-capped AgNPs were synthesized by ultrasound-assisted chemical reduction. Characterization of the AgNPs involved UV–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. Citrobacter sp. A1 and Enterococcus sp. C1 were exposed to varying concentrations of AgNPs, and cell viability was determined. Scanning electron microscopy was performed to evaluate the morphological alteration of both species upon exposure to AgNPs at 1000 mg/L. Results The synthesized AgNPs were spherical in shape, with an average particle size of 15 nm. The AgNPs had different but prominent effects on either Citrobacter sp. A1 or Enterococcus sp. C1. At an AgNP concentration of 1000 mg/L, Citrobacter sp. A1 retained viability for 6 hours, while Enterococcus sp. C1 retained viability only for 3 hours. Citrobacter sp. A1 appeared to be more resistant to AgNPs than Enterococcus sp. C1. The cell wall of both strains was found to be morphologically altered at that concentration. Conclusion Minute and spherical AgNPs significantly affected the viability of the two bacterial strains selected from the environment. Enterococcus sp. C1 was more vulnerable to AgNPs, probably due to its cell wall architecture and the absence of silver resistance-related genes

The influences of melt-compounding parameters on the tensile properties of low filler loading of untreated-MWCNTs polypropylene (PP) nanocomposites.

This study is to investigate the effects of addition self synthesised multi-walled carbon nanotubes (MWCNTs), to the final properties of polypropylene (PP) matrix nanocomposites. The influences of melt blending parameters were evaluated, where the interrelationship between the temperatures of compounding and roller rotor speed of sh earing blade parameter, to the tensile properties of fabricated composites were studied. MWCNT was synthesised in the laboratory scale; by using the floating catalyst chemical vapour deposition(FC-CVD) method. Pre-compounding work is begun with de-agglomeration of MWCNT which carried out by combining the ultrasonication and mechanical stirrer means simultaneously. Carbon nanotubes produced was first verified by using SEM and TEM imaging microscopy t echniques. It was later integrated with the thermoplastic PP matrix, via melt blending process through internally mixing approach. Very low weight percentage of chemically untreated MWCNT (0, 0.25, 0.50, 0.75 & 1.00 wt. %) was added into PP and later was compression moulded to the thin sheet of composites film. Composites were prepared by varying the compounding temperature into three processing temperature namely 165, 175 & 185°C and also into three shearing speed of roller rotor blade, 40, 60 & 80 rpm respectively. Later, it was mechanically tested via tensile testing following the ASTM D-638 standard method. The interrelationship between each parameter of compounding to the mechanical tensile properties was tested. It was shown that, the additional of very low loading of untreated-MWCNT filler content, does give moderate effects on reinforcement to the tensile properties of composite. Different compounding parameter gives significant difference to the pattern of plot which was comparable between each other

Target Localization in MIMO OFDM Radars Adopting Adaptive Power Allocation among Selected Sub-Carriers

Multiple-input multiple-output (MIMO) radar has been introduced to enhance the performance of classical radar systems. Nevertheless, radar cross sections (RCS) fluctuations remains a known problem in radars. Target localization using narrowband signal produces reduced accuracy due to RCS fluctuations. One of the solution to this problem is utilization of frequency diversity of wideband signal. This paper presents target localization in MIMO radars using an adaptive orthogonal frequency division multiplexing (OFDM) waveform for effective frequency diversity utilization. Each transmitting antenna transmits an OFDM signal in different time slots and received by the each receiving antenna in the receiver array. A joint direction-of-departure (DOD) and direction-of-arrival (DOA) estimation scheme is applied to each of the OFDM sub-carrier using two-way multiple signal classification (MUSIC) algorithm. The estimation results at each sub-carrier are combined based on majority decision using angle histogram (non-parametric approach) to formulate the final wideband angle estimation. In addition, an adaptive power allocation among the sub-carriers is implemented, where the system evaluates the signal quality at each sub-carrier and consequently formulates a feedback to the MIMO transmitting side. The following transmission will comprise of OFDM waveform that focuses the transmit power at selected sub-carriers only. The sub-carrier selection is based on singular values obtained from singular value decomposition operation at each of the sub-carrier. The performance of the proposed scheme is evaluated through numerical simulations as well as validation by experiments in a radio anechoic chamber. It was demonstrated that the usage of larger number of sub-carriers improves the angle estimation accuracy

Compaction characteristics of lime-treated tropical soil

Like soils of other regions in the world, some tropical soils are also associated with problems of low strength. To improve engineering characteristics of soils, several methods have been employed worldwide which are categorized as mechanical, chemical, thermal and electrical. The aim of this research is to compare the compaction characteristics of untreated and lime-treated soils. Soil samples obtained from three different points within a project site in Klang, Selangor were utilized in this study. Each sample was subjected to Eades and Grimm's test in accordance with ASTM D6276-99a to determine the appropriate lime dosage for soil stabilization. The required lime dosage was found between 1.3% and 3.4%. Then each untreated soil and soil sample mixed with 5% lime, higher than that obtained from Eades and Grimm's tests were compacted in accordance with BS 1377:1990. Generally, each soil sample achieved lower values of maximum dry density after treated with 5% lime than those of the untreated soils. Such observations were in good agreement with those obtained by previous researchers working on lime-treated soils. Nonetheless, the optimum moisture content of the lime-treated sample from Points 1 was slightly higher than that of the untreated sample. This finding was different from those obtained by previous researchers. Such contradicting observation might be due to the type and quantity of mineralogical contents of the soils studied

Strength and durability of cement-treated lateritic soil

The transportation infrastructure, including low-volume roads in some regions, needs to be constructed on weak ground, implying the necessity of soil stabilization. Untreated and cement-treated lateritic soil for low-volume road suitability were studied based on Malaysian standards. A series of unconfined compressive strength (UCS) tests was performed for four cement doses (3%, 6%, 9%, 12%) for different curing times. According to Malaysian standards, the study suggested 6% cement and 7 days curing time as the optimum cement dosage and curing time, respectively, based on their 0.8 MPa UCS values. The durability test indicated that the specimens treated with 3% cement collapsed directly upon soaking in water. Although the UCS of 6% cement-treated specimens decreased against wetting–drying (WD) cycles, the minimum threshold based on Malaysian standards was still maintained against 15 WD cycles. On the contrary, the durability of specimens treated with 9% and 12% cement represented a UCS increase against WD cycles. FESEM results indicated the formation of calcium aluminate hydrate (CAH), calcium silicate hydrate (CSH), and calcium aluminosilicate hydrate (CASH) as well as shrinking of pore size when untreated soil was mixed with cement. The formation of gels (CAH, CSH, CASH) and decreasing pore size could be clarified by EDX results in which the increase in cement content increased calcium

Fluorescence dynamics of graphene quantum dots for detecting lard substance

Graphene Quantum Dots (GQD) is used for detecting lard substance. It is discovered that the fluorescence for a GQD with a size approximately 5nm in size will have a peak at 675nm. Introducing lard substance to the GQD will induce a broad fluorescence spectrum at the range of 415 till 715nm. Higher fluorescence is observed from 760nm till 860nm showing the dynamics fluorescence changes when lard is applied. These fluorescence dynamics when lard is introduced is due to the functional groups of Carbon-Carbon interaction between GQD and lard

The barriers and causes of building information modelling usage for interior design industry

Building Information Modeling (BIM) has since developed alongside the improvement in the construction industry, purposely to simulate the design, management, construction and documentation. It facilitates and monitors the construction through visualization and emphasizes on various inputs to virtually design and construct a building using specific software. This study aims to identify and elaborate barriers of BIM usage in interior design industry in Malaysia. This study is initiated with a pilot survey utilising sixteen respondents that has been randomly chosen. Respondents are attached with interior design firms that are registered by Lembaga Arkitek Malaysia (LAM). The research findings are expected to provide significant information to encourage BIM adoption among interior design firms