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

Shear thinning and frequency dependent behaviour of adsorbed polymer layers Part I. Experimental aspects and a first order analysis

Nanorheological measurements were carried out using an oscillatory AFM technique to investigate the viscoelastic properties of adsorbed hydroxypropyl guar (HPG) layers. The oscillations were performed at frequencies between 300 Hz and 1 kHz, with applied oscillation amplitudes of 2 nm. Qualitative data analysis was carried out using complex viscosity and complex modulus transfer functions based on a hydrodynamic lubrication model. The results indicated viscous behaviour at large surface separations and viscoelastic behaviour in the region of polymer layer overlap, as would be expected for adsorbed polymer layers. However, the adsorbed HPG layers also showed an indication of frequency dependent viscoelastic behaviour and shear thinning (reduction of viscosity with frequency). Furthermore, there appeared to be an unanticipated correlation between the apparent thickness of the adsorbed layers and the viscoelastic properties of the system, which may be attributed to the shear thinning behaviour of the layers

Experimental Evaluation of Hydraulic Performance of Outlet Structures with Baffle Blocks under Super critical Flows

The design of outlet transition in field irrigation system requires the flow attaining a uniform velocity at the end of such structures. In addition, super critical flow condition requires maximizing the dissipation of hydraulic energy possessed by the flowing water to hold its erosion capacity to a minimum. Floor baffle blocks incorporated in the outlet transition are useful for the above objectives. This laboratory investigation attempts to evaluate the effects of the relative sizes and arrangements of different types of baffle blocks on hydraulic performances of outlet transition of different configurations operating at super critical flow conditions. Dimensional analysis techniques were used to develop dimensionless ratios describing the geometry and the flow within an outlet transition containing certain types of appurtenance structures. The solution was evaluated in the laboratory with respect to measurable elements of the flow to achieve standardization and general evaluation of the effectiveness of the different types of baffle blocks. The results are presented in the form of dimensionless plots, which show the variation of the ratios developed earlier, with the controlled variation of Froude numbers. Expanding channel outlet transitions of straight-wall type of angle 10 0 , 20 0 and 30 o with two expansion ratios of 4 and 6 were tested with and without floor baffles. The outlets with baffles are generally found to be effective in creating optimum flow conditions than the plain outlets. The use of baffles also resulted in higher dissipation of energy within the outlets, with baffles having curved upstream edge (in plan) dissipated up to 42.7% more energy than the plain outlets

Low Noise, High Gain RF Front End Receiver at 5.8GHz for WiMAX Application

This paper presents the design of a high gain, low noise direct conversion Radio frequency(RF) front-end receiver system. The Front end receiver is designed to operate at 5.8 GHz in compliant with IEEE 802.16 WiMAX standard. The system consists of a low noise amplifier (LNA), a radio frequency amplifier (RFA), a power divider and two band pass filters. The design process involved the use of software such as ADS 2000A, Ansoft Designer and MathCad. FET FHX76 LP is used in the design of the LNA due to its low noise figure and high impedance input. As for the RFA design,FET EPA018A was used. The LNA and the RFA used T lumped reactive element network and microstrip line matching network. Two 3 dBπ -attenuators were inserted at the input and output of the RFA to isolate the system from the reflected load power. A Wilkinson power divider is developed for two equal power structures using impedance microstrip line technique. Microstrip technology was used for designing the Chebyshev filter. The result of each module for the front end is presented

Dissipation of Hydraulic Energy by Curved Baffle Blocks

Experimental evaluation of the effects of relative size, curvature and location of curved floor baffle blocks in the dissipation of energy and control of hydraulic jump is presented. The flow over floor blocks with curved upstream edges (in plan) was described by a set of dimensionless ratios using dimensional analysis techniques. The solution was evaluated in the laboratory with respect to measurable elements of the flow. The results have indicated that, for all flow conditions, the curved blocks are generally more effective in lowering the downstream kinetic energy than regular straight edges blocks; thereby, creating optimum flow conditions having lower capacity for erosion of the downstream channel bed together with economy in structural requirements

Diagnosis of lipomatous hypertrophy of the atrial septum by two-dimensional echocardiography

Originally described in 1964, lipomatous hypertrophy of the atrial septum currently remains a diagnosis established primarily at autopsy. Clinical interest in this disorder has centered on the reported association with supraventricular arrhythmias and sudden death. Because two-dimensional echocardiography allows detailed assessment of atrial septal configuration, we reviewed two-dimensional echocardiographic reports obtained over a 1 year period and identified 17 patients who had features consistent with lipomatous hypertrophy of the atrial septum. Nine were men and the average age was 70 years. Autopsy confirmation of the echographic findings was possible in one patient. In nine patients, ideal body weight was exceeded by 10% or more. The atrial septum viewed from the subcostal transducer position showed a distinctive echo-dense globular thickening sparing the valve of the fossa ovalis. The resultant tomographic image of the atrial septum had a characteristic dumbbell appearance. The mean thickness of the atrial septum was 21 mm (range 15 to 29). Seven patients had supraventricular arrhythmias, and eight had P wave abnormalities.The two-dimensional echocardiographic features described are distinctive and suggest that this technique is the procedure of choice not only for establishing the diagnosis of lipomatous hypertrophy of the atrial septum but also for providing a means for prospective follow-up of patients with this little known entity

The Effect of Ursolic Acid and Hyperinsulinemia on the Liver and Kidney Function of Alloxan-Induced Diabetic Male Rabbits

The study aimed to examine the effect of extracted and standard ursolic acid in addition to hyperinsulinemia compared to vitamin B complex on the liver and kidney function of alloxan-induced diabetic male rabbits. The liver and kidney functions were determined and analyzed by one–way of a NOVA at variance software at a P-Value of 0.05. The result showed a significant decrease in aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and uric acid values in the groups treated with standard and extraction ursolic acid(UA) compared to the diabetic group. The rabbit group that was treated with vitamin B complex recorded a significant decrease in the three liver enzymes, uric acid, and creatinine values than the diabetic group. In addition, the rabbit group that was treated with hyperinsulinemia recorded a significant increase in aspartate aminotransferase (AST) and creatinine values than the diabetic rabbit group. While the histological results in the groups treated with standard and extraction ursolic acid had a clear ameliorative effect in liver and kidney function tests better than hyperinsulinemia, also vitamin B complex caused some good effects

A comparison of fracture strength among different brands of translucent zirconia crown restorations

Objectives: As the development of translucent zirconia crown using CAD/CAM technology, the usage of full zirconia crown is gradually increased. The purpose of this study was to investigate the highest fracture strength of translucent zirconia full zirconia crowns among different brands of translucent zirconia. Methods: Maxillary 1stpremolar resin teeth were prepared the total circumferential axial reduction was about (1 mm), and axial taper of 6°. Three brands of translucent zirconia (Whitepeaks, Imes-icor and Dentaldirect) that was used in three groups, every group contain five full zirconia crowns using CAD/CAM system (CAD/CAM system 250i, Imes-icor, Germany). The samples seated on the resin die using. All specimens were tested with a universal testing machine. Single load-to-fracture was applied on the lingual aspect of the facial cusp at a rate of 1mm/min. The specimens were thoroughly evaluated for bulk fracture with fractography. Results: Statistically high significant difference (p < 0.00) was found between the groups. The fracture strength of the groups varied Whitepeaks crowns was (2737.5 ± 106) N, which was significantly higher than the two overall mean fracture strength measured for the Imes-icor crowns (3620 ± 40) N and Dental direct crowns (3830 ± 130) N, the Dental direct highest fracture strength than other groups. Conclusions. The fracture strength of Dental direct crowns is considerably higher than that of Whitepeaks crown, The fracture strength of all the groups made of monolithic high translucent Y-TZP is exceeded human maximum bite force, sufficient for clinical use for the majority of patients.

Chemical and biological investigations of Delonix regia (Bojer ex Hook.) Raf.

U radu je opisana izolacija pet sastojaka petroleterske i diklormetanske frakcije metanolnog ekstrakta kore biljke Delonix regia: lupeol (1), epilupeol (2), β-sitosterol (3), stigmasterol (4) i p-metoksibenzaldehid (5). Nadalje, testirano je antimikrobno djelovanje različitih ekstrakata difuzijskom metodom na disku (15 μg mm2). Zone inhibicije za sastojke topljive u petroleteru, tetraklormetanu i diklormetanu bile su 914 mm, 1113 mm, odnosno 920 mm, dok je zona inhibicije standarda kanamicina bila 2025 mm. U biološkom pokusu smrtnosti morskih kozica najveću toksičnost pokazali su spojevi topljivi u tetraklormetanu (LC50 = 0,83 μg mL1), dok je topljivost sastojaka topljivih u petroleteru i diklormetanu bila LC50 14,94, odnosno 3,29 μg mL1, a standarda vinkristin sulfata 0,812 μg mL1. Ovo je prvo izvješće o izolaciji sastojaka, antimikrobnom djelovanju i citotoksičnosti biljke D. regia.In this study five compounds, lupeol (1), epilupeol (2), β-sitosterol (3), stigmasterol (4) and p-methoxybenzaldehyde (5) were isolated from the petroleum ether and dichloromethane fractions of a methanolic extract of the stem bark of Delonix regia. Antimicrobial screening of the different extracts (15 μg mm2) was conducted by disc diffusion method. The zones of inhibition demonstrated by the petroleum ether, carbon tetrachloride and dichloromethane fractions ranged from 914 mm, 1113 mm and 920 mm, respectively, compared to kanamycin standard with the zone of inhibition of 2025 mm. In brine shrimp lethality bioassay, the carbon tetrachloride soluble materials demonstrated the highest toxicity with LC50 of 0.83 μg mL1, while petroleum ether and dichloromethane soluble partitionates of the methanolic extract revealed LC50 of 14.94 and 3.29 μg mL1, respectively, in comparison with standard vincristine sulphate with LC50 of 0.812 μg mL1. This is the first report on compounds separation from D. regia, their antimicrobial activity and cytotoxicity