Microtiter spectrophotometric biofilm production assay analyzed with metrological methods and uncertainty evaluation

The microbial biofilm is a structure often developed by microorganisms when performing their harmful effects, both in the medical and industrial fields. Therefore, methods allowing identification and analysis of the biofilm play a fundamental role in determining the kind of intervention needed to avoid these effects. The microtiter spectrophotometric assay is recognized as the gold standard method to quantify a biofilm and to analyze the anti-biofilm activity of various substances. The aim of the present work is to validate this method through an uncertainty evaluation, covering eight different microbial species.     

Hyaluronan-coated poly(propylene imine) dendrimers as biomimetic nanocarriers of doxorubicin

A coating technology based on low molecular weight hyaluronic acid (HA) and ferulic acid (FA) was applied to the coating of low generation poly(propylene imine) dendrimers through a biocompatible hexa(ethylene glycol) spacer. The ensuing HA-FA-HEG-PPID dendrimeric materials showed interesting loading capability (between 7.65% and 9.08%) regarding anticancer agent doxorubicin, and their interactions with the drug appeared to hamper the drug release in the physiological environment. Thus, the stable nanostructured loaded delivery systems were able to internalize into cells expressing the HA receptor CD44 and to demonstrate high cytotoxicity comparable to that shown by equivalent amounts of free doxorubicin. Thus, HA-FA-HEG-PPID dendrimeric materials were proposed as biocompatible drug carriers capable of transporting anticancer doxorubicin to tumor cells.     

Effect of palladium on gold in core-shell catalyst for electrooxidation of ethanol in alkaline medium

In this paper the effect of small amounts of palladium deposited on gold nanoparticles supported on Vulcan XC-72 carbon (core-shell structure denoted Au@Pd/C) is studied. Different nominal atomic compositional ratios of Au@Pd_x maintaining fixed gold nuclei and varying the amount of palladium (x = 0.10; 0.80 and 1.60) were synthesized via seed growth method for the ethanol oxidation reaction in alkaline medium. UV–Vis spectrometric, X-ray powder diffraction, X-ray energy dispersive spectroscopy, transmission electron microscopy and electrochemical measurements were performed for the characterization of these catalysts. Electrocatalytic activity toward ethanol oxidation on Au@Pd/C catalysts were investigated by cyclic voltammetry and chronoamperometry showed that Au@Pd_0.10/C electrocatalyst has the highest current density and low onset potential for ethanol oxidation reaction in alkaline medium. In-situ Fourier transform infrared spectroscopy measurements demonstrated that acetate is the main product of ethanol oxidation and CO₂ can be slightest observed, the latter could be visualized in greater quantity on catalyst Au@Pd_0.80/C catalyst.     

SnCo nanowire array as negative electrode for lithium-ion batteries

Amorphous SnCo alloy nanowires (NWs) grown inside the channels of polycarbonate membranes by potentiostatic codeposition of the two metals (SnCo-PM) were tested vs. Li by repeated galvanostatic cycles in ethylene carbonate-dimethylcarbonate - LiPF₆ for use as negative electrode in lithium ion batteries. These SnCo electrodes delivered an almost constant capacity value, near to the theoretical for an atomic ratio Li/Sn of 4.4 over more than 35 lithiation-delithiation cycles at 1 C. SEM images of fresh and cycled electrodes showed that nanowires remain partially intact after repeated lithiation-delithiation cycles; indeed, several wires expanded and became porous. Results of amorphous SnCo nanowires grown inside anodic alumina membranes (SnCo-AM) are also reported. The comparison of the two types of NW electrodes demonstrates that the morphology of the SnCo-PM is more suitable than that of the SnCo-AM for electrode stability over cycling. Optimization of NW technology should thus be a promising route to enhancing the mechanical strength and durability of tin-based electrodes.     

Mires: a publish/subscribe middleware for sensor networks

A wireless sensor network (WSN) consists of a large number of small devices with computational power, wireless communication and sensing capability. These networks have been developed for a wide range of applications, such as habitat monitoring, object tracking, precision agriculture, building monitoring and military systems. Meanwhile, middleware systems have also been proposed in to facilitate both the development of these applications and provide common application services. The development of middleware for sensor networks, however, places new challenges on middleware developers due to the low availability of resources and processing capacity of the sensor nodes. In this context, this paper presents the design and implementation of a middleware for WSN named Mires. Mires incorporates characteristics of message-oriented middleware by allowing applications communicate in a publish/subscribe way. In order to illustrate the proposed middleware, we have also developed an environment-monitoring application and a data aggregation service.

A CMOS low-distortion fully differential power amplifier withdouble nested Miller compensation

A four-stage fully differential power amplifier using a double-nested Miller compensated structure is presented. The multiple-loop configuration used results in a lower harmonic distortion, at least in the audio band, compared to conventional three-stage amplifiers with nested Miller compensation. Design criteria and stability conditions for good stability of amplifiers using a multiple- (greater than two) loop topology are presented. The amplifier operates with a single power supply which has a minimum value of 3 V. With a 5-V supply, power dissipation is 10 mW and total harmonic distortion (THD) is -83 dB for a -V_p-p differential output signal at 10 kHz and a load of 50 Ω. With an 8 Ω load and for a 10-kHz, 4-V _p-p output signal, THD is -68 dB. The chip area is 0.625 mm ² in a 1.5-μm single-poly, double-metal, n-well CMOS technology     

PCM telephony: reduced architecture for a D/A converter and filtercombination

Large dynamic range and high power-supply rejection ratio (PSRR) are achieved in a pulse-code-modulation (PCM) decoder by using differential circuit techniques and by reducing the number of operational amplifiers on the interpolation filter to four (including the output buffer). This reduction is achieved by: (1) exploiting the sin x/x distortion and using a simple integrating configuration in the digital-to-analog converter; and (2) properly manipulating the signal flowgraph of the filter     

Investigation of GaAs]-x_x P crystals using the pseudo-kossel X-ray and photoluminescence techniques

Two indirect methods of determining composition in GaAs_{1-x x}P films grown epitaxially on GaAs substrates are discussed in this paper. In the first method precision lattice parameters, obtained using the pseudo-Kossel technique in back reflection, are compared to compositions determined with the electron microprobe. A plot of corrected lattice parameter vs. %GaP (microprobe) over the range of composition investigated (0.10 < x < 0.55) shows that Vegard’s law holds very closely in this system. The slope of the line is -0.002042 Å/%GaP while the intercept is within 0.028% of the established lattice parameter for GaAs. No point lies farther than 0.003 Å from the line describing Vegard’s law.     

Recovery of Staphylococcus aureus in Gray Mugil cephalus Roe (Bottarga): Investigation by an Integrated Cultural/Molecular Approach

In the Mediterranean area, salted and dried roe from the gray Mugil cephalus “bottarga” represent a speciality food with great commercial value. Bottarga is currently produced by a traditional handmade process and, the risk of human bacterial contamination during its manufacturing is still unknown; in this perspective the foodborne pathogen Staphylococcus aureus could potentially contaminate this product due to poor sanitation or bad handling during processing. The aim of this work is: to evaluate the contamination level of foodborne pathogens at different product manufacturing stages and, in addition, to describe a fast and realizable method for the rapid detection of S. aureus in bottarga samples in the field. A cultural procedure was initially used to investigate the occurrence of S. aureus and the other main foodborne pathogens in bottarga samples at the different manufacturing stages (from roe to final product). In addition, a molecular approach was used to rapidly determine the presence of total bacteria, S. aureus, and its potential toxigenicity. Of the 194 specimens analyzed, we identified: Clostridium perfringens, Enterococcus spp. and Enterobacteriaceae. However, some samples resulted as being contaminated with S. aureus (4% in roe and 8.7% in the final product). During the bottarga manufacturing process, we observed an increase in pathogen levels (from 10² to 10⁵ CFU/g) in contaminated samples, and entA and entB genotypes were identified. Reconstruction experiments suggest that the fresh roe and the bottarga (not completely dried) could represent a risk for the contamination and growth of pathogen bacteria.     

A 470 μA direct readout circuit for electret and MEMS digital microphones

A direct readout circuit configurable for electret or MEMS digital microphones is presented. The circuit includes a transducer buffer, a programmable preamplifier, a ΣΔ modulator, a bandgap reference, a clock detection circuit, and a stability recovery system. The prototype achieves a signal-to-noise-and distortion of 63 dB A-weighted at 1 Pa sound level with a consumption of 470 μA at 1.8 V supply voltage. The active area is 0.72 mm² in a 0.25 μm CMOS process with MIM capacitor option.