Role of surface charge and oxidative stress in cytotoxicity of organic monolayer-coated silicon nanoparticles towards macrophage NR8383 cells

Background - Surface charge and oxidative stress are often hypothesized to be important factors in cytotoxicity of nanoparticles. However, the role of these factors is not well understood. Hence, the aim of this study was to systematically investigate the role of surface charge, oxidative stress and possible involvement of mitochondria in the production of intracellular reactive oxygen species (ROS) upon exposure of rat macrophage NR8383 cells to silicon nanoparticles. For this aim highly monodisperse (size 1.6 ± 0.2 nm) and well-characterized Si core nanoparticles (Si NP) were used with a surface charge that depends on the specific covalently bound organic monolayers: positively charged Si NP-NH2, neutral Si NP-N3 and negatively charged Si NP-COOH. Results - Positively charged Si NP-NH2 proved to be more cytotoxic in terms of reducing mitochondrial metabolic activity and effects on phagocytosis than neutral Si NP-N3, while negatively charged Si NP-COOH showed very little or no cytotoxicity. Si NP-NH2 produced the highest level of intracellular ROS, followed by Si NP-N3 and Si NP-COOH; the latter did not induce any intracellular ROS production. A similar trend in ROS production was observed in incubations with an isolated mitochondrial fraction from rat liver tissue in the presence of Si NP. Finally, vitamin E and vitamin C induced protection against the cytotoxicity of the Si NP-NH2 and Si NP-N3, corroborating the role of oxidative stress in the mechanism underlying the cytotoxicity of these Si NP. Conclusion - Surface charge of Si-core nanoparticles plays an important role in determining their cytotoxicity. Production of intracellular ROS, with probable involvement of mitochondria, is an important mechanism for this cytotoxicit

A CMOS spectrum analyzer frontend for cognitive radio achieving +25dBm IIP3 and −169 dBm/Hz DANL

A dual RF-receiver preceded by discrete-step attenuators is implemented in 65nm CMOS and operates from 0.3– 1.0 GHz. The noise of the receivers is reduced by cross-correlating the two receiver outputs in the digital baseband, allowing attenuation of the RF input signal to increase linearity. With this technique a displayed average noise level below -169 dBm/Hz is obtained with +25 dBm IIP3, giving a spurious-free dynamic range of 89 dB in 1 MHz resolution bandwidth

A receiver with in-band IIP3>20dBm, exploiting cancelling of OpAmp finite-gain-induced distortion via negative conductance

Highly linear CMOS radio receivers increasingly exploit linear RF V-I conversion and passive down-mixing, followed by an OpAmp based Transimpedance Amplifier at baseband. Due to the finite OpAmp gain in wideband receivers operating with large signals, virtual ground is imperfect, inducing distortion currents. We propose to apply a negative conductance to cancel this distortion. In an RF receiver, this increases In-Band IIP3 from 9dBm to >20dBm, at the cost of 1.5dB extra NF and <10% power penalty. In 1MHz bandwidth, a Spurious-Free Dynamic Range of 85dB is achieved at <27mA up to 2GHz for 1.2V supply voltage

Cancellation of OpAmp virtual ground imperfections by a negative conductance applied to improve RF receiver linearity

High linearity CMOS radio receivers often exploit linear V-I conversion at RF, followed by passive down-mixing and an OpAmp-based Transimpedance Amplifier at baseband. Due to nonlinearity and finite gain in the OpAmp, virtual ground is imperfect, inducing distortion currents. This paper proposes a negative conductance concept to cancel such distortion currents. Through a simple intuitive analysis, the basic operation of the technique is explained. By mathematical analysis the optimum negative conductance value is derived and related to feedback theory. In- and out-of-band linearity, stability and Noise Figure are also analyzed. The technique is applied to linearize an RF receiver, and a prototype is implemented in 65 nm technology. Measurement results show an increase of in-band IIP3 from 9dBm to >20dBm, and IIP2 from 51 to 61dBm, at the cost of increasing the noise figure from 6 to 7.5dB and <10% power penalty. In 1MHz bandwidth, a Spurious-Free Dynamic Range of 85dB is achieved at <27mA up to 2GHz for 1.2V supply voltage

Kindermishandeling tijdens de tweede lockdown

Education and Child Studie

Improving parent-child interactions in maltreating families with the Attachment Video-feedback Intervention: parental childhood trauma as a moderator of treatment effects

Research is demonstrating the effectiveness of attachment-based interventions for maltreating families. However, parents' own traumatic childhood experiences may interfere with treatment effects. The current study investigated in a sample of maltreating families whether effects of the Attachment Video-feedback Intervention (AVI) on parent-child interactive quality were moderated by parental childhood trauma. Families were randomized to receive AVI (n= 29) or a Psychoeducative intervention (PI;n= 19), or they were in anon-randomized comparison group (RS;n= 40). Parents filled out the Childhood Trauma Questionnaire and videotapes of parent-child interactions were coded for interactive quality. Parents who received AVI showed improved parent-child interactive quality compared to parents in PI and RS groups. However, parents with more severe levels of childhood trauma showed less improvements. Future research should explore whether clinical attention with a specific focus on trauma would increase treatement effects.Education and Child Studie

Gebruik van de noodopvang tijdens de tweede lockdown

Education and Child Studie