The problem of a metal impurity in an oxide: ab-initio study of electronic and structural properties of Cd in Rutile TiO2

In this work we undertake the problem of a transition metal impurity in an oxide. We present an ab-initio study of the relaxations introduced in TiO2 when a Cd impurity replaces substitutionally a Ti atom. Using the Full-Potential Linearized-Augmented-Plane-Wave method we obtain relaxed structures for different charge states of the impurity and computed the electric-field gradients (EFGs) at the Cd site. We find that EFGs, and also relaxations, are dependent on the charge state of the impurity. This dependence is very remarkable in the case of the EFG and is explained analyzing the electronic structure of the studied system. We predict fairly anisotropic relaxations for the nearest oxygen neighbors of the Cd impurity. The experimental confirmation of this prediction and a brief report of these calculations have recently been presented [P.R.L. 89, 55503 (2002)]. Our results for relaxations and EFGs are in clear contradiction with previous studies of this system that assumed isotropic relaxations and point out that no simple model is viable to describe relaxations and the EFG at Cd in TiO2 even approximately.Comment: 11 pages, 8 figures, Revtex 4, published in Physical Review

Impact of amplifier errors on position loop accuracy of high-precision moving stages

To maximise essential system performance parameters, this research combines electrical, mechanical and position control models of a high-precision mechatronic system. The degradation of system performance induced by identified amplifier errors is analysed to reveal the significance of each error mechanism. The simplified outline of a mechatronic system is given to which models of the power amplifier are added in order to emulate the error mechanisms. Analysis of the impact of each error mechanism on the position accuracy of the mechatronic system is given from which specifications for the power amplifier can be obtained for a certain required position accuracy. Ensuing properly targeted requirements provide focused amplifier optimisation

In vitro efficacy of artemisinin-based treatments against SARS-CoV-2

Effective and affordable treatments for patients suffering from coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), are needed. We report in vitro efficacy of Artemisia annua extracts as well as artemisinin, artesunate, and artemether against SARS-CoV-2. The latter two are approved active pharmaceutical ingredients of anti-malarial drugs. Concentration–response antiviral treatment assays, based on immunostaining of SARS-CoV-2 spike glycoprotein, revealed that treatment with all studied extracts and compounds inhibited SARS-CoV-2 infection of VeroE6 cells, human hepatoma Huh7.5 cells and human lung cancer A549-hACE2 cells, without obvious influence of the cell type on antiviral efficacy. In treatment assays, artesunate proved most potent (range of 50% effective concentrations (EC50) in different cell types: 7–12 µg/mL), followed by artemether (53–98 µg/mL), A. annua extracts (83–260 µg/mL) and artemisinin (151 to at least 208 µg/mL). The selectivity indices (SI), calculated based on treatment and cell viability assays, were mostly below 10 (range 2 to 54), suggesting a small therapeutic window. Time-of-addition experiments in A549-hACE2 cells revealed that artesunate targeted SARS-CoV-2 at the post-entry level. Peak plasma concentrations of artesunate exceeding EC50 values can be achieved. Clinical studies are required to further evaluate the utility of these compounds as COVID-19 treatment

Mental fatigue after very severe closed head injury: Sustained performance, mental effort, and distress at two levels of work-load in a driving simulator

In patients with very severe closed head injury (CHI), returning to work is often problematic. The present study focuses on a persistent complaint of these patients, viz. mental fatigue. To study this, the effect of sustained workload is assessed in a continuous dynamic divided attention task. Three types of measures are employed: performance loss with time-on-task, and subjective reports and cardiovascular measures of mental effort and distress. Eight very severe CHI patients (mean post-traumatic amnesia duration 51 days, mean age 23 years, (SD 6.4) and eight hospital controls (mean age 29 years, (SD 5.9) were tested. No differences were found between the patients and controls in the effects of task load on performance and the amount of mental effort, even in very demanding simulated work conditions. This parallels previous findings in less demanding laboratory tasks of sustained attention. Effects of CHI were found on both subjective and physiological indicators of distress. Compared to the controls, patients showed stronger effects on systolic blood pressure and subjectively experienced load

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Impact of amplifier errors on position loop accuracy of high precision moving stages

A generic approach to model the position control of an electromechanical system is described that includes several potential error mechanisms originating from the power amplifier, independent of the actual amplifier implementation. The simplified outline of a mechatronic system is given to which models of the power amplifier are added in order to emulate the error mechanisms. Analysis of the impact of each error mechanism on the position accuracy of the mechatronic system is given from which boundary specifications for the power amplifier can be obtained for a certain required position accuracy

Charge-based zero-voltage switching of a flying capacitor resonant pole inverter with trapezoidal filter current

An advanced charge-based Zero-Voltage Switching (ZVS) modulation strategy for a Flying Capacitor Resonant Pole Inverter (FC RPI) with trapezoidal filter current is presented, resulting in full operating range ZVS, decreased rms value of the circulating filter current, and increased switching frequency. A charge-based model that correctly incorporates the nonlinear parasitic output capacitances of the switches is used to ensure ZVS. Increased efficiency of the multilevel RPI configuration is achieved due to minimized rms and peak value of the circulating filter current. Interleaving of multiple switching cells using simple phase control to increase the apparent switching frequency and lower the stress on filter components is investigated. The presented modulation strategy is verified using simulations from which proper operation is concluded

High-Voltage Actuation System for Future Generation Lithography systems - Power Amplifier

Current motion systems in lithography machines operate at a bus voltage of 600V after a steady increase in the past decades. Increasing the voltage has the advantage of delivering more power without the cost of an increase in mass and volume of power cables. However, this requires a significant breakthrough in power amplifier technology since fast switching MOSFETs can only be used reliably up to 600 V and for higher voltages only slower switching devices are available

Impact of amplifier errors on position loop accuracy of high precision moving stages

A generic approach to model the position control of an electromechanical system is described that includes several potential error mechanisms originating from the power amplifier, independent of the actual amplifier implementation. The simplified outline of a mechatronic system is given to which models of the power amplifier are added in order to emulate the error mechanisms. Analysis of the impact of each error mechanism on the position accuracy of the mechatronic system is given from which boundary specifications for the power amplifier can be obtained for a certain required position accuracy