The formic acid electrooxidation reaction was evaluated on an iridium electrode at room temperature in 0.5 M HCOOH + 0.5 M H
2
SO
4
solution, using a flow cell. Chronoamperometric experiments allowed ...establishing the dependence of the electrocatalytic activity on potential, which reaches a maximum around 0.55 V. The open circuit chronopotentiometric transient was also measured. Moreover, the voltammetric stripping profile was also obtained at each analysed potential, enabling the evaluation of the presence of adsorbed carbon monoxide (CO
ad
) on the electrode surface through its electrooxidation charge. It was found that it is high at low potentials, and then it decays vanishing at 0.5 V. From the analysis of the results obtained, it was concluded that CO
ad
is originated from the spontaneous dissociative adsorption of HCOOH, producing the inhibition of reaction sites at low potentials. Meanwhile the water discharge generates adsorbed hydroxil (OH
ad
), which inhibits the reaction at high potentials. A reaction mechanism was proposed and discussed, and the Ir electrocatalytic activity was compared with those of platinum, palladium and rhodium, evaluated under similar experimental conditions.
Background: The period of adolescence confers significant vulnerability to mental health problems that may persist into adulthood, causing significant mental health problems to the individual and to ...society at large However, the majority of what is known about adolescent mental health is rom developed countries. Objective: This study sought to fill the knowledge gap by investigating the influence of peer pressure and substance use on the mental health of in-school adolescents. Methodology: A cross-sectional research design was adopted for this study alongside purposive method for sampling of the participants The sample size was made up of 288 in-school adolescents between the ages of 13 to 22 years, with an average age of 17.02±1.92 drawn from three government schools in Oyo state's capital city. Results: The findings of this study revealed that peer pressure and substance use have a negative impact on mental health. Furthermore, both variables predicted mental health jointly, but only substance use predicted mental health independently. We also discovered no significant gender variation in adolescent mental health. Conclusion: We concluded that substance use is a risk factor for adolescent mental health, as revealed by the outcome of this study. Key Recommendation: As a result, it was recommended that timely and comprehensive mental health interventions should target this population's substance use.
We present a novel Active Magnetic Shield (AMS), designed and implemented for the n2EDM experiment at the Paul Scherrer Institute. The experiment will perform a high-sensitivity search for the ...electric dipole moment of the neutron. Magnetic-field stability and control is of key importance for n2EDM. A large, cubic, 5 m side length, magnetically shielded room (MSR) provides a passive, quasi-static shielding-factor of about
10
5
for its inner sensitive volume. The AMS consists of a system of eight complex, feedback-controlled compensation coils constructed on an irregular grid spanned on a volume of less than 1000 m
3
around the MSR. The AMS is designed to provide a stable and uniform magnetic-field environment around the MSR, while being reasonably compact. The system can compensate static and variable magnetic fields up to
±
50
μ
T
(homogeneous components) and
±
5
μ
T/m
(first-order gradients), suppressing them to a few
μ
T
in the sub-Hertz frequency range. The presented design concept and implementation of the AMS fulfills the requirements of the n2EDM experiment and can be useful for other applications, where magnetically silent environments are important and spatial constraints inhibit simpler geometrical solutions.
The hydrogen oxidation reaction was studied on a nanostructured rhodium electrode at different rotation rates in alkaline solution. The electrode was prepared via sputtering on a glassy carbon disc ...support and it was characterized by atomic force microscopy and cyclic voltammetry. The real surface area was evaluated by CO stripping voltammetry. Experimental current density (j) – overpotential (η) curves of the hydrogen oxidation reaction were obtained in the range −0.015 ≤ η/V ≤ 0.40 at different rotation rates (900 ≤ ω/rpm ≤ 4900). The resulting curves were correlated by kinetic expressions derived from the Tafel-Heyrovsky-Volmer mechanism with a Frumkin type adsorption of the reaction intermediate and the kinetic parameters were evaluated. It was verified that over this overpotential region the reaction in alkaline solution proceeds mainly through the Tafel-Volmer route. These results were compared with those previously obtained in acid solutions.
•Kinetic study of the hydrogen oxidation reaction in alkaline solution.•Nanostructured rhodium supported on glassy carbon.•Experimental polarization curves at different rotation rates.•Tafel-Heyrovsky-Volmer mechanism and Frumkin type adsorption.•Reaction proceeds mainly through the Tafel-Volmer route.
The HCOOH electrooxidation reaction (FAO) was experimentally studied on rhodium electrode using a flow cell in a 0.5-M HCOOH + 0.5-M H
2
SO
4
solution. It was obtained the steady-state ...current-potential curve by chronoamperometry, which demonstrated that the FAO is verified in the potential region 0.45 < E/V < 0.70. The amount of adsorbed CO on the electrode surface as a function of potential was quantified by stripping voltammetry after changing to a 0.50-M H
2
SO
4
solution at closed electric circuit. It was established that the spontaneous dissociative adsorption of HCOOH on rhodium produces irreversibly adsorbed CO only for potential values E ≤ 0.40 V, and therefore, the FAO takes place in the absence of CO
ad
. These results can explain the current-potential profiles obtained when the FAO is studied by cyclic voltammetry at different values of the potential scan limits, where the behaviour is strongly influenced by the inhibition of reaction sites due to the adsorbed CO. A kinetic mechanism for the FAO on rhodium is proposed on the basis of the results obtained, which are also in agreement with recently published spectroscopic measurements.
Graphical Abstract
The kinetics of the formic acid electrooxidation reaction (FAO) on rhodium electrode on steady state was studied. It was demonstrated that adsorbed CO is not a reaction intermediate, being only an inhibitor. A kinetic mechanism compatible with experimental as well as previous spectroscopic evidences was proposed.
In 2010, a chimpanzee died at Copenhagen Zoo following an outbreak of respiratory disease among chimpanzees in the zoo. Identification of coxsackie B3 virus, a common human pathogen, as the causative ...agent, and its severe manifestation, raise questions about pathogenicity and transmissibility among humans and other primates.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Brushless Direct Current (BLDC) motors have been used in a wide range of fields. In some critical applications, failures in these machines can cause operational disasters and cost lives if they are ...not detected in advance. The classical methods for detecting incipient faults in BLDC motors perform processing of the current signal to obtain the required information. In this work, the SAC-DM (Signal Analysis based on Chaos using Density of Maxima) technique is applied for the first time in the diagnosis of failures of electromechanical systems from sound signals. Wavelet Multiresolution Analysis (WMA) is used to separate a chaotic signal component from the sound emitted by the motor. This work demonstrates that it is feasible to perform dynamic eccentricity diagnosis in BLDC motors by identifying variations of the SAC-DM of the sound signal. The technique exposed in this work requires low computational cost and achieves high success rate. To validate the method, tests were carried out on a small BLDC motor normally used in Unmanned Aerial Vehicle (UAV), demonstrating the ability of the method to detect the speed of the motor in 95.89% of the cases and to detect eccentricity problems at a fixed speed in 88.34% of the cases.
Selenium-containing chrysin (SeChry) and 3,7,3′,4′-tetramethylquercetin (SePQue) derivatives were synthesized by a microwave-based methodology. In addition to their improvement in terms of DPPH ...scavenging and potential GPx-like activities, when tested in a panel of cancer cell lines both selenium-derivatives revealed consistently to be more cytotoxic when compared with their oxo and thio-analogues, evidencing the key role of selenocabonyl moiety for these activities. In particular, SeChry elicited a noteworthy cytotoxic activity with mean IC50 values 18- and 3-fold lower than those observed for chrysin and cisplatin, respectively. Additionally, these seleno-derivatives evidenced an ability to overcome cisplatin and multidrug resistance. Notably, a differential behavior toward malignant and nonmalignant cells was observed for SeChry and SePQue, exhibiting higher selectivity indexes when compared with the chalcogen-derivatives and cisplatin. Our preliminary investigation on the mechanism of cytotoxicity of SeChry and SePQue in MCF-7 human mammary cancer cells demonstrated their capacity to efficiently suppress the clonal expansion along with their ability to hamper TrxR activity leading to apoptotic cell death.
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