Evaluation of Kinetic Pseudo-Order in the Photocatalytic Degradation of Ofloxacin

Ofloxacin is a highly efficient and widely used antibiotic drug. It is classified as a refractory pollutant due to its poor biodegradability. Consequently, it is commonly found in water sources, requiring efficient methods for its removal. Advanced oxidation processes (AOPs) offer efficient alternatives since those yield complete degradation not achieved in adsorption or membrane processes. Previous studies suggest ofloxacin degradation follows a pseudo-first or -second order processes, whereas for full removal of refractory pollutants—lower pseudo-orders are required. Monitoring the actual “pseudo-order” degradation kinetics of ofloxacin is needed to evaluate any proposed AOP process. This study presents a simple procedure to evaluate pseudo-orders of AOPs. Photolysis of 20 μM ofloxacin solutions follow pseudo-zero order kinetics, with half-life times (t1/2) of approx. 60 min. TiO2 heterogenous catalysts have been shown to have no influence at low concentrations (0.2 mg L−1), but a significant reduction of half-life time (t1/2 = 20 min) and increase in pseudo-order (0.8) is measured at 2.0 mg L−1. Similar results are obtained with homogenous catalysis by 2.0 mg L−1 H2O2. The combination of H2O2 and TiO2 catalysts shows additional reduction in half-time life with increase in the pseudo-order to 1.2. The conclusions are (1) heterogenous and homogenous photocatalysis can effectively degrade ofloxacin, (2) combined photocatalysis yields higher pseudo-order, being less prone to achieve full removal, and (3) analysis of specific pseudo-orders in AOPs of refractory pollutants helps to further elucidate the efficiency of the processes.

Evaluation of Kinetic Pseudo-Order in the Photocatalytic Degradation of Oflaxicin

Ofloxacin is a highly efficient and widely used antibiotic drug. It is classified as a refractory pollutant due to its poor biodegradability. Consequently, it is commonly found in water sources, requiring efficient methods for its removal. Advanced Oxidation Processes (AOPs) offer efficient alternatives since those yield complete degradation not achieved in adsorption or membrane processes. Previous studies suggest ofloxacin degradation follows a pseudo-first or -second order processes, whereas for full removal of refractory pollutants – lower pseudo-orders are required. Monitoring the actual “pseudo-order” degradation kinetics of ofloxacin is needed to evaluate any proposed AOP process. This study presents a simple procedure to evaluate pseudo-orders of AOPs. Photolysis of 20 mM ofloxacin solutions follow pseudo-zero order kinetics, with half-life times (t1/2) of approx. 60 min. TiO2 heterogenous catalyst show to have no influence at low concentration (0.2 mg L-1) but a significant reduction of half-life time (t1/2 = 20 min) and increase in pseudo-order (0.8) is measured at 2.0 mg L-1. Similar results are obtained with homogenous catalysis by 2.0 mg L-1 H2O2. The combination of H2O2 and TiO2 catalysts shows additional reduction in half-time life with increase in the pseudo-order to 1.2. The conclusions are (1) heterogenous and homogenous photocatalysis can effectively degrade ofloxacin, (2) combined photocatalysis yields higher pseudo-order, being less prone to achieve full removal, (3) analysis of specific pseudo-orders in AOPs of refractory pollutants helps to further elucidate the efficiency of the processes.

Updated nationally determined contributions collectively raise ambition levels but need strengthening further to keep Paris goals within reach

By September 2021, 120 countries had submitted new or updated Nationally Determined Contributions (NDCs) to the UNFCCC in the context of the Paris Agreement. This study analyses the greenhouse gas (GHG) emissions and macroeconomic impacts of the new NDCs. The total impact of the updated NDCs of these countries on global emission levels by 2030 is an additional reduction of about 3.7 GtCO2e, compared to the previously submitted NDCs. This increases to about 4.1 GtCO2e, if also the lower projected emissions of the other countries are included. However, this total reduction needs to be four times greater to be consistent with keeping global temperature increase to well below 2 °C, and even eight times greater for 1.5 °C. Seven G20 economies have pledged stronger emission reduction targets for 2030 in their updated NDCs, leading to additional aggregated GHG emission reductions of about 3.1 GtCO2e, compared to those in the previous NDCs. The socio-economic impacts of the updated NDCs are limited in major economies, while structural shifts occur away from fossil fuel supply sectors and towards renewable electricity. However, two G20 economies have submitted new targets that will lead to an increase in emissions of about 0.3 GtCO2e, compared to their previous NDCs. The updated NDCs of non-G20 economies contain further net reductions. We conclude that countries should strongly increase the ambition levels of their updated NDC submissions to keep the climate goals of the Paris Agreement within reach.

Frequency of surveillance testing necessary to reduce transmission of the Delta variant of SARS-CoV-2

We estimate the reduction in transmission of SARS-CoV-2 achievable by surveillance testing of a susceptible population at different frequencies, comparing the cases of both the original Wuhan strain and the Delta variant. We estimate the viral dynamics using viral copy number at first detection combined with considerations arising from aerosol transmission. We take into account the recent findings that infected vaccinated adults may have live viral loads at the same level as infected unvaccinated adults. Our estimates suggest that twice weekly testing, which was adequate for the original strains of SARS-CoV-2 will be insufficient on its own to contain the spread of the Delta variant of concern. We exclude consideration of contact tracing since the rapidity of the onset of viral titre in the case of the Delta variant suggests that unless contact tracing and quarantine are performed very rapidly (ie. much less than a day), these mitigations will be of minimal impact in reducing transmission. These crude estimates do not take into account heterogeneity of susceptibility, social activity, and compliance, nor do they include the additional reduction in transmission that could be achieved by masking and social distancing. In the setting of a large public university, these considerations suggest that risk-targeted testing of vaccinated students, staff and faculty combined with surveillance testing of all unvaccinated individuals is the most efficient way to reduce transmission of COVID-19.

Synthesis of benzotriazole-intercalated dispersions of molybdenum, tungsten and vanadium oxides for tribochemical applications

The effect of dispersed particles of lamellar molybdenum, tungsten and vanadium oxides on the lubrication properties of mineral oil was investigated. It is shown that in the presence of particles of hexagonal molybdenum oxide the coefficient of friction falls two-fold (from 0.08 to 0.04) exhibiting further decrease under high mechanical load, i. e. molybdenum oxide behaves as an adaptive lubricant. The intercalation of benzotriazole into molybdenum oxide ensures additional reduction of mechanical wearing due to suppressing the tribocorrosion.

Effect of Physical Fields on Highly Resinous Oil

This paper studies the effect of physical fields (i.e. ultrasonic and constant magnetic fields) on structural and energy properties (viscosity, limiting shear stress, pour point, activation energy of viscous flow) as well as kinetic (antioxidant) properties of highly resinous problematic oil. The results were obtained via viscometry, determining of pour point and voltammetric method of oxygen electroreduction. It was shown that the treatment of studied oil by acoustic and magnetic fields lead to decrease in viscosity and temperature parameters. Combined treatment displays an additional reduction of viscosity and pour point

Effect of Microstructure and Relative Humidity on Strength and Creep of Gypsum

The wide range of gypsum facies observed all over the world and the strong heterogeneity that may be present even within a single facies often cause an inhomogeneous mechanical response that, if neglected, may be particularly dangerous in the framework of underground excavations. In addition, gypsum is particularly sensible to the presence of water. The high relative humidity conditions often registered in underground gypsum quarries may imply an additional worsening of mechanical properties. In the present study, the strength and the creep response of a natural gypsum rock facies are investigated, considering the influence of material heterogeneity and relative humidity conditions. The heterogeneity of the material, quantified with MIP and SEM analyses, is observed to strongly affect the mechanical response. To this intrinsic mechanical variability, the influence of an external parameter as the relative humidity is observed to generate an additional reduction of material strength and to increase the creep strain rate in the long-term tests. The effect of all these elements in the underground quarry framework is discussed and a constitutive model of these experimental results is provided.

COVID-19 Implications of the Physical Interaction of Artificial Fog on Respiratory Aerosols

Introduction Artificial fog is used in the film, television, and live entertainment industries to enhance lighting, as a visual effect, and to create a specific sense of mood or atmosphere. This study investigated whether the suspension time of respiratory aerosols spiked with tagged DNA tracers would change in the presence of glycerin- or glycol-containing artificial fogs. Methods & Materials Respiratory aerosols with tagged DNA tracers were sprayed into a closed environment without and with glycerin- or glycol-containing artificial fog, with air samples taken at regular intervals to determine the decay of tagged DNA tracer over time. The study treatments included Control (no fog), Glycerin Low (3 mg/m3), Glycerin High (~15 mg/m3), Glycol Low (~5 mg/m3), and Glycol High (~40 mg/m3). Results All artificial fog treatments had lower mean log reduction curves compared to the Control treatment. Compared to the Control and Glycerin Low treatments, the differences in mean log reduction for nearly all other artificial fog treatments were statistically significant (p<0.001); the difference between Control and Glycerin Low treatments was not statistically significant (p=0.087). The differences in mean log reduction between treatments using the same artificial fog type were not statistically significant. Conclusion Artificial fog use does not increase suspension time of respiratory aerosols, and therefore does not appear to increase the risk of airborne transmission of diseases from respiratory aerosols, such as COVID-19. Of the two types of artificial fogs investigated, that containing glycol decreased suspension time more than that containing glycerin. In practice, the additional reduction in suspension time provided by the physical interaction of respiratory aerosols with artificial fog does not suggest any practical benefit for using artificial fog as a control measure.

Spin distillation cooling of ultracold Bose gases

We study the spin distillation of spinor gases of bosonic atoms and find two different mechanisms in $${}^{52}$$ 52 Cr and $$^{23}$$ 23 Na atoms, both of which can cool effectively. The first mechanism involves dipolar scattering into initially unoccupied spin states and cools only above a threshold magnetic field. The second proceeds via equilibrium relaxation of the thermal cloud into empty spin states, reducing its proportion in the initial component. It cools only below a threshold magnetic field. The technique was initially demonstrated experimentally for a chromium dipolar gas (Naylor et al. in Phys Rev Lett 115:243002, 2015), whereas here we develop the concept further and provide an in-depth understanding of the required physics and limitations involved. Through numerical simulations, we reveal the mechanisms involved and demonstrate that the spin distillation cycle can be repeated several times, each time resulting in a significant additional reduction of the thermal atom fraction. Threshold values of magnetic field and predictions for the achievable temperature are also identified.