Application of the surface potential data to elucidate interfacial equilibrium at ceria/aqueous electrolyte interface

Interfacial properties of ceria (CeO2) nanoparticles and highly organized ceria crystal planes {111} and {100} in the aqueous electrolyte solution were studied. It was confirmed by high resolution electron spectroscopy that a primary ceria nanoparticle consists mostly of two crystal planes {111} and {100} with different surface sites exposed to the aqueous electrolyte solution. Interfacial properties of ceria nanoparticles are directly related to the reactivity and surface densities of existing surface sites. However, surface characterization (potentiometric titrations and electrophoretic measurements) provides only some kind of average surface properties i.e. average surface charge densities and surface potentials. The point of zero charge (pHpzc) of ceria nanoparticles was measured to be between 6.4 and 8.7, depending on the electrolyte concentration, and the isoelectric point at pHiep = 6.5. With the purpose of understanding ceria nanoparticles surface charging the inner surface potentials of ceria macro crystal planes {111} and {100} were measured for the first time, by means of single crystal electrodes, as a function of pH and ionic strength. The inner surface potential directly affects the state of ionic species bound to a certain surface plane and is thus an essential parameter governing interfacial equilibrium. From the measured Ψ 0(pH) data and applying the Multi Site Complexation Model the thermodynamic equilibrium constants of doubly-coordinated ≡Ce2-OH (at the {100} ceria crystal plane) as well as singly-coordinated ≡Ce1-OH and triply-coordinated ≡Ce3-OH (at the {111} ceria crystal plane) were evaluated. The Ψ 0(pH) function differs for two examined ceria planes, however the inner surface potentials of both planes depend on ionic strength having a broad electroneutrality region between pH = 6 and pH = 9

Diffusion of cosmic-ray electrons in M 51 observed with LOFAR at 54 MHz

Context. The details of cosmic-ray transport have a strong impact on galaxy evolution. The peak of the cosmic-ray energy distribution is observable in the radio continuum using the electrons as proxy. Aims. We measure the length that the cosmic-ray electrons (CRE) are transported during their lifetime in the nearby galaxy M 51 across one order of magnitude in cosmic-ray energy (approximately 1-10 GeV). To this end we use new ultra-low frequency observations from the LOw Frequency ARay (LOFAR) at 54 MHz and ancillary data between 144 and 8350 MHz. Methods. As the the CRE originate from supernova remnants, the radio maps are smoothed in comparison to the distribution of the star formation. By convolving the map of the star-formation rate (SFR) surface density with a Gaussian kernel, we can linearise the radio-SFR relation. The best-fitting convolution kernel is then our estimate of the CRE transport length. Results. We find that the CRE transport length increases at low frequencies, as expected since the CRE have longer lifetimes. The CRE transport length is $l_{\rm CRE} = \sqrt{4Dt_{\rm syn}}$, where $D$ is the isotropic diffusion coefficient and $t_{\rm syn}$ is the CRE lifetime as given by synchrotron and inverse Compton losses. We find that the data can be well fitted by diffusion, where $D=(2.14\pm 0.13) \times 10^{28}~\rm cm^2\,s^{-1}$. With $D\propto E^{0.001\pm 0.185}$, the diffusion coefficient is independent of the CRE energy $E$ in the range considered. Conclusions. Our results suggest that the transport of GeV-cosmic ray electrons in the star-forming discs of galaxies is governed by energy-independent diffusion.Comment: Accepted to Astronomy and Astrophysics. 11 pages, 5 figures, 2 table

Structural characterization and electrical properties of sintered magnesium-titanate ceramics

In this article the influence of ball miling process on structure of MgO-TiO2 system, as well as the electrical properties of samples after sintering, was investigated. The mixtures of MgO-TiO2 powders were mechanically activated in a planetary ball mill for the time period from 0 to 120 min. The influence of mechanical activation and sintering on the lattice vibrational spectra was studied by Raman spectroscopy at room temperature. Structural investigations have been performed on produced powders. Nitrogen adsorption method was used to determine the BET specific surface area and pore size distribution. Unusual results have been obtained: specific surface area continuosly decreased up to 40 min of activation and increased after that, reaching its minimun value of 5.5 m(2)/g. The Raman spectra of activated powders have shown that anatase modes have been decreasing in intensity and broadening as the time of activation extended. Also, the additional modes attributed to TiO2 II, srilankite and rutile phases started to appear as a consequence of activation. The small differences noticed in the Raman spectra of sintered samples have been explained by structural modification of MgTiO3 phase due to the presence of defects. The effects of activation and sintering process on microstructure were investigated by scanning electron microscopy (SEM). The electrical measurements showed difference in dielectric constant (epsilon(r)), loss tangent (tg delta) and specific resistance (rho) as a function of time of mechanical treatment

A faithful 2-dimensional TQFT

It has been shown in this paper that the commutative Frobenius algebra QZ5 ⊗ Z(Q3) provides a complete invariant for two-dimensional cobordisms, i.e., that the corresponding twodimensional quantum field theory is faithful. Zsigmondy's Theorem is essential to the proof of this result

Barriers to health care professionals in detecting more domestic violence

Introduction. Identification of victims of domestic violence among the women using the healthcare is not sufficient. Objective. The aim of this study is to identify the barriers that prevent health care professionals in identifying domestic violence more often. Method. A questionnaire was distributed to health workers in the Health center of Kraljevo, by e-mail. Results. The study comprised 136 health care workers, 73.3% female and 26.7% male. 70.6% were doctors and 29.4% technicians. The mean age of respondents was 38.93 ± 7.7, (range 31-50), with the average 11.36 ± 7.74 years of service. The social barriers were significantly more present among female health workers (p=0.037). The most frequent answer is the lack of guidelines. This answer is significantly in correlation with professional qualification (p=0.002). The prominent institutional barriers are overwork (53.7%), lack of information about the procedures (significantly present among doctors, p=0.003), and the fear for their own safety (46.3%). Barriers associated to the health care workers themselves have the least number of responses, with limited time as the most important, followed by lack of training (44.9%) and lack of knowledge, that is significantly related to gender (p=0.002) and to qualifications (p=0.009). Women expect more authority in their work, p=0.035. Among the 4 groups of barriers, the majority of answers is related to the victims of violence themselves (43.9%), statistically more significant among doctors, p=0.004, predominantly responding that victims hide the violent behavior of their partners (65.4%). Conclusion. Provide continuous education about domestic violence and evaluation of knowledge, encourage the victims to trust the health system, raise awareness about the judgment of violence, and skillfully inform the women of resources in the community

Mice genotyping using buccal swab samples: an improved method

Routine methods used to genotype mice involve isolation of DNA from partially amputated neonate's tail, toe, or ear. The inevitable drawbacks of such techniques are the animal's pain response and the increased time and funds required for DNA purification. In order to implement a noninvasive and simple protocol for mouse DNA isolation, we have improved the method based on samples collected by swabbing of the inner cheek. Combining alkaline and temperature lysis, it was possible to isolate a DNA solution ready for PCR in less than an hour. Testing the method on three different mouse lines showed that it is highly efficient, the volume of the PCR samples could be reduced to 25 microl, and fragments up to 800 bp were successfully amplified. This protocol reduces animal discomfort, shortens the time for DNA isolation, and enables amplification of larger DNA fragments with optimal success rate, thus considerably facilitating large-scale genotyping of different mouse lines

Oxidative stress response in neural stem cells exposed to different superparamagnetic iron oxide nanoparticles

Igor M Pongrac,1 Ivan Pavičić,2 Mirta Milić,2 Lada Brkič Ahmed,1 Michal Babič,3 Daniel Horák,3 Ivana Vinković Vrček,2 Srećko Gajović1 1School of Medicine, Croatian Institute for Brain Research, University of Zagreb, 2Institute for Medical Research and Occupational Health, Zagreb, Croatia; 3Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic Abstract: Biocompatibility, safety, and risk assessments of superparamagnetic iron oxide nanoparticles (SPIONs) are of the highest priority in researching their application in biomedicine. One improvement in the biological properties of SPIONs may be achieved by different functionalization and surface modifications. This study aims to investigate how a different surface functionalization of SPIONs – uncoated, coated with D-mannose, or coated with poly-L-lysine – affects biocompatibility. We sought to investigate murine neural stem cells (NSCs) as important model system for regenerative medicine. To reveal the possible mechanism of toxicity of SPIONs on NSCs, levels of reactive oxygen species, intracellular glutathione, mitochondrial membrane potential, cell-membrane potential, DNA damage, and activities of SOD and GPx were examined. Even in cases where reactive oxygen species levels were significantly lowered in NSCs exposed to SPIONs, we found depleted intracellular glutathione levels, altered activities of SOD and GPx, hyperpolarization of the mitochondrial membrane, dissipated cell-membrane potential, and increased DNA damage, irrespective of the surface coating applied for SPION stabilization. Although surface coating should prevent the toxic effects of SPIONs, our results showed that all of the tested SPION types affected the NSCs similarly, indicating that mitochondrial homeostasis is their major cellular target. Despite the claimed biomedical benefits of SPIONs, the refined determination of their effects on various cellular functions presented in this work highlights the need for further safety evaluations. This investigation helps to fill the knowledge gaps on the criteria that should be considered in evaluating the biocompatibility and safety of novel nanoparticles. Keywords: superparamagnetic iron oxide nanoparticles, biocompatibility, oxidative stress, genotoxicity, murine neural stem cell

Diffusion of cosmic-ray electrons in M 51 observed with LOFAR at 54 MHz

Context. The details of cosmic-ray transport have a strong impact on galaxy evolution. The peak of the cosmic-ray energy distribution is observable in the radio continuum using the electrons as proxy. Aims. We aim to measure the distance that the cosmic-ray electrons (CREs) are transported during their lifetime in the nearby galaxy M 51 across one order of magnitude in cosmic-ray energy (approximately 1–10 GeV). To this end, we use new ultra-low frequency observations from the LOw Frequency ARay (LOFAR) at 54 MHz and ancillary data between 144 and 8350 MHz. Methods. As the CREs originate from supernova remnants, the radio maps are smoothed in comparison to the distribution of the star formation. By convolving the map of the star formation rate (SFR) surface density with a Gaussian kernel, we can linearise the radio–SFR relation. The best-fitting convolution kernel is then our estimate of the CRE transport length. Results. We find that the CRE transport length increases at low frequencies, as expected since the CRE have longer lifetimes. The CRE transport length is $l_{\mathrm{CRE}}=\sqrt{4 D t_{\mathrm{syn}}}$, where D is the isotropic diffusion coefficient and tsyn is the CRE lifetime as given by synchrotron and inverse Compton losses. We find that the data can be well fitted by diffusion, where D = (2.14 ± 0.13)×1028 cm2 s−1. With D ∝ E0.001 ± 0.185, the diffusion coefficient is independent of the CRE energy E in the range considered. Conclusions. Our results suggest that the transport of GeV-cosmic ray electrons in the star-forming discs of galaxies is governed by energy-independent diffusion