Properties and antibacterial activity of MnFe2O4 nanoparticles obtained by pulsed laser ablation in liquid

In this study, MnFe2O4 nanoparticles (NPs) were fabricated via pulsed laser ablation in liquid. Chemical and structural composition, microstructure, magnetic and antibacterial properties were characterized. Spinel was found as the main crystalline phase, while Fe2O3 and Mn2O3 were observed as the major secondary phases, all identified by X-ray diffractometry (XRD). Observation by Transmission Electron Microscopy (TEM) indicated that most of the nanoparticles were spherical in shape and found in agglomerates, most likely because of their magnetic nature. Moreover, Fast Fourier Transform of selective area electron diffraction patterns pointed at the existence of crystalline particles. The coercive field (Hc) and saturation magnetization (Ms) values determined for these NPs were found to increase with decreasing temperature. Their antibacterial properties were evaluated using the viable bacteria counting technique (colony) for MnFe2O4 concentrations of 100 and 300 μg/mL with Bacillus subtilis, Salmonella typhimurium, Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli strains

Detail investigation of thermoelectric performance and magnetic properties of Cs-doped Bi2Sr2Co2Oy ceramic materials

Bi2Sr2-xCsxCo2Oy materials with 0 = x = 0.15, have been fabricated via the classical ceramic technique. XRD results have indicated that undoped and Cs-substituted samples are composed of Bi2Sr2Co2Oy phase as the major one. Microstructural studies have demonstrated the formation of a liquid phase, which allows a drastic grain growth. This factor is responsible for a drastic improvement of relative density, reaching about 95% of the theoretical one for 0.125 Cs content. On the other hand, electrical resistivity has been reduced up to 14 mO cm at 650 °C for 0.125 Cs content, around 40% lower than the obtained in undoped samples. As a consequence, Seebeck coefficient has been decreased due to the raise in charge carrier concentration. The highest power factor at 650 °C (0.21 mW/K2 m) has been found for 0.125 Cs substituted sample, about 40% larger than the obtained in undoped samples, and very similar to the notified in single crystals (0.26 mW/K2 m). Magnetisation with respect to temperature results have demonstrated that measured samples have a paramagnetic property above 50 K, except 0.10 Cs. Magnetic hysteresis curves have shown that the slopes and the magnitudes have increased with decreasing temperature

Drastic microstructural modification of Bi2Ca2Co2Oy ceramics by Na doping and laser texturing

Bi2Ca2-xNaxCo2Oy materials with x = 0 = x = 0.125, have been prepared either by sintering through the classical ceramic method, or textured using the laser floating zone technique. XRD results have shown that Bi2Ca2Co2Oy phase is the major one, independently of the Na content, in both kind of samples. SEM studies have shown a drastic microstructural modification between sintered and laser-textured materials. Na-doping increases density and grain sizes in sintered materials, while it enhances grain alignment in laser-grown materials. Moreover, it decreases secondary phase content in all cases. Electrical resistivity is also drastically reduced through texturing, when compared to the sintered samples, and Na-doping further decreases it. The lowest values determined in the laser-textured samples (26 mO cm at 650 °C) are around 40% lower than the best in sintered materials. On the other hand, S has been only slightly affected for Na-doping or processing method for all samples. Consequently, the highest power factor at 650 °C (0.18 mW/K2 m) has been obtained in laser-grown 0.075Na-doped samples, which is around 20 and 70% higher than the measured in undoped laser-textured samples, and sintered ones, respectively. Se han preparado materiales de composición Bi2Ca2-xNaxCo2Oy, con x = 0 ≤ x ≤ 0,125, por el método de estado sólido, además de texturarlos mediante la técnica de zona flotante inducida por láser. Los resultados de XRD han mostrado que la fase Bi2Ca2Co2Oy aparece como la mayoriraria, independientemente del contenido de Na, en ambos tipos de muestras. Los estudios SEM han encontrado una drástica modificación microestructural entre materiales sinterizados y texturados. El dopado con Na aumenta la densidad y el tamaño de grano en materiales sinterizados, mientras que mejora la orientación de los granos en materiales texturados. Además, disminuye el contenido de fases secundarias en todos los casos. La resistividad eléctrica disminuye drásticamente con el texturado, en comparación con las muestras sinterizadas, mientras que el dopado con Na la disminuye aún más. Los valores más bajos determinados en muestras texturadas (26 mΩ cm a 650 °C) son alrededor del 40% menor que los mejores datos publicados en materiales sinterizados. Por otro lado, S solo se ha visto afectado levemente, tanto por el dopado como por el método de procesado. En consecuencia, el máximo factor de potencia a 650 °C (0,18 mW/K2 m) se ha obtenido en muestras dopadas con 0,075 Na y texturadas, que es alrededor de un 20 a un 70% superior al medido en muestras texturadas sin dopar y sinterizadas, respectivamente

Antimicrobial Activity of Flavonoids against Extended-Spectrum &#946-Lactamase (ES&#946L)-Producing Klebsiella pneumoniae

Purpose: In the present study, six flavonoids (5,7-dimethoxyflavanone-4'-O-&#946-D-glucopyranoside, 5,7- dimethoxyflavanone-4'-O-[2''-O-(5'''-O-trans-cinnamoyl)-&#946-D-apiofuranosyl]-&#946-D-glucopyranoside, naringenin-7-O-&#946-D-glucopyranoside, 5,7,3'-trihydroxy-flavanone-4'-O-&#946-D-glucopyranoside, rutin, and nicotiflorin) isolated from Galium fissurense, Viscum album ssp. album and Cirsium hypoleucum were screened against extended-spectrum &#946-lactamase producing multidrug-resistant (trimetoprimesulphametoxazole, sulbactam-ampicillin, clavulonate-amoxicilin, ceftriaxon, cefepime, imipenem, ceftazidime, tobramicin, gentamicin, ofloxacin, ciprofloxacin) bacteria Klebsiella pneumoniae (ES&#946Ls). Methods: We performed susceptibility testing according to the Clinical and Laboratory Standards Institute (CLSI, formerly NCCLS) and used an inhibition endpoint for determination of the minimum inhibition concentrations (MICs). Results: All the flavonoids showed in vitro antimicrobial activity against all the isolated strains of K. pneumoniae similar to the control antibacterial (ofloxacin) at the concentrations of 32 - 64 μg ml-l; another control, ampicillin, had no activity. Since, ES&#946L-producing strains are known to be resistant to all &#946-lactam antibiotics, our results fall notably within the concentration range for antimicrobial activity. Conclusion: To the best of our knowledge, this is the first report of the study of the activity of these flavonoids against (ES&#946L)-producing K. pneumoniae and may throw light to the low-toxicity of flavonoids, and their potentials for developing therapies for infections caused by ES&#946L-producing bacteria in the future. Further work is under investigation to identify their precise antibacterial mechanism. Keywords: Antimicrobial activity, ES&#946Ls, Flavonoids, Klebsiella pneumoniae, Ofloxacin, Ampicillin.Tropical Journal of Pharmaceutical Research Vol. 7(4) 2008: pp. 1151-115

Thermal Conductivity and Thermoelectric Power of Yb-Substituted Bi-2212 Superconductor

In the present study, Bi2Sr2CaCu2-xYbxO8+y where x = 0.0, 0.05, 0.1 and 0.25, superconductor materials were textured using the Laser Floating Zone technique. After annealing the as-grown materials, they were characterized by thermal conductivity (¿-T), thermoelectric power (S-T), and electrical resistivity (R-T) measurements performed from room temperature down to 20 K. The thermoelectric power is positive in all cases and is found to increase with decreasing temperature, reaching the maximum value (peak) around the samples TC values and dropping rapidly to zero below TC. Electrical resistivity measurements show a slight decrease of TC when Yb substitution is raised. In spite of this effect, TC values are higher than 90 K in all cases. On the other hand, Yb substitution also decreases thermal conductivity, compared with the undoped samples

Effect of Yb substitution in Bi-2212 ceramics prepared by laser floating zone technique

In the present work, the influence of Yb substitution for Bi on the structural, electrical and magnetic properties of textured Bi-2212 ceramics has been investigated. X-ray diffraction studies indicated that the major peaks correspond to the Bi-2212 phase. The SEM images clearly show that there is an increase in the number of secondary phases with raising Yb content while all samples maintain similar grain morphology. Magnetic analysis of all samples has been done by magnetic hysteresis measurements, indicating that an enhancement in the M-H loops is obtained by a low Yb doping. The critical current density of samples was calculated from the M-H curves by using Bean’s critical state model, indicating that sample with 0.05 Yb substitution possesses the highest Jc values.The authors wish to thank the Gobierno de Aragón and Fondo Social Europeo (Grupos de Investigacion Consolidados T12 and T87) and MINECO-FEDER (MAT2013-46505-C3-1-R) for financial support.Peer Reviewe

Effect of Na substitution on superconducting properties of Bi-2212 ceramics prepared by Sinter-Forged process

Bulk textured Bi2Sr2Ca1-xNaxCu2Oy (x = 0.0, 0.05, 0.075 0.1, 0.15, and 0.20) ceramics have been prepared by a polymer solution method followed by sinter-forging process. The microstructure and superconducting properties of textured samples were affected by Na substitution. According to XRD data, all samples show that Bi-2212 phase is the major one, and main peaks corresponded to the (00l) diffractions confirming that the crystallographic c-axis is perpendicular to the surface. SEM micrographs showed that samples are composed of well-stacked and oriented grains. The best critical temperature, TC, was measured as 85.6 K for x = 0.075. The critical current density Jc, values decrease gradually with the increase of applied magnetic field. The maximum calculated Jc was 1.38 × 105 A/cm2 at 10 K for 0.075 Na sample which is about four times higher than the 0.34 × 105 A/cm2 value determined for the pure sample. The anisotropic properties of these textured materials have been investigated using magnetic measurements

Estimating the return on investment of selected infection prevention and control interventions in healthcare settings for preparing against novel respiratory viruses: modelling the experience from SARS-CoV-2 among health workers.

Insufficient infection prevention and control (IPC) practices in healthcare settings increase the SARS-CoV-2 infection risk among health workers. This study aimed to examine the level of preparedness for future outbreaks. We modelled the experience from the COVID-19 pandemic and assessed the return on investment on a global scale of three IPC interventions to prevent SARS-CoV-2 infections among health workers: enhancing hand hygiene; increasing access to personal protective equipment (PPE); and combining PPE, with a scale-up of IPC training and education (PPE+). Our analysis covered seven geographic regions, representing a combination of World Health Organization (WHO) regions and the Organisation for Economic Co-operation and Development (OECD) countries. Across all regions, we focused on the first 180 days of the pandemic in 2020 between January 1st and June 30th. We used an extended version of a susceptible-infectious-recovered compartmental model to measure the level of IPC preparedness. Data were sourced from the WHO COVID-19 Detailed Surveillance Database. In all regions, the PPE + intervention would have averted the highest number of new SARS-CoV-2 infections compared to the other two interventions, ranging from 6562 (95% CI 4873-8779) to 38,170 (95% CI 33,853-41,901) new infections per 100,000 health workers in OECD countries and in the South-East Asia region, respectively. Countries in the South-East Asia region and non-OECD countries in the Western Pacific region were poised to achieve the highest level of savings by scaling up the PPE + intervention. Our results not only support efforts to make an economic case for continuing investments in IPC interventions to halt the COVID-19 pandemic and protect health workers, but could also contribute to efforts to improve preparedness for future outbreaks. This work was funded by WHO, with support by the German Federal Ministry of Health for the WHOResearch and Development Blueprint for COVID-19

Thermal conductivity and thermoelectric power of potassium and sodium-substituted Bi-2212 superconductor prepared by PEI technique

In the present study, thermal conductivity (κ − T), thermoelectric power (S − T), and figure of merit (ZT) measurements from room temperature down to 20 K of polycrystalline Bi2Sr2Ca1−xNaxCu2O8+y and Bi2Sr2Ca1−xKxCu2O8+y superconductors prepared by a polymer solution technique using polyethyleneimine, PEI, have been carried out. The thermoelectric power, S(T), of samples have both negative (at high T) and positive values (at low T), and are found to increase with decreasing temperature, reaching their maximum values (peaks) around their Tc values and dropping rapidly to zero below Tc. Na and K substitutions also have a considerable effect on the thermal conductivity, κ. Namely, with increasing Na concentration the magnitude of κ is decreased, but for the K substitution, the magnitude of κ is drastically increased for x = 0.75.This work is supported by the Research Fund of Çukurova University, Adana, Turkey, under Grant Contract Nos FBE.2013YL45 and FEF2013BAP22. A. Sotelo and M. A. Madre wish to thank the Gobierno de Aragon and the Fondo Social Europeo (Research Group T12) and MINECO-FEDER (Project MAT2013-46505-C3-1-R) for the financial support.Peer Reviewe

Effect of Ce substitution on the magnetoresistivity and flux pinning energy of the Bi2Sr2Ca1-x CexCu2O8+δ superconductors

In this study, the effect of Ce doping on the properties of Bi 2Sr2Ca1-x Ce x Cu2O 8+δ ceramic superconductors, with x=0.0, 0.01, 0.05, 0.1, and 0.25, has been investigated. Samples' precursors were prepared using the conventional solid state method and subsequently textured using the Laser Floating Zone technique. The magnetoresistance measurements were studied under various applied magnetic fields. The activation energies, irreversibility fields (H irr ), upper critical fields (H c2) and coherence lengths at 0 K (ξ(0)) were calculated from the resistivity versus temperature (ρ-T) curves, under DC magnetic fields up to 5 T. The thermally activated flux flow model has been applied in order to calculate the flux pinning energies. The results indicated that H c2(0) varied from 416.19 to 115 T and the flux pinning energies varied from 1.46 to 0.042 eV at 0 T. © 2013 Springer Science+Business Media New York.This work is supported by the Research Fund of Çukurova University, Adana, Turkey, under grant contracts No: FEF2011YL27 and FEF2013BAP11. A. Sotelo and M.A. Madre wish to thank the Gobierno de Aragón (Research Group T12), for financial support. M.A. Madre also acknowledges the MINECO-FEDER (Project MAT2011-22719) for funding.Peer Reviewe