Morphology, phase and chemical composition of the nanostructures formed in the systems containing lanthanum, cerium, and silver

X-ray phase and thermogravimetric analysis, scanning electron microscopy and energy-dispersion spectroscopy were used to study the products of phase formation during the precipitation of lanthanum and cerium salts in the presence of silver nitrate and recipients of precipitators, nucleating agents and hydrolysis regulators. Thermogravimetric analysis shows the completion of the La(OH)3 lattice dehydroxylation process at a temperature of ~ 300 °С and probable destruction of sulfates at a temperature of ~ 340 °С. The phase interaction of lanthanum oxide(III) with silver ends at T ~ 400 °C. The DTG curve shows a two-stage weight loss, which characterizes the destruction of lanthanum and silver hydroxides (250 °C) and the removal of sulfates (~ 340 °C), respectively. According to the TG, the total weight loss is 21.6 %. For the cerium-containing system the only endothermic effect of dehydroxylation of cerium hydroxide at T = 250 °C with its conversion into cerium dioxide is observed. The destruction of nitrates (anionic component of solutions) takes place at the temperature of 400 °C. Weight loss takes place at T = 150 °C and is 53.9 %. Thus, on the basis of TG-DTA data, it can be assumed that the formation of composites particles based on lanthanum and cerium oxides, modified with silver, ends at the temperature of 400 °C. The X-ray diffraction data shows that at the initial stage the system undergoes the formation of cerium and lanthanum hydroxides, and during lyophilization of the precipitate (T = 160 °C) the crystal lattice of hydroxides partial dehydroxylation takes place with the formation of trigonal oxides La2O3 and Ce2O3. It has been found that the presence of silver cations in the solution can affect the phase composition of lyophilized structures and the formation of the CeO2 phase. It is shown that the hydroxylamine chloride injection into the system can initiate the silver restoration on the lanthanum oxide surface and also partially restore it to the LaO phase. Temperature treatment of the samples (T = 400 °С) promotes homogenization of the precipitate composition: formation of 30 nm cerium dioxide particles with silver clusters evenly distributed on its surface, and hexagonal lanthanum oxide plates with individual silver particles as the second phase. In three-component systems, two modifications of lanthanum oxides (trigonal and cubic), cerium dioxide and metallic silver are formed. It is found that the chemical composition of the precipitates contains the main elements – La, Ce, O, Ag and impurity – S or Cl, as the anionic component of the initial solutions, N and K in the composition of the initial suspension. It is shown that the morphology of the samples is represented by hexagonal structures of lanthanum hydroxide and oxide, spherical and pseudocubic particles of cerium dioxide and lanthanum oxide, spherical clusters of silver.

Physicochemical parameters affecting norovirus adhesion to ready-to-eat foods

The adhesion of noroviruses to strawberry, turkey slices, ham and Cheddar cheese was studied using murine norovirus (MNV-1) as a surrogate for human norovirus (NoV). Based on plaque assay, the recovery and the adhesion of the MNV-1 depended on the food type (turkey vs strawberry), pH of the initial suspension buffer (pH 4 vs pH 7) and food fat composition (C8 vs C18). Recovery of infectious particles from turkey was 68% compared to 9.4% from strawberry. On turkey, adhesion of MNV-1 was lower at pH 7 (pH of fecal matter) and virus particles adhered to this pH were recovered more easily (33,875 PFU) than at pH 4 (pH of vomitus). The presence of fat and the composition of fatty acids seemed to increase MNV-1 recovery and adherent viral particles recovered but did not affect adhesion (68% on fat-free turkey and regular turkey). Adherent MNV-1 particles recovered from stainless steel coated with saturated fatty acid (C8, C14, C18) increased significantly with chain length ( p< 0.05), but adhesion did not seem to change. Using liquid droplet contact angle to measure surface energy, it was deduced that hydrophobic interactions contribute considerably to the adhesion of MNV-1 to stainless steel, PVC and HDPE. IMPORTANCE Ready-to-eat (RTE) foods are major vehicles of transmission of foodborne viral pathogens including NoV. The high incidence of gastroenteritis caused by viruses is due largely to their persistence in the environment and adhesion to different kinds of surfaces in the food industry including the foods themselves. In comparison with bacteria, adhesion of viruses to surfaces is poorly understood. Better knowledge of the physicochemical parameters involved in the adhesion of NoV to ready-to-eat foods is essential to devising effective strategies for reducing the persistence and thus the transmission of this virus.

756 Adapting Undergraduate Teaching in the COVID 19 Era

Aim The COVID-19 pandemic has drastically impacted medical education, particularly in terms of content delivery and clinical placement efficacy. The initial suspension of placements was devised to limit exposure and redirect medical staff to critical areas. Nevertheless, clinical placements are an important pillar of the undergraduate curriculum and new techniques must be developed to better facilitate its delivery. Our aim was to create a programme that effectively met the required curriculum learning outcomes for medical students. Method In September 2020, students from Queen’s University, Belfast, returned to placement following months of online and distance learning. Having previously focused on bedside and case-based teaching, our priority remained with patient and student safety. Complimentary non-clinical and simulation methods were introduced including laparoscopic skills, suture and knot tying sessions and foundation competencies. Rating scale questionnaires were distributed over a four-week period following each session. Results 32 sessions were carried out and 53 questionnaires returned. Three key areas were reviewed; teaching delivery, usefulness of session and content/relevance, with each area scored out of 10. Collectively across all sessions, 94.3%, 92.4% and 88.7% respectively were scored 9 or greater for each key area. Conclusions The COVID-19 crisis has led to the development of alternative methods of undergraduate teaching. The insurance of patient safety whilst preparing students for their future career is a priority. We have successfully developed an effective and useful placement that blends clinical knowledge and skill-based learning. Given the ongoing pandemic and redirection of resources, further novel ways of teaching should be considered.

Virtual Pathology Elective Provides Uninterrupted Medical Education and Impactful Pathology Education During the COVID-19 Pandemic

As students do not qualify as essential health care workers, medical education faced severe disruptions during the COVID-19 pandemic including initial suspension of all in-person lectures and on-site rotations. Our Pathology Department was among the first at Northwestern to offer a completely virtual rotation with the goals of: (1) providing a comprehensive introduction to the practice of anatomic and clinical pathology, (2) emphasizing uninterrupted and continued excellence in education, and (3) minimizing exposure risk during the pandemic. The innovative 2-week curriculum incorporated diverse teaching modalities including live and recorded lectures; live and recorded video demonstrations; interactive small group discussions; interactive virtual sign-outs; and written and multimedia assignments, quizzes, and projects. The virtual elective ran from March to July 2020 with 52 total participating medical students. On post-rotation evaluations, students rated the pathology virtual elective 4.7/5.0 compared to other virtual rotations and 4.0/5.0 compared to all rotations (including in-person and virtual). Furthermore, continual improvements were made to the established framework based on rotation feedback such that curriculum content was more abundant and more favorably rated by the last cohort when compared to the first. Finally, although students identified interest in over 10 different medical specialties, all participants expressed increased interest in choosing pathology as a specialty and better understanding of pathology’s role in patient care. We hope our detailed description of creating and evaluating a completely virtual elective rotation serves as a model for other departments to improve pathology education and visibility.

Study of Sensitivity of Porous Thick-Film Elements Based on SnO2 towards Hydrogen Concentration in Air

The semiconductor gas sensors with low power consumption have high sensitivity and fast response and their manufacturing technologies permit to reduce the dimensions of the transducer. In production of the semiconductor gas sensors the formation of metal-oxide sensitive layer is an important issue, in particular, the process of combination of the high-porous metal-oxide layer and integrated structures. In the paper, the results of the study on experimental transducers of the composition of gas with porous gas-sensitive layer have been presented. The gas-sensitive layer has been formed by the method of suspension inkjet printing of SnO based suspension with further annealing. The comparison of the sensitivity of the experimental samples of the gas composition transducers with the gas-sensitive layers, formed from two variants of initial suspension: based on pure SnO and SnO doped with Cr and Nb, has been performed. The dependence of variation of conductivity of the gas composition of the integrated transducer specimen on the H concentration in the air has been obtained. It has been found that the gas-sensitive layer based on SnO with Cr and Nb additives has higher sensitivity to changes in the detected gas concentration due to higher effective surface area and suppressed grains agglomeration.

Lessons from Yemen: Diphtheria and Polio Campaign in the Context of COVID-19

Yemen conducted a diphtheria campaign in five governorates between 4 July and 19 July 2020, followed by a polio campaign in 13 governorates between 25 July and 17 August 2020. The study aimed at documenting lessons from conducting the campaigns within the context of COVID-19 pandemic in Yemen after their initial suspension in March 2020. The lessons could contribute to the evidence on the feasibility of maintaining and continuing vaccination campaigns in the context of COVID-19. The descriptive study relied on key informants and content analysis of planning and budgeting documents and daily monitoring reports as data sources. The COVID-19 precautions, including masks, gloves, hand sanitizers, and reduced crowding and social distancing, were applied during the campaigns. These measures minimized concerns over COVID-19, enabling the campaigns to go on, achieving 75% of its target for diphtheria and 96% of the polio campaign&rsquo;s target. The provision of personal protective equipment increased the campaign&rsquo;s perceived safety, leading to its smooth implementation. The measures constituted only about 4 percent of the entire cost of the campaign. The lessons learned will inform the planning and implementation of other upcoming vaccination-related activities in Yemen. This is also a good case study and experience for sharing with other countries.