Spatially Confined Redox Chemistry in Periodic Mesoporous Hydridosilica-Nanosilver Grown in Reducing Nanopores

Cataloged from PDF version of article.Periodic mesoporous hydridosilica, PMHS, is shown for the first time to function as both a host and a mild reducing agent toward noble metal ions. In this archetypical study, PMHS microspheres react with aqueous Ag(I) solutions to form Ag(0) nanopartides housed in different pore locations of the mesostructure. The dominant reductive nucleation and growth process involves groups located within the pore walls and yields molecular scale Ag(0) nanoclusters trapped and stabilized in the pore walls of the PMHS microspheres that emit orange-red photoluminescence. Lesser processes initiated with pore surface SiH groups produce some larger spherical and worm-shaped Ag(0) nanoparticles within the pore voids and on the outer surfaces of the PMHS microspheres. The intrinsic reducing power demonstrated in this work for the pore walls of PMHS speaks well for a new genre of chemistry that benefits from the mesoscopic confinement of Si-H groups

Periodic Mesoporous Hydridosilica-Synthesis of an "Impossible" Material and its Thermal Transformation into Brightly Photoluminescent Periodic Mesoporous Nanocrystal Silicon-Silica Composite

Cataloged from PDF version of article.There has always been a fascination with "impossible" compounds, ones that do not break any rules of chemical bonding or valence but whose structures are unstable and do not exist. This instability can usually be rationalized in terms of chemical or physical restrictions associated with valence electron shells, multiple bonding, oxidation states, catenation, and the inert pair effect. In the pursuit of these "impossible" materials, appropriate conditions have sometimes been found to overcome these instabilities and synthesize missing compounds, yet for others these tricks have yet to be uncovered and the materials remain elusive. In the scientifically and technologically important field of periodic mesoporous silicas (PMS), one such "impossible" material is periodic mesoporous hydridosilica (meso-HSiO1.5). It is the archetype of a completely interrupted silica open framework material: its pore walls are comprised of a three-connected three-dimensional network that should be so thermodynamically unstable that any mesopores present would immediately collapse upon removal of the mesopore template. In this study we show that meso-HSiO1.5 can be synthesized by template-directed self-assembly of HSi(OEt)3 under aqueous acid-catalyzed conditions and after template extraction remains stable to 300 °C. Above this temperature, bond redistribution reactions initiate a metamorphic transformation which eventually yields periodic mesoporous nanocrystalline silicon-silica, meso-ncSi/SiO2, a nanocomposite material in which brightly photoluminescent silicon nanocrystallites are embedded within a silica matrix throughout the mesostructure. The integration of the properties of silicon nanocrystallinity with silica mesoporosity provides a wealth of new opportunities for emerging nanotechnologies. © 2011 American Chemical Society

Bovine serum albumin-imprinted magnetic poly(2-pyrrolidone) microparticles for protein recognition

This study reports on the synthesis and adsorption properties of molecularly imprinted porous magnetic microparticles (MIP) based on the biodegradable and sustainable poly(2-pyrrolidone) (PPD or PA4). These new PPD MIP materials were obtained via activated anionic ring-opening polymerization of 2-pyrroldone carried out at 40 °C, in the presence of iron fillers and bovine serum albumin (BSA) as a template. Neither solvent, nor additional crosslinking or porogen agents were used in the PPD MIP synthesis. Analogously, PPD particles without BSA imprinting (NIP) were also produced. Depending on the microparticles composition, their yields were in the 55–70 wt% range, the average size varying between 8 and 25 μm. After characterization of the surface topography of all samples, their adsorption capacity toward the BSA target was assessed as a function of the adsorption time, protein concentration and pH of the medium. All three PPD MIP samples displayed adsorption capacity toward BSA being up to one order of magnitude higher as compared to other BSA-imprinted polymer systems. It was found that the rebinding of BSA on MIP is best described by the Langmuir isotherm, whereas for rebinding on NIP the Freundlich isotherm was the more adequate model. On this basis, the nature of the adsorption on MIP and NIP was discussed. The adsorption toward two other proteins, namely Ovalbumin and Cytochrome C was also tested. The newly synthesized BSA-imprinted PPD MIP displayed selective adsorption for the BSA target being dependent on the pH values of the medium. The easy recovery of the Fe-containing MIP and the capacity of all MIP samples for multiple sorption/desorption cycles was demonstrated.The authors gratefully acknowledge the financial support of the project TSSiPRO NORTE-01-0145-FEDER-000015, supported by the regional operation program NORTE2020, under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund, as well as the support by National Funds through Fundação para a Ciência e Tecnologia (FCT), project UID/CTM/50025/2019. N. Dencheva is also grateful for the financial support of FCT in the frames of the strategic project UID/CTM/50025/2013 and the personal pro gram-contract CTTI-51/18-IP

Periodic mesoporous hydridosilica-synthesis of an "impossible" material and its thermal transformation into brightly photoluminescent periodic mesoporous nanocrystal silicon-silica composite

There has always been a fascination with "impossible" compounds, ones that do not break any rules of chemical bonding or valence but whose structures are unstable and do not exist. This instability can usually be rationalized in terms of chemical or physical restrictions associated with valence electron shells, multiple bonding, oxidation states, catenation, and the inert pair effect. In the pursuit of these "impossible" materials, appropriate conditions have sometimes been found to overcome these instabilities and synthesize missing compounds, yet for others these tricks have yet to be uncovered and the materials remain elusive. In the scientifically and technologically important field of periodic mesoporous silicas (PMS), one such "impossible" material is periodic mesoporous hydridosilica (meso-HSiO1.5). It is the archetype of a completely interrupted silica open framework material: its pore walls are comprised of a three-connected three-dimensional network that should be so thermodynamically unstable that any mesopores present would immediately collapse upon removal of the mesopore template. In this study we show that meso-HSiO1.5 can be synthesized by template-directed self-assembly of HSi(OEt)3 under aqueous acid-catalyzed conditions and after template extraction remains stable to 300 °C. Above this temperature, bond redistribution reactions initiate a metamorphic transformation which eventually yields periodic mesoporous nanocrystalline silicon-silica, meso-ncSi/SiO2, a nanocomposite material in which brightly photoluminescent silicon nanocrystallites are embedded within a silica matrix throughout the mesostructure. The integration of the properties of silicon nanocrystallinity with silica mesoporosity provides a wealth of new opportunities for emerging nanotechnologies. © 2011 American Chemical Society

Analysis of spatial relationships in three dimensions: tools for the study of nerve cell patterning

<p>Abstract</p> <p>Background</p> <p>Multiple technologies have been brought to bear on understanding the three-dimensional morphology of individual neurons and glia within the brain, but little progress has been made on understanding the rules controlling cellular patterning. We describe new matlab-based software tools, now available to the scientific community, permitting the calculation of spatial statistics associated with 3D point patterns. The analyses are largely derived from the Delaunay tessellation of the field, including the nearest neighbor and Voronoi domain analyses, and from the spatial autocorrelogram.</p> <p>Results</p> <p>Our tools enable the analysis of the spatial relationship between neurons within the central nervous system in 3D, and permit the modeling of these fields based on lattice-like simulations, and on simulations of minimal-distance spacing rules. Here we demonstrate the utility of our analysis methods to discriminate between two different simulated neuronal populations.</p> <p>Conclusion</p> <p>Together, these tools can be used to reveal the presence of nerve cell patterning and to model its foundation, in turn informing on the potential developmental mechanisms that govern its establishment. Furthermore, in conjunction with analyses of dendritic morphology, they can be used to determine the degree of dendritic coverage within a volume of tissue exhibited by mature nerve cells.</p

Molasses, cassava and cottonseed meal as supplements to fresh and ensiled sugarcane tops

Foram realizados experimentos para determinar a resposta de crescimento do gado Zebu e Holandês aos olhos de cana frescos ou ensilados suplementados e não suplementados. Os suplementos estudados foram o melaço, mandioca e farelo de algodão. Os ganhos de peso do gado alimentado com silagem sem suplemento foram significativamente mais baixos do que os que se alimentaram com olhos de cana frescos sem suplemento. Os dados sobre a utilização da energia, contudo, indicaram que o problema ligava-se à palatalidade e não à utilização do nutriente. Os olhos de cana frescos apenas, mantiveram o peso corporal, enquanto que o gado recebendo silagem perdeu peso. Nem o melaço, nem as raízes de mandioca fornecidos na dose de 0,5 kg por 100 kg de peso corporal tiveram qualquer efeito estimulante como suplemento dos olhos de cana. O farelo de algodão, por sua vez, causou um estímulo de 0,78 kg por cabeça e por dia, quando fornecido na mesma dose. Os valores de energia líquida para manutenção e produção foram determinados para os olhos de cana e para o farelo de algodão por uma técnica comparativa de abate, usando a gravidade específica das carcaças de um grupo inicial servido como amostra, sendo todos os animais abatidos no fim do estudo. A energia líquida para a manutenção dos olhos de cana, tanto frescos como ensilados foi 1,04 megcal por kg de matéria seca, enquanto que a energia liquida para a produção foi 0,46 megcal por kg de matéria seca. Os valores correspondentes para o farelo de algodão foram 1,62 e 1,27 megcal por kg de matéria seca. Dessa forma, para manutenção os olhos de cana valeram 64% de farelo de algodão como uma fonte de energia, mas para a produção, os olhos de cana valeram apenas 36% do valor do farelo de algodão.A 2 x 2 x 4 factorially designed experiment involving fresh and ensiled sugar cane tops, Holstein and Zebu cattle, and no supplement, molasses, cassava roots and cottonseed meal was conducted for a period of 112 days. The Holstein cattle averaged 264 kg in body weight initially, and the Zebus weighed an average of 246 kg initially. Six head from each breed were slaughtered to determine initial body composition by the specific gravity technique. The mean shrunk weight of the animals slaughtered was 257 kg for the Holsteins and 251 kg for the Zebus. The Holsteins contained 9.9% body fat at the start of the experiment, and the Zebus contained 8.6% fat. This difference was not statistically significant. Animals were fed in groups of three, with the fresh or ensiled cane tops allowed ad libitum and the supplements fed at their rate of 0.5 kg of supplement per 100 kg of body weight. Including all animals and all supplements, those animals fed silage ate significantly less dry matter and gained significantly less than those fed fresh cops. The consumption of either molasses or cassava roots with fresh or ensiled tops caused a significant drop in dry matter consumption from cane tops. The dry matter consumed form the supplement, however, was sufficient to maintain the daily weight change when compared to no supplement. There was no significant difference, therefore, in the gains of the usupplemented animals and those fed molasses or cassava roots. Thus, a cottonseed meal supplement of 0.5 kg per 100 kg of body weight caused an average stimulation of weight gain of 0.78 kg per day. Although there was no significant difference between Holsteins and Zebus in shrunk weight gain, there was a significant difference using gain in empty body weight. The failure of the shrunk weight gain to show a difference between breeds is due to the difference in reticulo-rumen fill, the Zebus having less fill than the Holsteins. The Zebus were also fatter, and caused a greater energy retention than that of the Holsteins. It appears from this comparison that, on a dry matter basis, fresh or ensiled sugarcane tops are comparable to Bermudagrass hay in energy value. The cottonseed meal used in this trial had a net energy for production comparable to barley or corn but a lower value for maintenance

Spin-polarized Zener tunneling in (Ga,Mn)As

We investigate spin-polarized inter-band tunneling through measurement of (Ga,Mn)As based Zener tunnel diode. By placing the diode under reverse bias, electron spin polarization is transferred from the valence band of p-type (Ga,Mn)As to the conduction band of an adjacent n-GaAs layer. The resulting current is monitored by injection into a quantum well light emitting diode whose electroluminescence polarization is found to track the magnetization of the (Ga,Mn)As layer as a function of both temperature and magnetic field.Comment: 11 pages, 4 figures. Submitted, Physical Review B15 Rapid Communication

A mixed treatment comparison meta-analysis of metaphylaxis treatments for bovine respiratory disease in beef cattle

Citation: Abell, K. M., Theurer, M. E., Larson, R. L., White, B. J., & Apley, M. (2017). A mixed treatment comparison meta-analysis of metaphylaxis treatments for bovine respiratory disease in beef cattle. Journal of Animal Science, 95(2), 626-635. doi:10.2527/jas2016.1062The objective of this project was to evaluate the effects of antimicrobials approved for parenteral metaphylactic use in feeder and stocker calves on morbidity and mortality for bovine respiratory disease with the use of a mixed treatment comparison meta-analysis. An initial literature review was conducted in April 2016 through Pubmed, Agricola, and CAB (Commonwealth Agricultural Bureau) for randomized controlled trials for metaphylaxis antimicrobial administered parentally to incoming feedlot or stocker calves within 48 h of arrival. The final list of publications included 29 studies, with a total of 37 trials. There were 8 different metaphylactic antimicrobials. Final event outcomes were categorized into bovine respiratory disease (BRD) morbidity cumulative incidence d 1 to <= 60 of the feeding period, BRD morbidity cumulative incidence d 1 to closeout of the feeding period, BRD mortality cumulative incidence d 1 to closeout of the feeding period, and BRD retreatment cumulative incidence morbidity d 1 to closeout of the feeding period. Network meta-analysis combined direct and indirect evidence for all the event outcomes to determine mean odds ratio (OR) with 95% credibility intervals (CrIs) for all metaphylactic antimicrobial comparisons. The "upper tier" treatment arms for morbidity d 1 to <= 60 included tulathromycin, gamithromycin, and tilmicosin. For BRD mortality cumulative incidence d 1 to closeout and BRD retreatment morbidity d 1 to closeout, classifying the treatment arms into tiers was not possible due to overlapping 95% CrIs. The results of this project accurately identified differences between metaphylactic antimicrobials, and metaphylactic antimicrobial options appear to offer different outcomes on BRD morbidity and mortality odds in feedlot cattle

Experiential Exposure as the Key to Recruiting Medical Students Into Pathology

Medical student interest and pursuit of a career in pathology have been steadily declining since 2015. We conducted three separate surveys of medical students to better understand these trends. In our first survey, we focused on assessing U.S. allopathic medical students understanding and perceptions of pathology. We later surveyed U.S. osteopathic medical students as a companion to the allopathic medical student survey, in which many similarities were discovered with some key differences. In our final survey, we specifically looked at curriculum differences between the U.S. allopathic medical schools that graduate the most students who enter pathology training programs (Group 1) versus those schools that graduate the fewest future pathologists (Group 2) to determine if the curriculum had an impact on medical student matriculation into pathology. Together, through these surveys, we were able to identify several remarkable recurring trends, presenting areas of targetable action. Here, we summarize themes from the three studies as well as a review of pertinent literature to offer best practices for exposing and engaging medical students to pathology and possibly recruiting students to consider pathology as a career