Frictional properties of light-activated antimicrobial polymers in blood vessels

The adhesion of microbes to catheter surfaces is a serious problem and the resulting infections frequently lead to longer hospitalisation and higher risk for the patient. Several approaches have been developed to produce materials that are less susceptible to microbial colonisation. One such approach is the incorporation of photoactivated compounds, such as Toluidine Blue O (TBO), in the polymeric matrix resulting in ‘light-activated antimicrobial materials’. The insertion and removal of catheters can cause tissue damage and patient discomfort through frictional forces; hence the lubricity of a catheter material is also very important. In this work the tribological performance of silicone and polyurethane containing TBO and gold nanoparticles were evaluated using two different surfaces, the inner part of the aorta and the superior vena cava of sheep. Static and kinetic friction coefficients of these materials were measured using a tribometric device developed for in vitro applications using dry materials and those lubricated with blood. It was found that neither the preparation process nor the presence of TBO or gold nanoparticles, had an effect on the friction factors in comparison to those of untreated materials. In all cases, static and kinetic friction coefficients on aorta tissue were higher than those on vena cava due to higher surface roughness of the aorta. The presence of blood as a lubricant resulted in lower friction coefficients.     

Joint modeling of anatomical and functional connectivity for population studies

We propose a novel probabilistic framework to merge information from diffusion weighted imaging tractography and resting-state functional magnetic resonance imaging correlations to identify connectivity patterns in the brain. In particular, we model the interaction between latent anatomical and functional connectivity and present an intuitive extension to population studies. We employ the EM algorithm to estimate the model parameters by maximizing the data likelihood. The method simultaneously infers the templates of latent connectivity for each population and the differences in connectivity between the groups. We demonstrate our method on a schizophrenia study. Our model identifies significant increases in functional connectivity between the parietal/posterior cingulate region and the frontal lobe and reduced functional connectivity between the parietal/posterior cingulate region and the temporal lobe in schizophrenia. We further establish that our model learns predictive differences between the control and clinical populations, and that combining the two modalities yields better results than considering each one in isolation.     

In vitro dissolution of bioactive glass S53P4 microspheres

Static and dynamic in vitro dissolution studies showed large differences for various size-fractions of non-porous, flame-sprayed commercial microspheres (45–500 µm) of bioactive glass S53P4. The smaller the spheres, the more their composition deviated from the nominal glass. The dissolution studies were carried out in simulated body fluid and tris(hydroxymethyl) aminomethane buffer for seven days. The ion concentrations in solutions were analyzed using inductively coupled plasma optical emission spectrometry, and the pH was measured as a function of time. Also, changes in the sphere size distribution and mass losses were determined. The calcium phosphate and the silica-rich layers at the sphere surfaces were investigated using scanning electron microscopy after several immersion times. The smallest (45–90 µm) spheres appeared almost inert. In contrast, typical silica-rich and calcium phosphate layers were identified at the largest spheres after three days of static and dynamic dissolutions. During the past years, bioactive glass microspheres have been added to paste-like injectable bone grafting materials, putties to enhance their molding properties. The obtained results provide a better understanding of the dissolution patterns of bioactive glass microspheres.     

On the construction of invertible filter banks on the 2-sphere

The theories of signal sampling, filter banks, wavelets, and "overcomplete wavelets" are well established for the Euclidean spaces and are widely used in the processing and analysis of images. While recent advances have extended some filtering methods to spherical images, many key challenges remain. In this paper, we develop theoretical conditions for the invertibility of filter banks under continuous spherical convolution. Furthermore, we present an analogue of the Papoulis generalized sampling theorem on the 2-Sphere. We use the theoretical results to establish a general framework for the design of invertible filter banks on the sphere and demonstrate the approach with examples of self-invertible spherical wavelets and steerable pyramids. We conclude by examining the use of a self-invertible spherical steerable pyramid in a denoising experiment and discussing the computational complexity of the filtering framework.     

Microstructure and Reliability Comparison of Different Pb-Free Alloys Used for Wave Soldering and Rework

This paper describes the results of an intensive microstructural and reliability study of pin-through-hole (PTH) and surface mount technology (SMT) components which were wave solder assembled using three groups of alloys: (1) near-eutectic Sn-Ag-Cu alloys such as SAC405 and SAC305, (2) low-Ag off-eutectic Pb-free alloys with an Ag content of about 1% and lower, and (3) eutectic Sn-Cu alloys with Ni and other additives. Both primary attach and reworked solder connections using solder fountain and hand rework were studied. The PTH connector types and SMT components were wave solder assembled on a test vehicle. Accelerated thermal cycling (ATC) was conducted at 0°C to 100°C for 6000 cycles. The difference in microstructures, intermetallic formation, Cu dissolution, grain coarsening, and crack formation is shown. The influence of the microstructure after assembly and rework on Weibull plot parameters and failure modes is described for 2512 resistors. Interconnect defects such as nonuniform phase distribution and void formation are discussed. The Sn-Cu-Ni- and Sn-Cu-Ag-Bi-based alloys tested in this study are recommended as potential suitable replacements for SAC305/405 in the wave solder process; no failure was detected up to 6000 cycles at 0°C to 100°C. Although SAC405 demonstrated better barrel fill and lower rate of crack propagation during ATC, after PTH rework, both of the alternative Pb-free alloys have a much lower Cu dissolution rate and definitely outperform SAC405 in ATC. SAC405 glue and wave resistors after primary attachment and rework demonstrate higher reliability than alternative alloys. Early failures relate to alternative alloy characteristics and should be considered for some applications.     

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

Developmental arrest of the preimplantation embryo is a multifactorial condition, characterized by lack of cellular division for at least 24 hours, hindering the in vitro fertilization cycle outcome. This systematic review aims to present the molecular drivers of developmental arrest, focusing on embryonic and parental factors. A systematic search in PubMed/Medline, Embase and Cochrane-Central-Database was performed in January 2021. A total of 76 studies were included. The identified embryonic factors associated with arrest included gene variations, mitochondrial DNA copy number, methylation patterns, chromosomal abnormalities, metabolic profile and morphological features. Parental factors included, gene variation, protein expression levels and infertility etiology. A valuable conclusion emerging through critical analysis indicated that genetic origins of developmental arrest analyzed from the perspective of parental infertility etiology and the embryo itself, share common ground. This is a unique and long-overdue contribution to literature that for the first time presents an all-inclusive methodological report on the molecular drivers leading to preimplantation embryos’ arrested development. The variety and heterogeneity of developmental arrest drivers, along with their inevitable intertwining relationships does not allow for prioritization on the factors playing a more definitive role in arrested development. This systematic review provides the basis for further research in the field.     

Novel method for the preparation of Cs-containing FAU(Y) catalysts for aniline methylation

Cs-containing FAU(Y)-type zeolite catalysts were prepared by conventional and novel ion exchange procedures followed by incipient wetness impregnation with CsOH. The novel ion exchange procedure involved hydrothermal treatment of NaY zeolite in aqueous solution of CsCl at 140–200 °C for 6–24 h. The samples were characterized by low-temperature nitrogen adsorption, X-ray fluorescence analysis, X-ray powder diffraction, scanning electron microscopy, ²³Na, ²⁷Al and ¹³³Cs magic angle spinning nuclear magnetic resonance, CO₂ and NH₃-Temperature programmed desorption. The results show that hydrothermal treatment at 200 °C allows to obtain higher degrees of ion-exchange (up to 83%) with respect to conventional method giving maximum 66%–69%. Catalytic properties of Cs-containing FAU(Y) were studied in aniline methylation. The yield of N-methylaniline is shown to correlate with catalyst’s basicity. The best catalyst performance was achieved over the catalyst with the highest ion-exchange degree impregnated with CsOH. The selectivity to N-methylaniline over this catalyst reached 96.4%.

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