Click Chemistry for the Assembly of Gold Nanorods and Silver Nanoparticles

The synthesis of compact nanostructures with highly integratedfunctionalities through the controlled assembly ofnanoparticles (NPs) is potentially of broad interest in researchfields such as drug delivery, multimodal imaging, andelectronic devices. This concept seems to be particularlyimportant in view of the emerging concept of theranostic,according to which both therapeutic and diagnostic capabilitiescan be present in two nanostructures. A key step, however,is how to combine individual nanostructures withoutloosing the original properties

Intra-Host Evolution Analyses in an Immunosuppressed Patient Supports SARS-CoV-2 Viral Reservoir Hypothesis.

Throughout the SARS-CoV-2 pandemic, several variants of concern (VOCs) have been identified, many of which share recurrent mutations in the spike glycoprotein's receptor-binding domain (RBD). This region coincides with known epitopes and can therefore have an impact on immune escape. Protracted infections in immunosuppressed patients have been hypothesized to lead to an enrichment of such mutations and therefore drive evolution towards VOCs. Here, we present the case of an immunosuppressed patient that developed distinct populations with immune escape mutations throughout the course of their infection. Notably, by investigating the co-occurrence of substitutions on individual sequencing reads in the RBD, we found quasispecies harboring mutations that confer resistance to known monoclonal antibodies (mAbs) such as S:E484K and S:E484A. These mutations were acquired without the patient being treated with mAbs nor convalescent sera and without them developing a detectable immune response to the virus. We also provide additional evidence for a viral reservoir based on intra-host phylogenetics, which led to a viral substrain that evolved elsewhere in the patient's body, colonizing their upper respiratory tract (URT). The presence of SARS-CoV-2 viral reservoirs can shed light on protracted infections interspersed with periods where the virus is undetectable, and potential explanations for long-COVID cases

Quantitative measurement of olivine composition in three dimensions using helical-scan X-ray micro-tomography

Olivine is a key constituent in the silicate Earth; its composition and texture informs petrogenetic understanding of numerous rock types. Here we develop a quantitative and reproducible method to measure olivine composition in three dimensions without destructive analysis, meaning full textural context is maintained. The olivine solid solution between forsterite and fayalite was measured using a combination of three-dimensional (3D) X-ray imaging techniques, 2D backscattered electron imaging, and spot-analyses using wavelength-dispersive electron probe microanalysis. The linear attenuation coefficient of natural crystals across a range of forsterite content from ∼73–91 mol% were confirmed to scale linearly with composition using 53, 60, and 70 kV monochromatic beams at I12-JEEP beamline, Diamond Light Source utilizing the helical fly-scan acquisition. A polychromatic X-ray source was used to scan the same crystals, which yielded image contrast equivalent to measuring the mol% of forsterite with an accuracy of 3 mm domains within a large crystal of San Carlos forsterite that varies by ∼2 Fo mol%. This offers a solution to an outstanding question of inter-laboratory standardization, and also demonstrates the utility of 3D, non-destructive, chemical measurement. To our knowledge, this study is the first to describe the application of XMT to quantitative chemical measurement across a mineral solid solution. Our approach may be expanded to calculate the chemistry of other mineral systems in 3D, depending upon the number, chemistry, and density of end-members

Developing a high-resolution photoacoustic microscopy platform

Existing optical imaging modalities including confocal microscopy, two-photon microscopy and optical coherence tomography do not image optical absorption directly. Photoacoustic imaging (also called optoacoustic imaging) is a new promising modality in biomedical imaging integrating the benefits of optics and acoustics. When biological tissue is irradiated with ultrashort laserpulses with durations of a few nanoseconds the light is absorbed according to the local absorption properties and is converted successively into heat and pressure by means of the thermoelastic effect. The motivation for photoacoustic imaging is to combine ultrasonic resolution with high contrast due to light absorption depending on the physiology of the examined biological tissue. The resolution of conventional photoacoustic imaging systems is not sufficient for in-vitro measurements of small tissue samples or individual cells. In this work, we present a high-resolution photoacoustic microscopy pla tform based on the SASAM acoustic microscope (Kibero GmbH, Germany) that allows high resolution imaging on living cells. The system based on an inverted optical microscope consists of a laser source for optical multi wavelength excitation (diode- or solidstate- laser) which emits nanosecond laser pulses with a wavelength in the near infrared spectrum (optical window). We use different ultrasound transducers in the frequency range up to 300 MHz for detection of the pressure transients. Read out electronics combined with reconstruction algorithms for photoacoustic imaging allows converting the recorded signals into a spatial representation of the absorbed energy. Furthermore, the possibility of using nanoscaled contrast agents for photoacoustic contrast enhancement is presented. In addition to the photoacoustic imaging mode all common optical modalities are implemented. Pure acoustic imaging and optical transmission mode are used for reference imaging

Failure analysis of ParaPost drills that fractured in service: A retrieval analysis study

The aim was to determine the fracture mechanism of two clinically failed ParaPost drills. First, the fracture planes were analyzed by scanning electron microscopy (SEM). The drill end of one of the fractured pieces of each drill was then embedded in resin and after being metallographically ground and polished, was chemically etched. The microstructure and elemental composition were then examined by SEM/EDS analysis while hardness was determined with a Vickers testing device. Fracto-graphic analysis revealed that both drills failed in a brittle manner and showed a pattern characteristic of a quasicleavage fracture mode. SEM and EDS analysis revealed a random distribution of a second phase enriched in Mo, W, and V, probably appended to (Mo, W, V)xC carbides, while the alloy composition is similar to M3 tool steel, a high-speed molybdenum tool steel. The microhardness of a ParaPost Drill #1 was found to be HV 862±29 and that for a Drill #2 was 846±16, with no significant differences (p > 0.05). In both cases, fracture originated from surface points acting as stress concentrators and facilitating brittle fracture in the quasi-cleavage mode indicating that failure rate might be further minimized by a better instrument design

MISORIENTATION DEPENDENCE OF DIFFUSION INDUCED GRAIN BOUNDARY MIGRATION (DIGM) IN ORIENTED Cu (Zn) BICRYSTALS

Diffusion induced grain boundary migration (DIGM) has been studied in the Cu(Zn) system using Cu bicrystals with initially symmetrical tilt grain boundaries (GBs) of the {011} type produced by diffusion bonding. The misorientation has been varied systematically over the range from 10.1 to 171.9°. Measurements of the GB velocity showed it to have a strong dependence on the misorientation angle. The morphology of DIGM has been studied by optical microscopy. As a special morphological phenomenon, faceting has been investigated at a symmetrical Σ 19a/26.52° {011} GB

Failure analysis of eleven Gates Glidden drills that fractured intraorally during post space preparation. A retrieval analysis study

The purpose of this study was to determine the failure mechanism of clinically failed Gates Glidden (GG) drills. Eleven retrieved GG drills (sizes #1 to #3) which fractured during root canal preparation were collected and the fracture location was recorded based on macroscopic observation. All fracture surfaces were investigated by a SEM. Then the fractured parts were embedded in acrylic resin and after metallographic preparation, the microstructure and elemental composition was evaluated by SEM and EDS. The Vickers hardness (HV) of all specimens was also determined. Macroscopic examination and SEM analysis showed that the drills failed near the hand piece end by torsional fatigue with fatigue cracks initiating at several locations around the circumference and propagating toward the center. Final fracture followed by a tensile overloading at the central region of cross section. Microstructural analysis, hardness measurements and EDS show that the drills are made of a martensitic stainless steel like AISI 440C. Based on the findings of this study, clinicians should expect fatigue fracture of GG drills that have small size during root canal preparation. Selection of a more fatigue resistant stainless steel alloy and enhancing the instrument design might reduce the incidence of quasi-cleavage fracture on GG drills. © 2018 Walter de Gruyter GmbH, Berlin/Boston 2018