Pnictogen-Rich Heterocycles Derived from a Phosphadiazonium Cation.

Heterocycles that pair main group elements and nitrogen are extremely important within the π-conjugated heterocycles research community. Compared to the vast number of boron-nitrogen heterocycles, those that include phosphorus are less common. Furthermore, the use of phosphorus-nitrogen triple bonds of any type to prepare such compounds is unprecedented.

Colloidal Self-Assembly of Silver Nanoparticle Clusters for Optical Metasurfaces.

Optical metasurfaces are two-dimensional assemblies of nanoscale optical resonators and could constitute the next generation of ultrathin optical components. The development of methods to manufacture these nanostructures on a large scale is still a challenge, while most performance demonstrations were obtained with lithographically fabricated metasurfaces that are restricted to small scales. Self-assembly fabrication routes are promising alternatives and have been used to produce original nanoresonators.

On the Stereochemistry of the NH Bond Activation of Ammonia or Amines by Disilenes: Predictability.

The stereochemistry of the addition of NH to the stereoisomers of 1,2-di-tert-butyl-1,2-bis(2,4,6-triisopropylphenyl)disilene (Z-5 or E-5) is 100 % stereospecific giving two isomeric disilylamines 6 and 7, respectively, derived from syn-addition to the stereoisomeric disilenes. Variable time normalization analysis studies of the reaction of tetramesityldisilene (3) with isopropylamine ( PrNH ) revealed that the order in both amine and disilene is 1. The kinetic isotope effect for the addition of PrNH / PrND to tetramesityldisilene was determined to be 3.

Periodic Spiral Ripples on VS Flakes: A Tip-Enhanced Raman Investigation.

Using atmospheric-pressure chemical vapor deposition, we have synthesized vanadium disulfide (VS) flakes with a metallic 1T phase that display nanoscale spiral surface ripples. To understand the origin of these chiral patterns in these transition metal dichalcogenides, tip-enhanced Raman spectroscopy and Kelvin probe force microscopies were jointly used to investigate their crystal structure, possible oxidation, and electronic properties, respectively. We found that the surface corrugation consists of small crystalline domains with distinct orientations.

COVID-19 Vaccine Acceptance and Its Risk Factors in Iranian Health Workers 2021.

Background: Ensuring vaccine acceptance in societies is a growing challenge for healthcare systems worldwide. This study aimed to identify factors associated with vaccine acceptance rates.

Methods: This cross-sectional study was conducted as a national web-based survey from February 9-13, 2021, just before the release of the COVID-19 vaccine in Shiraz, Iran.

The Hidden Flower in WS Flakes: A Combined Nanomechanical and Tip-Enhanced Raman Exploration.

We report on tungsten disulfide (WS) flakes grown by chemical vapor deposition (CVD), which exhibit a flower-like surface structure above the primary few-layer flake with a triangular shape. The fine structure is only revealed in the mechanical, chemical, and electronic properties of the flake but not in the topography. The origin of this structure is the peculiar one-step growth during the CVD process that permits to control the sulfur concentration at any time.

Investigating the Performances of Wide-Field Raman Microscopy with Stochastic Optical Reconstruction Post-Processing.

Super-resolution fluorescence microscopy based on localization algorithms has tremendously impacted the field of imaging by improving the spatial resolution of optical measurements with specific blinking fluorophores and concomitant reduction of acquisition time. In vibrational spectroscopy and imaging, various methods have been developed to surpass the diffraction limit including near-field scattering methods, such as in tip-enhanced Raman and infrared spectroscopies. Although these scanning-probe techniques can provide exquisite spatial resolution, they often require long acquisition times and tedious fabrication of nano-scale scanning probes.

Blood pressure changes during alemtuzumab infusion for multiple sclerosis patients.

Background And Purpose: Blood pressure (BP) changes during alemtuzumab infusions are poorly understood. The aim of this study was to examine BP changes during alemtuzumab infusions in persons with multiple sclerosis (PwMS).

Methods: This was a retrospective cohort review of systolic (S) and diastolic (D) BP in PwMS receiving alemtuzumab.

Deciphering tip-enhanced Raman imaging of carbon nanotubes with deep learning neural networks.

Recent release of open-source machine learning libraries presents opportunities to unify machine learning with nanoscale research, thus improving effectiveness of research methods and characterization protocols. This paper outlines and demonstrates the effectiveness of such a synergy with artificial neural networks to provide for an accelerated and enhanced characterization of individual carbon nanotubes deposited over a surface. Our algorithms provide a rapid diagnosis and analysis of tip-enhanced Raman spectroscopy mappings and the results show an improved spectral assignment of spectral features and spatial contrast of the collected images.

Imaging the Surface of a Hand-Colored 19th Century Daguerreotype.

Daguerreotypes are valued artifacts that constitute a unique historical photographic memory of the 19th century. Understanding their surface chemistry is important in order to conserve and, when necessary, to restore them. Colored highlights were often added by hand to emphasize different features on the daguerreotype's subjects.

Stress-related hormones and glycinebetaine interplay in protection of photosynthesis under abiotic stress conditions.

Plants subjected to abiotic stresses such as extreme high and low temperatures, drought or salinity, often exhibit decreased vegetative growth and reduced reproductive capabilities. This is often associated with decreased photosynthesis via an increase in photoinhibition, and accompanied by rapid changes in endogenous levels of stress-related hormones such as abscisic acid (ABA), salicylic acid (SA) and ethylene. However, certain plant species and/or genotypes exhibit greater tolerance to abiotic stress because they are capable of accumulating endogenous levels of the zwitterionic osmolyte-glycinebetaine (GB).

Dye distance mapping using waveguide evanescent field fluorescence microscopy and its application to cell biology.

Previous studies have measured the distance between cells and the substratum at sites of adhesion via the emission of a fluorescent dye and waveguide methods. Here, we demonstrate a novel approach to measure the position of fluorescent dyes above a waveguide surface in the 10-200 nm distance range throughout an entire area, yielding a 2D dye distance map or a 3D contour plot. The dye is located in a multilayered Langmuir Blodgett (LB) film or in the plasma membrane of a cell.

Waveguide evanescent field scattering microscopy: bacterial biofilms and their sterilization response via UV irradiation.

Waveguide Evanescent Field Scattering (WEFS) microscopy is introduced as a new and simple tool for label-free, high contrast imaging of bacteria and bacteria sensors. Bacterial microcolonies and single bacteria were discriminated both by their bright field images and by their evanescent scattering intensity. By comparing bright field images with WEFS images, the proportion of planktonic: sessile (i.

Orientation distribution of highly oriented type I collagen deposited on flat samples with different geometries.

The structural arrangement of type I collagen in vivo is critical for the normal functioning of tissues, such as bone, cornea, tendons, and blood vessels. At present, there are no established low-cost techniques for fabricating aligned collagen structures for applications in regenerative medicine. Here, we report on a straightforward approach to fabricate collagen films, with defined orientation distributions of collagen fibrillar aggregates within a matrix of oriented collagen molecules on flat sample surfaces.

Large area periodic, systematically changing, multishape nanostructures by laser interference lithography and cell response to these topographies.

The fabrication details to form large area systematically changing multishape nanoscale structures on a chip by laser interference lithography (LIL) are described. The feasibility of fabricating different geometries including dots, ellipses, holes, and elliptical holes in both x- and y- directions on a single substrate is shown by implementing a Lloyd's interferometer. The fabricated structures at different substrate positions with respect to exposure time, exposure angle and associated light intensity profile are analyzed.

Influence of electrostatic forces on particle propulsion in the evanescent field of silver ion-exchanged waveguides.

The effect of electrostatic interaction between carboxylate- and amino-functionalized polystyrene particles and a charged waveguide surface on the propulsion speed in optical tweezers is considered to be a function of the pH and ionic strength. It was shown that with the variation of the pH of the aqueous solution in which the particles were immersed, a systematic change in propulsion speed with a maximum speed could be achieved. The appearance of a maximum speed was ascribed to changes in the particle-waveguide separation as a result of the combination of two forces: Coulomb repulsion/attraction and induced dipole forces.

Label-free mapping of osteopontin adsorption to calcium oxalate monohydrate crystals by tip-enhanced Raman spectroscopy.

In the ectopic biomineralization of calcium oxalate kidney stones, the competition between calcium oxalate monohydrate (COM) formation and its inhibition by the phosphoprotein osteopontin (OPN) plays a key role in COM stone-forming processes. To get more insights into these processes, tip-enhanced Raman spectroscopy (TERS) was used to provide surface-specific information about the adsorption of OPN to faces of COM crystals. In TERS, the surface plasmon resonance of a metallic AFM tip is locally excited when the tip is placed in the optical near-field of a laser focused on the crystal surface.