Intrinsic Coexistence of Miscibility and Segregation in Gold-Silver Nanoalloys.

Bimetallic nanoparticles are used in numerous applications in catalysis, plasmonics or fuel cell technology. The addition of the second metal to the nanoparticles allows enhancing and fine-tuning their properties by choosing their composition, size, shape and environment. However, the crucial additional parameter of chemical structure within the particle is difficult to predict and access experimentally, even though segregated core-shell structures and random alloys can have drastically different physicochemical properties.

Atomic Structure and 3D Shape of a Multibranched Plasmonic Nanostar from a Single Spatially Resolved Electron Diffraction Map.

Despite the interest in improving the sensitivity of optical sensors using plasmonic nanoparticles (NPs) (rods, wires, and stars), the full structural characterization of complex shape nanostructures is challenging. Here, we derive from a single scanning transmission electron microscope diffraction map (4D-STEM) a detailed determination of both the 3D shape and atomic arrangement of an individual 6-branched AuAg nanostar (NS) with high-aspect-ratio legs. The NS core displays an icosahedral structure, and legs are decahedral rods attached along the 5-fold axes at the core apexes.

High precision orientation mapping from 4D-STEM precession electron diffraction data through quantitative analysis of diffracted intensities.

The association of scanning transmission electron microscopy (STEM) and detection of a diffraction pattern at each probe position (so-called 4D-STEM) represents one of the most promising approaches to analyze structural properties of materials with nanometric resolution and low irradiation levels. This is widely used for texture analysis of materials using automated crystal orientation mapping (ACOM). Herein, we perform orientation mapping in InP nanowires exploiting precession electron diffraction (PED) patterns acquired by an axial CMOS camera.

Exploring mobility data for enhancing HIV care engagement in Black/African American and Hispanic/Latinx individuals: a longitudinal observational study protocol.

Introduction: Increasing engagement in HIV care among people living with HIV, especially those from Black/African American and Hispanic/Latinx communities, is an urgent need. Mobility data that measure individuals' movements over time in combination with sociostructural data (eg, crime, census) can potentially identify barriers and facilitators to HIV care engagement and can enhance public health surveillance and inform interventions.

Methods And Analysis: The proposed work is a longitudinal observational cohort study aiming to enrol 400 Black/African American and Hispanic/Latinx individuals living with HIV in areas of the USA with high prevalence rates of HIV.

Effects of an Online Community Peer-support Intervention on COVID-19 Vaccine Misinformation Among Essential Workers: Mixed-methods Analysis.

Introduction: Public health efforts to reduce the spread of coronavirus disease 2019 (COVID-19) have been plagued by vaccine hesitancy and misinformation. Social media has contributed to spreading misinformation by creating online environments where people find information or opinions that reinforce their own. Combating misinformation online will be essential to prevent and manage the spread of COVID-19.

Feasibility and Acceptability of Online Recruitment and an Online Brief Mindfulness Intervention Among Patients With Sickle Cell Disease.

Background Pain among young adult patients with sickle cell disease (PWSCD) is a highly significant public health problem associated with reduced quality of life. Due to issues uniquely affecting PWSCD, including distrust of research, challenging life situations, debilitating pain, stigma, and logistical challenges (e.g.

A HOPE Online Community Peer Support Intervention for Help Seeking: A Randomized Controlled Trial.

Objective: A 6-week study was conducted to test the effectiveness of the Harnessing Online Peer Education (HOPE) intervention on anxiety, help seeking (requests for electronic resources [e-resources] on anxiety reduction), and online engagement.

Methods: Three hundred participants with moderate to severe anxiety (i.e.

Improving Quantitative EDS Chemical Analysis of Alloy Nanoparticles by PCA Denoising: Part II. Uncertainty Intervals.

Analytical studies of nanoparticles (NPs) are frequently based on huge datasets derived from hyperspectral images acquired using scanning transmission electron microscopy. These large datasets require machine learning computational tools to reduce dimensionality and extract relevant information. Principal component analysis (PCA) is a commonly used procedure to reconstruct information and generate a denoised dataset; however, several open questions remain regarding the accuracy and precision of reconstructions.

Microhardness and surface roughness of Biodentine exposed to mouthwashes.

Aim: This study evaluates Vickers microhardness and surface roughness in Biodentine cement (M1) and glass-ionomer cement Fuji IX (M2), both immersed in mouthwash.

Materials And Methods: Fifty-four samples were randomly distributed in distilled water (S1), Listerine Cool Mint (S2), and Colgate Plax (S3). Each sample was put in a flask with mouthwash for 2 min, under vibration, twice a day for 21 days.

Association Between the Placement of a Double-J Catheter and the Risk of Urinary Tract Infection in Renal Transplantation Recipients: A Retrospective Cohort Study of 1038 Patients.

Background: The incidence of urinary complications in transplantation is 2% to 20%, which can be decreased with the use of a double-J catheter. The objective of this study was to determine the association between the use of the catheter and the probability of urinary tract infection (UTI).

Methods: We studied a retrospective cohort of 1038 patients divided into 2 groups: those treated with vs without a double-J catheter.

Public Attitudes About COVID-19 in Response to President Trump's Social Media Posts.

This cross-sectional study examines public beliefs about the coronavirus disease 2019 (COVID-19) pandemic in response to President Trump’s social media posts during and after his infection with the virus.

Association Between Generalized Anxiety Disorder Scores and Online Activity Among US Adults During the COVID-19 Pandemic: Cross-Sectional Analysis.

Background: Evidence from past pandemics suggests that fear, uncertainty, and loss of control during large-scale public health crises may lead to increased pandemic-related information seeking, particularly among persons predisposed to high anxiety. In such groups, a greater consumption of information pertaining to the COVID-19 pandemic may increase anxiety.

Objective: In this study, we examine the association between online activity and Generalized Anxiety Disorder 7 (GAD-7) scores in the United States.

Marginal and internal fit of CAD/CAM frameworks in multiple implant-supported restorations: Scanning and milling error analysis.

Background: Despite computer-aided design and computer-aided manufacturing (CAD/CAM) technology improving prosthesis fit, errors inherent to digital workflow still exist.

Purpose: To measure scanning/milling errors, and identify factors influencing marginal (MD) and internal discrepancy (ID).

Materials And Methods: After scanning, 22 conical abutments in 5 master casts, 6 suprastructures with more than 2 implants (3, 4, and 6) were CAD designed.

Different growth regimes in InP nanowire growth mediated by Ag nanoparticles.

We report on the existence of two different regimes in one-step Ag-seeded InP nanowire growth. The vapor-liquid-solid-mechanism is present at larger In precursor flows and temperatures, ∼500 °C, yielding high aspect ratio and pure wurtzite InP nanowires with a semi-spherical metal particle at the thin apex. Periodic diameter oscillations can be achieved under extreme In supersaturations at this temperature range, showing the presence of a liquid catalyst.

Interaction between lamellar twinning and catalyst dynamics in spontaneous core-shell InGaP nanowires.

Semiconductor nanowires oriented along the [211] direction usually present twins parallel to their axis. For group IV nanowires this kind of twin allows the formation of a catalyst-nanowire interface composed of two equivalent {111} facets. For III-V nanowires, however, the twin will generate two facets with different polarities.

Development of a quartz tuning-fork-based force sensor for measurements in the tens of nanoNewton force range during nanomanipulation experiments.

Understanding the mechanical properties of nanoscale systems requires new experimental and theoretical tools. In particular, force sensors compatible with nanomechanical testing experiments and with sensitivity in the nN range are required. Here, we report the development and testing of a tuning-fork-based force sensor for in situ nanomanipulation experiments inside a scanning electron microscope.

Spatial modulation of above-the-gap cathodoluminescence in InP nanowires.

We report the observation of light emission on wurtzite InP nanowires excited by fast electrons. The experiments were performed in a scanning transmission electron microscope using an in-house-built cathodoluminescence detector. Besides the exciton emission, at 850 nm, emission above the band gap from 400 to 800 nm was observed.

Spontaneous periodic diameter oscillations in InP nanowires: the role of interface instabilities.

We have observed that thin InP nanowires generated by vapor-liquid-solid growth display spontaneous periodic diameter oscillations when large group III supersaturations are used. Diameter variations are associated with a large number of stacking faults and crystallographic phase changes(wurtzite/zinc-blende); also the axial distance between oscillations depends on the indium precursor flow used during the run. We attribute the morphology changes to a substantial deformation of the triple phase line (vapor-liquid-solid) at the catalyst nanoparticle edge originated from multistep nucleation during growth.

Enhanced Eshelby twist on thin Wurtzite InP nanowires and measurement of local crystal rotation.

We have performed a detailed study of the lattice distortions of InP wurtzite nanowires containing an axial screw dislocation. Eshelby predicted that this kind of system should show a crystal rotation due to the dislocation induced torque. We have measured the twisting rate and the dislocation Burgers vector on individual wires, revealing that nanowires with a 10-nm radius have a twist up to 100% larger than estimated from elasticity theory.

Kinetic effects in InP nanowire growth and stacking fault formation: the role of interface roughening.

InP nanowire polytypic growth was thoroughly studied using electron microscopy techniques as a function of the In precursor flow. The dominant InP crystal structure is wurtzite, and growth parameters determine the density of stacking faults (SF) and zinc blende segments along the nanowires (NWs). Our results show that SF formation in InP NWs cannot be univocally attributed to the droplet supersaturation, if we assume this variable to be proportional to the ex situ In atomic concentration at the catalyst particle.

Intrinsic stability of the smallest possible silver nanotube.

Recently, Lagos et al. [Nature Nanotech. 4, 149 (2009)] reported the discovery of the smallest possible Ag nanotube with a square cross section.

Mechanical deformation of nanoscale metal rods: when size and shape matter.

Face centered cubic metals deform mainly by propagating partial dislocations generating planar fault ribbons. How do metals deform if the size is smaller than the fault ribbons? We studied the elongation of Au and Pt nanorods by in situ electron microscopy and ab initio calculations. Planar fault activation barriers are so low that, for each temperature, a minimal rod size is required to become active for releasing elastic energy.

Temperature effects on the occurrence of long interatomic distances in atomic chains formed from stretched gold nanowires.

The origin of long interatomic distances in suspended gold atomic chains formed from stretched nanowires remains the object of debate despite the large amount of theoretical and experimental work. Here, we report new atomic resolution electron microscopy observations acquired at room and liquid-nitrogen temperatures and theoretical results from ab initio quantum molecular dynamics on chain formation and stability. These new data are suggestive that the long distances are due to contamination by carbon atoms originating from the decomposition of adsorbed hydrocarbon molecules.