Tunneling Spectroscopy of Two-Dimensional Materials Based on Via Contacts.

We introduce a novel planar tunneling architecture for van der Waals heterostructures based on via contacts, namely, metallic contacts embedded into through-holes in hexagonal boron nitride (hBN). We use the via-based tunneling method to study the single-particle density of states of two different two-dimensional (2D) materials, NbSe2 and graphene. In NbSe2 devices, we characterize the barrier strength and interface disorder for barrier thicknesses of 0, 1, and 2 layers of hBN and study the dependence on the tunnel-contact area down to (44 ± 14)2 nm2. For 0-layer hBN devices, we demonstrate a crossover from diffusive to point contacts in the small-contact-area limit. In graphene, we show that reducing the tunnel barrier thickness and area can suppress effects due to phonon-assisted tunneling and defects in the hBN barrier. This via-based architecture overcomes limitations of other planar tunneling designs and produces high-quality, ultraclean tunneling structures from a variety of 2D materials.

Segmented information, segregated outcomes: Housing affordability and neighborhood representation on a voucher-focused online housing platform and three mainstream alternatives.

Online platforms have become an integral component of the housing search process in the United States and other developed contexts, but recent studies have demonstrated that these platforms offer uneven representation of different neighborhoods. In this study, we use listings covering the largest 50 U.S. metropolitan areas to assess how GoSection8, a platform uniquely focused on affordable housing and voucher-assisted households, compares with "mainstream" alternatives of Craigslist, Apartments.com and Zillow. Through descriptive and regression analyses of the housing and neighborhoods represented on these websites and a new way of measuring the distribution of rental housing opportunities, we advance a multisource perspective on the role of online information exchanges in housing search processes. Specifically, we find that GoSection8 and mainstream alternatives capture spatially-segmented information about housing markets, with GoSection8 ads representing units that are more affordable but also more constrained to higher-poverty neighborhoods where assisted households are already concentrated. The findings suggest that disadvantaged households are potentially funneled toward high-poverty, isolated neighborhoods by the operation of stratified information systems available for online housing searches.

Low-temperature exposure has immediate and lasting effects on the stress tolerance, chemotaxis and proteome of entomopathogenic nematodes.

Temperature is one of the most important factors affecting soil organisms, including the infective stages of parasites and entomopathogenic nematodes, which are important biological control agents. We investigated the response of 2 species of entomopathogenic nematodes to different storage regimes: cold (9°C), culture temperature (20°C) and temperature swapped from 9 to 20°C. For Steinernema carpocapsae, cold storage had profound effects on chemotaxis, stress tolerance and protein expression that were retained in temperature-swapped individuals. These effects included reversal of chemotactic response for 3 (prenol, methyl salicylate and hexanol) of the 4 chemicals tested, and enhanced tolerance to freezing (−10°C) and desiccation (75% RH). Label-free quantitative proteomics showed that cold storage induced widespread changes in S. carpocapsae, including an increase in heat-shock proteins and late embryogenesis abundant proteins. For Heterorhabditis megidis, cold storage had a less dramatic effect on chemotaxis (as previously shown for proteomic expression) and changes were not maintained on return to 20°C. Thus, cold temperature exposure has significant effects on entomopathogenic nematodes, but the nature of the change depends on the species. Steinernema carpocapsae, in particular, displays significant plasticity, and its behaviour and stress tolerance may be manipulated by brief exposure to low temperatures, with implications for its use as a biological control agent.

A multicentre longitudinal study of flortaucipir (18F) in normal ageing, mild cognitive impairment and Alzheimer's disease dementia.

The advent of tau-targeted PET tracers such as flortaucipir (18F) (flortaucipir, also known as 18F-AV-1451 or 18F-T807) have made it possible to investigate the sequence of development of tau in relationship to age, amyloid-ß, and to the development of cognitive impairment due to Alzheimer's disease. Here we report a multicentre longitudinal evaluation of the relationships between baseline tau, tau change and cognitive change, using flortaucipir PET imaging. A total of 202 participants 50 years old or older, including 57 cognitively normal subjects, 97 clinically defined mild cognitive impairment and 48 possible or probable Alzheimer's disease dementia patients, received flortaucipir PET scans of 20 min in duration beginning 80 min after intravenous administration of 370 MBq flortaucipir (18F). On separate days, subjects also received florbetapir amyloid PET imaging, and underwent a neuropsychological test battery. Follow-up flortaucipir scans and neuropsychological battery assessments were also performed at 9 and 18 months. Fifty-five amyloid-ß+ and 90 amyloid-ß- subjects completed the baseline and 18-month study visits and had valid quantifiable flortaucipir scans at both time points. There was a statistically significant increase in the global estimate of cortical tau burden as measured by standardized uptake value ratio (SUVr) from baseline to 18 months in amyloid-ß+ but not amyloid-ß- subjects (least squared mean change in flortaucipir SUVr : 0.0524 ± 0.0085, P < 0.0001 and 0.0007 ± 0.0024 P = 0.7850, respectively), and a significant association between magnitude of SUVr increase and baseline tau burden. Voxel-wise evaluations further suggested that the regional pattern of change in flortaucipir PET SUVr over the 18-month study period (i.e. which regions exhibited the greatest change) also varied as a function of baseline global estimate of tau burden. In subjects with lower global SUVr, temporal lobe regions showed the greatest flortaucipir retention, whereas in subjects with higher baseline SUVr, parietal and frontal regions were increasingly affected. Finally, baseline flortaucipir and change in flortaucipir SUVr were both significantly (P < 0.0001) associated with changes in cognitive performance. Taken together, these results provide a preliminary characterization of the longitudinal spread of tau in Alzheimer's disease and suggest that the amount and location of tau may have implications both for the spread of tau and the cognitive deterioration that may occur over an 18-month period.

Standardization of amyloid quantitation with florbetapir standardized uptake value ratios to the Centiloid scale.

INTRODUCTION: Klunk et al. recently proposed a means of standardizing quantitation of amyloid burden from positron emission tomography scans to a common Centiloid scale, and we have applied that method to florbetapir. METHODS: Florbetapir and Pittsburgh compound B scans were acquired for 46 mixed clinical presentation subjects within 18 ± 20 days. Florbetapir and Pittsburgh compound B cortical standardized uptake value ratio (SUVr) values were well correlated for both standard Centiloid (R2 = 0.894) and Avid (R2 = 0.901) volume of interests (VOIs). The methods of Klunk et al. were applied to establish a conversion first from florbetapir SUVr values obtained using standard Centiloid VOIs to Centiloids and then from Avid VOIs (Joshi et al.) to Centiloids. RESULTS: The equation for conversion of florbetapir SUVr from Avid VOIs to the Centiloid scale was as follows: Florbetapir Centiloids = 183 × SUVrAvid - 177. The threshold that discriminated neuropathologically verified none or sparse versus moderate to frequent plaques in autopsy-confirmed data is 24.1 Centiloids. DISCUSSION: These findings may allow improved tracer-independent amyloid quantitation.

FRET-based homogeneous immunoassay on a nanoparticle-based photonic crystal.

The potential of fluorescence resonance energy transfer (FRET) in a photonic crystal (PC) nanostructured array to enhance the speed and sensitivity of a protein-based immunoassay was tested. Forty-nanometer carboxylated particles conjugated with donor-labeled capture antibodies were trapped by electrophoresis and used as a FRET energy donor. The PC array was able to enhance fluorescent excitation and emission by phase matching. To provide a proof of concept for this FRET-based homogeneous assay on a PC chip, an immunoassay was tested with a simple immunoglobulin G (IgG)-based reaction. A standard curve was generated by testing two different antibody reaction times: 20 min. and 1 min. The results were compared directly to those obtained from a FRET assay that used a modern, high-sensitivity plate reader with a 96-well plate and a reaction time of 1 h. The rabbit-IgG detection limits of the FRET-based homogeneous assay on the PC were 0.001 and 0.1 µg/mL for incubation times of 20 and 1 min, respectively; the sensitivities were 10(3) and 10 times better than the 96-well plate reader, respectively. Thus, FRET on a PC immunoplatform was shown to be a facile, effective, rapid, and sensitive detection technology.

Potential toxicity of up-converting nanoparticles encapsulated with a bilayer formed by ligand attraction.

The cellular toxicity of nanoparticles that were capped with a bilayered ligand was studied using an up-converting (UC) phosphor material as a representative nanoparticle (NP). The results indicate that although UC NPs are known to be nontoxic, the toxicity of the NPs depends strongly on ligand coordination conditions, in addition to the other commonly known parameters such as size, structure, surface charge etc. Oleate-capped hydrophobic NaYF4:Yb,Er NPs were surface modified to yield three extreme conditions: bare particles that were stripped of the oleate ligands; particles with covalently bound poly(ethylene glycol) (PEG) ligands; and particles with an bilayer of PEG-oleate ligands using the oleate surface group that was remained after synthesis. It was found that the bare particles and the covalent PEG NPs induced little toxicity. However, particles that were rendered biocompatible by forming a bilayer with an amphiphilic ligand (i.e., PEG-oleate) resulted in significant cell toxicity. These findings strongly suggest that the PEG-oleate group dissociated from the bilayered oleate-capped NPs, resulting in significant toxicity by exposing the hydrophobic oleate-capped NPs to the cell. Based on results with bare particles, the NaLnF4:Yb,Er (Ln = Y, Gd) up-converting phosphors are essentially less-toxic. Capping and functionalizing these particles with ligand intercalation may, however, not be a suitable method for rendering the NPs suitable for bioapplication as the ligand can potentially dissociate upon cellular interaction, leading to significant toxicity.

Nanotechnology and toxicology.

The Pacific Basin Consortium session on Nanotechnology and toxicology brought together experts from biology and the physical sciences and engineering to discuss the environmental and health impacts of nanotechnology and nanomaterials in particular. The discussion included new findings in the area of inhalation toxicology as well as aquatic toxicology. Opportunities for engineering new forms of particles for toxicology studies were also presented.

Combustion By-Products and their Health Effects--combustion engineering and global health in the 21st century: issues and challenges.

The 13th International Congress on Combustion By-Products and their Health Effects was held in New Orleans, Louisiana from May 15 to 18, 2013. The congress, sponsored by the Superfund Research Program, National Institute of Environmental Health Sciences, and National Science Foundation, brought together international academic and government researchers, engineers, scientists, and policymakers. With industrial growth, increased power needs and generation and coal consumption and their concomitant emissions, pernicious health effects associated with exposures to these emissions are on the rise. This congress provides a unique platform for interdisciplinary exchange and discussion of these topics. The formation, conversion, control, and health effects of combustion by-products, including particulate matter and associated heavy metals, persistent organic pollutants, and environmentally persistent free radicals, were discussed during the congress. This review will summarize and discuss the implications of the data presented.

Photonic crystal lab-on-a-chip for detecting staphylococcal enterotoxin B at low attomolar concentration.

Nanoscale wells have been fabricated in a chip to construct a photonic crystal that is used for enhanced immunoassays of a common food-borne toxin, Staphylococcal enterotoxin B (SEB). The nanostructure of the photonic crystal (PC) in the array enhanced the fluorescent signal due to a guided mode resonance. Nanoparticles were used as the solid substrate for attachment of capture antibodies; the particles were then isolated in individual wells of the chip by using an electrophoretic particle entrapment system (EPES). The standard curve generated from the chip consisted of two log-linear regions: the first region with a greater sensitivity, limited by the Kd of the antibody, resembling the 96-well plate ELISA and the other that shows greater than six orders of linearity extending to attomolar concentrations, which is unique to the device we have developed. SEB dissolved in phosphate buffered saline was resolved to levels as low as 35 aM with 10(6)-fold better limit of detection than a conventional 96-well-ELISA. Different concentrations of SEB spiked into milk were tested to assess the reliability of the device and the efficacy of the extended log-linear regime in a "real" food matrix. The presence of the milk did not significantly alter the limit of detection. With very low amounts of sample (less than 10 µL) and fast read-out time, the PC-based system shows great promise for the detection of a wide range of target molecules with close to a single molecule level of sensitivity.

Novel lanthanide-labeled metal oxide nanoparticles improve the measurement of in vivo clearance and translocation.

The deposition, clearance and translocation of europium-doped gadolinium oxide nanoparticles in a mouse lung were investigated experimentally. Nanoparticles were synthesized by spray flame pyrolysis. The particle size, crystallinity and surface properties were characterized. Following instillation, the concentrations of particles in organs were determined with inductively coupled plasma mass spectrometry. The protein corona coating the nanoparticles was found to be similar to the coating on more environmentally relevant nanoparticles such as iron oxide. Measurements of the solubility of the nanoparticles in surrogates of biological fluids indicated very little propensity for dissolution, and the elemental ratio of particle constituents did not change, adding further support to the contention that intact nanoparticles were measured. The particles were intratracheally instilled into the mouse lung. After 24 hours, the target organs were harvested, acid digested and the nanoparticle mass in each organ was measured by inductively coupled plasma mass spectrometry (ICP-MS). The nanoparticles were detected in all the studied organs at low ppb levels; 59% of the particles remained in the lung. A significant amount of particles was also detected in the feces, suggesting fast clearance mechanisms. The nanoparticle system used in this work is highly suitable for quantitatively determining deposition, transport and clearance of nanoparticles from the lung, providing a quantified measure of delivered dose.

Move-In Fees as a Residential Sorting Mechanism Within Online Rental Markets.

An increasing number of American renters within major metropolitan housing markets rely on online platforms such as Craigslist to find rental units. Landlords that advertise rentals on these websites have been found to tailor the language used in their listings in reference to surrounding neighborhood demographics to influence prospective tenants' rental searches. This work investigates the underexplored subject of move-in fees, referring to upfront costs to secure a lease, such as security deposits, application charges, and advanced rent payments that can affect whether a prospective renter can afford an advertised unit. This study advances a framework for how housing researchers can assess variations in landlord discourse within online housing marketplaces using text analysis methods and web scraping. It then illustrates how the resulting measures about move-in fees have distinct variations in prevalence along sociodemographic, spatial, and policy measures through a series of descriptive analyses, with subsequent conclusions toward policy implications designed to assist low-income renters with overcoming financial barriers in securing rental housing.

Non-small cell lung cancer chemotherapy treatment outcomes and ethnicity: a twenty-year single-centre patterns of care study.

AIM: To investigate the treatment of patients with advanced-stage non-small cell lung cancer (NSCLC) over a 20-year period in a single Aotearoa New Zealand centre with reference to the use of systemic anti-cancer chemotherapy (SACT) and to explore ethnic disparities in treatment and outcomes. METHOD: Using a SACT database maintained by the Oncology Department at Waikato Hospital, Hamilton, Aotearoa New Zealand from 2000 to 2021 we derived summary statistics for patient factors and SACT regimens by ethnicity (Maori and non-Maori). We investigated Kaplan-Meier all-cause survival by ethnicity and SACT. Logistic regression was used to estimate the odds ratios of surviving 12 months and receiving first and second SACT. RESULTS: One thousand and fifty-seven patients with advanced NSCLC were included, with 30% identified as Maori and 53% treated with SACT. The median survival for non-Maori and Maori receiving SACT was 11.9 and 8.5 months respectively (unadjusted odds ratio of surviving 12 months: 1.968; 95% CI: 1.352-2.865; p<0.001). Non-Maori receiving SACT were 86.2% more likely to survive 12 months than Maori. There were no ethnic disparities in the proportion of patients receiving first-line SACT; however, non-Maori were 1.5 times more likely to receive a second SACT than Maori. CONCLUSION: Significant ethnic difference between Maori and non-Maori exists for both survival and receipt of second-line SACT.

Followback Clusters, Satellite Audiences, and Bridge Nodes: Coengagement Networks for the 2020 US Election.

The 2020 United States (US) presidential election was - and has continued to be - the focus of pervasive and persistent mis- and disinformation spreading through our media ecosystems, including social media. This event has driven the collection and analysis of large, directed social network datasets, but such datasets can resist intuitive understanding. In such large datasets, the overwhelming number of nodes and edges present in typical representations create visual artifacts, such as densely overlapping edges and tightly-packed formations of low-degree nodes, which obscure many features of more practical interest. We apply a method, coengagement transformations, to convert such networks of social data into tractable images. Intuitively, this approach allows for parameterized network visualizations that make shared audiences of engaged viewers salient to viewers. Using the interpretative capabilities of this method, we perform an extensive case study of the 2020 United States presidential election on Twitter, contributing an empirical analysis of coengagement. By creating and contrasting different networks at different parameter sets, we define and characterize several structures in this discourse network, including bridging accounts, satellite audiences, and followback communities. We discuss the importance and implications of these empirical network features in this context. In addition, we release open-source code for creating coengagement networks from Twitter and other structured interaction data.

Early tau detection in flortaucipir images: validation in autopsy-confirmed data and implications for disease progression.

BACKGROUND: There is an increasing interest in utilizing tau PET to identify patients early in Alzheimer's disease (AD). In this work, a temporal lobe composite (Eτ) volume of interest (VOI) was evaluated in a longitudinal flortaucipir cohort and compared to a previously described global neocortical VOI. In a separate autopsy-confirmed study, the sensitivity of the Eτ VOI for identifying intermediate (B2) neurofibrillary tangle (NFT) pathology was evaluated. METHODS: A total of 427 subjects received flortaucipir, florbetapir, MRI, and cognitive evaluation at baseline and 18 months. In a separate autopsy study, 67 subjects received ante-mortem flortaucipir scans, and neuropathological findings were recorded according to NIA-AA recommendations by two experts. Two VOIs: Eτ comprising FreeSurfer volumes (bilateral entorhinal cortex, fusiform, parahippocampal, and inferior temporal gyri) transformed to MNI space and a previously published global AD signature-weighted neocortical VOI (ADsignature) (Devous et al., J Nucl Med 59:937-43, 2018), were used to calculate SUVr relative to a white matter reference region (PERSI) (Southekal et al., J Nucl Med Off Publ Soc Nucl Med 59:944-51, 2018). SUVr cutoffs for positivity were determined based on a cohort of young, cognitively normal subjects. Subjects were grouped based on positivity on both VOIs (Eτ+/ADsignature+; Eτ+/ADsignature-; Eτ-/ADsignature-). Groupwise comparisons were performed for baseline SUVr, 18-month changes in SUVr, neurodegeneration, and cognition. For the autopsy study, the sensitivity of Eτ in identifying intermediate Braak pathology (B2) subjects was compared to that of AD signature-weighted neocortical VOI. The average surface maps of subjects in the Eτ+/ADsignature- group and B2 NFT scores were created for visual evaluation of uptake. RESULTS: Sixty-four out of 390 analyzable subjects were identified as Eτ+/ADsignature-: 84% were Aß+, 100% were diagnosed as MCI or AD, and 59% were APOE ε4 carriers. Consistent with the hypothesis that Eτ+/ADsignature- status reflects an early stage of AD, Eτ+/ADsignature- subjects deteriorated significantly faster than Eτ-/ADsignature- subjects, but significantly slower than Eτ+/ADsignature+ subjects, on most measures (i.e., change in ADsignature SUVr, Eτ ROI cortical thickness, and MMSE). The ADsignature VOI was selective for subjects who came to autopsy with a B3 NFT score. In the autopsy study, 12/15 B2 subjects (including 10/11 Braak IV) were Eτ+/ADsignature-. Surface maps showed that flortaucipir uptake was largely captured by the Eτ VOI regions in B2 subjects. CONCLUSION: The Eτ VOI identified subjects with elevated temporal but not global tau (Eτ+/ADsignature-) that were primarily Aß+, APOE ε4 carriers, and diagnosed as MCI or AD. Eτ+/ADsignature- subjects had greater accumulation of tau, greater atrophy, and higher decline on MMSE in 18 months compared to Eτ-/ADsignature- subjects. Finally, the Eτ VOI identified the majority of the intermediate NFT score subjects in an autopsy-confirmed study. As far as we know, this is the first study that presents a visualization of ante-mortem FTP retention patterns that at a group level agree with the neurofibrillary tangle staging scheme proposed by Braak. These findings suggest that the Eτ VOI may be sensitive for detecting impaired subjects early in the course of Alzheimer's disease.

Accelerated immunoassays based on magnetic particle dynamics in a rotating capillary tube with stationary magnetic field.

A rapid and simple magnetic particle-based immunoassay has been demonstrated in a capillary mixing system. Antibody-coated micrometer size superparamagnetic polystyrene (SPP) particles were used in an assay for rabbit IgG in a sandwich (noncompetitive) format. The kinetics of the assay was compared between a plate-based system and a single capillary tube. The interaction between the antigen (R-IgG) and the antibody (anti-R-IgG) that was carried by the SPP particles in a rotating capillary was tested under a stationary magnetic field. Competing magnetic and viscous drag forces helped to enhance the interaction between the analyte and the capture antibodies on the particles. The dimensionless Mason number (Mn) was employed to characterize the magnetic particle dynamics; a previously determined critical Mason number (Mn(c)) was employed as a guide to the appropriate experimental conditions of magnetic field strength and rotational speed of the capillary. The advantage of the rotating capillary system included a short assay time and a reduced reactive volume (20 µL). The results show that the immunoassay kinetics were improved by the formation of chains of the SPP particles for the conditions that corresponded to the critical Mason number.

Debtors' Blocks: How Monetary Sanctions Make Between-neighborhood Racial and Economic Inequalities Worse.

Although recent scholarship has enumerated many individual-level consequences of criminal legal citations and sentences involving fines and fees, we know surprisingly little about the structural consequences of monetary sanctions or legal financial obligations (LFOs). We use social disorganization and critical race theories to examine neighborhood-level associations between and among LFO sentence amounts, poverty, and racial and ethnic demographics. Using longitudinal data from the Washington State Administrative Office of the Courts, and the American Community Survey, we find LFOs are more burdensome in high-poverty communities and of color, and that per-capita rates of LFOs sentenced are associated with increased future poverty rates across all neighborhoods.

Combining interventions to reduce the spread of viral misinformation.

Misinformation online poses a range of threats, from subverting democratic processes to undermining public health measures. Proposed solutions range from encouraging more selective sharing by individuals to removing false content and accounts that create or promote it. Here we provide a framework to evaluate interventions aimed at reducing viral misinformation online both in isolation and when used in combination. We begin by deriving a generative model of viral misinformation spread, inspired by research on infectious disease. By applying this model to a large corpus (10.5 million tweets) of misinformation events that occurred during the 2020 US election, we reveal that commonly proposed interventions are unlikely to be effective in isolation. However, our framework demonstrates that a combined approach can achieve a substantial reduction in the prevalence of misinformation. Our results highlight a practical path forward as misinformation online continues to threaten vaccination efforts, equity and democratic processes around the globe.

Upconversion in NaYF(4):Yb, Er nanoparticles amplified by metal nanostructures.

Upconversion (UC) fluorescence in NaYF(4):Yb, Er nanoparticles amplified by metal nanostructures was compared in two nanostructure geometries: gold nanoshells surrounding nanoparticles and silver nanostructures adjacent to the nanoparticles, both placed on a dielectric silica surface. Enhanced UC luminescence signals and modified lifetimes induced by these two metals were observed in our study. The UC luminescence intensities of green and red emissions were enhanced by Ag nanostructures by a factor of approximately 4.4 and 3.5, respectively. The corresponding UC lifetimes were reduced ∼ 1.7-fold and ∼ 2.4-fold. In NaYF(4):Yb, Er nanoparticles encapsulated in gold nanoshells, higher luminescence enhancement factors were obtained (∼9.1-fold for the green emission and ∼ 6.7-fold for the red emission). However, the Au shell coating extended the red emission by a factor of 1.5 and did not obviously change the lifetime of green emission. The responsible mechanisms such as plasmonic enhancement and surface effects are discussed.