Decision on non-conveyance of patients suspected of COVID-19 in a novel arrangement with assessment visits by paramedics at home.

BACKGROUND: During the first weeks of the outbreak of the coronavirus disease 2019 (COVID-19), the North Denmark emergency medical services authorised paramedics to assess patients suspected of COVID-19 at home, and then decide if conveyance to a hospital was required. The aim of this study was to describe the cohort of patients who were assessed at home and their outcomes in terms of subsequent hospital visits and short-term mortality. METHODS: This was a historical cohort study in the North Denmark Region with consecutive inclusion of patients suspected of COVID-19 who were referred to a paramedic's assessment visit by their general practitioner or an out-of-hours general practitioner. The study was conducted from 16 March to 20 May 2020. The outcomes were the proportion of non-conveyed patients who subsequently visited a hospital within 72 hours of the paramedic's assessment visit and mortality at 3, 7 and 30 days. Mortality was estimated using a Poisson regression model with robust variance estimation. RESULTS: During the study period, 587 patients with a median age of 75 (IQR 59-84) years were referred to a paramedic's assessment visit. Three of four patients (76.5%, 95% CI 72.8;79.9) were non-conveyed, and 13.1% (95% CI 10.2;16.6) of the non-conveyed patients were subsequently referred to a hospital within 72 hours of the paramedic's assessment visit. Within 30 days from the paramedic's assessment visit, mortality was 11.1% [95% CI 6.9;17.9] among patients directly conveyed to a hospital and 5.8% [95% CI 4.0;8.5] among non-conveyed patients. Medical record review revealed that deaths in the non-conveyed group had happened among patients with 'do-not-resuscitate' orders, palliative care plans, severe comorbidities, age ≥ 90 years or nursing home residents. CONCLUSIONS: The majority (87%) of the non-conveyed patients did not visit a hospital for the following three days after a paramedic's assessment visit. The study implies that this newly established prehospital arrangement served as a kind of gatekeeper for the region's hospitals in regard to patients suspected of COVID-19. The study also demonstrates that implementation of non-conveyance protocols should be accompanied by careful and regular evaluation to ensure patient safety.

Versatile technique for assessing thickness of 2D layered materials by XPS.

X-ray photoelectron spectroscopy (XPS) has been utilized as a versatile method for thickness characterization of various two-dimensional (2D) films. Accurate thickness can be measured simultaneously while acquiring XPS data for chemical characterization of 2D films having thickness up to approximately 10 nm. For validating the developed technique, thicknesses of few-layer graphene (FLG), MoS2 and amorphous boron nitride (a-BN) layer, produced by microwave plasma chemical vapor deposition (MPCVD), plasma enhanced chemical vapor deposition (PECVD), and pulsed laser deposition (PLD) respectively, were accurately measured. The intensity ratio between photoemission peaks recorded for the films (C 1s, Mo 3d, B 1s) and the substrates (Cu 2p, Al 2p, Si 2p) is the primary input parameter for thickness calculation, in addition to the atomic densities of the substrate and the film, and the corresponding electron attenuation length (EAL). The XPS data was used with a proposed model for thickness calculations, which was verified by cross-sectional transmission electron microscope (TEM) measurement of thickness for all the films. The XPS method determines thickness values averaged over an analysis area which is orders of magnitude larger than the typical area in cross-sectional TEM imaging, hence provides an advanced approach for thickness measurement over large areas of 2D materials. The study confirms that the versatile XPS method allows rapid and reliable assessment of the 2D material thickness and this method can facilitate in tailoring growth conditions for producing very thin 2D materials effectively over a large area. Furthermore, the XPS measurement for a typical 2D material is non-destructive and does not require special sample preparation. Therefore, after XPS analysis, exactly the same sample can undergo further processing or utilization.

Predicting vertical phase segregation in polymer-fullerene bulk heterojunction solar cells by free energy analysis.

Blends of poly(3-hexylthiophene) (P3HT) and C61-butyric acid methyl ester (PCBM) are widely used as a model system for bulk heterojunction active layers developed for solution-processable, flexible solar cells. In this work, vertical concentration profiles within the P3HT:PCBM active layer are predicted based on a thermodynamic analysis of the constituent materials and typical solvents. Surface energies of the active layer components and a common transport interlayer blend, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), are first extracted using contact angle measurements coupled with the acid-base model. From this data, intra- and interspecies interaction free energies are calculated, which reveal that the thermodynamically favored arrangement consists of a uniformly blended "bulk" structure capped with a P3HT-rich air interface and a slightly PCBM-rich buried interface. Although the "bulk" composition is solely determined by P3HT:PCBM ratio, composition near the buried interface is dependent on both the blend ratio and interaction free energy difference between solvated P3HT and PCBM deposition onto PEDOT:PSS. In contrast, the P3HT-rich overlayer is independent of processing conditions, allowing kinetic formation of a PCBM-rich sublayer during film casting due to limitations in long-range species diffusion. These thermodynamic calculations are experimentally validated by angle-resolved X-ray photoelectron spectroscopy (XPS) and low energy XPS depth profiling, which show that the actual composition profiles of the cast and annealed films closely match the predicted behavior. These experimentally derived profiles provide clear evidence that typical bulk heterojunction active layers are predominantly characterized by thermodynamically stable composition profiles. Furthermore, the predictive capabilities of the comprehensive free energy approach are demonstrated, which will enable investigation of structurally integrated devices and novel active layer systems including low band gap polymers, ternary systems, and small molecule blends.

Control over position, orientation, and spacing of arrays of gold nanorods using chemically nanopatterned surfaces and tailored particle-particle-surface interactions.

The synergy of self- and directed-assembly processes and lithography provides intriguing avenues to fabricate translationally ordered nanoparticle arrangements, but currently lacks the robustness necessary to deliver complex spatial organization. Here, we demonstrate that interparticle spacing and local orientation of gold nanorods (AuNR) can be tuned by controlling the Debye length of AuNR in solution and the dimensions of a chemical contrast pattern. Electrostatic and hydrophobic selectivity for AuNR to absorb to patterned regions of poly(2-vinylpyridine) (P2VP) and polystyrene brushes and mats was demonstrated for AuNR functionalized with mercaptopropane sulfonate (MS) and poly(ethylene glycol), respectively. For P2VP patterns of stripes with widths comparable to the length of the AuNR, single- and double-column arrangements of AuNR oriented parallel and perpendicular to the P2VP line were obtained for MS-AuNR. Furthermore, the spacing of the assembled AuNR was uniform along the stripe and related to the ionic strength of the AuNR dispersion. The different AuNR arrangements are consistent with predictions based on maximization of packing of AuNR within the confined strip.

Canopy dynamics in nanoscale ionic materials.

Nanoscale ionic materials (NIMS) are organic-inorganic hybrids in which a core nanostructure is functionalized with a covalently attached corona and an ionically tethered organic canopy. NIMS are engineered to be liquids under ambient conditions in the absence of solvent and are of interest for a variety of applications. We have used nuclear magnetic resonance (NMR) relaxation and pulse-field gradient (PFG) diffusion experiments to measure the canopy dynamics of NIMS prepared from 18-nm silica cores modified by an alkylsilane monolayer possessing terminal sulfonic acid functionality, paired with an amine-terminated ethylene oxide/propylene oxide block copolymer canopy. Carbon NMR studies show that the block copolymer canopy is mobile both in the bulk and in the NIMS and that the fast (ns) dynamics are insensitive to the presence of the silica nanoparticles. Canopy diffusion in the NIMS is slowed relative to the neat canopy, but not to the degree predicted from the diffusion of hard-sphere particles. Canopy diffusion is not restricted to the surface of the nanoparticles and shows unexpected behavior upon addition of excess canopy. Taken together, these data indicate that the liquid-like behavior in NIMS is due to rapid exchange of the block copolymer canopy between the ionically modified nanoparticles.

Selective growth of vertical ZnO nanowire arrays using chemically anchored gold nanoparticles.

A selective growth method for ZnO vertical nanowire arrays is demonstrated using self-assembled gold nanoparticles as the growth catalyst. Gold nanoparticles functionalized with bifunctional (thiol-phosphonic acid) ligands assemble rapidly and selectively onto a patterned ZnO seed layer. Vertical ZnO nanowire arrays are grown by the vapor-liquid-solid (VLS) deposition method from the ZnO seed layer through the catalytic effect of the bound gold nanoparticles. This synthesis method offers a number of advantages for producing ZnO nanowires because it permits selective placement through directed self-assembly of gold nanoparticles, enables rapid growth, eliminates vacuum deposition processing, and minimizes the amount of gold waste when compared to traditional methods that require vapor deposition of gold films.

Alkanephosphonates on hafnium-modified gold: a new class of self-assembled organic monolayers.

A new method for assembling organic monolayers on gold is reported that employs hafnium ions as linkers between a phosphonate headgroup and the gold surface. Monolayers of octadecylphosphonic acid (ODPA) formed on gold substrates that had been pretreated with hafnium oxychloride are representative of this new class of organic thin films. The monolayers are dense enough to completely block assembly of alkanethiols and resist displacement by alkanethiols. The composition and structure of the monolayers were investigated by contact angle goniometry, XPS, PM-IRRAS, and TOF-SIMS. From these studies, it was determined that this assembly strategy leads to the formation of ODPA monolayers similar in quality to those typically formed on metal oxide substrates. The assembly method allows for the ready generation of patterned surfaces that can be easily prepared by first patterning hafnium on the gold surface followed by alkanephosphonate assembly. Using the bifunctional (thiol-phosphonate) 2-mercaptoethylphosphonic acid (2-MEPA), we show that this new assembly chemistry is compatible with gold-thiol chemistry and use TOF-SIMS to show that the molecule attaches through the phosphonate functionality in the patterned region and through the thiol in the bare gold regions. These results demonstrate the possibility of functionalizing metal substrates with monolayers typically formed on metal oxide surfaces and show that hafnium-gold chemistry is complementary and orthogonal to well-established gold-thiol assembly strategies.

Synthesis and structural evolution of rusb3, a new metastable skutterudite compound.

A thin-layer synthesis technique was used to synthesize bulk amounts of the metastable phase, RuSb(3), a novel compound with the skutterudite structure. The compound crystallized at 350 degrees C and was stable to 525 degrees C. When annealed above 550 degrees C, it decomposed into RuSb(2) and Sb. Rietveld refinement of X-ray diffraction data showed the presence of excess Sb residing in the interstitial site in the skutterudite structure. X-ray diffraction and thermal analysis experiments allowed us to examine the evolution of the sample as a function of annealing and determine the reaction pathway. The activation energy for the crystallization of the compound was determined to be 3 eV/nucleation event, while the activation energy for decomposition was approximately 8 eV.