Here, we present a hot injection synthesis of colloidal Ag chalcogenide nanocrystals (Ag(2)Se, Ag(2)Te, and Ag(2)S) that resulted in exceptionally small nanocrystal sizes in the range between 2 and 4 nm. Ag chalcogenide nanocrystals exhibit band gap energies within the near-infrared spectral region, making these materials promising as environmentally benign alternatives to established infrared active nanocrystals containing toxic metals such as Hg, Cd, and Pb. We present Ag(2)Se nanocrystals in detail, giving size-tunable luminescence with quantum yields above 1.7%. The luminescence, with a decay time on the order of 130 ns, was shown to improve due to the growth of a monolayer thick ZnSe shell. Photoconductivity with a quantum efficiency of 27% was achieved by blending the Ag(2)Se nanocrystals with a soluble fullerene derivative. The co-injection of lithium silylamide was found to be crucial to the synthesis of Ag chalcogenide nanocrystals, which drastically increased their nucleation rate even at relatively low growth temperatures. Because the same observation was made for the nucleation of Cd chalcogenide nanocrystals, we conclude that the addition of lithium silylamide might generally promote wet-chemical synthesis of metal chalcogenide nanocrystals, including in as-yet unexplored materials.

Although a large diversity of single-component and binary superlattices from colloidal nanocrystals have been demonstrated, applications of such ordered nanocrystal assemblies are still hampered due to a lack of control over the self-assembly processes over large areas. A reel-to-reel compatible large-area coating technique for solutions is given by doctor blade casting, which is applied here to deposit colloidal nanocrystals onto various substrates. The self-assembly process is demonstrated for magnetic nanocrystals, having a high potential for applications in magnetic memory devices. Shape-controlled (spherical and cubic) and monodisperse nanocrystals with a Wustite core and a cobalt ferrite shell are used in particular. Doctor blade casting of these colloidal nanocrystals results in films exhibiting hexagonally closely packed arrangements, which are formed by a top-down growth, as is evidenced by cross sectional transmission electron microscopy. The ordering in the topmost layer extends over large areas, although some defects and irregularities are found. The degree and quality of self-assembly is quantified by analyzing plan view images of the assemblies by means of the decay of their autocorrelation function. This analysis reveals that the degree of ordering obtained by doctor blade casting outperforms those provided by alternative deposition techniques such as inkjet printing or drop casting. The results for the coherent lengths deduced from the autocorrelation analysis are shown to be consistent with those from grazing-incidence small-angle X-ray scattering, giving coherence length on the order of 1000 nm.

This analysis examines whether the coronavirus disease 2019 (COVID-19) emergency sick leave provision of the bipartisan Families First Coronavirus Response Act (FFCRA) reduced the spread of the virus. Using a difference-in-differences strategy, we compared changes in newly reported COVID-19 cases in states where workers gained the right to take paid sick leave (treatment group) versus in states where workers already had access to paid sick leave (control group) before the FFCRA. We adjusted for differences in testing, day-of-the-week reporting, structural state differences, general virus dynamics, and policies such as stay-athome orders. Compared with the control group and relative to the pre-FFCRA period, states that gained access to paid sick leave through the FFCRA saw around 400 fewer confirmed cases per state per day. This estimate translates into roughly one prevented case per day per 1,300 workers who had newly gained the option to take up to two weeks of paid sick leave.

The objective of this paper is to estimate and test multifactor versions of the Cox-Ingersoll-Ross (CIR) model of the nominal term structure of interest rates. The proposed state-space approach integrates time series and cross-sectional aspects ofthe CIR model, is consistent with the underlying economic model, and can use information from all available points of the term structure. We recover estimates of the underlying factors that are consistent with the assumptions about the stochastic processes and compare them with factors obtained from standard factor analysis. We perform thorough diagnostic checking and thereby provide new evidence regarding conclusions about the adequacy of the CIR model. We present empirical results for U.S. Treasury market data. Although the specification of multifactor CIR models is sufficiently flexible for the shape of the term structure, we find strong evidence against the adequacy of the CIR model.