I replicate and extend the seminal work of Camerer et al. (“Labor Supply of New York City Cabdrivers: One Day at a Time,” Quarterly Journal of Economics, 112 1997, 407–441), who find that the wage ...elasticity of daily hours of work for New York City taxi drivers is negative and conclude that their labor supply behavior is consistent with reference dependence. In contrast, my analysis of the complete record of all trips taken in NYC taxi cabs from 2009 to 2013 shows that drivers tend to respond positively to unanticipated as well as anticipated increases in earnings opportunities. Additionally, using a discrete choice stopping model, the probability of a shift ending is strongly positively related to hours worked but at best weakly related to income earned. I find substantial heterogeneity across drivers in their elasticities, but the estimated elasticities are generally positive and rarely substantially negative. I find that new drivers with smaller elasticities are more likely to exit the industry, whereas drivers who remain quickly learn to be better optimizers (have positive labor supply elasticities that grow with experience). These results are consistent with the neoclassical optimizing model of labor supply and suggest that consideration of gain-loss utility and income reference dependence is not an important factor in the daily labor supply decisions of taxi drivers.
Missing data are common in statistical analyses, and imputation methods based on random forests (RF) are becoming popular for handling missing data especially in biomedical research. Unlike standard ...imputation approaches, RF-based imputation methods do not assume normality or require specification of parametric models. However, it is still inconclusive how they perform for non-normally distributed data or when there are non-linear relationships or interactions.
To examine the effects of these three factors, a variety of datasets were simulated with outcome-dependent missing at random (MAR) covariates, and the performances of the RF-based imputation methods missForest and CALIBERrfimpute were evaluated in comparison with predictive mean matching (PMM).
Both missForest and CALIBERrfimpute have high predictive accuracy but missForest can produce severely biased regression coefficient estimates and downward biased confidence interval coverages, especially for highly skewed variables in nonlinear models. CALIBERrfimpute typically outperforms missForest when estimating regression coefficients, although its biases are still substantial and can be worse than PMM for logistic regression relationships with interaction.
RF-based imputation, in particular missForest, should not be indiscriminately recommended as a panacea for imputing missing data, especially when data are highly skewed and/or outcome-dependent MAR. A correct analysis requires a careful critique of the missing data mechanism and the inter-relationships between the variables in the data.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Plastic pollution is ubiquitous throughout the marine environment, yet estimates of the global abundance and weight of floating plastics have lacked data, particularly from the Southern Hemisphere ...and remote regions. Here we report an estimate of the total number of plastic particles and their weight floating in the world's oceans from 24 expeditions (2007-2013) across all five sub-tropical gyres, costal Australia, Bay of Bengal and the Mediterranean Sea conducting surface net tows (N = 680) and visual survey transects of large plastic debris (N = 891). Using an oceanographic model of floating debris dispersal calibrated by our data, and correcting for wind-driven vertical mixing, we estimate a minimum of 5.25 trillion particles weighing 268,940 tons. When comparing between four size classes, two microplastic <4.75 mm and meso- and macroplastic >4.75 mm, a tremendous loss of microplastics is observed from the sea surface compared to expected rates of fragmentation, suggesting there are mechanisms at play that remove <4.75 mm plastic particles from the ocean surface.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The low‐temperature (<−35 °C) reduction of the trivalent uranium monoarene complex {(Ad,MeArO)3mes}U (1), with potassium spheres in the presence of a slight excess of 2.2.2‐cryptand, affords the ...quantitative conversion of 1 into the uranium(II) monoarene complex K(2.2.2‐crypt)((Ad,MeArO)3mes)U (1‐K). The molecular and electronic structure of 1‐K was established experimentally by single‐crystal X‐ray diffraction, variable‐temperature 1H NMR and X‐band EPR spectroscopy, solution‐state and solid‐state magnetism studies, and optical absorption spectroscopy. The electronic structure of the complex was further investigated by DFT calculations. The complete body of evidence confirms that 1‐K is a uranium(II) monoarene complex with a 5f 4 electronic configuration supported by δ backbonding and that the nearly reversible, room‐temperature reduction observed for 1 at −2.495 V vs. Fc/Fc+ is principally metal‐centered.
U2 rocks: The molecular and electronic structure of a uranium(II) monoarene complex with a 5f 4 electronic configuration supported by δ backbonding was established experimentally by single‐crystal X‐ray diffraction, variable‐temperature 1H NMR and X‐band EPR spectroscopy, solution‐state and solid‐state magnetism studies, and optical absorption spectroscopy. The electronic structure of the complex was further investigated by DFT calculations.
Glioblastoma is the most common malignant primary brain tumor. Overall, the prognosis for patients with this disease is poor, with a median survival of <2 years. There is a slight predominance in ...males, and incidence increases with age. The standard approach to therapy in the newly diagnosed setting includes surgery followed by concurrent radiotherapy with temozolomide and further adjuvant temozolomide. Tumor‐treating fields, delivering low‐intensity alternating electric fields, can also be given concurrently with adjuvant temozolomide. At recurrence, there is no standard of care; however, surgery, radiotherapy, and systemic therapy with chemotherapy or bevacizumab are all potential options, depending on the patient's circumstances. Supportive and palliative care remain important considerations throughout the disease course in the multimodality approach to management. The recently revised classification of glioblastoma based on molecular profiling, notably isocitrate dehydrogenase (IDH) mutation status, is a result of enhanced understanding of the underlying pathogenesis of disease. There is a clear need for better therapeutic options, and there have been substantial efforts exploring immunotherapy and precision oncology approaches. In contrast to other solid tumors, however, biological factors, such as the blood‐brain barrier and the unique tumor and immune microenvironment, represent significant challenges in the development of novel therapies. Innovative clinical trial designs with biomarker‐enrichment strategies are needed to ultimately improve the outcome of patients with glioblastoma.
The electrochemical generation of individual H2 nanobubbles at Pt nanodisk electrodes immersed in a 0.5 M H2SO4 solution is reported. A sudden drop in current associated with the transport-limited ...reduction of protons is observed in the i–V response at Pt nanodisk electrodes with radii of less than 50 nm. This decrease in current (∼95% blockage) corresponds to the formation of a single H2 nanobubble attached to the nanoelectrode that blocks proton transport to the surface. The current at which nanobubble formation occurs, i nb p, is independent of scan rate and H2SO4 concentration (for H2SO4 > 0.1 M), indicating a critical concentration profile of electrogenerated H2 required to nucleate a nanobubble. Finite element simulation based on Fick’s first law, combined with the Young–Laplace equation and Henry’s law, indicates that the concentration of H2 near the nanoelectrode surface at i nb p exceeds the saturation concentration necessary to generate a nanobubble with a size comparable to the electrode size. The rapid dissolution of the nanobubble due to the high inner Laplace pressure is precisely balanced by the electrogeneration of H2 at the partially exposed Pt surface, resulting in a dynamically stabilized nanobubble. Preliminary measurements of the i–t response during nanobubble formation indicate a two-step nucleation and growth mechanism with time scales on the order of 100 μs (or less) and ∼1 ms, respectively.
•Ingestion of plastic by marine fish and sharks is understudied.•Attacks on plastic were estimated using apparent bite marks on beached items.•16% of items had apparent bite marks, extrapolated to ...1.3tons a year for one area.•Bottle shapes, and blue or yellow colors, were attacked more frequently.•Tooth widths of marks ranged from 1 to 20mm, suggesting many species ingest plastic.
One of the primary threats to ocean ecosystems from plastic pollution is ingestion by marine organisms. Well-documented in seabirds, turtles, and marine mammals, ingestion by fish and sharks has received less attention until recently. We suggest that fishes of a variety of sizes attack drifting plastic with high frequency, as evidenced by the apparent bite marks commonly left behind. We examined 5518 plastic items from random plots on Kamilo Point, Hawai’i Island, and found 15.8% to have obvious signs of attack. Extrapolated to the entire amount of debris removed from the 15km area, over 1.3tons of plastic is attacked each year. Items with a bottle shape, or those blue or yellow in color, were attacked with a higher frequency. The triangular edges or punctures left by teeth ranged from 1 to 20mm in width suggesting a variety of species attack plastic items. More research is needed to document the specific fishes and rates of plastic ingestion.
Altering amaterial’s catalytic properties requires identifying structural features that give rise to active surfaces. Grain boundaries create strained regions in polycrystalline materials by ...stabilizing dislocations and may provide a way to create high-energy surfaces for catalysis that are kinetically trapped. Although grain-boundary density has previously been correlated with catalytic activity for some reactions, direct evidence that grain boundaries create surfaces with enhanced activity is lacking. We used a combination of bulk electrochemical measurements and scanning electrochemical cell microscopy with submicrometer resolution to show that grain-boundary surface terminations in gold electrodes are more active than grain surfaces for electrochemical carbon dioxide (CO₂) reduction to carbon monoxide (CO) but not for the competing hydrogen (H₂) evolution reaction. The catalytic footprint of the grain boundary is commensurate with its dislocation-induced strain field, providing a strategy for broader exploitation of grain-boundary effects in heterogeneous catalysis.
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