Effect of Workload History on Task Performance

Objective: This study investigated the effects of workload history (specifically, sudden shifts in workload) on performance. Background: In 1993 the National Research Council identified workload transition as an important concern for human factors researchers. The study of workload history suggests that what an individual has been doing prior to a point in time has an effect on subsequent performance. One trend emerging from workload history studies is that a general decrement in performance is most likely to occur following a decrease in task demand. Method: The 198 participants were randomly assigned to a high-to-low or low-to-high condition. Participants performed a version of the Bakan Vigilance Task while correct responses, response times, and total errors were recorded. Results: Results supported previous research suggesting a workload decrease results in a performance decrement. More importantly, this study reports that either a sudden increase or decrease could lead to a loss in accuracy and a slowing of response time in a longer time course. Conclusion: An explanation of the decrement is offered in terms of adaptation models. In addition, a follow-up study suggested that the decrement is a result of something inherent in the workload shift rather than an effect of fatigue. Application: Workload history (more specifically, a workload shift) has significant implications for many work environments. These implications are particularly salient in occupations where individuals are confronted with varying levels of workload demand, especially safety-sensitive occupations.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Efecto de dos fuentes y cinco dosis de potasio sobre la acumulacion de fitomasa y la absorcion de nutrientes en maiz para ensilaje

Resumen (Spanish, English)66 P.Se sembró un híbrido de maíz semitardío (Asgrow 899) el 20 de Noviembre de 1994 en la Estación Experimental de la Facultad de Ciencias Agrarias de la Universidad de Talca, para estudiar el efecto de cinco dosis de potasio: 0, 50, 100, 150 y 200 kg de K2O ha-1, proveniente de dos fuentes de fertilizante; nitrato y cloruro de potasio, sobre la acumulación de fitomasa y la absorción de N, K+, Mg++, Ca++ y Na+. Las combinaciones de dosis y fuentes de potasio se analizaron mediante un experimento factorial distribuido en bloques al azar, con cuatro repeticiones. Se realizaron tres evaluaciones a partir de emergencia de plantas, en los estados 2.5, 5 y 8 de la escala de Hanway, midiendo fitomasa seca acumulada y concentraciones (%) de N, K+, Mg++, Ca++ y Na+ en plantas. Los resultados mostraron una positiva respuesta a la aplicación de K para acumulación de fitomasa (BMS), indistintamente de la fuente fertilizante, alcanzando las mayores respuestas con la aplicación de 50 kg de K2O ha-1 y, a partir 100 K2O ha-1, rendimientos máximos. Dosis superiores a las señaladas sólo incrementaron el contenido de K+ en plantas. Las concentraciones de N, K+ y Mg++ en plantas disminuyeron a través de la temporada; Ca++ y Na+ aumentaron hacia la madurez. El contenido de N en plantas aumentó por la aplicación de K, pero los incrementos fueron significativos hasta dosis de 50 kg de K2O ha-1, existiendo una relación lineal entre la absorción total de N y la acumulación de fitomasa. El cloruro no afectó la absorción de N. La absorción total de K+ aumentó en forma sostenida con aumentos de la fertilización potásica. La concentración promedio de Mg++ y de Na+ en plantas disminuyó por la aplicación de K, específicamente; con dosis mayores a 50 kg de K2O ha-1; esto sugiere un antagonismo entre K+ y Mg++ y, entre K+ y Na+, por competencia de sitios de unión a los transportadores de la membrana plasmática durante la absorción. La concentración de Ca++ aumentó por la fertilización potásica y sólo con dosis de 200 kg de K2O ha-1, la concentración final de Ca++ tendió a bajar, siendo similar a la agregación de 50 kg de K2O ha-1. Se discute la existencia de un antagonismo entre K+ y Ca++. Pese a estos resultados, la composición promedio de las plantas no se vio afectada, con respecto a los estándares nutricionales

Analytical solution of generalized Burton--Cabrera--Frank equations for growth and post--growth equilibration on vicinal surfaces

We investigate growth on vicinal surfaces by molecular beam epitaxy making use of a generalized Burton--Cabrera--Frank model. Our primary aim is to propose and implement a novel analytical program based on a perturbative solution of the non--linear equations describing the coupled adatom and dimer kinetics. These equations are considered as originating from a fully microscopic description that allows the step boundary conditions to be directly formulated in terms of the sticking coefficients at each step. As an example, we study the importance of diffusion barriers for adatoms hopping down descending steps (Schwoebel effect) during growth and post-growth equilibration of the surface.Comment: 16 pages, REVTeX 3.0, IC-DDV-94-00

Probing Ionization Energies for Trace Gas Identification: The Micro Photo Electron Ionization Detector (PEID)

Micro gas sensors detect the presence of substances, but can hardly identify them. We developed a novel approach of probing referenceable ionization energies. It extends the photoionization principle towards tunable energies via replacement of photons by accelerated photo electrons. The device comprises UV-LED illumination, an atmospherically stable photoelectron emission layer with a nano-vacuum electronics accelerator realized in thin film technology and charged particle measurement. A voltage variation at the accelerator provides electrons of tunable energies. We were able to prove that variable electron energies can be used for substance detection. The resulting system reaches ambient conditions operability. The actual limitations and challenges are discussed

Evolution of Housing Prices in Chile

The availability of real estate data is clearly limited in Chile, which makes more complex the discussion of the possible vulnerabilities of households and the financial sector to risks arising from real estate markets. This paper proposes a set of housing price indicators for measuring the potential pressures that could be developing in the credit market. Using these price measures, we find that the recent sustained rise in home prices coincides with the sustained increase in disposable income and the decreasing trend of long-term interest rates, factors that have strongly driven the expansion of mortgage loans.

Subtidal macrozoobenthos communities from northern Chile during and post El Niño 1997–1998

Despite a large amount of climatic and oceanographic information dealing with the recurring climate phenomenon El Niño (EN) and its well known impact on diversity of marine benthic communities, most published data are rather descriptive and consequently our understanding of the underlying mechanisms and processes that drive community structure during EN are still very scarce. In this study, we address two questions on the effects of EN on macrozoobenthic communities: (1) how does EN affect species diversity of the communities in northern Chile? and (2) is EN a phenomenon that restarts community assembling processes by affecting species interactions in northern Chile? To answer these questions, we compared species diversity and co-occurrence patterns of soft-bottoms macrozoobenthos communities from the continental shelf off northern Chile during (March 1998) and after (September 1998) the strong EN event 1997–1998. The methods used varied from species diversity and species co-occurrence analyses to multivariate ordination methods. Our results indicate that EN positively affects diversity of macrozoobenthos communities in the study area, increasing the species richness and diversity and decreasing the species dominance. EN represents a strong disturbance that affects species interactions that rule the species assembling processes in shallow-water, sea-bottom environments

Microevolution of Pandemic Vibrio parahaemolyticus Assessed by the Number of Repeat Units in Short Sequence Tandem Repeat Regions

The emergence of the pandemic strain Vibrio parahaemolyticus O3:K6 in 1996 caused a large increase of diarrhea outbreaks related to seafood consumption in Southeast Asia, and later worldwide. Isolates of this strain constitutes a clonal complex, and their effectual differentiation is possible by comparison of their variable number tandem repeats (VNTRs). The differentiation of the isolates by the differences in VNTRs will allow inferring the population dynamics and microevolution of this strain but this requires knowing the rate and mechanism of VNTRs' variation. Our study of mutants obtained after serial cultivation of clones showed that mutation rates of the six VNTRs examined are on the order of 10−4 mutant per generation and that difference increases by stepwise addition of single mutations. The single stepwise mutation (SSM) was deduced because mutants with 1, 2, 3, or more repeat unit deletions or insertions follow a geometric distribution. Plausible phylogenetic trees are obtained when, according to SSM, the genetic distance between clusters with different number of repeats is assessed by the absolute differences in repeats. Using this approach, mutants originated from different isolates of pandemic V. parahaemolyticus after serial cultivation are clustered with their parental isolates. Additionally, isolates of pandemic V. parahaemolyticus from Southeast Asia, Tokyo, and northern and southern Chile are clustered according their geographical origin. The deepest split in these four populations is observed between the Tokyo and southern Chile populations. We conclude that proper phylogenetic relations and successful tracing of pandemic V. parahaemolyticus requires measuring the differences between isolates by the absolute number of repeats in the VNTRs considered

Designing artificial fluorescent proteins: Squaraine-LmrR biophosphors for high performance deep-red biohybrid light-emitting diodes

Biophosphors with fluorescent proteins (FPs) are promising candidates to replace rare-earth color down-converting filters for white light-emitting diodes (LEDs). There is, however, a lack of deep-red FPs meeting high photostabilities, photoluminescence quantum yields (ϕ), and throughput expression yields. Herein, a new approach for the design of highly emissive and stable deep-red biophosphors combining an artificial FP (Lactococcal multidrug resistance Regulator (LmrR) as protein host and an archetypal red-emitting squaraine (S) as guest) with a polymer network is demonstrated toward high performing deep-red biohybrid LEDs (Bio-HLEDs). At first, the best protein pocket (aromaticity, polarity, charge, etc.) to stabilize S in water is determined using four LmrR variants (position 96 with tryptophan, histidine, phenylalanine, and alanine). Computational and time-resolved spectroscopic findings suggest that the tryptophan is instrumental toward achieving artificial red-emitting FPs with ϕ > 50% stable over weeks. These features are further enhanced in the polymer coating (ϕ > 65% stable over months) without affecting emission color. Finally, deep-red Bio-HLEDs are fabricated featuring external quantum efficiencies of 7% and stabilities of ≈800 h. This represents threefold enhancement compared to reference devices with S-polymer color filters. Overall, this work highlights a new design for highly emissive deep-red biophosphors, achieving record performance in deep-red protein-LEDs.The authors acknowledge the European Union's Horizon 2020 research and innovation FET-OPEN under grant agreement ARTIBLED No. 863170. R.D.C. acknowledges the ERC-Co InOutBioLight No. 816856. P.B.C. acknowledges financial support from the Ministry of Science, Innovation and Universities of Spain under the Beatriz Galindo Programme (No. MCIU-19-BEAGAL 18/0224), from MCIN/AEI/10.13039/501100011033 grant No. PGC2018-095953-B-I00 and from the Technical University of Munich (TUM) under the TUM Global Visiting Professor Programme. A.L.C. acknowledges support by the European Research Council ERC-CoG-648071-ProNANO and ERC-PoC-841063-NIMM; and Agencia Estatal de Investigación, Spain (No. PID2019-111649RB-I00). This work was performed under the Maria de Maeztu Units of Excellence Program from the Spanish State Research Agency Grant No. MDM-2017-0720 (CIC biomaGUNE).Peer reviewe