The Complementarity between Foreign and Native IT Workers: Evidence from an Industry-Level Analysis

This study investigates if foreign information technology (IT) workers complement or substitute for native IT workers within the production function framework. We first examine the differences between foreign and native IT workers in their skill sets and then test their complementarity/substitution relationship using an US industry-level dataset obtained by matching the productivity data to the Current Population Survey. Our findings suggest that foreign and native IT workers are complements rather than substitutes. The results of this study shed light on this important issue and bear theoretical and practical implications

Measuring Risk from IT Initiatives Using Implied Volatility

We propose an underrecognized measure to capture changes in firm risk from information technology (IT) announcements: implied volatility (IV) from a firm’s exchange-traded options. An IV is obtained from a priced stock option and represents the option market’s expectation of the firm’s average stock return volatility over the remaining duration of the option. Using the change in IV around IT announcements, we can directly assess changes in IT-induced firm risk. IVs are straightforward to obtain, and are forward-looking based on option market investors’ estimates of future stock return volatility. They do not rely on historical volatility that is confounded with other events. In addition, options have different expiration dates—each with an IV—allowing us to distinguish between short- and long-term risk. We show how a change in IV can be employed to assess changes in short- and long-term firm risk from IT announcements and demonstrate this methodological innovation empirically using a set of IT announcements that have been utilized in previous studies

Substitutive First-party Content as a Strategic Decision for Platform Growth – Evidence from a B2B Platform

This paper examines the effect of substitutive first-party content (SFPC) as a strategic variable by a business-to-business (B2B) e-commerce platform. Constructing a unique time-series dataset, we find that SFPC’s impact differs in the early stage of the platform and in the later stage when it has a larger user base and has transformed itself into a service provider. In the early stage, increasing SFPC can attract more buyers to trade but may crowd out sellers, leading to an insignificant impact on total trading volume. In the second stage, however, SFPC no longer hurts seller participation and increases total trading volume. We also find that SFPC could attract new users consistently across the two stages. Our findings suggest a strategic role of SFPC to mitigate the “chicken‐and‐egg problem ” in the early stage of a two-sided B2B platform and to continuously grow platform size when it becomes more established

Temperature Controls Guest Uptake and Release from Zn4L4 Tetrahedra.

We report the preparation of triazatruxene-faced tetrahedral cage 1, which exhibits two diastereomeric configurations (T1 and T2) that differ in the handedness of the ligand faces relative to that of the octahedrally coordinated metal centers. At lower temperatures, T1 is favored, whereas T2 predominates at higher temperatures. Host-guest studies show that T1 binds small aliphatic guests, whereas T2 binds larger aromatic molecules, with these changes in binding preference resulting from differences in cavity size and degree of enclosure. Thus, by a change in temperature the cage system can be triggered to eject one bound guest and take up another.This work was supported by the European Research Council (695009) and the UK Engineering and Physical Sciences Research Council (EPSRC EP/M008258/1). The authors thank the Department of Chemistry NMR Facility at the University of Cambridge for performing some NMR experiments and the EPSRC UK National Mass Spectrometry Facility at Swansea University for carrying out high-resolution mass spectrometry. D.Z. acknowledges a Herchel Smith Research Fellowship from the University of Cambridge. J.D.T. acknowledges the Rashkind Family Endowment and the Chenery Endowment from Randolph-Macon College

The prevalence of tinnitus in China: a systematic review of the literature

Purpose: The aim of the present study was to identify reports of the prevalence of tinnitus in China and to present these findings in a review format.Method: We assessed and collated published prevalence estimates of tinnitus and tinnitus severity, creating a narrative synthesis of the data from publications identified from a combination of Chinese and English language databases.Results: A total of 23 studies were included. Tinnitus prevalence ranged from 4.3% - 51.33% but varied with age and gender. The highest increase in prevalence from previous decade in age occurs during the fifth and sixth decades, and the highest prevalence was in the seventh decade at 32.47%. There is also evidence that tinnitus prevalence is related to certain risk factors including comorbid disorders. Conclusions: The prevalence of tinnitus in mainland China in this study is consistent with global data. With increasing awareness of the prevalence of tinnitus in China, the development of epidemiological standards is a priorit

Atomically dispersed Fe in a C2N based catalyst as a sulfur host for efficient lithium-sulfur batteries

Altres ajuts: ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. J.L. is a Serra Húnter Fellow and is grateful to ICREA Academia program.Lithium-sulfur batteries (LSBs) are considered to be one of the most promising next generation energy storage systems due to their high energy density and low material cost. However, there are still some challenges for the commercialization of LSBs, such as the sluggish redox reaction kinetics and the shuttle effect of lithium polysulfides (LiPS). Here a 2D layered organic material, CN, loaded with atomically dispersed iron as an effective sulfur host in LSBs is reported. X-ray absorption fine spectroscopy and density functional theory calculations prove the structure of the atomically dispersed Fe/CN catalyst. As a result, Fe/CN-based cathodes demonstrate significantly improved rate performance and long-term cycling stability. Fe/CN-based cathodes display initial capacities up to 1540 mAh g at 0.1 C and 678.7 mAh g at 5 C, while retaining 496.5 mAh g after 2600 cycles at 3 C with a decay rate as low as 0.013% per cycle. Even at a high sulfur loading of 3 mg cm, they deliver remarkable specific capacity retention of 587 mAh g after 500 cycles at 1 C. This work provides a rational structural design strategy for the development of high-performance cathodes based on atomically dispersed catalysts for LSBs

Preparation and enhanced properties of Fe3O4 nanoparticles reinforced polyimide nanocomposites

Polyimide (PI) nanocomposite reinforced with Fe3O4 nanoparticles (NPs) at various NPs loadings levels of 5.0, 10.0, 15.0, and 20.0 wt% were prepared. The chemical interactions of the Fe3O4 NPs/PI nanocomposites were characterized using Fourier Transform Infrared (FT-IR) spectroscopy. X-ray Diffraction (XRD) results revealed that the addition of NPs had a significant effect on the crystallization of PI. Scanning electron microscope (SEM) and the atomic force microscope (AFM) were used to characterize the dispersion and surface morphology of the Fe3O4 NPs and the PI nanocomposites. The obtained optical band gap of the nanocomposites characterized using Ultraviolet-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS) was decreased with increasing the Fe3O4 loading. Differential scanning calorimetry (DSC) results showed a continuous increase of Tg with increasing the Fe3O4 NPs loading. Some differences were observed in the onset decomposition temperature between the pure PI and nanocomposites since the NPs and the PI matrix were physically entangled together to form the nanocomposites. The contact angle of pure PI was larger than that of Fe3O4/PI nanocomposites films, and increased with increasing the loading of Fe3O4. The degree of swelling was increased with increasing the Fe3O4 loading and the swelling time. The dielectric properties of the nanocomposite were strongly related to the Fe3O4 loading levels. The Fe3O4/PI magnetic property also had been improved with increasing the loading of the magnetic nanoparticles

Evolution of chloroplast retrograde signaling facilitates green plant adaptation to land

Chloroplast retrograde signaling networks are vital for chloroplast biogenesis, operation, and signaling, including excess light and drought stress signaling. To date, retrograde signaling has been considered in the context of land plant adaptation, but not regarding the origin and evolution of signaling cascades linking chloroplast function to stomatal regulation. We show that key elements of the chloroplast retrograde signaling process, the nucleotide phosphatase (SAL1) and 3'-phosphoadenosine-5'-phosphate (PAP) metabolism, evolved in streptophyte algae-the algal ancestors of land plants. We discover an early evolution of SAL1-PAP chloroplast retrograde signaling in stomatal regulation based on conserved gene and protein structure, function, and enzyme activity and transit peptides of SAL1s in species including flowering plants, the fern Ceratopteris richardii, and the moss Physcomitrella patens. Moreover, we demonstrate that PAP regulates stomatal closure via secondary messengers and ion transport in guard cells of these diverse lineages. The origin of stomata facilitated gas exchange in the earliest land plants. Our findings suggest that the conquest of land by plants was enabled by rapid response to drought stress through the deployment of an ancestral SAL1-PAP signaling pathway, intersecting with the core abscisic acid signaling in stomatal guard cells

Flat band magnetism and helical magnetic order in Ni-doped SrCo2_2As2_2

A series of Sr(Co$_{1-x}$Ni$_x$)$_2$As$_2$ single crystals was synthesized allowing a comprehensive phase diagram with respect to field, temperature, and chemical substitution to be established. Our neutron diffraction experiments revealed a helimagnetic order with magnetic moments ferromagnetically (FM) aligned in the $ab$ plane and a helimagnetic wavevector of $q=(0,0,0.56)$ for $x$ = 0.1. The combination of neutron diffraction and angle-resolved photoemission spectroscopy (ARPES) measurements show that the tuning of a flat band with $d_{x^2-y^2}$ orbital character drives the helimagnetism and indicates the possibility of a quantum order-by-disorder mechanism.Comment: 9 pages, 12 figures, Supplementary Material available upon request, accepted by Phys. Rev.

A genetic variation map for chicken with 2.8 million single-nucleotide polymorphisms

We describe a genetic variation map for the chicken genome containing 2.8 million single-nucleotide polymorphisms ( SNPs). This map is based on a comparison of the sequences of three domestic chicken breeds ( a broiler, a layer and a Chinese silkie) with that of their wild ancestor, red jungle fowl. Subsequent experiments indicate that at least 90% of the variant sites are true SNPs, and at least 70% are common SNPs that segregate in many domestic breeds. Mean nucleotide diversity is about five SNPs per kilobase for almost every possible comparison between red jungle fowl and domestic lines, between two different domestic lines, and within domestic lines - in contrast to the notion that domestic animals are highly inbred relative to their wild ancestors. In fact, most of the SNPs originated before domestication, and there is little evidence of selective sweeps for adaptive alleles on length scales greater than 100 kilobases