Search results for " sample"
showing 10 items of 456 documents
Simultaneous determination of traditional and emerging illicit drugs in sediments, sludges and particulate matter
2015
An analytical method for determining traditional and emerging drugs of abuse in particulate matter, sewage sludge and sediment has been developed and validated. A total of 41 drugs of abuse and metabolites including cocainics, tryptamines, amphetamines, arylcyclohexylamines, cathinones, morphine derivatives, pyrrolidifenones derivatives, entactogens, piperazines and other psychostimulants were selected. Samples were ultrasound extracted with McIlvaine buffer and methanol, and the extracts were cleaned up by solid phase extraction (SPE) using Strata-X cartridges. Drugs were eluted using methanol and methanol-dichloromethane and determined by liquid chromatography tandem mass spectrometry. Th…
The invasion history of Elodea canadensis and E. nuttallii (Hydrocharitaceae) in Italy from herbarium accessions, field records and historical litera…
2022
AbstractWe analysed the invasion history of two North American macrophytes (Elodea canadensis and E. nuttallii) in Italy, through an accurate census of all available herbarium and field records, dating between 1850 and 2019, and a rich literature collection describing the initial introduction and naturalisation phase that supports the results obtained by the occurrence records. Elodea canadensis arrived in Italy before 1866 and had two invasion phases, between the 1890s and 1920s and between the 1990s and 2000s; E. nuttallii, probably arrived in the 1970s, started invading in 2000 and the invasion is still ongoing. Botanical gardens and fish farming played a crucial role in dispersal and na…
Complementarities in innovation strategy: do intangibles play a role in enhancing firm performance?
2017
This article assesses the role of investments in intangible capital and their potential complementarities as a way to improve firm productivity. We focus on the three intangible resources that, according to the literature, have the greatest strategic importance: research and development (R & D), advertising, and human capital. To test our hypotheses, we use a large sample of Spanish manufacturing firms and consider estimates of total factor productivity through a generalized method of moments approach. Our results show evidence of complementarities between R & D and advertising investments and between advertising and human capital. However, they are not conclusive in the case of R & D and h…
Export markets: substitutes, complements, or independent?
2020
Using a large sample of export transactions in Spain over the period 2010–2017, we explore whether firms treat export markets as substitutes, complements, or independent. We find that an exogenous ...
The monitoring role of female directors over accounting quality
2017
Recent research in accounting suggests female directors exert more stringent monitoring over the financial reporting process than their male counterparts. However, an emerging literature in finance and economics provides mixed findings and questions whether females in leadership roles significantly differ from their male counterparts. Building on this literature, we re-examine the link between the presence of female directors, gender biases, and financial statements quality. Using a large sample of UK firms we find that a larger percentage of women among independent directors is significantly associated with lower earnings management practices. However, we show that this relation disappears…
Do foreign workers reduce trade barriers? Microeconomic evidence
2015
This paper provides evidence that foreign workers reduce firms' trade costs and thus increase the probability that firms export. This informs both the literature on trade costs and the microeconomic literature on firms' export behaviour. We identify the nationality of each worker in a large sample of German establishments, and relate this to the exporting behaviour of these establishments. We allow for the possible endogeneity of an establishment's workforce by instrumenting the share of foreign workers with the regional distribution of foreign workers in the wider labour market. We find a significant effect of worker nationality on exporting which is not driven by the industrial, occupatio…
US deficit sustainability revisited: A multiple structural change approach
2008
In this article we re-examine the long-run sustainability of US budget deficits, using Bai and Perron's multiple structural change approach. While the deficit would have been weakly sustainable over the full sample (1947:1–2005:3), strong sustainability would appear only between January 1982 and February 1996.
Determinants of COVID-19 Vaccine Rollouts and Their Effects on Health Outcomes
2022
Background Vaccination against the coronavirus disease (SARS-CoV-2) is understood to be the key way out of the COVID-19 pandemic. Limited evidence exists on the determinants of vaccine rollouts and their health effects at the country level. Objective Examine the determinants of COVID-19 vaccine rollouts and their effects on health outcomes. Methods Ordinary least squares regressions with standard errors clustered at the country level for Cross-section and Panel daily data of vaccinations and various health outcomes (new COVID-19 cases, fatalities, intensive care unit (ICU) admissions) for an unbalanced sample of about 200 countries during the period 16 December 2020 to 20 June 2021. Results…
Sharing economy and incumbents' pricing strategy: The impact of Airbnb on the hospitality industry
2019
Abstract In this paper, we examine how the emergence of sharing economy platforms influences incumbents' price responses. Grounding on the literature on price reactions to new entrants and on the unique characteristics of the sharing economy, we argue that the effect of the penetration of the sharing economy on incumbents' prices is not straightforward, and actually depends on the type of incumbents as well as certain product/service offer characteristics. Indeed, relying on a large sample of hotel price offerings from the Italian market, we find that the effect of the growing relevance of the sharing economy (exemplified by Airbnb) on incumbents' prices depends on the type of incumbents (l…
Cryogenic 35GHz pulse ENDOR probehead accommodating large sample sizes: Performance and applications.
2009
The construction and performance of a cryogenic 35GHz pulse electron nuclear double resonance (ENDOR) probehead for large samples is presented. The resonator is based on a rectangular TE(102) cavity in which the radio frequency (rf) B(2)-field is generated by a two turn saddle ENDOR coil crossing the resonator along the sample axis with minimal distance to the sample tube. An rf power efficiency factor is used to define the B(2)-field strength per square-root of the transmitted rf power over the frequency range 2-180MHz. The distributions of the microwave B(1)- and E(1)-field, and the rf B(2)-field are investigated by electromagnetic field calculations. All dielectrics, the sample tube, and…