Estimating nonresponse bias and mode effects in a mixed mode survey

In mixed-mode surveys, it is difficult to separate sample selection differences from mode-effects that can occur when respondents respond in different interview settings. This paper provides a framework for separating mode-effects from selection effects by matching very similar respondents from different survey modes using propensity score matching. The answer patterns of the matched respondents are subsequently compared. We show that matching can explain differences in nonresponse and coverage in two Internet-samples. When we repeat this procedure for a telephone and Internet-sample however, differences persist between the samples after matching. This indicates the occurrence of mode-effects in telephone and Internet surveys. Mode-effects can be problematic; hence we conclude with a discussion of designs that can be used to explicitly study mode-effects

Stable carbon and radiocarbon isotope compositions of particle size fractions to determine origins of sedimentary organic matter in an estuary

Stable and radioactive carbon isotopic compositions of particle size fractions of a surface sediment from the Ems-Dollard estuary vary considerably with particle size. The organic material in the fine fractions (<20 µm) has considerably higher 14C values (14a~80%) than that in the coarse fractions (52%) and has higher δ13C values (average of -23‰ and -25.6‰, respectively). This shows that OM in the fine and the coarse fractions has different sources. The organic carbon in the fractions with particle sizes <20 µm is mainly imported from the North Sea. The contribution of material from the Ems river appears negligible. The carbon isotopic composition of the coarse fractions points to a terrestrial contribution. Discrete organic fragments are found of both terrestrial and marine/estuarine origin.

Observations of cold dust in nearby elliptical galaxies

Spectral energy distribution (SED) analyses that include new millimeter to far-infrared (FIR) observations obtained with continuum instruments on the Nobeyama and James Clerk Maxwell Telescopes and the Infrared Space Observatory are presented for seven nearby (<45 Mpc) FIR-bright elliptical galaxies. These are analyzed together with archival FIR and shortwave radio data obtained from the NASA/IPAC Extragalactic Database (NED). The radio to infrared SEDs are best-fitted by power law plus graybody models of dust residing in the central galactic regions within a 2.4 kpc diameter and with temperatures between ~21 and 28 K, emissivity index simeq2, and masses from ~1.6 to 19 × 105 M☉. The emissivity index is consistent with dust constituting amorphous silicate and carbonaceous grains previously modeled for stellar-heated dust observed in the Galaxy and other nearby extragalactic sources. Using updated dust absorption coefficients for this type of dust, dust masses are estimated that are similar to those determined from earlier FIR data alone, even though the latter results implied hotter dust temperatures. Fluxes and masses that are consistent with the new FIR and submillimeter data are estimated for dust cooler than 20 K within the central galactic regions. Tighter physical constraints for such cold, diffuse dust (if it exists) with low surface brightness will need sensitive FIR to submillimeter observations with the Spitzer Space Telescope, SCUBA2, or ALMA

Editorial: The rise of collaborative mapping: Trends and future directions

The nature of map production and the dissemination of spatially referenced information have changed radically over the last decade. This change has been marked by an explosion of user generated spatial content via Web 2.0, access to a rising tide of big data streams from remotely-sensed and public data archives, and the use of mobile phones and other sensors as mapping devices. All of these developments have facilitated a much wider use of geodata, transforming ordinary citizens into neogeographers. This increase in user-generated content has resulted in a blurring of the boundaries between the traditional map producer, i.e., national mapping agencies and local authorities, and citizens as consumers of this information. Citizens now take an active role in mapping different types of features on the Earth's surface as volunteers, either by providing observations on the ground or tracing data from other sources, such as aerial photographs or satellite imagery. OpenStreetMap (OSM) and Ushahidi are two well-known examples of a growing collection of collaborative mapping communities that are building rich spatial datasets, which are openly accessible

Is er iets mis met de aandacht van het schoolkind?

Incidenteel klagen leerkrachten bij het lager onderwijs en voortgezet onderwijs over slechte concentratie van kinderen. Dit artikel bevat een verslag van een systematische inventarisatie van deze klacht. Het artikel begint met een theoretische beschouwing van verschillende vormen van aandacht. Vervolgens wordt ingegaan op de relevantie hiervan voor aandacht in de klas. Daarna worden de resultaten van een landelijke enquête onder ervaren leerkrachten bij het gewoon lager onderwijs beschreven. Gevraagd was naar veranderingen bij het schoolkind ten aanzien van met aandacht samenhangend gedrag. De antwoorden wijzen op toegenomen concentratie- en impulsiviteitsproblemen. Mogelijke oorzaken worden genoemd. Ten slotte worden suggesties gedaan voor een meer objectieve bepaling van aandacht en concentratievermogen van het schoolkind, en voor onderzoek naar preventie en behandeling van de problemen

Logistics services and Lean Six Sigma implementation: a case study

Purpose: This paper analyses the application of Lean Six Sigma framework for supporting continuous improvement in logistics services. Both the lean philosophy and the Six Sigma methodology have become two of the most important initiatives for continuous improvement in organizations. The combination of both alternatives - Lean Six Sigma (LSS) - brings significant benefits for companies applying this method and its influence in logistics services can be relevant. Design/methodology/approach: A case study on the logistics services of a large consumer electronics company is performed. In this sector, high quality in logistics services is crucial. Using within-case and cross-case analyses, the paper discusses the implementation of LSS in two internal logistics processes. Findings: The paper identifies important implementation aspects when applying LSS to logistics services, such as continuous improvement structure, strategic analysis, cross-functional teams, and process management. Furthermore, the paper discusses the potential in logistics services of the DMAIC approach and tools like VSM, SIPOC and Process Mapping. Practical implications: The paper analyses two logistics processes where LSS has been applied - a payment process and a request-to-ship process. The analysis of both processes offers relevant information about organizational implementation in a logistics services environment, about process improvement and about the use of LSS tools. Originality/value: Firstly, this paper addresses the gap in literature about LSS and logistics’ activities. Furthermore, the case company, with more than 9.000 employees and distributing its products to more than 100 countries, constitutes a valuable source of information to obtain insights in the implications of implementing LSS in logistics services