A Search Model with a Quasi-Network

In a standard search model the expected duration of unemployment is independent of the duration of previous employment, as well as of the current length of the unemployment spell. This paper offers a network mechanism to generate these correlations. Here, employed workers invest in social contacts with other employed workers, which will help them find jobs in the event of unemployment. These social contacts "depreciate" because they can also become unemployed and unemployed contacts are assumed to be useless. In this model the longer you have been working, the more contacts you are likely to have, and the more contacts you have the shorter your expected unemployment duration will be. The model is a simple and tractable way of introducing network ideas in one of the workhorses of labour and macroeconomics. The model also suggests that networks are less productive during periods of high unemployment, mainly because high unemployment destroys part of the network. In addition, the model provides guidance for indirect inference of network effects from the data.

Mathisson's helical motions demystified

The motion of spinning test particles in general relativity is described by Mathisson-Papapetrou-Dixon equations, which are undetermined up to a spin supplementary condition, the latter being today still an open question. The Mathisson-Pirani (MP) condition is known to lead to rather mysterious helical motions which have been deemed unphysical, and for this reason discarded. We show that these assessments are unfounded and originate from a subtle (but crucial) misconception. We discuss the kinematical explanation of the helical motions, and dynamically interpret them through the concept of hidden momentum, which has an electromagnetic analogue. We also show that, contrary to previous claims, the frequency of the helical motions coincides exactly with the zitterbewegung frequency of the Dirac equation for the electron.Comment: To appear in the Proceedings of the Spanish Relativity Meeting 2011 (ERE2011), "Towards new paradigms", Madrid 29 August - 2 September 201

Evaluation and Validation of Global Land Surface Products Derived from Landsat, MODIS, and VIIRS

Data at medium and coarse resolution from the Landsat, MODIS, and VIIRS instruments provide crucial and indispensable time-series for the land component of the study of global change. This talk will be divided into two main sections. In the first part, a summary of the status of the processing, archiving, and early (Launch +6 months) on-orbit evaluation of the VIIRS Land Environmental Data Records (EDRs), will be presented. In the second part, results from an uncertainty analysis of MODIS- and Landsat-based albedo retrievals, based on collocated comparisons with tower and airborne multiangular measurements collected at the Cloud and Radiation Testbed (CART) site during the 2007 Cloud and Land Surface Interaction Campaign (CLASIC'07), will be discussed

Políticas de Amizade Internacional na Cooperação Judiciária em Matéria Penal – A Não-Extradição de Nacionais Brasileiros e Portugueses para Terceiros Estados (Comparação com o Direito da UE)

This article addresses different implications of nationality in international cooperation in criminal matters, especially in extradition law. Most States, particularly of the civil law tradition, have a longstanding practice not to deliver their own citizens to foreign criminal justice systems. This article begins by reviewing the rationales of the classic nationality exception and contrasts it with the approach of States of the common law tradition, which have no objections of principle to extraditing their own nationals. It then looks into the extradition relations between Brazil and Portugal, following which it provides a brief critical appraisal of the adequacy of the nationality exception in an increasingly globalised world. With these foundational issues settled, the article moves on to questioning what are the effects of interstate affinity upon extradition. It concludes that, in addition to (immediate or direct) effects between the States involved, affinity can also have meaningful (indirect) implications to third States: States which are linked by peculiar (historical, legal, political) bonds sometimes refuse to extradite each other’s nationals to other States. In this regard, the article analyses of the state affairs among the Member States of the European Union following the groundbreaking case law initiated by the Court of Justice in 2016, and compares this recent legal development with the regime that has been in place between Brazil and Portugal since 1971.O presente artigo analisa as diferentes implicações da nacionalidade sobre a cooperação judiciária internacional em matéria penal, especialmente sobre o direito da extradição. A maioria dos Estados, em particular os da tradição jurídica continental, tem uma longa tradição de não entregar os seus cidadãos para sistemas de justiça criminal estrangeiros. O artigo começa por se debruçar sobre as razões que estão na base desta tradição e faz um contraste com a abordagem seguida pelos Estados da tradição jurídica anglo-americana, que tendem a não levantar objeções à extradição de seus nacionais. Em seguida o artigo atenta nas relações de extradição entre o Brasil e Portugal, fazendo uma breve avaliação crítica da regra da não extradição de nacionais num mundo progressivamente globalizado. Com estas questões essenciais tratadas, o artigo prossegue então para aquela que constitui a sua questão central, que é a de saber que efeitos a existência de laços de afinidade ou proximidade entre Estados pode ter sobre a matéria da extradição. A conclusão proposta é a de que, para além de efeitos (imediatos ou diretos) entre os Estados em causa, essa afinidade se pode também projetar (de modo indireto) sobre Estados terceiros: de facto, por vezes, os Estados que se encontram ligados por peculiares laços históricos, jurídicos e/ou políticos também recusam a extradição para outros Estados dos nacionais um do outro. A este respeito o artigo analisa a situação dos Estados Membros da União Europeia desde a inovadora jurisprudência iniciada pelo Tribunal de Justiça em 2016, comparando este recente desenvolvimento com o regime que já vigora entre o Brasil e Portugal desde 1971

The moderator role of Gender in the Unified Theory of Acceptance and Use of Technology (UTAUT): A study on users of Electronic Document Management Systems

Venkatesh et al. [1] tried to integrate predictability capabilities from the different existing models of technology acceptance. This produced the Unified Theory of Acceptance and Use of Technology (UTAUT). This comprehensive model resulted in the identification of common aspects. It proposed several constructs with a greater explanatory power and analyzed moderating drivers, such as age, Gender, experience and voluntariness of use. By doing so, UTAUT identifies three major drivers of behavioral intention: performance expectancy, effort expectancy and social influence. On the other hand, facilitating conditions and behavioral intention were identified as determinant factors of actual use [1]. In addition to previous considerations about UTAUT, empirical research has scarcely analyzed the moderating role of Gender [2]. This is why this paper particularly aims to fill this gap. Hofstede [3] describes strength, competitiveness and guidance for material success as social roles linked to male values, whilst modesty, tenderness, sensitivity and concern for the quality of life are values associated with women. With respect to UTAUT, existing studies have shown that performance expectancy positively influences behavioral intention more strongly for men (cf. [4], [5], [6] and [7]). Moreover, it has been observed that effort expectancy positively influences behavioral intention more strongly for women (cf. [4], [5] and [6]), while social influence positively affects behavioral intention more strongly for women (cf. [5], [7] and [8]). In our research, with the aim of testing the moderating effects of Gender, a sample of 2,175 users of Electronic Document Management Systems (EDMS) in Portuguese municipalities was used. Taking into account that Gender is a categorical variable, we have adopted a multi-group or multi-sample analysis [9] -dividing the sample into two groups (male = 748; female = 1,427) and estimating each group of observations separately. Before comparing the groups, an analysis of the measurement invariance was carried out to make sure that the construct measures were invariant between both groups [10]. Once the metric invariance had been assessed, we carried out a set of multi-group analyses –interpreting statistically-significant differences in path coefficients as moderating effects. On the one hand, the parametric approach considering both equal variances and different variances has been used [11, 12]. On the other hand, we have applied non-parametric approaches exemplified by the permutation test [13], and Henseler’s PLS multi-group analysis [10, 12, 14]. This study notes slight differences in the results of the aforementioned methods. As a result, the moderating effect of Gender on the relation between performance expectancy and behavioral intention showed that this relationship is stronger among men than women. Finally, a discussion on the implications of Gender as a moderator for the UTAUT model is included

Determinants of User Acceptance of a Local eGovernment Electronic Document Management System (EDMS)

On numerous occasions the significant value of the investments involved in the development of eGovernment and the expectations of governmental information systems use do not correspond to the rate of effective use. This scenario makes it difficult to justify the development of electronic government by governments and local authorities among its citizens. It is therefore important to understand the factors that influence the employees' intention of using governmental information systems. With the aim of understanding the determining factors of using an Electronic Document Management System (EDMS) in the context of Portuguese municipalities, this study develops an empirical analysis using the Unified Theory of Acceptance and Use of Technology (UTAUT) model, (Venkatesh et al., 2003). This model's application for information systems research in the governmental context has a weak expression and is unique in EDMS research. This empirical research follows a realist and positivist approach. Data was collected from a survey answered by 2,175 employees of Portuguese municipalities (EDMS users). Partial Least Squares (PLS) was used to test the model proposed. The results showed that Intention to Use is positively affected by Performance Expectancy, Effort Expectancy, Social Influence and Facilitating Conditions. With respect to the EDMS Use, the results showed that it is positively influenced by Intention to Use and Facilitating Conditions. The main result indicates that EDMS users believe that the use of this information system will help them to obtain performance benefits in their work. However, the increasing use of EDMS is not very influenced by the system's perceived ease of use. In short, this study provides a contribution to the Information Systems Acceptance and Adoption literature in local eGovernmental contexts. In addition, our contribution empirically tests the model for implementation in governmental organizations and provides a better understanding of the adoption and use of an EDM

Evaluation of MODIS and VIIRS Cloud-Gap-Filled Snow-Cover Products for Production of an Earth Science Data Record

MODerate resolution Imaging Spectroradiometer (MODIS) cryosphere products have been available since 2000 following the 1999 launch of the Terra MODIS and the 2002 launch of the Aqua MODIS and include global snow-cover extent (SCE) (swath, daily, and 8 d composites) at 500 m and 5 km spatial resolutions. These products are used extensively in hydrological modeling and climate studies. Reprocessing of the complete snow-cover data record, from Collection 5 (C5) to Collection 6 (C6) and Collection 6.1 (C6.1), has provided improvements in the MODIS product suite. Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Collection 1 (C1) snow-cover products at a 375 m spatial resolution have been available since 2011 and are currently being reprocessed for Collection 2 (C2). Both the MODIS C6.1 and the VIIRS C2 products will be available for download from the National Snow and Ice Data Center beginning in early 2020 with the complete time series available in 2020. To address the need for a cloud-reduced or cloud-free daily SCE product for both MODIS and VIIRS, a daily cloud-gap-filled (CGF) snow-cover algorithm was developed for MODIS C6.1 and VIIRS C2 processing. MOD10A1F (Terra) and MYD10A1F (Aqua) are daily, 500 m resolution CGF SCE map products from MODIS. VNP10A1F is the daily, 375 m resolution CGF SCE map product from VIIRS. These CGF products include quality-assurance data such as cloud-persistence statistics showing the age of the observation in each pixel. The objective of this paper is to introduce the new MODIS and VIIRS standard CGF daily SCE products and to provide a preliminary evaluation of uncertainties in the gap-filling methodology so that the products can be used as the basis for a moderate-resolution Earth science data record (ESDR) of SCE. Time series of the MODIS and VIIRS CGF products have been developed and evaluated at selected study sites in the US and southern Canada. Observed differences, although small, are largely attributed to cloud masking and differences in the time of day of image acquisition. A nearly 3-month time-series comparison of Terra MODIS and S-NPP VIIRS CGF snow-cover maps for a large study area covering all or parts of 11 states in the western US and part of southwestern Canada reveals excellent correspondence between the Terra MODIS and S-NPP VIIRS products, with a mean difference of 11 070 sqkm, which is 0.45 % of the study area. According to our preliminary validation of the Terra and Aqua MODIS CGF SCE products in the western US study area, we found higher accuracy of the Terra product compared with the Aqua product. The MODIS CGF SCE data record beginning in 2000 has been extended into the VIIRS era, which should last at least through the early 2030s