High ZT of 1.34 at 766 K and a record high average ZT above 1 in the temperature range of 300-864 K are attained in n-type PbTe by engineering the temperature-dependent carrier concentration and weakening electron–phonon coupling upon Ga doping. The experimental studies and first principles band structure calculations show that doping with Ga introduces a shallow level impurity contributing extrinsic carriers and imparts a deeper impurity level that ionizes at higher temperatures. This adjusts the carrier concentration closer to the temperature-dependent optimum and thus maximizes the power factor in a wide temperature range. The maximum power factor of 35 µW cm−1 K−2 is achieved for the Pb0.98Ga0.02Te compound, and is maintained over 20 µWcm−1 K−2 from 300 to 767 K. Band structure calculations and X-ray photoelectron spectroscopy corroborate the amphoteric role of Ga in PbTe as the origin of shallow and deep levels. Additionally, Ga doping weakens the electron–phonon coupling, leading to high carrier mobilities in excess of 1200 cm2 V−1 s−1. Enhanced point defect phonon scattering yields a reduced lattice thermal conductivity. This work provides a new avenue, beyond the conventional shallow level doping, for further improving the average ZT in thermoelectric materials.
Deborah Golden, Erdreich, Lauren , Roberman, Sveta , Golden, Deborah , Erdreich, Lauren , ו Roberman, Sveta . 2018. “The ‘Well-Invested’child”. Mothering, Education And Culture: Russian, Palestinian And Jewish Middle-Class Mothers In Israeli Society, Pp. 63–103.
In economies with multi-level governments, why would a change in the fiscal rule of a government in one level lead to a fiscal response by a government in a different level? The literature focused primarily on the standard common-pool problem, while giving little attention to the potential role of complementarity or substitutability (CS) between the public goods supplied by the two governments. This paper fills this gap by focusing on the latter channel. First, we illustrate its potential key role in determining the sign of the vertical reaction through a generic model of vertical fiscal interactions. Second, we propose a novel strategy for identifying it, by considering an empirical design that confines the common-pool channel to specific locations. We implement this design through a quasi-natural experiment: the 1980 U.S. Crude Oil Windfall Act, which increased federal tax collections from sale of crude oil, thereby affecting the tax base of oil rich states specifically. This latter feature enables attributing the vertical fiscal reactions of the remaining states to the CS channel. Following this strategy, via a difference-in-differences approach, we decompose the sources of the vertical fiscal reactions arising from this federal tax change and find that those attributed to the CS channel: (i) account for approximately 38% of the overall vertical fiscal response; (ii) point at complementarity between state and federal public goods, most notably in transportation and welfare expenditures; (iii) are manifested primarily via changes in states' sales and income taxation.
The quantification of household food waste is an essential part of setting policies and waste reduction goals, but it is very difficult to estimate. Current methods include either direct measurements (physical waste surveys) or measurements based on self-reports (diaries, interviews, and questionnaires). The main limitation of the first method is that it cannot always trace the waste source, i.e., an individual household, whereas the second method lacks objectivity. This article presents a new measurement method that offers a solution to these challenges by measuring daily produced food waste at the household level. This method is based on four main principles: (1) capturing waste as it enters the stream, (2) collecting waste samples at the doorstep, (3) using the individual household as the sampling unit, and (4) collecting and sorting waste daily. We tested the feasibility of the new method with an empirical study of 192 households, measuring the actual amounts of food waste from households as well as its composition. Household food waste accounted for 45% of total waste (573 g/day per capita), of which 54% was identified as avoidable. Approximately two thirds of avoidable waste consisted of vegetables and fruit. These results are similar to previous findings from waste surveys, yet the new method showed a higher level of accuracy. The feasibility test suggests that the proposed method provides a practical tool for policy makers for setting policy based on reliable empirical data and monitoring the effectiveness of different policies over time.
Some have argued that stigmatization of individuals with intellectual disabilities may be rooted in the terms used to describe the condition, others have maintained that stigma may be inherent in the condition itself, not in the label used. This study took advantage of a recent change in terminology introduced in Israel to examine differences in stigma attached to the term intellectual disability in comparison with the previous term, mental retardation. An online questionnaire, based on the Multidimensional Attitudes Scale (Findler, Vilchinsky, & Werner, 2007), was completed by 226 lay persons. Participants were presented with a questionnaire using either the term intellectual disability or mental retardation and asked to report on stereotypes, prejudice, and discrimination in response to a vignette. Moderate levels of stigma were found. An indirect effect was found between dangerousness and withdrawal behavior mediated by negative affect, and between low ability and withdrawal behavior mediated by negative affect. The term used was not found to be associated with stigma. It is possible that previous stigma attached to the term, mental retardation, was transferred to the new term, intellectual disability.
Aim/PurposeIn this paper, we analyze the phenomenon of "classroom WhatsApp groups", in which a teacher and students from a particular classroom interact with one another, while specifically focusing on the student perspective of these interactions.BackgroundThe instant messaging application WhatsApp enables quick, interactive multimedia communication in closed groups, as well as one-on-one interactions between selected group members. Yet, very little is known about the extent, nature and purposes of these practices, the limitations and affordances, the type of discourse and conflicts that develop in these spaces, and the extent to which it affects teacher-student interactions outside of WhatsApp (e.g., the social climate in class, the teacher’s status, teacher-student and student-student relations), especially from the students’ perspective.MethodologyOur methodology combines questionnaires, personal interviews and focus groups with Israeli secondary school students (N = 88).ContributionThe present study adds to the expanding body of empirical research on social media use in educational settings by specifically focusing on a heretofore underexposed aspect, namely secondary school student-teacher communication in the popular instant messaging application WhatsApp. We report on findings from the student perspective and discuss the advantages and limitations of this form of communication sphere, and on the social functions of the different classroom WhatsApp groups in secondary school students’ everyday life.FindingsThe combined findings reveal that classroom WhatsApp groups have become a central channel of communication for school-related topics. It is used primarily for organizational purposes (sending and receiving updates and managing learning activities), as well as a means for teachers to enforce discipline. Students mentioned many advantages of WhatsApp communication, such as easy access, the ability to create communities, the ability to safeguard personal privacy, and the communication format (written, mediated, personal or group). However, they also recognized limitations (i.e., communication overload) and challenged teacher ability to monitor and affect student interactions in social media, even when they are present in these WhatsApp classroom groups. Finally, we report on the role of parallel, sans-teacher WhatsApp groups, which are characterized as back stage discourse arenas that accompany the front stage offline classroom activities and the ”official” classroom WhatsApp group.Recommendationsfor PractitionersThe combined findings of this study indicate how WhatsApp-based, joint teacher-student groups can serve a variety of educational purposes, namely organizational, instructional, and educational-disciplinary. In addition, and in spite of teachers concerns, students are aware of the challenges inherent to the use of WhatsApp for communication with their teachers. Some of the main characteristics that prevent teachers from using other ubiquitous digital communication media, such as Facebook or Twitter, are not relevant when it comes to WhatsApp. Both teachers and students view WhatsApp as a favored channel of communication, because of the low exposure to personal information and minimal invasion of privacy.Future ResearchThe qualitative methodology of this paper limits the ability to generalize the current findings to other contexts and population groups. Future research should preferably explore the generalizability of our findings to larger sections of teenage populations. It should also explore similarities and differences with other age groups. Finally, the present study was set in a particular country (Israel). Local norms of cellphone use and of appropriate teacher-student interaction, as well as locally developed media domestication patterns may differ from country to country and/or from one cultural group to another. Future research should then include and compare the current findings with data from different countries and cultures in order to complete the picture.
Given that their main function is to forge durable commitments, it is notable that many international treaties change over time through the practice of renegotiation. While some agreements have remained intact after their initial conclusion, others are amended, updated, or replaced. Why are some international agreements renegotiated while others remain stable? This paper offers a systematic analysis of treaty renegotiation by presenting theoretical propositions and testing them in the context of bilateral investment treaties (BITs). We argue that states renegotiate when they learn new information about the legal and political consequences of their treaty commitments, and that such learning is most likely to take place when states are involved in investor-state dispute settlement cases. Employing an original data set on renegotiated BITs, we find robust empirical support for the learning argument. We conclude by discussing implications for the study of institutional change and the evolving investment regime.
Claims and accusations of political bias are common in many countries. The essence of such claims is a denunciation of alleged violations of political neutrality in the context of media coverage, legal and bureaucratic decisions, academic teaching etc. Yet the acts and messages that give rise to such claims are also embedded within a context of intergroup competition. Thus, in evaluating the seriousness of, and the need for taking a corrective action in reaction to a purported politically biased act people may consider both the alleged normative violation and the political implications of the act/message for the evaluator’s ingroup. The question thus arises whether partisans react similarly to ingroup-aiding and ingroup-harming actions or messages which they perceive as politically biased. In three separate studies, conducted in two countries, we show that political considerations strongly affect partisans’ reactions to actions and messages that they perceive as politically biased. Namely, ingroup-harming biased messages/acts are considered more serious and are more likely to warrant corrective action in comparison to ingroup-aiding biased messages/acts. We conclude by discussing the implications of these findings for the implementations of measures intended for correcting and preventing biases, and for the nature of conflict and competition between rival political groups.
