פרסומים

In the framework of a private-value auction first-price, we consider the seller as a player in a game with the buyers in which he has private information about their realized values. We ask whether the seller can benefit by using his private information strategically. We find that in fact, depending upon his information, set of signals, and commitment power the seller may indeed increase his revenue by strategic transmission of his information. We study mainly the case of partial truthful commitment (VC) in which the seller can commit to send only truthful (verifiable) messages. We show that in the case of two buyers with values distributed independently uniformly on [0,1], a seller informed of the private values of the buyers, can achieve a revenue close to 1/2 by sending verifiable messages (compared to 1/3 in the standard auction), and this is the largest revenue that he can reach with any signaling strategy and any level of commitment. The case studied here provides valuable insight into the issue of strategic use of information which applies more generally.

ABSTRACTWhat role does news content play in explaining inter-party hostility? We argue that affective polarization is influenced by exposure to one of the most dominant ways to cover politics: strategy coverage. While previous studies have pointed to the negative consequences of covering politicians? strategies and campaign tactics, we find that this reporting style decreases out-party hostility. Our findings are based on two separate studies: (1) a survey experiment and (2) a cross-sectional analysis that increases external validity by combining survey data with computational content analysis of the articles respondents were exposed to by their primary news sources throughout the 2016 US presidential campaign (415,604 articles from 157 American news outlets). The results demonstrate that despite the wide criticism of the tendency of journalists to focus on political strategies, such coverage may ease inter-party tensions in American politics.

What role does news content play in explaining inter-party hostility? We argue that affective polarization is influenced by exposure to one of the most dominant ways to cover politics: strategy coverage. While previous studies have pointed to the negative consequences of covering politicians’ strategies and campaign tactics, we find that this reporting style decreases out-party hostility. Our findings are based on two separate studies: (1) a survey experiment and (2) a cross-sectional analysis that increases external validity by combining survey data with computational content analysis of the articles respondents were exposed to by their primary news sources throughout the 2016 US presidential campaign (415,604 articles from 157 American news outlets). The results demonstrate that despite the wide criticism of the tendency of journalists to focus on political strategies, such coverage may ease inter-party tensions in American politics.

Israeli agriculture has experienced rapid structural changes in recent decades, including the massive exit of farmers, a resulting increase in average farm size, a higher farm specialization and a higher reliance on non-farm income sources. The higher farm heterogeneity makes it necessary to examine changes in the entire farm size distribution rather than the common practice of analyzing changes in the average farm size alone. This article proposes a nonparametric analysis in which the change in the distribution of farm sizes between two periods is decomposed into several components, and the contributions of subgroups of farms to this change are analyzed. Using data on Israeli family farms, we analyze the changes in the farm size distribution in two separate time periods that are characterized by very different economic environments, focusing on the different contributions of full-time farms and part-time farms to the overall distributional changes. We found that between 1971 and 1981, a period characterized by stability and prosperity, the farm size distribution has shifted to the right with relatively minor changes in higher moments of the distribution. On the other hand, between 1981 and 1995, a largely unfavorable period to Israeli farmers, the change in the distribution was much more complex. While the overall change in the size distribution of farms was smaller in magnitude than in the earlier period, higher moments of the distribution were not less important than the increase in the mean and led to higher dispersion of farm sizes. Between 1971 and 1981, the contributions of full- and part-time farms to the change in the size distribution were quite similar. Between 1981 and 1995, however, full-time farms contributed mostly to the growth in the average farm size, while the average farm size among part-time farms actually decreased, and their contribution to the higher dispersion of farm sizes was quantitatively larger. This highlights the need to analyze the changes in the entire farm size distribution rather than focusing on the mean alone, and to allow for differences between types of farms.

The intrinsically disordered protein, α-synuclein, implicated in synaptic vesicle homeostasis and neurotransmitter release, is also associated with several neurodegenerative diseases. The different roles of α-synuclein are characterized by distinct structural states (membrane-bound, dimer, tetramer, oligomer, and fibril), which are originated from its various monomeric conformations. The pathological states, determined by the ensemble of α-synuclein monomer conformations and dynamic pathways of interconversion between dominant states, remain elusive due to their transient nature. Here, we use inter-dye distance distributions from bulk time-resolved Forster resonance energy transfer as restraints in discrete molecular dynamics simulations to map the conformational space of the α-synuclein monomer. We further confirm the generated conformational ensemble in orthogonal experiments utilizing far-UV circular dichroism and cross-linking mass spectrometry. Single-molecule protein-induced fluorescence enhancement measurements show that within this conformational ensemble, some of the conformations of α-synuclein are surprisingly stable, exhibiting conformational transitions slower than milliseconds. Our comprehensive analysis of the conformational ensemble reveals essential structural properties and potential conformations that promote its various functions in membrane interaction or oligomer and fibril formation.

Tubulin self-association is a critical process in microtubule dynamics. The early intermediate structures, energetics, and their regulation by fluxes of chemical energy, associated with guanosine triphosphate (GTP) hydrolysis, are poorly understood. We reconstituted an in vitro minimal model system, mimicking the key elements of the nontemplated tubulin assembly. To resolve the distribution of GTP- and guanosine diphosphate (GDP)-tubulin structures, at low temperatures (∼10 °C) and below the critical concentration for the microtubule assembly, we analyzed in-line size-exclusion chromatography-small-angle X-ray scattering (SEC-SAXS) chromatograms of GTP- and GDP-tubulin solutions. Both solutions rapidly attained steady state. The SEC-SAXS data were consistent with an isodesmic thermodynamic model of longitudinal tubulin self-association into 1D oligomers, terminated by the formation of tubulin single rings. The analysis showed that free dimers coexisted with tetramers and hexamers. Tubulin monomers and lateral association between dimers were not detected. The dimer-dimer longitudinal self-association standard Helmholtz free energies were -14.2 ± 0.4 k(B)T (-8.0 ± 0.2 kcal mol(-1)) and -13.1 ± 0.5 k(B)T (-7.4 ± 0.3 kcal mol(-1)) for GDP- and GTP-tubulin, respectively. We then determined the mass fractions of dimers, tetramers, and hexamers as a function of the total tubulin concentration. A small fraction of stable tubulin single rings, with a radius of 19.2 ± 0.2 nm, was detected in the GDP-tubulin solution. In the GTP-tubulin solution, this fraction was significantly lower. Cryo-TEM images and SEC-multiangle light-scattering analysis corroborated these findings. Our analyses provide an accurate structure-stability description of cold tubulin solutions.

Photosynthetic organisms have adapted to survive a myriad of extreme environments from the earth’s deserts to its poles, yet the proteins that carry out the light reactions of photosynthesis are highly conserved from the cyanobacteria to modern day crops. To investigate adaptations of the photosynthetic machinery in cyanobacteria to excessive light stress, we isolated a new strain of cyanobacteria, Cyanobacterium aponinum 0216, from the extreme light environment of the Sonoran Desert. Here we report the biochemical characterization and the 2.7 Å resolution structure of trimeric photosystem I from this high-light tolerant cyanobacterium. The structure shows a new conformation of the PsaL C-terminus that supports trimer formation of cyanobacterial photosystem I. The spectroscopic analysis of this photosystem I revealed a decrease in far-red absorption, which is attributed to a decrease in the number of long wavelength chlorophylls. Using these findings, we constructed two chimeric PSIs in Synechocystis sp. PCC 6803 demonstrating how unique structural features in photosynthetic complexes can change spectroscopic properties, allowing organisms to thrive under different environmental stresses.

Obesity is a global epidemic causing morbidity and impaired quality of life. The melanocortin receptor 4 (MC4R) is at the crux of appetite, energy homeostasis, and body-weight control in the central nervous system and is a prime target for anti-obesity drugs. Here, we present the cryo-EM structure of the human MC4R-Gs signaling complex bound to the agonist setmelanotide, a cyclic peptide recently approved for the treatment of obesity. The work reveals the mechanism of MC4R activation, highlighting a molecular switch that initiates satiation signaling. In addition, our findings indicate that Ca2+ is required for agonist but not antagonist efficacy. These results fill a gap in understanding MC4R activation and could guide the design of future weight management drugs.

Obesity is a global epidemic that causes morbidity and impaired quality of life. The melanocortin receptor 4 (MC4R) is at the crux of appetite, energy homeostasis, and body-weight control in the central nervous system and is a prime target for anti-obesity drugs. Here, we present the cryo-electron microscopy (cryo-EM) structure of the human MC4R-Gs signaling complex bound to the agonist setmelanotide, a cyclic peptide recently approved for the treatment of obesity. The work reveals the mechanism of MC4R activation, highlighting a molecular switch that initiates satiation signaling. In addition, our findings indicate that calcium (Ca2+) is required for agonist, but not antagonist, efficacy. These results fill a gap in the understanding of MC4R activation and could guide the design of future weight-management drugs.

Despite a myriad of available pharmacotherapies for the treatment of type 2 diabetes (T2D), challenges still exist in achieving glycemic control. Several novel glucose-lowering strategies are currently under clinical investigation, highlighting the need for more robust treatments. Previously, we have shown that suppressing peroxisome proliferator-activated receptor gamma coactivator 1-alpha activity with a small molecule (SR18292, ) can reduce glucose release from hepatocytes and ameliorate hyperglycemia in diabetic mouse models. Despite structural similarities in to known β-blockers, detailed structure-activity relationship studies described herein have led to the identification of analogues lacking β-adrenergic activity that still maintain the ability to suppress glucagon-induced glucose release from hepatocytes and ameliorate hyperglycemia in diabetic mouse models. Hence, these compounds exert their biological effects in a mechanism that does not include adrenergic signaling. These probe molecules may lead to a new therapeutic approach to treat T2D either as a single agent or in combination therapy.

 Despite visions of social network technology (SNT) for collaborative knowledge construction, recent research in secondary schools suggest that students use these tools mainly for knowledge sharing of study-related artifacts. We extend these findings to higher education settings and report on two survey studies that map characteristics of students’ self-directed use of SNTs for study purposes, in undergraduate university programs (N = 264) and teacher training colleges (N = 449). The combined findings confirm that students use SNTs extensively for uploading, linking and downloading study-related artifacts in peer-directed SNT groups. They regard these practices positively and believe they improve academic achievements. Sharing was predicted by positive attitudes toward sharing and collectivist value orientations, motivated overall by prosocial reasons and less frequent in competitive study programs. Use of shared materials was associated with performance-avoidance achievement goals and lower GPA. Findings, directions for future research and implications are discussed in the context of learning theories, as well the knowledge sharing literature. 

Recent approaches in the research on walkable environments and wellbeing go beyond correlational analysis to consider the specific characteristics of individuals and their interaction with the immediate environment. Accordingly, a need has been accentuated for new human-centered methods to improve our understanding of the mechanisms underlying environmental effects on walking and consequently on wellbeing. Immersive virtual environments (IVEs) were suggested as a potential method that can advance this type of research as they offer a unique combination between controlled experimental environments that allow drawing causal conclusions and a high level of environmental realism that supports ecological validity. The current study pilot tested a walking simulator with additional sensor technologies, including biosensors, eye tracking and gait sensors. Results found IVEs to facilitate extremely high tempo-spatial-resolution measurement of physical walking parameters (e.g., speed, number of gaits) along with walking experience and wellbeing (e.g., electrodermal activity, heartrate). This level of resolution is useful in linking specific environmental stimuli to the psychophysiological and behavioral reactions, which cannot be obtained in real-world and self-report research designs. A set of guidelines for implementing IVE technology for research is suggested in order to standardize its use and allow new researchers to engage with this emerging field of research.

Recent approaches in the research on walkable environments and wellbeing go beyond correlational analysis to consider the specific characteristics of individuals and their interaction with the immediate environment. Accordingly, a need has been accentuated for new human-centered methods to improve our understanding of the mechanisms underlying environmental effects on walking and consequently on wellbeing. Immersive virtual environments (IVEs) were suggested as a potential method that can advance this type of research as they offer a unique combination between controlled experimental environments that allow drawing causal conclusions and a high level of environmental realism that supports ecological validity. The current study pilot tested a walking simulator with additional sensor technologies, including biosensors, eye tracking and gait sensors. Results found IVEs to facilitate extremely high tempo-spatial-resolution measurement of physical walking parameters (e.g., speed, number of gaits) along with walking experience and wellbeing (e.g., electrodermal activity, heartrate). This level of resolution is useful in linking specific environmental stimuli to the psychophysiological and behavioral reactions, which cannot be obtained in real-world and self-report research designs. A set of guidelines for implementing IVE technology for research is suggested in order to standardize its use and allow new researchers to engage with this emerging field of research.

Recent approaches in the research on walkable environments and wellbeing go beyond correlational analysis to consider the specific characteristics of individuals and their interaction with the immediate environment. Accordingly, a need has been accentuated for new human-centered methods to improve our understanding of the mechanisms underlying environmental effects on walking and consequently on wellbeing. Immersive virtual environments (IVEs) were suggested as a potential method that can advance this type of research as they offer a unique combination between controlled experimental environments that allow drawing causal conclusions and a high level of environmental realism that supports ecological validity. The current study pilot tested a walking simulator with additional sensor technologies, including biosensors, eye tracking and gait sensors. Results found IVEs to facilitate extremely high tempo-spatial-resolution measurement of physical walking parameters (e.g., speed, number of gaits) along with walking experience and wellbeing (e.g., electrodermal activity, heartrate). This level of resolution is useful in linking specific environmental stimuli to the psychophysiological and behavioral reactions, which cannot be obtained in real-world and self-report research designs. A set of guidelines for implementing IVE technology for research is suggested in order to standardize its use and allow new researchers to engage with this emerging field of research.