The main mechanism of the dielectric relaxation process of ordinary hexagonal ice (ice I-h) and its temperature dependence remains unclear. The most interesting and as yet unexplained feature of ice is the presence of the dynamical crossover in relaxation time behavior around T-c = 230 +/- 3 K. Since there are no phase transitions in the ice at this temperature (first or second order), we cannot correlate the origin of this crossover with any structural change. Here we present a model according to which the temperature of the crossover is defined by the polarization mechanism. The dielectric relaxation driven by the diffusion of L-D orientational Bjerrum defects (at high temperature, T > T-c) is transformed into a dielectric relaxation dominated by the diffusion of intrinsic ionic H3O+/OH- defects (at low temperature, T < T-c). In the framework of the model, we propose an analytical equation for the complex dielectric permittivity that takes into account the contribution of both types of defects.
There are several approximations to the exchange-correlation functional in density-functional theory, which accurately predict total energy-related properties of many-electron systems, such as binding energies, bond lengths, and crystal structures. Other approximations are designed to describe potential-related processes, such as charge transfer and photoemission. However, the development of a functional which can serve the two purposes simultaneously is a long-standing challenge. Trying to address it, we employ in the current work the ensemble generalization procedure proposed by Kraisler and Kronik [Phys. Rev. Lett. 110, 126403 (2013)]. Focusing on the prediction of the ionization potential via the highest occupied Kohn-Sham eigenvalue, we examine a variety of exchange-correlation approximations: the local spin-density approximation, semi-local generalized gradient approximations, and global and local hybrid functionals. Results for a test set of 26 diatomic molecules and single atoms are presented. We find that the aforementioned ensemble generalization systematically improves the prediction of the ionization potential, for various systems and exchange-correlation functionals, without compromising the accuracy of total energy-related properties. We specifically examine hybrid functionals. These depend on a parameter controlling the ratio of semi-local to non-local functional components. The ionization potential obtained with ensemble-generalized functionals is found to depend only weakly on the parameter value, contrary to common experience with non-generalized hybrids, thus eliminating one aspect of the so-called “parameter dilemma” of hybrid functionals.
Establishment of seedlings is a key factor in achievement of uniform field stands and, consequently, stable yields. Under Mediterranean conditions, soil moisture in the upper layer is limited and seedlings may be exposed to frequent dehydration events. The presence of the Reduced height (Rht)-B1b and Rht-D1b semi-dominant dwarfing alleles results in insensitivity to gibberellin (GAI) and, hence, poor emergence from deep sowing. Introduction of alternative dwarfing genes and, thereby, preservation of the gibberellin response (GAR) and coleoptile length, contributes to better emergence from deep sowing. Initially 47 wheat cultivars carrying different Rht alleles were screened for their ability to emerge from deep sowing, and then 17 of them were selected for detailed physiological characterization in the field. The modern wheat lines containing GAI alleles showed significantly lower percentages of emergence from deep sowing than the GAR lines, i.e., 52 and 74%, respectively. Differences in early developmental stages were associated with grain yield, as indicated by a reduction of 37.3% in the modern GAI cultivars. Our results demonstrate the potential of alternative dwarfing genes for improving seedling establishment and grain yields in Mediterranean-like environments.
This paper shows that cultural and material threats exist side by side, serving different psychological functions, and that they manifest in differential attitudes towards immigrants from different ethnic or racial origins. While culturally threatened individuals prefer immigrants akin to themselves, as opposed to those from different races and cultures, the materially threatened prefer immigrants who are different from themselves who can be expected not to compete for the same resources. We test our hypotheses using multilevel structural equation modelling, based on data from twenty countries in the 2002 wave of the European Social Survey. The disaggregation of these two types of perceived threat reveals responsiveness to the race of immigrants that is otherwise masked by pooling the two threat dimensions.
[Correction Notice: An Erratum for this article was reported in Vol 2(2) of Decision (see record 2015-14395-002). There was an error in the second paragraph of page 4, in the equation for the case of n = 2. The correct sentence is provided.] Probability estimation is an essential cognitive function in perception, motor control, and decision making. Many studies have shown that when making decisions in a stochastic operant conditioning task, people and animals behave as if they underestimate the probability of rare events. It is commonly assumed that this behavior is a natural consequence of estimating a probability from a small sample, also known as sampling bias. The objective of this article is to challenge this common lore. We show that, in fact, probabilities estimated from a small sample can lead to behaviors that will be interpreted as underestimating or as overestimating the probability of rare events, depending on the cognitive strategy used. Moreover, this sampling bias hypothesis makes an implausible prediction that minute differences in the values of the sample size or the underlying probability will determine whether rare events will be underweighted or overweighed. We discuss the implications of this sensitivity for the design and interpretation of experiments. Finally, we propose an alternative sequential learning model with a resetting of initial conditions for probability estimation and show that this model predicts the experimentally observed robust underweighting of rare events. (PsycINFO Database Record (c) 2016 APA, all rights reserved)
Probability estimation is an essential cognitive function in perception, motor control, and decision making. Many studies have shown that when making decisions in a stochastic operant conditioning task, people and animals behave as if they underestimatethe probability of rare events. It is commonly assumed that this behavior is a natural consequence of estimating a probability from a small sample, also known as sampling bias. The objective of this paper is to challenge this common lore. We show that in fact, probabilities estimated from a small sample can lead to behaviors that will be interpreted as underestimatingor as overestimating the probability of rare events, depending on the cognitive strategy used. Moreover, this sampling bias hypothesis makes an implausible prediction that minute differences in the values of the sample size or the underlying probability will determine whether rare events will be underweighted or overweighed. We discuss the implications of this sensitivity for the design and interpretation of experiments. Finally, we propose an alternative sequential learning model with a resetting of initial conditions for probability estimation and show that this model predicts the experimentally-observed robust underweighting of rare events.
Hybrid semiconductor–metal nanoparticles are interesting materials for use as photocatalysts due to their tunable properties and chemical processibility. Their function in the evolution of hydrogen in photocatalytic water splitting is the subject of intense current investigation. Here, the effects of the surface coatings on the photocatalytic function are studied, with Au‐tipped CdS nanorods as a model hybrid nanoparticle system. Kinetic measurements of the hydrogen evolution rate following photocatalytic water reduction are performed on similar nanoparticles but with different surface coatings, including various types of thiolated alkyl ligands and different polymer coatings. The apparent hydrogen evolution quantum yields are found to strongly depend on the surface coating. The lowest yields are observed for thiolated alkyl ligands. Intermediate values are obtained with L‐glutathione and poly(styrene‐co ‐maleic anhydride) polymer coatings. The highest efficiency is obtained for polyethylenimine (PEI) polymer coating. These pronounced differences in the photocatalytic efficiencies are correlated with ultrafast transient absorption spectroscopy measurements, which show a faster bleach recovery for the PEI‐coated hybrid nanoparticles, consistent with faster and more efficient charge separation. These differences are primarily attributed to the effects of surface passivation by the different coatings affecting the surface trapping of charge carriers that compete with effective charge separation required for the photocatalysis. Further support of this assignment is provided from steady‐state emission and time‐resolved spectral measurements, performed on related strongly fluorescing CdSe/CdS nanorods. The control and understanding of the effect of the surface coating of the hybrid nanosystems on the photocatalytic processes is of importance for the potential application of hybrid nanoparticles as photocatalysts.
"הטיית השיפוט בדיעבד" מוגדרת כתופעה פסיכולוגית שבה פרטים מעריכים יתר על המידה את ההסתברות שהיו מעניקים להתרחשות תוצאה מסוימת של אירוע, לאחר היוודע להם שתרחיש זה אכן התקיים ואחרי שעמדו על תוצאותיו. הספרות המחקרית עשירה בהוכחות לקיומה של תופעה זו, ולפיכך במאמר זה נבחן סוגיה זו מזווית אחרת, אשר למיטב ידיעתנו טרם נבחנה: כיצד אדם הנמצא בעמדת שיפוט בדיעבד משפיע על אופן קבלת ההחלטות אצל גורם אחר הנתון לשיפוט זה? כלומר האם הגורם הנמצא בעמדת קבלת החלטות מושפע מכך שגורם השופט אותו עושה זאת לאחר היוודע לו תוצאות החלטותיו? חשיבותו של מחקר זו טמונה בכך שהשפעה ממשית של תופעה זו על מקבלי החלטות עשויה להביא לפגיעה בשיקוליהם המקצועיים והענייניים ולגרום לכך שהרצון להימנע מנשיאה באשמה יהיה שיקול מרכזי בהכרעתם.
במסגרת מחקר זה ערכנו ניסוי פרטני בקרב 81 סטודנטים, אשר בחן את נטייתם של הנבדקים לסיכון או לשמרנות בבחירותיהם כאשר הם נתונים לשיפוט בדיעבד.
תוצאות המחקר מלמדות כי אנשים הנתונים לשיפוטו של אדם בעל ידע בדיעבד על תוצאות החלטותיהם נוטים להירתע מסיכון יותר מאלה הנתונים לשיפוטו של אדם אשר אינו חשוף לידע זה במסגרת שיפוטו. למסקנה זו השלכה ישירה על תהליכי קבלת החלטות בכלל ועל תחום המדיניות הציבורית בפרט.
Polyacrylonitrile?phenolic composites display excellent in-plane properties but perform poorly when out-of-plane, through-thickness properties are considered. Composite architectures with carbon nanotubes, either dispersed within the matrix or bound to a fabric, in traditional composites have the potential to alleviate this weakness. However, effective reinforcement of composites using carbon nanotubes is difficult, due to poor dispersion and interfacial stress transfer and has thus far been met with limited success and at high costs. This paper describes an innovative and cost-effective technology to improve these inferior mechanical properties by using an exceptionally stable protein, SP1, for CNT attachment to PAN fabric, forming a three-dimensional nano-reinforced structure. This work confirms remarkable improvements in interlaminar shear strength and through-thickness tensile strength of SP1/CNT-reinforced polyacrylonitrile composites.
Frank Kammerzell. 2015. “Egyptian Verb Classifiers”. בתוך Proceedings Of The Xth International Congress Of Egyptologists, Rhodes May 22-29, 2008, Pp. 1395-1416. Leuven: Peeters.
There are several approximations to the exchange-correlation functional in density-functional theory, which accurately predict total energy-related properties of many-electron systems, such as binding energies, bond lengths, and crystal structures. Other approximations are designed to describe potential-related processes, such as charge transfer and photoemission. However, the development of a functional which can serve the two purposes simultaneously is a long-standing challenge. Trying to address it, we employ in the current work the ensemble generalization procedure proposed by Kraisler and Kronik [Phys. Rev. Lett. 110, 126403 (2013)]. Focusing on the prediction of the ionization potential via the highest occupied Kohn-Sham eigenvalue, we examine a variety of exchange-correlation approximations: the local spin-density approximation, semi-local generalized gradient approximations, and global and local hybrid functionals. Results for a test set of 26 diatomic molecules and single atoms are presented. We find that the aforementioned ensemble generalization systematically improves the prediction of the ionization potential, for various systems and exchange-correlation functionals, without compromising the accuracy of total energy-related properties. We specifically examine hybrid functionals. These depend on a parameter controlling the ratio of semi-local to non-local functional components. The ionization potential obtained with ensemble-generalized functionals is found to depend only weakly on the parameter value, contrary to common experience with non-generalized hybrids, thus eliminating one aspect of the so-called “parameter dilemma” of hybrid functionals.
