Job security and long-term investment: an experimental analysis

We investigate an experimental labor market setting in which we introduce the novel aspect that workers have the chance of investing money in a long-term project in order to increase their income. We find a strong relationship between what happens inside the labor market (worker's performance) and what happens outside the labor market (long-term investment). Contrary to the theoretical predictions with selfish preferences, we find that the mere presence of long-term projects acts as an effort-enforcement device; this effect seems to be driven by an increase in long-term employment relationships. In the other direction, long-term labor relationships seem to provide a safer environment for undertaking successful long-term projects. This article also considers three different types of experimental labor contracts. We find that performance-based dismissal barriers, whereby firms are required to retain workers if they have satisfied the effort level required by firms, lead to more long-term employment relationships and higher overall productivity. As theory predicts, the presence of renewable dismissal barriers makes it likely that workers will provide the desired effort level. Firms appear to correctly anticipate this, leading to greater social efficiency

High-pressure structural investigation of several zircon-type orthovanadates

Room temperature angle-dispersive x-ray diffraction measurements on zircon-type EuVO4, LuVO4, and ScVO4 were performed up to 27 GPa. In the three compounds we found evidence of a pressure-induced structural phase transformation from zircon to a scheelite-type structure. The onset of the transition is near 8 GPa, but the transition is sluggish and the low- and high-pressure phases coexist in a pressure range of about 10 GPa. In EuVO4 and LuVO4 a second transition to a M-fergusonite-type phase was found near 21 GPa. The equations of state for the zircon and scheelite phases are also determined. Among the three studied compounds, we found that ScVO4 is less compressible than EuVO4 and LuVO4, being the most incompressible orthovanadate studied to date. The sequence of structural transitions and compressibilities are discussed in comparison with other zircon-type oxides.Comment: 34 pages, 2 Tables, 11 Figure

First-order phase transition in a 2D random-field Ising model with conflicting dynamics

The effects of locally random magnetic fields are considered in a nonequilibrium Ising model defined on a square lattice with nearest-neighbors interactions. In order to generate the random magnetic fields, we have considered random variables $\{h\}$ that change randomly with time according to a double-gaussian probability distribution, which consists of two single gaussian distributions, centered at $+h_{o}$ and $-h_{o}$, with the same width $\sigma$. This distribution is very general, and can recover in appropriate limits the bimodal distribution ($\sigma\to 0$) and the single gaussian one ($ho=0$). We performed Monte Carlo simulations in lattices with linear sizes in the range $L=32 - 512$. The system exhibits ferromagnetic and paramagnetic steady states. Our results suggest the occurence of first-order phase transitions between the above-mentioned phases at low temperatures and large random-field intensities $h_{o}$, for some small values of the width $\sigma$. By means of finite size scaling, we estimate the critical exponents in the low-field region, where we have continuous phase transitions. In addition, we show a sketch of the phase diagram of the model for some values of $\sigma$.Comment: 13 pages, 9 figures, accepted for publication in JSTA

High-pressure stability and compressibility of APO4 (A = La, Nd, Eu, Gd, Er, and Y) orthoposphates: A synchrotron powder x-ray diffraction study

Room temperature angle-dispersive x-ray diffraction measurements on zircon-type YPO4 and ErPO4, and monazite-type GdPO4, EuPO4, NdPO4, and LaPO4 were performed in a diamond-anvil cell up to 27 GPa using neon as pressure-transmitting medium. In the zircon-structured oxides we found evidence of a reversible pressure-induced structural phase transformation from zircon to a monazite-type structure. The onset of the transition is near 17-20 GPa. In LaPO4 a non-reversible transition is found around 26 GPa, being a barite-type structure proposed for the high-pressure phase. In the other three monazites, this structure is found to be stable up to highest pressure reached in the experiments. No additional phase transitions or evidences of chemical decomposition are found in the experiments. The equations of state and axial compressibility for the different phases are also determined. In particular, we found that in a given compound the monazite structure is less compressible than zircon structure, being this fact related to the larger packing efficiency of monazite compared with zircon. The differential bond compressibility of different polyhedra is also reported and related the anisotropic compressibility of both structures. Finally, the sequence of structural transitions and compressibilities are discussed in comparison with other orhtophosphates.Comment: 38 pages, 10 figures, 2 table

Complex high-pressure polymorphism of barium tungstate

We have studied BaWO 4 under compression at room temperature by means of x-ray diffraction and Raman spectroscopy. When compressed with neon as a pressure-transmitting medium (quasihydrostatic conditions), we found that BaWO 4 transforms from its low-pressure tetragonal structure into a much denser monoclinic structure. This result confirms our previous theoretical prediction based on ab initio calculations that the scheelite to BaWO 4-II transition occurs at room temperature if kinetic barriers are suppressed by pressure. However, our experiment without any pressure- transmitting medium has resulted in a phase transition to a completely different structure, suggesting nonhydrostaticity may be responsible for previously reported rich polymorphism in BaWO 4. The crystal structure of the low- and high-pressure phases from the quasihydrostatic experiments has been Rietveld refined. Additionally, for the tetragonal phase the effects of pressure on the unit-cell volume and lattice parameters are discussed. Finally, the pressure evolution of the Raman modes of different phases is reported and compared with previous studies. © 2012 American Physical Society.This research was supported by Spanish MEC (Grant No. MAT2010-21270-C04-01/04), MALTA Consolider Ingenio 2010 (Grant No. CSD2007-00045), and Vicerrectorado de Investigacion y Desarrollo of the Universitat Politecnica de Valencia (Grants No. UPV2011-0914 PAID-05-11 and No. UPV2011-0966 PAID-06-11). XRD data were collected at HPCAT, Advanced Photon Source (APS), Argonne National Laboratory. HPCAT is supported by CIW, CDAC, UNLV, and LLNL through funding from DOE-NNSA, DOE-BES, and NSF. APS is supported by DOE-BES under Contract No. DEAC02-06CH11357.Gomis Hilario, O.; Sans, JA.; Lacomba-Perales, R.; Errandonea, D.; Meng, Y.; Chervin, JC.; Polian, A. (2012). Complex high-pressure polymorphism of barium tungstate. 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The development of social preferences

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordThis paper examines how social preferences develop with age. This is done using a range of mini-dictator games from which we classify 665 subjects into a variety of behavioural types. We expand on previous developmental studies of pro-sociality and parochialism by analysing individuals aged 9–67, and by employing a cross country study where participants from Spain interact with participants from different ethnic groups (Arab, East Asian, Black and White) belonging to different countries (Morocco, China, Senegal and Spain). We identify a ‘U-shaped’ relationship between age and egalitarianism that had previously gone unnoticed, and appeared linear. An inverse “U-shaped” relationship is found to be true for altruism. A gender differential is found to emerge in teenage years, with females becoming less altruistic but more egalitarian than males. In contrast to the majority of previous economic studies of the development of social preferences, we report evidence of increased altruism, and decreased egalitarianism and spite expressed towards black individuals from Senegal

Energy levels of periodic solutions of the circular 2+2 Sitnikov problem

We study a 2+2 body problem introduced in a previous paper as the circular double Sitnikov problem. Since the secondary bodies are moving on the same perpendicular line where evolve the primaries, almost every solution is a collision orbit. We extend the solutions beyond collisions with a symplectic regularization and study the set of energy surfaces that contain periodic orbits and their foliations .Comment: 20 pages, 5 figures. This is not the final version

A combined high-pressure experimental and theoretical study of the electronic band-structure of scheelite-type AWO4 (A = Ca, Sr, Ba, Pb) compounds

The optical-absorption edge of single crystals of CaWO4, SrWO4, BaWO4, and PbWO4 has been measured under high pressure up to ~20 GPa at room temperature. From the measurements we have obtained the evolution of the band-gap energy with pressure. We found a low-pressure range (up to 7-10 GPa) where alkaline-earth tungstates present a very small Eg pressure dependence (-2.1 < dEg/dP < 8.9 meV/GPa). In contrast, in the same pressure range, PbWO4 has a pressure coefficient of -62 meV/GPa. The high-pressure range is characterized in the four compounds by an abrupt decrease of Eg followed by changes in dEg/dP. The band-gap collapse is larger than 1.2 eV in BaWO4. We also calculated the electronic-band structures and their pressure evolution. Calculations allow us to interpret experiments considering the different electronic configuration of divalent metals. Changes in the pressure evolution of Eg are correlated with the occurrence of pressure-induced phase transitions. The band structures for the low- and high-pressure phases are also reported. No metallization of any of the compounds is detected in experiments nor is predicted by calculations.Comment: 26 pages, 1 table, 6 figure