Universal long-time behavior of nuclear spin decays in a solid

Journal ArticleMagnetic resonance studies of nuclear spins in solids are exceptionally well suited to probe the limits of statistical physics. We report experimental results indicating that isolated macroscopic systems of interacting nuclear spins possess the following fundamental property: spin decays that start from different initial configurations quickly evolve towards the same long-time behavior. This long-time behavior is characterized by the shortest ballistic microscopic time scale of the system and therefore falls outside of the validity range for conventional approximations of statistical physics. We find that the nuclear free-induction decay and different solid echoes in hyperpolarized solid xenon all exhibit sinusoidally modulated exponential long-time behavior characterized by identical time constants. This universality was previously predicted on the basis of analogy with resonances in classical chaotic systems

Wetting and Growth Behaviors in Adsorbed Systems with Long-Range Forces

The growth and possible wetting behaviors of an adsorbed film are studied employing a solid-on-solid model in the presence of a hard wall and external potential V(h) which is of long range. The model is analyzed with the use of position-space renormalization-group methods within the Migdal approximation. The existence of wetting transitions and their nature depends on the asymptotic behavior of V(h) at large distances. We find that critical wetting cannot take place in this model. From what is known of V(h), we conclude that wetting can be observed only along the gas-liquid phase boundary; however, first-order transitions between thin and thick films, which may be experimentally difficult to distinguish from wetting, can be observed along any phase boundary. The nature of the global phase diagram depends on the form of V(h) and several general behaviors are presented. In particular, in the layering subregime we find that the limit of layering critical points is indeed the bulk roughening temperature as had been suggested by de Oliveira and Griffiths. The scaling of these layering critical points is given explicitly

Analytical Investigation of Innovation Dynamics Considering Stochasticity in the Evaluation of Fitness

We investigate a selection-mutation model for the dynamics of technological innovation,a special case of reaction-diffusion equations. Although mutations are assumed to increase the variety of technologies, not their average success ("fitness"), they are an essential prerequisite for innovation. Together with a selection of above-average technologies due to imitation behavior, they are the "driving force" for the continuous increase in fitness. We will give analytical solutions for the probability distribution of technologies for special cases and in the limit of large times. The selection dynamics is modelled by a "proportional imitation" of better technologies. However, the assessment of a technology's fitness may be imperfect and, therefore, vary stochastically. We will derive conditions, under which wrong assessment of fitness can accelerate the innovation dynamics, as it has been found in some surprising numerical investigations.Comment: For related work see http://www.helbing.or

Analisis Perilaku Agresif Siswa Ditinjau dari Aspek Tingkat Pendidikan, Ekonomi, Pekerjaan Orang Tua Siswa Dismpn 4 Pekanbaru

At school, most teens showed a negative behavior, one of which is aggressive behavior, which is an act of deliberate on other people, causing physical and psychological pain on other people. While the things that affect aggressive behavior can come from parents, among others, the level of education, the economy and the job of parents. The objectives of this research are: 1) to obtain an image of aggressive behavior of students in terms of parental education level, 2) to obtain an image of aggressive behavior of students in terms of parent economy, and 3) to obtain a picture of aggressive behavior of students in terms of parent work. The population of this study is all students of class VIII in SMPN 4 Pekanbaru consisting of 10 classes. A sample of 144 students. This research is a quantitative study with descriptive approach surve. Instrument data collection using a questionnaire which is then analyzed by grouping data and calculating the percentage. the results of this research are: 1) The dominant student behavior is very aggressive of his parents with high education (7.6%). The student's aggressive behavior is highly educated (64.6%). While the behavior of students who are not aggressive parents are highly educated (0.7%). 2) dominant student behavior is very aggressive parent at middle economic level equal to (6.2%). The aggressive student behavior of his parents is at the middle economic level of (39.6%). While the student's non-aggressive behavior is at the middle economic level of (0.7%). 3). The dominant student behavior is very aggressive his parents work as private employees (6.9%). Then the aggressive student behavior of his parents worked as civil servants (18.1%). While the behavior of students who are not aggressive have parents who work as entrepreneurs (11.8%)

Pengaruh Layanan Bimbingan Kelompok terhadap Tingkat Penyesuaian Diri Siswa Kelas X Smk Kehutanan Negeri Pekanbaru Tahun Ajaran 2014/2015

The research is entitled “the effect of group counseling toward the self adjustment level of the tenth grade forestry vocational school of pekanbaru in 2014/2015 academic year. It is aimed at 1) finding out the level of self adjustment of the tenth grade students before the group counseling was implemented. 2) finding out the ongoing implementation process of counseling the tenth grade students. 3) finding out the level of self adjustment of the tenth grade students after the group counseling was implemented. 4) finding out the differences between pre-implemetation and post-implementation of group counseling toward tenth grade students' self adjustment level. 5) finding out whether there is an effect of group counseling toward tenth grade students' self adjustment level. The research subjects are 100 students of the tenth grade of forestry vocational school of pekanbaru. 30% of the population that is equal to 30 persons were taken as samples by using random sampling. As a description of students' self adjustment level before the implemetation of group counseling, most of them are categorized as unfavorable, a small portion of the students are categorized as very unfavorable, and none of them are categorized as pretty good, good, and very good. While, as a description of post-implemetation of group counseling, the students' self adjustment level are 16,67% categorized as good, mostly 83,33% are categorized as very good, and none of them are categorized as very unfavorable, pretty unfavorable, and very unfavorable. Based on the hypothesis result test, it shoes that there is significant effect of group discussion toward students' self adjustment which is amounted to 48%

Asymptotic and intermediate long-time behavior of nuclear free induction decays in polycrystalline solids and powders

Free induction decay (FID) measured by nuclear magnetic resonance (NMR) in a polycrystalline solid is the isotropic average of the FIDs for individual single crystallites. It has been recently proposed theoretically and verified experimentally that the long-time behavior of single-crystal FIDs has the universal form of exponentially decaying sinusoidal oscillations. Polycrystalline averaging complicates the situation theoretically, while the available experimental evidence is also ambiguous. Exponentially decaying sinusoidal oscillations have been observed for Xe-129 in polycrystalline solid xenon but not for F-19 in the powder of CaF2. In this paper, we present the first principles FID calculations for the powders of both CaF2 and solid xenon. In both cases, the asymptotic long-time behavior has the expected form of exponentially decaying sinusoidal oscillations, which is determined by the single crystallite FID with the slowest exponential decay. However, this behavior appears only at rather small values of the signal that have not yet been measured in experiments. At intermediate times accessible experimentally, a polycrystalline FID depends on the distribution of the exponential decay constants and oscillation frequencies for single crystallite FIDs. In CaF2, these parameters are relatively broadly distributed, and as a result, the sinusoidal long-time oscillations become somewhat washed out. In contrast, the single crystallite parameters are more clustered in solid xenon, and, as a result, the experimentally observable range is characterized by well-defined oscillation frequency and exponential decay constant even though both of these parameters do not represent the true long-time behavior. The above difference of the intermediate FID behavior originates from the difference of the crystal structures of solid xenon and CaF2.Comment: 16 pages, 5 figure

Bunching Transitions on Vicinal Surfaces and Quantum N-mers

We study vicinal crystal surfaces with the terrace-step-kink model on a discrete lattice. Including both a short-ranged attractive interaction and a long-ranged repulsive interaction arising from elastic forces, we discover a series of phases in which steps coalesce into bunches of n steps each. The value of n varies with temperature and the ratio of short to long range interaction strengths. We propose that the bunch phases have been observed in very recent experiments on Si surfaces. Within the context of a mapping of the model to a system of bosons on a 1D lattice, the bunch phases appear as quantum n-mers.Comment: 5 pages, RevTex; to appear in Phys. Rev. Let

Universal Long-time Behavior of Nuclear Spin Decays in a Solid

Magnetic resonance studies of nuclear spins in solids are exceptionally well suited to probe the limits of statistical physics. We report experimental results indicating that isolated macroscopic systems of interacting nuclear spins possess the following fundamental property: spin decays that start from different initial configurations quickly evolve towards the same long-time behavior. This long-time behavior is characterized by the shortest ballistic microscopic timescale of the system and therefore falls outside of the validity range for conventional approximations of statistical physics. We find that the nuclear free induction decay and different solid echoes in hyperpolarized solid xenon all exhibit sinusoidally modulated exponential long-time behavior characterized by identical time constants. This universality was previously predicted on the basis of analogy with resonances in classical chaotic systems.Comment: 4 pages main paper + 3 pages supporting material, 3 figure

Bose-Einstein Condensation at a Helium Surface

Path Integral Monte Carlo was used to calculate the Bose-Einstein condensate fraction at the surface of a helium film at $T=0.77 K$, as a function of density. Moving from the center of the slab to the surface, the condensate fraction was found to initially increase with decreasing density to a maximum value of 0.9 before decreasing. Long wavelength density correlations were observed in the static structure factor at the surface of the slab. Finally, a surface dispersion relation was calculated from imaginary-time density-density correlations.Comment: 8 pages, 5 figure