A Modified Approach to Single-Spin Detection Using Magnetic Resonance Force Microscopy

The magnetic moment of a single spin interacting with a cantilever in magnetic resonance force microscopy (MRFM) experiences quantum jumps in orientation rather than smooth oscillations. These jumps cannot be detected by a conventional MRFM based on observation of driven resonant oscillations of a cantilever. In this paper, we propose a method which will allow detection of the magnetic signal from a single spin using a modification of a conventional MRFM. We estimate the opportunity to detect the magnetic signal from a single proton.Comment: 4 pages LaTex, 4 figures in GIF forma

Moral choice when harming is unavoidable

Past research suggests that actors seek to minimize harm often at the cost of maximizing social welfare. However, this prior research has confounded a desire to minimize the negative impact caused by one’s actions (harm aversion) with a desire to avoid causing any harm whatsoever (harm avoidance). Across six studies (*N* = 2,152), we demonstrate that these two motives are distinct. Specifically, we find that when decision-makers can completely avoid committing a harmful act they strongly prefer to do so. However, harming often cannot be avoided, and decision-makers must choose between committing less harm for less benefit or committing more harm for more benefit. In these cases, harm aversion diminishes substantially, and decision-makers become increasingly willing to commit greater harm to obtain greater benefits. Thus, value-tradeoffs that decision-makers refuse to accept when it is possible to completely avoid committing harm can suddenly become desirable when some harm must be committed

Isovector Giant Dipole Resonance of Stable Nuclei in a Consistent Relativistic Random Phase Approximation

A fully consistent relativistic random phase approximation is applied to study the systematic behavior of the isovector giant dipole resonance of nuclei along the $\beta$-stability line in order to test the effective Lagrangians recently developed. The centroid energies of response functions of the isovector giant dipole resonance for stable nuclei are compared with the corresponding experimental data and the good agreement is obtained. It is found that the effective Lagrangian with an appropriate nuclear symmetry energy, which can well describe the ground state properties of nuclei, could also reproduce the isovector giant dipole resonance of nuclei along the $\beta$-stability line.Comment: 4 pages, 1 Postscript figure, to be submitted to Chin.Phys.Let

Discipline and desire: on the relative importance of willpower and purity in signaling virtue

What does it mean to act virtuously? We examine lay perceptions of virtue, and show that different psychological drivers of virtuous behavior are relevant for different types of actions. When evaluating non-moral virtuous behavior, such as choosing to skip dessert, attributions of virtue depend on perceived willpower (i.e., the extent to which someone overcomes temptation in service of acting virtuous). In contrast, when evaluating moral virtuous behavior, such as choosing to be faithful to a spouse, attributions of virtue depend on perceived purity (i.e., the extent to which someone lacks temptation to sin and thereby does not need to exert willpower in service of acting virtuously). Study 1 demonstrates that when people describe their own actions, they associate willpower with non-moral virtuous behavior, and purity with moral virtuous behavior. Studies 2 & 3 examine judgments of others and show that as behaviors become moralized, people elevate the importance of purity relative to willpower when ascribing virtue. Finally, Study 4 examines perceptions of those who are “reformed”—having eliminated their previous sinful desires such that they no longer feel tempted. For non-moral behaviors, reformed individuals are seen as strong-willed and thus highly virtuous. However, for moral behaviors, reformed individuals are still seen as somewhat impure, and are judged to be less virtuous than those have never felt tempted by a particular vice. These results underscore how construing behaviors in moral terms shifts what people consider to be virtuous

Quantum Measurement of a Single Spin using Magnetic Resonance Force Microscopy

Single-spin detection is one of the important challenges facing the development of several new technologies, e.g. single-spin transistors and solid-state quantum computation. Magnetic resonance force microscopy with a cyclic adiabatic inversion, which utilizes a cantilever oscillations driven by a single spin, is a promising technique to solve this problem. We have studied the quantum dynamics of a single spin interacting with a quasiclassical cantilever. It was found that in a similar fashion to the Stern-Gerlach interferometer the quantum dynamics generates a quantum superposition of two quasiclassical trajectories of the cantilever which are related to the two spin projections on the direction of the effective magnetic field in the rotating reference frame. Our results show that quantum jumps will not prevent a single-spin measurement if the coupling between the cantilever vibrations and the spin is small in comparison with the amplitude of the radio-frequency external field.Comment: 16 pages RevTeX including 4 figure

The Fermi-Pasta-Ulam problem: 50 years of progress

A brief review of the Fermi-Pasta-Ulam (FPU) paradox is given, together with its suggested resolutions and its relation to other physical problems. We focus on the ideas and concepts that have become the core of modern nonlinear mechanics, in their historical perspective. Starting from the first numerical results of FPU, both theoretical and numerical findings are discussed in close connection with the problems of ergodicity, integrability, chaos and stability of motion. New directions related to the Bose-Einstein condensation and quantum systems of interacting Bose-particles are also considered.Comment: 48 pages, no figures, corrected and accepted for publicatio

Cosmological models with linearly varying deceleration parameter

We propose a new law for the deceleration parameter that varies linearly with time and covers Berman's law where it is constant. Our law not only allows one to generalize many exact solutions that were obtained assuming constant deceleration parameter, but also gives a better fit with data (from SNIa, BAO and CMB), particularly concerning the late time behavior of the universe. According to our law only the spatially closed and flat universes are allowed; in both cases the cosmological fluid we obtain exhibits quintom like behavior and the universe ends with a big-rip. This is a result consistent with recent cosmological observations.Comment: 12 pages, 7 figures; some typo corrections; to appear in International Journal of Theoretical Physic

Doping dependence of phonon and quasiparticle heat transport of pure and Dy-doped Bi_2Sr_2CaCu_2O_{8+\delta} single crystals

The temperature and magnetic-field (H) dependences of thermal conductivity (\kappa) of Bi_2Sr_2CaCu_2O_{8+\delta} (Bi2212) are systematically measured for a broad doping range by using both pure Bi2212 single crystals with tuned oxygen contents and Bi_2Sr_2Ca_{1-x}Dy_xCu_2O_{8+\delta} (Dy-Bi2212) single crystals with different Dy contents x. In the underdoped samples, the quasiparticle (QP) peak below T_c is strongly suppressed, indicating strong QP scattering by impurities or oxygen defects, whereas the phonon conductivity is enhanced in moderately Dy-doped samples and a phonon peak at 10 K is observed for the first time in Bi2212 system, which means Dy^{3+} ions not only introduce the impurities or point defects but also stabilize the crystal lattice. The subkelvin data show that the QP heat conductivity gradually decreases upon lowering the hole doping level. The magnetic-field dependence of \kappa at temperature above 5 K is mainly due to the QP scattering off vortices. While the underdoped pure Bi2212 show very weak field dependence of \kappa, the Dy-doped samples present an additional "dip"-like term of \kappa(H) at low field, which is discussed to be related to the phonon scattering by free spins of Dy^{3+} ions. For non-superconducting Dy-Bi2212 samples with x \simeq 0.50, an interesting "plateau" feature shows up in the low-T \kappa(H) isotherms with characteristic field at 1 -- 2 T, for which we discuss the possible revlevance of magnon excitations.Comment: 11 pages, 11 figures, accepted for publication in Phys. Rev.

Reconciling loss aversion and gain seeking in judged emotions

Is the pain of a loss greater in magnitude the pleasure of a comparable gain? Studies that compare positive feelings about a gain to negative feelings about a comparable loss have found many answers. The pain associated with a loss can be greater than, less than or equal to the pleasure of a comparable gain. We offer a new way to test loss aversion with emotions that gives reliable results. This method is based on the emotional reactions to the reference point, a positive change and a negative change. When we manipulate the reference point, two distinct patterns emerge. Pain surpasses pleasure (loss aversion) when the reference point is positive. Furthermore, pleasure exceeds pain (gain seeking) when the reference point is negative. A reference-dependent form of prospect theory accounts for the results. If the carriers of utility are changes from any salient reference point – not just the status quo – both loss aversion and gain seeking are predicted. The relative strength of emotions depends on where you start

APOLLO: a quality assessment service for single and multiple protein models

Summary: We built a web server named APOLLO, which can evaluate the absolute global and local qualities of a single protein model using machine learning methods or the global and local qualities of a pool of models using a pair-wise comparison approach. Based on our evaluations on 107 CASP9 (Critical Assessment of Techniques for Protein Structure Prediction) targets, the predicted quality scores generated from our machine learning and pair-wise methods have an average per-target correlation of 0.671 and 0.917, respectively, with the true model quality scores. Based on our test on 92 CASP9 targets, our predicted absolute local qualities have an average difference of 2.60 Å with the actual distances to native structure