Sticky physics of joy: On the dissolution of spherical candies

Assuming a constant mass-decrease per unit-surface and -time we provide a very simplistic model for the dissolution process of spherical candies. The aim is to investigate the quantitative behavior of the dissolution process throughout the act of eating the candy. In our model we do not take any microscopic mechanism of the dissolution process into account, but rather provide an estimate which is based on easy-to-follow calculations. Having obtained a description based on this calculation, we confirm the assumed behavior by providing experimental data of the dissolution process. Besides a deviation from our prediction caused by the production process of the candies below a diameter of 2 mm, we find good agreement with our model-based expectations. Serious questions on the optimal strategy of enjoying a candy will be addressed, like whether it is wise to split the candy by breaking it with the teeth or not

Optimal control of magnetization dynamics in ferromagnetic heterostructures by spin--polarized currents

We study the switching-process of the magnetization in a ferromagnetic-normal-metal multilayer system by a spin polarized electrical current via the spin transfer torque. We use a spin drift-diffusion equation (SDDE) and the Landau-Lifshitz-Gilbert equation (LLGE) to capture the coupled dynamics of the spin density and the magnetization dynamic of the heterostructure. Deriving a fully analytic solution of the stationary SDDE we obtain an accurate, robust, and fast self-consistent model for the spin-distribution and spin transfer torque inside general ferromagnetic/normal metal heterostructures. Using optimal control theory we explore the switching and back-switching process of the analyzer magnetization in a seven-layer system. Starting from a Gaussian, we identify a unified current pulse profile which accomplishes both processes within a specified switching time.Comment: 5 figure

Effects of Group II Metabotropic Glutamate Receptor Modulation on Ethanol- and Sucrose-Seeking and Consumption in the Rat

Rationale Previous studies suggest that group II metabotropic glutamate receptors (mGluR2/3) are involved in regulating ethanol seeking and consumption. Objective The mGluR2/3 agonist LY379268 (LY37) and selective mGluR2 positive allosteric modulator biphenyl-indanone A (BINA) were used to investigate the relative contribution of mGlu2 and mGlu3 receptors on ethanol and sucrose seeking and consumption. A microinjection study was then performed to examine the role of nucleus accumbens (NAc) core mGluR2/3 on ethanol-seeking. Methods For the systemic experiments, separate groups of male Wistar rats [LY37 (0-2.0 mg/kg); BINA (0-20 mg/kg)] were trained to complete a response requirement (RR) resulting in access to 10% ethanol or 2% sucrose (in separate groups) for a 20-minute drinking period. Animals then underwent consummatory testing (weekly drug injections with RR1) followed by appetitive testing (weekly drug injections followed by extinction session). A separate group of male Wistar rats was surgically implanted with bilateral guide cannulae directed towards the NAc core and had weekly microinjections followed by an extinction session. Results Systemic administration of the mGluR2/3 agonist LY37 significantly reduced ethanol- and sucrose-seeking. The same treatment also reduced sucrose consumption and body weight (24-hours post injection). Systemic administration of the selective mGluR2 PAM BINA, however, had no effect on either seeking or consumption of ethanol or sucrose. Intra-accumbens core LY37 significantly reduced ethanol-seeking. Conclusions: These findings suggest that systemic mGluR2/3 agonism, but not allosteric modulation of mGluR2, reduces reinforcer seeking. In particular, NAc core group II mGluR may be involved in regulating ethanol-seeking

Prime Ideals in Infinite Products of Commutative Rings

In this work we present descriptions of prime ideals and in particular of maximal ideals in products $R = \prod D_\lambda$ of families $(D_\lambda)_{\lambda \in \Lambda}$ of commutative rings. We show that every maximal ideal is induced by an ultrafilter on the Boolean algebra $\prod \mathcal{P}(\max(D_\lambda))$. If every $D_\lambda$ is in a certain class of rings including finite character domains and one-dimensional domains, then this leads to a characterization of the maximal ideals of $R$. If every $D_\lambda$ is a Pr\"ufer domain, we depict all prime ideals of $R$. Moreover, we give an example of a (optionally non-local or local) Pr\"ufer domain such that every non-zero prime ideal is of infinite height

Intravenous Alcohol Self-Administration in the P Rat

Alcohol consumption produces a complex array of effects that can be divided into two types: the explicit pharmacological effects of ethanol (which can be temporally separate from time of intake) and the more temporally “relevant” effects (primarily olfactory and taste) that bridge the time from intake to onset of the pharmacological effects. Intravenous (IV) self-administration of ethanol limits the confounding “non-pharmacological” effects associated with oral consumption, allows for controlled and precise dosing, and bypasses first order absorption kinetics, allowing for more direct and better-controlled assessment of alcohol’s effect on the brain. IV ethanol self-administration has been reliably demonstrated in mouse and human experimental models; however, models of IV self-administration have been historically problematic in the rat. An operant multiple-schedule study design was used to elucidate the role of each component of a compound IV-ethanol plus oral-sucrose reinforcer. Male alcohol-preferring P rats had free access to both food and water during all IV self-administration sessions. Animals were trained to press a lever for orally delivered 1% sucrose (1S) on a fixed ratio 4 schedule, and then surgically implanted with an indwelling jugular catheter. Animals were then trained to respond on a multiple FR4-FR4 schedule composed of alternating 2.5-min components across 30-min sessions. For the multiple schedule, two components were used: an oral 1S only and an oral 1S plus IV 20% ethanol (25 mg/kg/injection). Average total ethanol intake was 0.47 ± 0.04 g/kg. We found significantly higher earning of sucrose-only reinforcers and greater sucrose-lever error responding relative to the compound oral-sucrose plus IV-ethanol reinforcer. These response patterns suggest that sucrose, not ethanol, was responsible for driving overall responding. The work with a compound IV ethanol-oral sucrose reinforcer presented here suggests that the existing intravenous ethanol self-administration methodology cannot overcome the aversive properties of ethanol via this route in the rat

Network topology of interlocked chiral particles

Self-assembly of chiral particles with an L-shape is explored by Monte-Carlo computer simulations in two spatial dimensions. For sufficiently high packing densities in confinement, a carpet-like texture emerges due to the interlocking of L-shaped particles, resembling a distorted smectic liquid crystalline layer pattern. From the positions of either of the two axes of the particles, two different types of layers can be extracted, which form distinct but complementary entangled networks. These coarse-grained network structures are then analyzed from a topological point of view. We propose a global charge conservation law by using an analogy to uniaxial smectics and show that the individual network topology can be steered by both confinement and particle geometry. Our topological analysis provides a general classification framework for applications to other intertwined dual networks.Comment: 11 pages, 11 figure

Thermodynamically Stable One-Component Metallic Quasicrystals

Classical density-functional theory is employed to study finite-temperature trends in the relative stabilities of one-component quasicrystals interacting via effective metallic pair potentials derived from pseudopotential theory. Comparing the free energies of several periodic crystals and rational approximant models of quasicrystals over a range of pseudopotential parameters, thermodynamically stable quasicrystals are predicted for parameters approaching the limits of mechanical stability of the crystalline structures. The results support and significantly extend conclusions of previous ground-state lattice-sum studies.Comment: REVTeX, 13 pages + 2 figures, to appear, Europhys. Let

Spiranthes vernalis Engelm. & A. Gray

https://thekeep.eiu.edu/herbarium_specimens_byname/21408/thumbnail.jp

Transition-metal interactions in aluminum-rich intermetallics

The extension of the first-principles generalized pseudopotential theory (GPT) to transition-metal (TM) aluminides produces pair and many-body interactions that allow efficient calculations of total energies. In aluminum-rich systems treated at the pair-potential level, one practical limitation is a transition-metal over-binding that creates an unrealistic TM-TM attraction at short separations in the absence of balancing many-body contributions. Even with this limitation, the GPT pair potentials have been used effectively in total-energy calculations for Al-TM systems with TM atoms at separations greater than 4 AA. An additional potential term may be added for systems with shorter TM atom separations, formally folding repulsive contributions of the three- and higher-body interactions into the pair potentials, resulting in structure-dependent TM-TM potentials. Towards this end, we have performed numerical ab-initio total-energy calculations using VASP (Vienna Ab Initio Simulation Package) for an Al-Co-Ni compound in a particular quasicrystalline approximant structure. The results allow us to fit a short-ranged, many-body correction of the form a(r_0/r)^{b} to the GPT pair potentials for Co-Co, Co-Ni, and Ni-Ni interactions.Comment: 18 pages, 5 figures, submitted to PR