Colloidal dynamics in polymer solutions: Optical two-point microrheology measurements

We present an extension of the two-point optical microrheology technique introduced by Crocker \textit{et al.} [Phys. Rev. Lett. \textbf{85}, 888 (2000)] to high frequencies. The correlated fluctuations of two probe spheres held by a pair of optical tweezers within a viscoelastic medium are determined using optical interferometry. A theoretical model is developed to yield the frequency-dependent one- and two-particle response functions from the correlated motion. We demonstrate the validity of this method by determining the one- and two-particle correlations in a semi-dilute solution of polystyrene in decalin. We find that the ratio of the one- and two-particle response functions is anomalous which we interpret as evidence for a slip boundary condition caused by depletion of polymer from the surface of the particle

Fast Diffusion of Long Guest Rods in a Lamellar Phase of Short Host Particles

We investigate the dynamic behavior of long guest rod-like particles immersed in liquid crystalline phases formed by shorter host rods, tracking both guest and host particles by fluorescence microscopy. Counter-intuitively, we evidence that long rods diffuse faster than short rods forming the one-dimensional ordered smectic-A phase. This results from the larger and non-commensurate size of the guest particles as compared to the wavelength of the energy landscape set by the lamellar stack of liquid slabs. The long guest particles are also shown to be still mobile in the crystalline smectic-B phase, as they generate their own voids in the adjacent layers.Comment: 5 pages, 4 figures, Accepted in Phys. Rev. Let

Asymptotic Solutions for Mean-Field Slab Dynamos

We discuss asymptotic solutions of the kinematic $\alpha\omega$-dynamo in a thin disc (slab). Focusing upon the strong dynamo regime, in which the dynamo number $D$ satisfies $|D|\gg1$, we resolve uncertainties in the earlier treatments and conclude that some of the simplifications that have been made in previous studies are questionable. Comparing numerical solutions with asymptotic results obtained for $|D|\gg1$ and $|D|\ll1$ we find that the asymptotic solutions give a reasonably accurate description of the dynamo even far beyond their formal ranges of applicability. Indeed, our results suggest a simple analytical expression for the growth rate of the mean magnetic field that remains accurate in the range $-200< D< -10$ (which is appropriate for dynamos in spiral galaxies and accretion discs). Finally, we analyse the role of various terms in the dynamo equations to clarify the fine details of the dynamo process.Comment: "This is an Author's Original Manuscript of an article submitted for consideration in Geophysical and Astrophysical Fluid Dynamics [copyright Taylor & Francis]; Geophysical and Astrophysical Fluid Dynamics is available online at http://www.tandfonline.com/gafd

Modified Dispersion Relations from Closed Strings in Toroidal Cosmology

A long-standing problem of theoretical physics is the exceptionally small value of the cosmological constant $\Lambda \sim 10^{-120}$ measured in natural Planckian units. Here we derive this tiny number from a toroidal string cosmology based on closed strings. In this picture the dark energy arises from the correlation between momentum and winding modes that for short distances has an exponential fall-off with increasing values of the momenta.The freeze-out by the expansion of the background universe for these transplanckian modes may be interpreted as a frozen condensate of the closed-string modes in the three non-compactified spatial dimensions.Comment: 21 pages LaTeX. Clarification at end of Section 3. Modified Discussion Section. Two notes added. Title change

Interoceptive Ingredients of Body Ownership: Affective Touch and Cardiac Awareness in the Rubber Hand Illusion

This document is the Accepted Manuscript version of the following article: Laura Crucianelli, Charlotte Krahe, Paul M. Jenkinson, Aikaterini (Katerina) Fotopoulou, 'Interoceptive Ingredients of Body Ownership: Affective Touch and Cardiac Awareness in the Rubber Hand Illusion', Cortex, first published online 1 May 2017, available at doi: https://doi.org/10.1016/j.cortex.2017.04.018. © 2017 Elsevier Ltd. All rights reserved.The sense of body ownership represents a fundamental aspect of bodily self-consciousness. Using multisensory integration paradigms, recent studies have shown that both exteroceptive and interoceptive information contribute to our sense of body ownership. Interoception refers to the physiological sense of the condition of the body, including afferent signals that originate inside the body and outside the body. However, it remains unclear whether individual sensitivity to interoceptive modalities is unitary or differs between modalities. It is also unclear whether the effect of interoceptive information on body ownership is caused by exteroceptive ‘visual capture’ of these modalities, or by bottom-up processing of interoceptive information. This study aimed to test these questions in two separate samples. In the first experiment (N = 76), we examined the relationship between two different interoceptive modalities, namely cardiac awareness based on a heartbeat counting task, and affective touch perception based on stimulation of a specialized C tactile (CT) afferent system. This is an interoceptive modality of affective and social significance. In a second experiment (N = 63), we explored whether ‘off-line’ trait interoceptive sensitivity based on a heartbeat counting task would modulate the extent to which CT affective touch influences the multisensory process during the rubber hand illusion (RHI). We found that affective touch enhanced the subjective experience of body ownership during the RHI. Nevertheless, interoceptive sensitivity, as measured by a heartbeat counting task, did not modulate this effect, nor did it relate to the perception of ownership or of CT-optimal affective touch more generally. By contrast, this trait measure of interoceptive sensitivity appeared most relevant when the multisensory context of interoception was ambiguous, suggesting that the perception of interoceptive signals and their effects on body ownership may depend on individual abilities to regulate the balance of interoception and exteroception in given contexts.Peer reviewedFinal Accepted Versio

Onboard sampling of the rockfish and lingcod commerical passenger fishing vessel industry in northern and central California, January through December 1993

The Central California Marine Sport Fish Project has been collecting angler catch data on board Commercial Passenger Fishing Vessels (CPFVs) fishing for rockfish or lingcod since 1987. The program depends on the voluntary cooperation of CPFV owners and operators. This third report in a series presents data collected in 1993, refers to historical data from 1987 to 1992, and documents trends in species composition, angler effort, catch per unit effort (CPUE), and, for selected species, mean length and length frequency. Angler catches on board central and northern California CPFVs were sampled from 15 ports, ranging from Crescent City in the north to Port San Luis (Avila Beach) in the south. Technicians observed a total of 2385 anglers fishing on 248 CPFV trips. These observed anglers caught 29,622 fish of which Technicians determined 27,421 were kept. Over 60% of these fish were caught at Monterey or Morro Bay area ports. Only 18 of the 58 species each comprised at least one percent of the catch. The top ten species in order of abundance were blue, yellowtail, chilipepper, rosy, widow, canary, greenspotted, bocaccio, and vermilion rockfishes and lingcod. Blue and yellowtail rockfishes, and chilipepper, together comprised over 50% of the observed catch. Overall, rockfishes represented 35 species or 59% of the 58 identified species. In general, 1993 data indicated that in all port areas CPFV fishery resources, with a few exceptions, were in a viable and sustainable condition, similar to the previous 6 years. This study identified nine species, lingcod and eight rockfishes, with areas of concern which were primarily port-specific. Six of these ranked among the 10 most frequently observed species, five were schooling or migratory species, two were nearshore species, and three were offshore species. Trends of most concern continue to be declining catch per angler hour (CPAH) - of yellowtail rockfish in the Bodega Bay area, lingcod in shallow locations near the Monterey area, and yelloweye rockfish in the San Francisco area, as well as decreasing mean lengths of canary rockfish in the Monterey area and brown rockfish in the Morro Bay area. Populations of black rockfish, the species presently of greatest concern in the CPFV fishery, showed some positive signs this year. Also on the positive side, the Monterey and Morro Bay areas experienced an increased availability of newly-recruited smaller, juvenile vermilion rockfish in observed catches. Total catch estimates were within values observed in previous years. (132pp.