Comment on some proposed mechanisms for attenuation of third sound

Two explanations have been proposed for an apparent discrepancy between theoretical prediction and experimental measurement of third-sound attenuation. One of these proposes a new "macroscopic quantum uncertainly principle," and the other proceeds via nonlinear, anharmonic effects due to zero-point fluctuations. We argue that neither suggestion is acceptable

Physical Bias of Galaxies From Large-Scale Hydrodynamic Simulations

We analyze a new large-scale ($100h^{-1}$Mpc) numerical hydrodynamic simulation of the popular $\Lambda$CDM cosmological model, including in our treatment dark matter, gas and star-formation, on the basis of standard physical processes. The method, applied with a numerical resolution of $<200h^{-1}$kpc (which is still quite coarse for following individual galaxies, especially in dense regions), attempts to estimate where and when galaxies form. We then compare the smoothed galaxy distribution with the smoothed mass distribution to determine the "bias" defined as $b\equiv (\delta M/M)_{gal}/(\delta M/M)_{total}$ on scales large compared with the code numerical resolution (on the basis of resolution tests given in the appendix of this paper). We find that (holding all variables constant except the quoted one) bias increases with decreasing scale, with increasing galactic age or metallicity and with increasing redshift of observations. At the $8h^{-1}$Mpc fiducial comoving scale bias (for bright regions) is 1.35 at $z=0$ reaching to 3.6 at $z=3$, both numbers being consistent with extant observations. We also find that $(10-20)h^{-1}$Mpc voids in the distribution of luminous objects are as observed (i.e., observed voids are not an argument against CDM-like models) and finally that the younger systems should show a colder Hubble flow than do the early type galaxies (a testable proposition). Surprisingly, little evolution is found in the amplitude of the smoothed galaxy-galaxy correlation function (as a function of {\it comoving} separation). Testing this prediction vs observations will allow a comparison between this work and that of Kauffmann et al which is based on a different physical modelingmethod.Comment: in press, ApJ, 26 latex pages plus 7 fig

Probing the helium-graphite interaction

Two separate lines of investigation have recently converged to produce a highly detailed picture of the behavior of helium atoms physisorbed on graphite basal plane surfaces. Atomic beam scattering experiments on single crystals have yielded accurate values for the binding energies of several· states for both (^4)He and (^3)He, as well as matrix elements of the largest Fourier component of the periodic part of the interaction potential. From these data, a complete three-dimensional description of the potential has been constructed, and the energy band structure of a helium atom moving in this potential calculated. At the same time, accurate thermodynamic measurements were made on submonolayer helium films adsorbed on Grafoil. The binding energy and low-coverage specific heat deduced from these measurements are in excellent agreement with those calculated from the band structures

Single atom-scale diamond defect allows large Aharonov-Casher phase

We propose an experiment that would produce and measure a large Aharonov-Casher (A-C) phase in a solid-state system under macroscopic motion. A diamond crystal is mounted on a spinning disk in the presence of a uniform electric field. Internal magnetic states of a single NV defect, replacing interferometer trajectories, are coherently controlled by microwave pulses. The A-C phase shift is manifested as a relative phase, of up to 17 radians, between components of a superposition of magnetic substates, which is two orders of magnitude larger than that measured in any other atom-scale quantum system.Comment: 5 pages, 2 figure

Sensing of Fluctuating Nanoscale Magnetic Fields Using NV Centres in Diamond

New magnetometry techniques based on Nitrogen-Vacancy (NV) defects in diamond allow for the imaging of static (DC) and oscillatory (AC) nanoscopic magnetic systems. However, these techniques require accurate knowledge and control of the sample dynamics, and are thus limited in their ability to image fields arising from rapidly fluctuating (FC) environments. We show here that FC fields place restrictions on the DC field sensitivity of an NV qubit magnetometer, and that by probing the dephasing rate of the qubit in a magnetic FC environment, we are able to measure fluctuation rates and RMS field strengths that would be otherwise inaccessible with the use of DC and AC magnetometry techniques. FC sensitivities are shown to be comparable to those of AC fields, whilst requiring no additional experimental overheads or control over the sample.Comment: 5 pages, 4 figure

Nanoscale magnetometry through quantum control of nitrogen-vacancy centres in rotationally diffusing nanodiamonds

The confluence of quantum physics and biology is driving a new generation of quantum-based sensing and imaging technology capable of harnessing the power of quantum effects to provide tools to understand the fundamental processes of life. One of the most promising systems in this area is the nitrogen-vacancy centre in diamond - a natural spin qubit which remarkably has all the right attributes for nanoscale sensing in ambient biological conditions. Typically the nitrogen-vacancy qubits are fixed in tightly controlled/isolated experimental conditions. In this work quantum control principles of nitrogen-vacancy magnetometry are developed for a randomly diffusing diamond nanocrystal. We find that the accumulation of geometric phases, due to the rotation of the nanodiamond plays a crucial role in the application of a diffusing nanodiamond as a bio-label and magnetometer. Specifically, we show that a freely diffusing nanodiamond can offer real-time information about local magnetic fields and its own rotational behaviour, beyond continuous optically detected magnetic resonance monitoring, in parallel with operation as a fluorescent biomarker.Comment: 9 pages, with 5 figure

Space into Time: English Canals and English Landscape Painting 1760-1835

England's canal network, critical to the nation's predominance in the development of modern industry, goes largely unnoticed today except by some scholars of transportation. As I suggest in my introduction, one of the reasons may be that since the Second World War the canals have been cleaned up and turned into an attraction for boaters and tourists. With their brightly painted cabins occupied by families on vacation, the boats, now motorized, glide slowly and silently past the bucolic banks of the canals. These are, in appearance, as originally proposed by the development companies and drawn and engraved for the newspapers: beautiful country spaces to be admired and enjoyed by the public. Another reason may be the exertion of a willful nostalgia: because the comparatively slow-moving canals can appear pre-industrial we choose to think of them that way. These choices have made the English canal system part of a pre-modern England, imagined just as the canals were being built. That England would always stand as "a living emblem" of itself remained for the most part uncontested (putting Cromwell to one side) until the construction of the canals. No narrative was required to explain the meaning of the countryside of estates and villages: they were "taken as a given" and had "no apparent origins". The canals visibly introduced time into what was perceived as an unchanging landscape. Time entered not only in the speed of transport on the canals but also in the factories that ran by the clock and the canals that ran by timetable. The geological layers unearthed in the digging of the canals revealed the passage of eons of time and the instability of the earth itself. Time entered in the movement of people and goods in bustling new towns that were in the interior of the country, made prosperous in part by the access the canals gave them to the seas. There was enthusiasm for the progress of English industry and science, a sense of national pride, and great expectations for the wealth of the country. There was a sense that if the old landscape and the new could not be reconciled, the identity of the nation would be lost. The general ambivalence about the changes the canals would bring began at the top with the landed nobility who first financed and built them. Their desire to extract wealth from their own lands overcame their fear of a dynamic population. Gainsborough, in his Cottage Door paintings, appealed to his audience's sense of nostalgia for the passing of the timeless English landscape at the very moment that the canals were being built and many of them were investing in them. Ambivalence is also present in Constable's attempts to cope with landscapes expressive of both time and space. The desire to return to an almost mythic prior time is palpable and his attempt to leap into the future with The Leaping Horse avoids the issue in the other direction. The heyday of canals, from 1765 to 1835, is the interstice between the early days of modernity in England and modern England in its full-blown glory. It is also a curious period in which the development of one technology, the canal, as it was elaborated in the landscape, propelled two generations of artists to work on the same problem: the visual representation of time and space. If one sets a later date for modernity (which I believe would be incorrect), one has the additional liability of facing a closed system of a time-based society and visual culture. By setting the onset of modernity in the 1760's, the anxiety and the failure of artists to develop the presence of both time and space in their work. At the very cusp of the period, in a work such as Turner's Dudley, Worcestershire, time does not empty space of meaning, any more than the supremacy of space in pre-modern England truly nullified time

Combining community-based research and local knowledge to confront asthma and subsistence-fishing hazards in Greenpoint/Williamsburg, Brooklyn, New York.

Activists in the environmental justice movement are challenging expert-driven scientific research by taking the research process into their own hands and speaking for themselves by defining, analyzing, and prescribing solutions for the environmental health hazards confronting communities of the poor and people of color. I highlight the work of El Puente and The Watchperson Project--two community-based organizations in the Greenpoint/Williamsburg neighborhood in Brooklyn, New York, that have engaged in community-based participatory research (CBPR) to address asthma and risks from subsistence-fish diets. The CBPR process aims to engage community members as equal partners alongside scientists in problem definition, information collection, and data analysis--all geared toward locally relevant action for social change. In the first case I highlight how El Puente has organized residents to conduct a series of asthma health surveys and tapped into local knowledge of the Latino population to understand potential asthma triggers and to devise culturally relevant health interventions. In a second case I follow The Watchperson Project and their work surveying subsistence anglers and note how the community-gathered information contributed key data inputs for the U.S. Environmental Protection Agency Cumulative Exposure Project in the neighborhood. In each case I review the processes each organization used to conduct CBPR, some of their findings, and the local knowledge they gathered, all of which were crucial for understanding and addressing local environmental health issues. I conclude with some observations about the benefits and limits of CBPR for helping scientists and communities pursue environmental justice

Measuring Neutrino Oscillations with Nuclear Reactors

Since the first direct observations of antineutrino events by Reines and Cowan in the 1950's [1], nuclear reactors have been an important tool in the study of neutrino properties. More recently, the study of neutrino oscillations has been a very active area of research. The pioneering observation of oscillations by the KamLAND experiment has provided crucial information on the neutrino mixing matrix. New experiments to study the remaining unknown mixing angle are currently under development. These recent studies and potential future developments will be discussed