Loyal Tongue, Liberal Mind: International Students’ Experiences on Dietary Acculturation in England

This study explores the dietary experiences of international students in a British university, and how these phenomena differ from what they experienced in their home country. Ten participants were recruited using purposive sampling. The inclusion criteria were international students who had lived in England for less than a year; those with diet-related health problems were excluded. Data were collected using semi-structured interviews and analyzed with Colaizzi’s method. This resulted in three main themes: changes in diet, new dietary experiences, and factors affecting dietary practices. Our findings also offer new insight about what international students might encounter relating to food and diet when studying abroad

Magnetic Fields in Stellar Jets

Although several lines of evidence suggest that jets from young stars are driven magnetically from accretion disks, existing observations of field strengths in the bow shocks of these flows imply that magnetic fields play only a minor role in the dynamics at these locations. To investigate this apparent discrepancy we performed numerical simulations of expanding magnetized jets with stochastically variable input velocities with the AstroBEAR MHD code. Because the magnetic field B is proportional to the density n within compression and rarefaction regions, the magnetic signal speed drops in rarefactions and increases in the compressed areas of velocity-variable flows. In contrast, B ~ n^0.5 for a steady-state conical flow with a toroidal field, so the Alfven speed in that case is constant along the entire jet. The simulations show that the combined effects of shocks, rarefactions, and divergent flow cause magnetic fields to scale with density as an intermediate power 1 > p > 0.5. Because p > 0.5, the Alfven speed in rarefactions decreases on average as the jet propagates away from the star. This behavior is extremely important to the flow dynamics because it means that a typical Alfven velocity in the jet close to the star is significantly larger than it is in the rarefactions ahead of bow shocks at larger distances, the one place where the field is a measurable quantity. We find that the observed values of weak fields at large distances are consistent with strong fields required to drive the observed mass loss close to the star. For a typical stellar jet the crossover point inside which velocity perturbations of 30 - 40 km/s no longer produce shocks is ~ 300 AU from the source

On The Use Of Polyurethane Matrix Carbon Fiber Composites For Strengthening Concrete Structures

Fiber-reinforced polymer (FRP) composite materials have effectively been used in numerous reinforced concrete civil infrastructure strengthening projects. Although a significant body of knowledge has been established for epoxy matrix carbon FRPs and epoxy adhesives, there is still a need to investigate other matrices and adhesive types. One such matrix/adhesive type yet to be heavily researched for infrastructure application is polyurethane. This thesis investigates use of polyurethane matrix carbon fiber composites for strengthening reinforced concrete civil infrastructure. Investigations on mirco- and macro-mechanical composite performance, strengthened member flexural performance, and bond durability under environmental conditioning will be presented. Results indicate that polyurethane carbon composites could potentially be a viable option for strengthening concrete structures

Conditional preparation of states containing a definite number of photons

A technique for conditionally creating single- or multimode photon-number states is analyzed using Bayesian theory. We consider the heralded N-photon states created from the photons produced by an unseeded optical parametric amplifier when the heralding detector is the time-multiplexed photon-number-resolving detector recently demonstrated by Fitch, et al. [Phys. Rev. A 68, 043814 (2003).] and simultaneously by Achilles, et al. [Opt. Lett. 28, 2387 (2003).]. We find that even with significant loss in the heralding detector, fields with sub-Poissonian photon-number distributions can be created. We also show that heralded multimode fields created using this technique are more robust against detector loss than are single-mode fields.Comment: 6 pages, 6 figures, reference added, typos corrected, content update

Systematic Errors in Cosmic Microwave Background Interferometry

Cosmic microwave background (CMB) polarization observations will require superb control of systematic errors in order to achieve their full scientific potential, particularly in the case of attempts to detect the B modes that may provide a window on inflation. Interferometry may be a promising way to achieve these goals. This paper presents a formalism for characterizing the effects of a variety of systematic errors on interferometric CMB polarization observations, with particular emphasis on estimates of the B-mode power spectrum. The most severe errors are those that couple the temperature anisotropy signal to polarization; such errors include cross-talk within detectors, misalignment of polarizers, and cross-polarization. In a B mode experiment, the next most serious category of errors are those that mix E and B modes, such as gain fluctuations, pointing errors, and beam shape errors. The paper also indicates which sources of error may cause circular polarization (e.g., from foregrounds) to contaminate the cosmologically interesting linear polarization channels, and conversely whether monitoring of the circular polarization channels may yield useful information about the errors themselves. For all the sources of error considered, estimates of the level of control that will be required for both E and B mode experiments are provided. Both experiments that interfere linear polarizations and those that interfere circular polarizations are considered. The fact that circular experiments simultaneously measure both linear polarization Stokes parameters in each baseline mitigates some sources of error.Comment: 19 pages, 9 figures, submitted to Phys. Rev.

Mosaicking with cosmic microwave background interferometers

Measurements of cosmic microwave background (CMB) anisotropies by interferometers offer several advantages over single-dish observations. The formalism for analyzing interferometer CMB data is well developed in the flat-sky approximation, valid for small fields of view. As the area of sky is increased to obtain finer spectral resolution, this approximation needs to be relaxed. We extend the formalism for CMB interferometry, including both temperature and polarization, to mosaics of observations covering arbitrarily large areas of the sky, with each individual pointing lying within the flat-sky approximation. We present a method for computing the correlation between visibilities with arbitrary pointing centers and baselines and illustrate the effects of sky curvature on the l-space resolution that can be obtained from a mosaic.Comment: 9 pages; submitted to Ap

Evolution of brown dwarf disks: A Spitzer survey in Upper Scorpius

We have carried out a Spitzer survey for brown dwarf (BD) disks in the ~5 Myr old Upper Scorpius (UpSco) star forming region, using IRS spectroscopy from 8 to 12\mu m and MIPS photometry at 24\mu m. Our sample consists of 35 confirmed very low mass members of UpSco. Thirteen objects in this sample show clear excess flux at 24\mu m, explained by dust emission from a circum-sub-stellar disk. Objects without excess emission either have no disks at all or disks with inner opacity holes of at least ~5 AU radii. Our disk frequency of 37\pm 9% is higher than what has been derived previously for K0-M5 stars in the same region (on a 1.8 sigma confidence level), suggesting a mass-dependent disk lifetime in UpSco. The clear distinction between objects with and without disks as well as the lack of transition objects shows that disk dissipation inside 5 AU occurs rapidly, probably on timescales of <~10^5 years. For the objects with disks, most SEDs are uniformly flat with flux levels of a few mJy, well modeled as emission from dusty disks affected by dust settling to the midplane, which also provides indirect evidence for grain growth. The silicate feature around 10\mu m is either absent or weak in our SEDs, arguing for a lack of hot, small dust grains. Compared with younger objects in Taurus, BD disks in UpSco show less flaring. Taken together, these results clearly demonstrate that we see disks in an advanced evolutionary state: Dust settling and grain growth are ubiquituous in circum-sub-stellar disks at ages of 5 Myr, arguing for planet forming processes in BD disks. For almost all our targets, results from high-resolution spectroscopy and high-spatial resolution imaging have been published before, thus providing a large sample of BDs for which information about disks, accretion, and binarity is available. (abridged)Comment: 39 pages, 7 figures, accepted for publication in Ap

Deep Observation of the Giant Radio Lobes of Centaurus A with the Fermi Large Area Telescope

The detection of high energy (HE) {\gamma}-ray emission up to about 3 GeV from the giant lobes of the radio galaxy Centaurus A has been recently reported by the Fermi-LAT Collaboration based on ten months of all-sky survey observations. A data set more than three times larger is used here to study the morphology and photon spectrum of the lobes with higher statistics. The larger data set results in the detection of HE {\gamma}-ray emission (up to about 6 GeV) from the lobes with a significance of more than 10 and 20 {\sigma} for the North and the South lobe, respectively. Based on a detailed spatial analysis and comparison with the associated radio lobes, we report evidence for a substantial extension of the HE {\gamma}-ray emission beyond the WMAP radio image in the case of the Northern lobe of Cen A. We reconstruct the spectral energy distribution (SED) of the lobes using radio (WMAP) and Fermi-LAT data from the same integration region. The implications are discussed in the context of hadronic and leptonic scenarios

Self-field effects upon the critical current density of flat superconducting strips

We develop a general theory to account self-consistently for self-field effects upon the average transport critical current density Jc of a flat type-II superconducting strip in the mixed state when the bulk pinning is characterized by a field-dependent depinning critical current density Jp(B), where B is the local magnetic flux density. We first consider the possibility of both bulk and edge-pinning contributions but conclude that bulk pinning dominates over geometrical edge-barrier effects in state-of-the-art YBCO films and prototype second-generation coated conductors. We apply our theory using the Kim model, JpK(B) = JpK(0)/(1+|B|/B0), as an example. We calculate Jc(Ba) as a function of a perpendicular applied magnetic induction Ba and show how Jc(Ba) is related to JpK(B). We find that Jc(Ba) is very nearly equal to JpK(Ba) when Ba > Ba*, where Ba* is the value of Ba that makes the net flux density zero at the strip's edge. However, Jc(Ba) is suppressed relative to JpK(Ba) at low fields when Ba < Ba*, with the largest suppression occurring when Ba*/B0 is of order unity or larger.Comment: 9 pages, 4 figures, minor revisions to add four reference

Monkeypox: another test for PCR

Monkeypox was declared a public health emergency of international concern by the World Health Organization (WHO) on 23 July 2022. Between 1 January and 23 July 2022, 16,016 laboratory confirmed cases of monkeypox and five deaths were reported to WHO from 75 countries on all continents. Public health authorities are proactively identifying cases and tracing their contacts to contain its spread. As with COVID-19, PCR is the only method capable of being deployed at sufficient speed to provide timely feedback on any public health interventions. However, at this point, there is little information on how those PCR assays are being standardised between laboratories. A likely reason is that testing is still limited on a global scale and that detection, not quantification, of monkeypox virus DNA is the main clinical requirement. Yet we should not be complacent about PCR performance. As testing requirements increase rapidly and specimens become more diverse, it would be prudent to ensure PCR accuracy from the outset to support harmonisation and ease regulatory conformance. Lessons from COVID-19 should aid implementation with appropriate material, documentary and methodological standards offering dynamic mechanisms to ensure testing that most accurately guides public health decisions