S-Z power spectrum produced by primordial magnetic fields

Primordial magnetic fields generated in the very early universe are one of the candidates for the origin of magnetic fields observed in galaxy clusters. After recombination, the Lorentz force acts on the residual ions and electrons to generate density fluctuations of baryons. Accordingly these fluctuations induce the early formation of dark halos which cause the Sunyaev-Zel'dovich (S-Z) effect in cosmic microwave background radiation. This additional S-Z effect due to primordial magnetic fields amplifies the angular power spectrum of cosmic microwave temperature anisotropies on small scales. This amplification depends on the comoving amplitude and the power law index of the primordial magnetic fields spectrum. Comparing with the small scale CMB observations, we obtained the constraints on the primordial magnetic fields, i.e., B < 2.0 nGauss for n=-2.9 or B < 1.0 nGauss for n=-2.6, where B is the comoving amplitude of magnetic fields at h^-1 Mpc and n is the power law index. Future S-Z measurements have the potential to give constraints tighter than those from temperature anisotropies and polarization of cosmic microwave background induced by the magnetic fields at the recombination epoch.Comment: 9 pages, 6 figures. accepted by MNRA

Water relations and irrigation requirements of onion (Allium Cepa L.): a review of yield and quality impacts

The results of international research on the water relations and irrigation needs of onions have been synthesized in an attempt to link fundamental studies on crop physiology to irrigation practices, and consequent impacts on crop yield, quality and storage. Following a brief introduction on its origins and centres of production, a synthesis of research on crop development including plant water relations, crop water requirements, yield response to water, irrigation systems and scheduling are presented. Most of the evidence stems from research conducted in arid and semi-arid regions notably the USA, India, Spain and Turkey. The findings confirm that onion seasonal water requirements are highly variable depending on agroclimate, location and season, as are the crop coefficients (Kc) which range from 0.4 to 0.7 (initial stage), 0.85 to 1.05 (middle development) and 0.6 to 0.75 (final stage). Seasonal irrigation needs are reported to vary from 225 to 1040 mm to produce between 10 and 77 t ha-1. The most sensitive stages for water stress are at emergence, transplanting and bulb formation. Final crop quality can also be affected by water excess. Water stress at specific stages can negatively impact on quality leading to reduced size and multi-centred bulbs. In recent years, pressure on water resources, retailer demands for quality assurance and rising production costs have meant that onion irrigation has switched from traditional low efficiency (furrow) methods to more efficient advanced (sprinkler and drip) technologies. For scheduling, optimal soil water potential thresholds for triggering irrigation were found to be between -17 kPa and -27 kPa for drip and furrow irrigation. Research is underway to maximize water use efficiency in onions, but the deficit irrigation regimes being tested under experimental conditions have yet to be adopted commercially

Sleep, Nutrition, and Injury Risk in Adolescent Athletes: A Narrative Review

This narrative review explores the impact of sleep and nutrition on injury risk in adolescent athletes. Sleep is viewed as essential to the recuperation process and is distinguished as an active participant in recovery through its involvement in growth, repair, regeneration, and immunity. Furthermore, the literature has shown that the sleep of athletes impacts elements of athletic performance including both physical and cognitive performance, recovery, injury risk, and mental well-being. For sleep to have a restorative effect on the body, it must meet an individual’s sleep needs whilst also lasting for an adequate duration and being of adequate quality, which is age-dependent. The literature has suggested that athletes have increased sleep needs compared to those of the general population and thus the standard recommendations may not be sufficient for athletic populations. Therefore, a more individualised approach accounting for overall sleep health may be more appropriate for addressing sleep needs in individuals including athletes. The literature has demonstrated that adolescent athletes achieve, on average, ~6.3 h of sleep, demonstrating a discrepancy between sleep recommendations (8–10 h) and actual sleep achieved. Sleep–wake cycles undergo development during adolescence whereby adaptation occurs in sleep regulation during this phase. These adaptations increase sleep pressure tolerance and are driven by the maturation of physiological, psychological, and cognitive functioning along with delays in circadian rhythmicity, thus creating an environment for inadequate sleep during adolescence. As such, the adolescent period is a phase of rapid growth and maturation that presents multiple challenges to both sleep and nutrition; consequently, this places a significant burden on an adolescent athletes’ ability to recover, thus increasing the likelihood of injury. Therefore, this article aims to provide a comprehensive review of the available literature on the importance of sleep and nutrition interactions in injury risk in adolescent athletes. Furthermore, it provides foundations for informing further investigations exploring the relation of sleep and nutrition interactions to recovery during adolescence

A Radio Census of Binary Supermassive Black Holes

Using archival VLBI data for 3114 radio-luminous active galactic nuclei, we searched for binary supermassive black holes using a radio spectral index mapping technique which targets spatially resolved, double radio-emitting nuclei. Only one source was detected as a double nucleus. This result is compared with a cosmological merger rate model and interpreted in terms of (1) implications for post-merger timescales for centralisation of the two black holes, (2) implications for the possibility of "stalled" systems, and (3) the relationship of radio activity in nuclei to mergers. Our analysis suggests that the binary evolution of paired supermassive black holes (both of masses >= 1e8 Msun) spends less than 500 Myr in progression from the merging of galactic stellar cores to within the purported stalling radius for supermassive black hole pairs. The data show no evidence for an excess of stalled binary systems at small separations. We see circumstantial evidence that the relative state of radio emission between paired supermassive black holes is correlated within orbital separations of 2.5 kpc.Comment: 11 Pages, 7 figures, accepted for publication in MNRA

Non-linear Structure Formation in Cosmologies with Early Dark Energy

We argue that a few per cent of "Early Dark Energy" can be detected by the statistics of nonlinear structures. The presence of Dark Energy during linear structure formation is natural in models where the present tiny Dark-Energy density is related to the age of the Universe rather than a new fundamental small parameter. Generalisation of the spherical collapse model shows that the linear collapse parameter delta_c is lowered. The corresponding relative enhancement of weak gravitational lensing on arc-minute scales lowers the value of sigma_8 inferred from a given lensing amplitude as compared to Lambda-CDM. In presence of Early Dark Energy, structures grow slower, such that for given sigma_8 the number of galaxies and galaxy clusters is substantially increased at moderate and high redshift. For realistic models, the number of clusters detectable through their thermal Sunyaev-Zel'dovich effect at redshift unity and above, e.g. with the Planck satellite, can be an order of magnitude larger than for Lambda-CDM.Comment: 10 pages, 12 figure

The Great Lakes Hydrography Dataset: Consistent, Binational Watersheds for the Laurentian Great Lakes Basin

Ecosystem‐based management of the Laurentian Great Lakes, which spans both the United States and Canada, is hampered by the lack of consistent binational watersheds for the entire Basin. Using comparable data sources and consistent methods, we developed spatially equivalent watershed boundaries for the binational extent of the Basin to create the Great Lakes Hydrography Dataset (GLHD). The GLHD consists of 5,589 watersheds for the entire Basin, covering a total area of approximately 547,967 km2, or about twice the 247,003 km2 surface water area of the Great Lakes. The GLHD improves upon existing watershed efforts by delineating watersheds for the entire Basin using consistent methods; enhancing the precision of watershed delineation using recently developed flow direction grids that have been hydrologically enforced and vetted by provincial and federal water resource agencies; and increasing the accuracy of watershed boundaries by enforcing embayments, delineating watersheds on islands, and delineating watersheds for all tributaries draining to connecting channels. In addition, the GLHD is packaged in a publically available geodatabase that includes synthetic stream networks, reach catchments, watershed boundaries, a broad set of attribute data for each tributary, and metadata documenting methodology. The GLHD provides a common set of watersheds and associated hydrography data for the Basin that will enhance binational efforts to protect and restore the Great Lakes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134077/1/jawr12435_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134077/2/jawr12435.pd

The nature and space density of fossil groups of galaxies

We describe the properties of a sample of galaxy groups with very unusual distributions of galaxy luminosities. The most extreme example has an X-ray luminosity similar to that of the Virgo cluster but has a very low richness, with only one galaxy brighter than L*, compared with six in Virgo. That one galaxy, however, is optically more luminous than any galaxy in Virgo and has an optical luminosity as bright as many of the central cD galaxies in rich Abell clusters. The characteristic feature of the fossil groups we study is that most of the light arises from one dominant, central galaxy. We define a fossil system and, based on this definition, construct a small X-ray selected, flux-limited sample of fossil groups with well known selection criteria. We confirm that these systems are indeed groups of galaxies, but dominated by one central luminous giant elliptical galaxy and with few, or no, L* galaxies. We find that fossil systems represent 8%-20% of all systems of the same X-ray luminosity. Fossil groups are at least as numerous as all poor and rich clusters combined, and are thus a possible site for the formation of luminous central cluster galaxies before infall into clusters occurs. The fossil systems in our sample have significantly higher X-ray luminosities than normal groups of similar total optical luminosities (or similar X-ray temperature, where the latter can be measured). These enhanced X-ray luminosities may be due to relatively cool gas in the innermost regions or due to a low central gas entropy. We interpret fossil groups as old, undisturbed systems which have avoided infall into clusters, but where galaxy merging of most of the L* galaxies has occurred. An early formation epoch, before that of most groups, could explain low central gas entropies and high X-ray luminosities.Comment: to appear in MNRAS, 13 pages, 8 figure

Sunyaev-Zel'dovich power spectrum with decaying cold dark matter

Recent studies of structures of galaxies and clusters imply that dark matter might be unstable and decay with lifetime $\Gamma^{-1}$ about the age of universe. We study the effects of the decay of cold dark matter on the Sunyaev-Zel'dovich (SZ) power spectrum. We analytically calculate the SZ power spectrum taking finite lifetime of cold dark matter into account. We find the finite lifetime of dark matter decreases the power at large scale ($l < 4000$) and increases at small scale ($l > 4000$). This is in marked contrast with the dependence of other cosmological parameters such as the amplitude of mass fluctuations $\sigma_{8}$ and the cosmological constant $\Omega_{\lambda}$ (under the assumption of a flat universe) which mainly change the normalization of the angular power spectrum. This difference allows one to determine the lifetime and other cosmological parameters rather separately. We also investigate sensitivity of a future SZ survey to the cosmological parameters including the life time, assuming a fiducial model $\Gamma^{-1} = 10 h^{-1} {\rm Gyr}$, $\sigma_{8} = 1.0$, and $\Omega_{\lambda} = 0.7$. We show that future SZ surveys such as ACT, AMIBA, and BOLOCAM can determine the lifetime within factor of two even if $\sigma_{8}$ and $\Omega_{\lambda}$ are marginalized.Comment: 7 pages, 5 figure

Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe

Observations of the high-redshift Universe with the 21 cm hyperfine line of neutral hydrogen promise to open an entirely new window onto the early phases of cosmic structure formation. Here we review the physics of the 21 cm transition, focusing on processes relevant at high redshifts, and describe the insights to be gained from such observations. These include measuring the matter power spectrum at z~50, observing the formation of the cosmic web and the first luminous sources, and mapping the reionization of the intergalactic medium. The epoch of reionization is of particular interest, because large HII regions will seed substantial fluctuations in the 21 cm background. We also discuss the experimental challenges involved in detecting this signal, with an emphasis on the Galactic and extragalactic foregrounds. These increase rapidly toward low frequencies and are especially severe for the highest redshift applications. Assuming that these difficulties can be overcome, the redshifted 21 cm line will offer unique insight into the high-redshift Universe, complementing other probes but providing the only direct, three-dimensional view of structure formation from z~200 to z~6.Comment: extended review accepted by Physics Reports, 207 pages, 44 figures (some low resolution); version with high resolution figures available at http://pantheon.yale.edu/~srf28/21cm/index.htm; minor changes to match published versio