Reconstructing an estimate of linear baryon acoustic oscillations (BAO) from an evolved galaxy field has become a standard technique in recent analyses. By partially removing non-linear damping ...caused by bulk motions, the real-space BAO peak in the correlation function is sharpened, and oscillations in the power spectrum are visible to smaller scales. In turn these lead to stronger measurements of the BAO scale. Future surveys are being designed assuming that this improvement has been applied, and this technique is therefore of critical importance for future BAO measurements. A number of reconstruction techniques are available, but the most widely used is a simple algorithm that decorrelates large-scale and small-scale modes approximately removing the bulk-flow displacements by moving the overdensity field. We consider the practical implementation of this algorithm, looking at the efficiency of reconstruction as a function of the assumptions made for the bulk-flow scale, the shot-noise level in a random catalogue used to quantify the mask and the method used to estimate the bulk-flow shifts. We also examine the efficiency of reconstruction against external factors including galaxy density, volume and edge effects, and consider their impact for future surveys. Throughout we make use of the mocks catalogues created for the Baryon Oscillation Spectroscopic Survey (BOSS) Date Release 11 samples covering 0.43 < z < 0.7 (CMASS) and 0.15 < z < 0.43 (LOWZ), to empirically test these changes.
Fe3O4/γ-Fe2O3 nanoparticles (NPs) based thin films were used as active layers in solid state resistive chemical sensors. NPs were synthesized by high temperature solution phase reaction. Sensing NP ...monolayers (ML) were deposited by Langmuir–Blodgett (LB) techniques onto chemoresistive transduction platforms. The sensing ML were UV treated to remove NP insulating capping. Sensors surface was characterized by scanning electron microscopy (SEM). Systematic gas sensing tests in controlled atmosphere were carried out toward NO2, CO, and acetone at different concentrations and working temperatures of the sensing layers. The best sensing performance results were obtained for sensors with higher NPs coverage (10 ML), mainly for NO2 gas showing interesting selectivity toward nitrogen oxides. Electrical properties and conduction mechanisms are discussed.
In this paper, among all transduction methodologies reported in the field of solid state chemical sensors, the attention has been focused onto the optical sensing characterization by using surface ...plasmon resonance (SPR) technique and its evolution towards active plasmonics. Activation of the transducer by application of an oscillating magnetic field in a transversal configuration is demonstrated to improve the gas sensing performance of classical SPR sensors. To this purpose a new transducer, composed of metallic and magnetic materials and a proper sensing layer have been chosen. TiO2 sensing layers have been prepared by two different experimental routes and their optical and morphological features investigated and correlated with their sensing performances. A comparison between classical SPR technique and a new sensing probe based onto magneto-plasmonic effect in resonance condition has been reported. Improved gas sensing performance in terms of sensitivity has been demonstrated in the presence of different alcohol vapours concentration mixed in dry air.
Abstract Highly multiplexed, fiber-fed spectroscopy is enabling surveys of millions of stars and galaxies. The performance of these surveys depends on accurately positioning fibers in the focal plane ...to capture target light. We describe a technique to measure the positioning accuracy of fibers by dithering fibers slightly around their ideal locations. This approach also enables measurement of the total system throughput and point-spread function delivered to the focal plane. We then apply this technique to observations from the Dark Energy Survey Instrument (DESI), and demonstrate that DESI positions fibers to within 0.″08 of their targets (5% of a fiber diameter) and achieves a system throughput within about 7% of expectations.
Abstract
Extremely metal-poor galaxies (XMPGs) at relatively low redshift are excellent laboratories for studying galaxy formation and evolution in the early universe. Much effort has been spent on ...identifying them from large-scale spectroscopic surveys or spectroscopic follow-up observations. Previous work has identified a few hundred XMPGs. In this work, we obtain a large sample of 223 XMPGs at
z
< 1 from the early data of the Dark Energy Spectroscopic Instrument (DESI). The oxygen abundance is determined using the direct
T
e
method based on the detection of the O
iii
λ
4363 line. The sample includes 95 confirmed XMPGs based on the oxygen abundance uncertainty; the remaining 128 galaxies are regarded as XMPG candidates. These XMPGs are only 0.01% of the total DESI observed galaxies. Their coordinates and other properties are provided in the paper. The most XMPGs have an oxygen abundance of ∼1/34
Z
⊙
, a stellar mass of about 1.5 × 10
7
M
⊙,
and a star formation rate of 0.22
M
⊙
yr
−1
. The two most XMPGs present distinct morphologies suggesting different formation mechanisms. The local environmental investigation shows that XMPGs preferentially reside in relatively low-density regions. Many of them fall below the stellar mass–metallicity relations (MZRs) of normal star-forming galaxies. From a comparison of the MZR with theoretical simulations, it appears that XMPGs are good analogs to high-redshift star-forming galaxies. The nature of these XMPG populations will be further investigated in detail with larger and more complete samples from the ongoing DESI survey.
We explore the biasing in the clustering statistics of haloes as compared to dark matter (DM) in simulations. We look at the second- and third-order statistics at large scales of the (intermediate) ...MICEL1536 simulation and also measure directly the local bias relation h=f(δ) between DM fluctuations, δ, smoothed over a top-hat radius R
s at a point in the simulation and its corresponding tracer h (i.e. haloes) at the same point. This local relation can be Taylor expanded to define a linear (b
1) and non-linear (b
2) bias parameter. The values of b
1 and b
2 in the simulation vary with R
s approaching a constant value around R
s > 30-60 Mpc h
−1. We use the local relation to predict the clustering of the tracer in terms of the one of DM. This prediction works very well (about per cent level) for the halo 2-point correlation ξ(r
12) for r
12 > 15 Mpc h
−1, but only when we use the biasing values that we found at very large smoothing radii R
s > 30-60 Mpc h
−1. We find no effect from stochastic or next-to-leading-order terms in the f(δ) expansion. However, we do find some discrepancies in the 3-point function that needs further understanding. We also look at the clustering of the smoothed moments, the variance and skewness which are volume-average correlations and therefore include clustering from smaller scales. In this case, we find that both next-to-leading-order and discreteness corrections (to the local model) are needed at the 10-20 per cent level. Shot-noise can be corrected with a term
, where σ2
e < 1, that is, always smaller than the Poisson correction. We also compare these results with the peak-background split predictions from the measured halo mass function. We find 5-10 per cent systematic (and similar statistical) errors in the mass estimation when we use the halo model biasing predictions to calibrate the mass.
The peak-background split argument is commonly used to relate the abundance of dark matter haloes to their spatial clustering. Testing this argument requires an accurate determination of the halo ...mass function. We present a maximum-likelihood method for fitting parametric functional forms to halo abundances which differs from previous work because it does not require binned counts. Our conclusions do not depend on whether we use our method or more conventional ones. In addition, halo abundances depend on how haloes are defined. Our conclusions do not depend on the choice of link length associated with the friends-of-friends halo finder, nor do they change if we identify haloes using a spherical overdensity algorithm instead. The large-scale halo bias measured from the matter–halo cross spectrum b× and the halo autocorrelation function bξ (on scales k∼ 0.03 h Mpc−1 and r∼ 50 h−1 Mpc) can differ by as much as 5 per cent for haloes that are significantly more massive than the characteristic mass M*. At these large masses, the peak-background split estimate of the linear bias factor b1 is 3–5 per cent smaller than bξ, which is 5 per cent smaller than b×. We discuss the origin of these discrepancies: deterministic non-linear local bias, with parameters determined by the peak-background split argument, is unable to account for the discrepancies we see. A simple linear but non-local bias model, motivated by peaks theory, may also be difficult to reconcile with our measurements. More work on such non-local bias models may be needed to understand the nature of halo bias at this level of precision.
The work reports on theoretical and nanoscale characterization of Au/Co/Au multilayers used as transducers in Magneto-optical Surface Plasmon Resonance (MOSPR) biosensors. Different aspects related ...to the optimization of transducers are discussed. In particular, optimized sensitivity is demonstrated to depend on the full multilayer total thickness, on the Co layer thickness and its position within the film, as well as on the discrepancy between the optical constants in very thin layers with respect to bulk values. Co layer thickness and position in the trilayer are optimized to provide the best compromise between magneto-optic (MO) activity and optical losses as well as to ensure large electromagnetic (EM) fields at the Au-dielectric interface. In this sense surface sensitivity can be maximized with respect to variations in the bulk properties of the measuring fluid and ensure higher performances with respect to traditional SPR biosensors. In parallel, a comprehensive study on the structural, morphological, chemical, magnetic and optical properties of layers composing the realized magneto-plasmonic (MP) transducers is reported by comparing the results of experimental and theoretical investigations. High resolution TEM (HR-TEM) images provided a deep insight on the interfaces morphologies thus revealing a significant discrepancy between modelled and real samples basically due to sizable roughness at each metal interface. As highlighted by hysteresis loop measurements, this parameter results having a critical role in tailoring the magnetic and consequently magneto-plasmonic properties of the trilayer transducers. As a proof of concept, a simple immunoassay relative to the study of an antibody-antigen interaction in liquid phase has been investigated.
Most individual fish in farmed and wild populations are infected with parasites. Upon dissection of fish, helminths from gut are often easily visible. Enteric helminths include several species of ...digeneans, cestodes, acanthocephalans and nematodes. Some insights into biology, morphology and histopathological effects of the main fish enteric helminths taxa will be described here. The immune system of fish, as that of other vertebrates, can be subdivided into specific and aspecific types, which in vivo act in concert with each other and indeed are interdependent in many ways. Beyond the small number of well-described models that exist, research focusing on innate immunity in fish against parasitic infections is lacking. Enteric helminths frequently cause inflammation of the digestive tract, resulting in a series of chemical and morphological changes in the affected tissues and inducing leukocyte migration to the site of infection. This review provides an overview on the aspecific defence mechanisms of fish intestine against helminths. Emphasis will be placed on the immune cellular response involving mast cells, neutrophils, macrophages, rodlet cells and mucous cells against enteric helminths. Given the relative importance of innate immunity in fish, and the magnitude of economic loss in aquaculture as a consequence of disease, this area deserves considerable attention and support.
Display omitted
•Fish innate cellular response.•Immune responses to different helminth taxa.•Co-occurrence of immune cell types in fish intestine-helminth systems.•Functions and relationship between intestinal immune cells.
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