We investigate the influence of mass inhomogeneities on the angular size-redshift test through a statistical analysis of angular size data for a large sample of milliarcsecond radio sources. The results are based on f...
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We investigate the influence of mass inhomogeneities on the angular size-redshift test through a statistical analysis of angular size data for a large sample of milliarcsecond radio sources. The results are based on flat models driven by nonrelativistic: matter plus a dark energy component in the form of a relic cosmological constant. To model the mass inhomogeneities we use the Zeldovich-Kantowski distance formula (also known as Dyer-Roeder distance redshift relation) which is characterized by the smoothness parameter alpha Marginalizing over the characteristic angular size 1 and assuming a Gaussian prior on the matter density parameter, i.e., Omega(m) = 0.35 +/- 0.07, the best fit model occurs at Omega(m) = 0.35 and alpha = 0.8. For an analysis without priors and minimizing chi(2) for the parameters 1, Omega(m) and alpha we find that a conventional homogeneous scenario (alpha = 1) with Omega(m) = 0.2 and D = 22.6h(-1) pc constitutes the best fit model for the present angular size data.
Significant progress in the chemistry of main group compounds (group 13, 14, and 15) containing homonuclear multiple bonds has been made over the past three decades. This feature article addresses the unique structura...
Significant progress in the chemistry of main group compounds (group 13, 14, and 15) containing homonuclear multiple bonds has been made over the past three decades. This feature article addresses the unique structural and bonding motifs of these compounds, with a particular emphasis on both iconic molecules and recent novel discoveries.
The chemical composition of growing media is a key factor for plant growth, impacting agricultural yield and sustainability. However, there is a lack of affordable chemical sensors for ubiquitous nutrient ion monitori...
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The chemical composition of growing media is a key factor for plant growth, impacting agricultural yield and sustainability. However, there is a lack of affordable chemical sensors for ubiquitous nutrient ion monitoring in agricultural applications. This work investigates using fully printed ion-sensor arrays to measure the concentrations of nitrate, ammonium, and potassium in mixed-electrolyte media. Ion sensor arrays composed of nitrate, ammonium, and potassium ion-selective electrodes and a printed silver-silver chloride (Ag/AgCl) reference electrode are fabricated and characterized in aqueous solutions in a range of concentrations that encompass what is typical for agricultural growing media (0.01 mm -1 m). The sensors are also tested in mixed-electrolyte solutions of NaNO3, NH4Cl, and KCl of varying concentrations, and the recorded potentials are input into Nernstian and artificial neural network models to compare the prediction accuracy of the models against ground truth. The artificial neural network models demonstrated higher accuracy over the Nernstian model, and the model using only ion-sensor inputs is 7.5% more accurate than the Nernstian model under the same conditions. By enabling more precise and efficient fertilizer application, these sensor arrays coupled to computational models can help increase crop yields, optimize resource use, and reduce environmental impact.
We have investigated the structural and electronic properties of a graphene nanoribbon with topological knotlike defects using first-principles calculations. As the knotted ribbon is stretched, we find two distinct me...
We have investigated the structural and electronic properties of a graphene nanoribbon with topological knotlike defects using first-principles calculations. As the knotted ribbon is stretched, we find two distinct metastable knot configurations. The first one, a self-tied knot configuration, is stable due to interlayer interactions. The second one, a tight-knot configuration, is stable due to the rehybridization of carbons atoms inside the knot, with the formation of additional covalent bonds, and of localized electronic states in the energy bandgap. Also, the tight-knot configuration has a spin-polarized ground state with a nonzero spin dipole moment.
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