Cosmological solutions of massive gravity on de Sitter

In the framework of the recently proposed models of massive gravity, defined with respect to a de Sitter reference metric, we obtain new homogeneous and isotropic solutions for arbitrary cosmological matter and arbitrary spatial curvature. These solutions can be classified into three branches. In the first two, the massive gravity terms behave like a cosmological constant. In the third branch, the massive gravity effects can be described by a time evolving effective fluid with rather remarkable features, including the property to behave as a cosmological constant at late time.Comment: 6 pages, 1 figure; discussion extended, a few references added, improved analysis in Section

Thermal quantum and classical correlations in two qubit XX model in a nonuniform external magnetic field

We investigate how thermal quantum discord (QD) and classical correlations (CC) of a two-qubit one-dimensional XX Heisenberg chain in thermal equilibrium depend on the temperature of the bath as well as on nonuniform external magnetic fields applied to two qubits and varied separately. We show that the behavior of QD differs in many unexpected ways from the thermal entanglement (EOF). For the nonuniform case (B1 = -B2), we find that QD and CC are equal for all values of (B1 = -B2) and for different temperatures. We show that, in this case, the thermal states of the system belong to a class of mixed states and satisfy certain conditions under which QD and CC are equal. The specification of this class and the corresponding conditions are completely general and apply to any quantum system in a state in this class satisfying these conditions. We further find that the relative contributions of QD and CC can be controlled easily by changing the relative magnitudes of B1 and B2. Finally, we connect our results with the monogamy relations between the EOF, CC and the QD of two qubits and the environment.Comment: 8 pages, 13 figures. We connect our results with the monogamy relations between the EOF, CC and the QD of two qubits and the environmen

Non-Linear Massive Gravity with Additional Primary Constraint and Absence of Ghosts

We complete the Hamiltonian analysis of specific model of non-linear massive gravity that was started in arXiv:1112.5267. We identify the primary constraint and corresponding secondary constraint. We show that they are the second class constraints and hence they lead to the elimination of the additional scalar mode. We also find that the remaining constraints are the first class constraints with the structure that corresponds to the manifestly diffeomorphism invariant theory. Finally we determine the number of physical degrees of freedom and we show that it corresponds to the number of physical modes of massive gravity.Comment: 13 page

The tribological characteristics of the cactus and mineral oil blends using four-ball tribotester

The oil derived from vegetables has been seen as an alternative to mineral oils for lubricants because of certain inherent technical properties, renewable source and their abilities to biodegrade. Vegetable oil is known to have a high viscosity index with a higher lubricity value compared to mineral oil. Despite its potentiality as a candidate alternative, vegetable oil has several limitations. It has a low wear resistance, and it is highly sensitive to temperatures with tribological characteristics. The majority of technical solutions, including additivation, chemical alterations, and blending, are being proposed as means of overcoming the listed limitations. This study seeks to investigate the characteristics of cactus oil with respect to its use as a bio-lubricant as well as the characteristics of environmentally friendly vegetable oil when they are mixed with mineral oils as alternative oil for petroleum, using the four-ball tribotester. The volumetric blending ratio was varied (20% to 80%) and these blends were performed at 1200 rpm, for one hour, with 40 kg of load at a temperature of 75ºC (ASTM D4172-B) standard. According to the results, it was found that the lowest wear scar diameter was 431.23μm, which was identified in the blend of 20% cactus oil with 80% mineral oil which symbolized by (CC20%), compared to that of neat cactus oil at 669.16 μm and mineral oil at 546.46 μm.In addition, the result also indicates that a 80% addition of cactus oil, the coefficient of friction tends to decrease compared to the values of neat cactus oil. Finally, it is concluded, the blends of cactus oil with commercial lubricant oil have better performance compared to commercial lubricant oil or neat cactus oil

Incoherent Transport through Molecules on Silicon in the vicinity of a Dangling Bond

We theoretically study the effect of a localized unpaired dangling bond (DB) on occupied molecular orbital conduction through a styrene molecule bonded to a n++ H:Si(001)-(2x1) surface. For molecules relatively far from the DB, we find good agreement with the reported experiment using a model that accounts for the electrostatic contribution of the DB, provided we include some dephasing due to low lying phonon modes. However, for molecules within 10 angstrom to the DB, we have to include electronic contribution as well along with higher dephasing to explain the transport features.Comment: 9 pages, 5 figure

Case studies of six CBFM-2 water bodies

The case studies report on how CBFM-2 interventions have affected aquatic productivity, income, employment and livelihoods in six case study sites, Beelbhora beel cluster (Kishoreganj), Sholuar beel (Narail), Chapundaha beel (Rangpur), Hamil beel (Tangail), Kutir beel (Kishoreganj) and Dikshi beel (Pabna).

COMPARATIVE PRODUCTIVE PERFORMANCE AND EGG CHARACTERISTICS OF PULLETS AND SPENT LAYERS

Production performance and egg quality characteristics of pullets and spent layers were compared in this study. Forty birds, each from the flocks of pullets (24 weeks old) and spent layers (76 weeks old) were selected as experimental birds. The birds from each age group were divided into five replicates, each comprising of eight birds. All the experimental birds were fed a commercial layer ration @ 110g/bird/day for 12 weeks. The data on egg production, feed consumption, egg weight and egg quality characteristics viz. shell thickness, shell weight, breaking strength, albumen diameter, albumen weight and yolk weight were recorded. The data thus collected were utilized for calculation of FCR, Haugh unit and yolk index values. The results revealed that pullets produced more eggs and utilized their feed more efficiently than spent layers. However, egg weight in spent layers was higher than in their counterparts. Pullets also produced eggs with thicker shell and higher Haugh unit values when compared to the spent layers. Feed consumption and yolk index values remained unaffected due to the age. Pullets also had better egg quality characteristics than those of spent layers

Green synthesis of silver nanoclusters via Melia azedarach plant and their potential towards catalytic reduction of 4-nitrophenol

Biomolecules present in the plant extracts have potential to reduce metal ions to nanoclusters by a single-step green synthesis approach. In the current study, we have synthesized the silver nanoclusters (AgNCs) from a medicinal plant, Melia azedarach and studied their catalytic activity toward the reduction of 4-nitophenol to 4-aminophenol and organic dyes. Morover, the phytochemical analysis of the plant extract was carried out in order to determine the bioactive compounds present in it. Metallic nature of the synthesized AgNCs was verified by X-ray diffraction study, while their morphology and size of was confirmed by transmission electron microscopy and Zetasizer, respectively. The study revealed that they were 56±2 nm in size and formed clusters. Fourier transformed infrared spectroscopy gives information about the different functional groups present in synthesized these NCs. Furthermore, the important catalytic applications, such as catalytic reduction of 4-nitrophenol in the presence of mild reducing agent NaBH4 and the catalytic degradation of organic dyes was monitored by FTIR. Therefore, these results indicate that the obtained nanomaterials have important applications in industrial areas.                     KEY WORDS: Green synthesis, Silver nanoclusters, Catalytic reduction, Characterization   Bull. Chem. Soc. Ethiop. 2021, 35(1), 197-206. DOI: https://dx.doi.org/10.4314/bcse.v35i1.1