Upper limit to ΩB\Omega_B in scalar-tensor gravity theories

In a previous paper (Serna & Alimi 1996), we have pointed out the existence of some particular scalar-tensor gravity theories able to relax the nucleosynthesis constraint on the cosmic baryonic density. In this paper, we present an exhaustive study of primordial nucleosynthesis in the framework of such theories taking into account the currently adopted observational constraints. We show that a wide class of them allows for a baryonic density very close to that needed for the universe closure. This class of theories converges soon enough towards General Relativity and, hence, is compatible with all solar-system and binary pulsar gravitational tests. In other words, we show that primordial nucleosynthesis does not always impose a very stringent bound on the baryon contribution to the density parameter.Comment: uuencoded tar-file containing 16 pages, latex with 5 figures, accepted for publication in Astrophysical Journal (Part 1

Synthesis and characterization of novel copolymers based on carbazole and anthracene, for optoelectronic applications

The goal of this work is to study a new copolymer which combines the Ecbz properties and those Ant. First, we describe the route for preparing the new copolymer. Then, we report characterization measurements based on solid-state Nuclear Magnetic Resonance (CP-MAS 13C NMR), Raman, IR absorption, UV–visible absorption, photoluminescence spectroscopy, Scanning Electron Microscopy (SEM), and X-ray diffraction

Novel 6-aryl-7-alkyl/aryl-[1,2,4]triazolo[4,3-a][1,3,5]triazine-5(6H)-thiones, processes for their preparation, characterization and evaluation of their in vitro antioxidant activity

ABSTRACT. A series of nine new 6-aryl-7-alkyl/aryl-[1,2,4]triazolo[4,3-a][1,3,5]triazine-5(6H)-thiones (2a-i) were synthesized by a reaction of N-triazol-3-yl imidates (1) with three different isothiocyanate derivatives (RNCS)  in refluxing toluene. The structures of the final heterocyclic compounds were confirmed by 1H-NMR, 13C-NMR, FT-IR, elemental analysis, and mass spectral analysis. The target compounds (2a-i) were in vitro screened for their activity as antioxidants using DPPH (2,2′-diphenyl-1-picrylhydrazyl) and FRAP (ferric reducing/antioxidant power) methods. The results revealed that some triazolotriazine-5-(6H)thiones exhibited antioxidant activity ranging from moderate to high. The obtained findings revealed that the triazolotriazine-5-(6H)thiones (2g, 2h, and 2i) have superiority among all compounds, It is obvious that the presence of a hydroxyl group in the structure is essential for the antioxidant properties and should be taken into consideration in further design of structures with potential antioxidant properties.                     KEY WORDS: Imidates, Isothiocyanates, Antioxidant, Triazole, DPPH, FRAP   Bull. Chem. Soc. Ethiop. 2021, 35(3), 565-572. DOI: https://dx.doi.org/10.4314/bcse.v35i3.

Time Dependence of Brans-Dicke Parameter w for an Expanding Universe

We have studied the time dependence of w for an expanding universe in the generalised B-D theory and have obtained its explicit dependence on the nature of matter contained in the universe,in different era.Lastly we discuss how the observed accelerated expansion of the present universe can be accomodated in the formalism.Comment: 10 pages,No figure

Network congestion management using Call Admission Control

Abstract: Call Admission Control schemes have been used extensively in improving mobile network quality. Signal quality degradation, interference and network congestion has been a real issue for Global System for Mobile Communication (GSM) as the number of mobile users increased rapidly. It has been an issue in providing a decent Quality of Service (QoS) to the network users especially during the period of high network traffic. It is essential to maintain a certain level of quality in handling mobile network congestion. Fortunately, Call Admission Control is a strategy that can provide credible QoS by limiting the number of connections into the cellular network thereby reducing network congestions, dropping of calls, interference and other QoS problems. In this paper, we discuss issues around mobile network congestion, overview of congestion management schemes, attributes and benefits of Call Admission Control (CAC). We also highlight different handoff schemes. We simulated a typical CAC scheme comparing the new call blocking probability and handoff call probability

Comparison of Source Rock Geochemistry of Selected Rocks from the Schei Point Group and Ringnes Formation, Sverdrup Basin, Arctic Canada

Organic-rich from the Schei Point group (middle to late Triassic in age) and the Ringnes formation (late Jurassic) from the Sverdrup basin of the Canadian arctic archipelago have been geochemically evaluated for source rock characterization. Most samples from the Schei Point group are organic-rich (\u3e 2% TOC) and are considered as immature to mature oil-prone source rocks [kerogen types I, I-II (IIA) and II (IIA)]. These kerogen types contain abundant AOM1, AOM2 and alginite (Tasmanales, Nostocopsis, Leiosphaeridia, acritarch and dinoflagellate) with variable amounts of vitrinite, inertinite and exinite. Samples from the Ringnes formation contain dominant vitrinite and inertinite with partially oxidized AOM2, alginite and exinite forming mostly immature to mature condensate- and gas-prone source rocks [kerogen type II- III (IIB), III and a few II (IIA)]. Schei Point samples contain higher bitumen extract, saturate hydrocarbons and saturate/aromatic ratio than the Ringnes samples. Triterpane and sterane (dominant C30) distribution patterns and stable carbon isotope of bitumen and kerogen suggest that the analyzed samples from the Schei Point group are at the onset of oil generation and contain a mixture of sapropelic (algal) and minor terrestrial humic organic matter. Sterane carbon number distributions in the Ringnes formation also suggest a mixed algal and terrestrial organic matter type. There are some variations in hopane carbon number distributions, but these are apparently a function of thermal maturity rather than significant genetic differences among samples. Pyrolysis-gas chromatography/mass spectrometry of the two samples with similar maturity shows that the Schei Point sample generates three times more pyrolyzate than the Ringnes sample. Both samples have a dominant aliphatic character, although the Ringnes sample contains phenol and an aromaticity that is higher than that of the Schei Point sample

Optical signal phase retrieval with low complexity DC-value method

We propose a novel method to reconstruct the optical signal phase information using direct detection. The method is suitable for minimum phase signals and it enables low complexity, low latency, and low tone power operation. Moreover, the proposed method offers low optical complexity solution for the short-reach links compared with the concurrent phase retrieval techniques. We apply the method to M-ary signals with the transmitted power of as low as 3 dBm, and we are able to reach 70 km for 100 Gb/s quadrature phase shift keying (QPSK) system without optical amplification. Our method is based on the single sideband (SSB) and DC-Value property of the minimum phase signal. The SSB and DC-Value properties are iteratively imposed on the amplitude signal in the frequency domain to recover the full complex field from a directly detected optical signal. The normalized mean square error (NMSE) value between the available amplitude information and reconstructed minimum phase signal amplitude decreases after each iteration, providing global minimum convergence. A constant scaling factor is exploited to improve the convergence speed. The scaling factor provides 6 dB, 4.5 dB, and 2.5 dB error vector magnitude (EVM) gains with 4, 5, and 8 iterations, respectively.publishe