1,397 research outputs found
Vacuumless topological defects in Lyra geometry
Few years ago, Cho and Vilenkin have proposed that topological defects can
arise in symmetry breaking models without having degenerate vacua. These types
of defects are known as vacuumless defects. In the present work, the
gravitational field of a vacuumless global string and global monopole have been
investigated in the context of Lyra geometry. We find the metric of the
vacuumless global string and global monopole in the weak field approximations.
It has been shown that the vacuumless global string can have repulsive whereas
global monopole exerts attractive gravitational effects on a test particle. It
is dissimilar to the case studied in general relativity.Comment: 14 pages, 9 figures. To appear in Astrophys.Space.Sc
Cu-based metalorganic systems: an ab initio study of the electronic structure
Within a first principles framework, we study the electronic structure of the
recently synthesized polymeric coordination compound
Cu(II)-2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene (CuCCP), which has been
suggested to be a good realization of a Heisenberg spin-1/2 chain with
antiferromagnetic coupling. By using a combination of classical with ab initio
quantum mechanical methods, we design on the computer reliable modified
structures of CuCCP aimed at studying effects of Cu-Cu coupling strength
variations on this spin-1/2 system. For this purpose, we performed two types of
modifications on CuCCP. In one case, we replaced H in the linker by i) an
electron donating group (NH2) and ii) an electron withdrawing group (CN), while
the other modification consisted in adding H2O and NH3 molecules in the
structure which change the local coordination of the Cu(II) ions. With the
NMTO-downfolding method we provide a quantitative analysis of the modified
electronic structure and the nature of the Cu-Cu interaction paths in these new
structures and discuss its implications for the underlying microscopic model.Comment: 18 pages, 11 figures, final versio
A new proposal for Galactic dark matter: Effect of f(T) gravity
It is still a challenging problem to the theoretical physicists to know the
exact nature of the galactic dark matter which causes the galactic rotational
velocity to be more or less a constant. We have proposed that the dark matter
as an effect of f(T) gravity. Assuming the flat rotation curves as input we
have shown that f(T) gravity can explain galactic dynamics. Here, we don' have
to introduce dark matter. Spacetime metric inspired by f(T) gravity describes
the region up to which the tangential velocity of the test particle is
constant. This inherent property appears to be enough to produce stable
circular orbits as well as attractive gravity.Comment: 7 pages and 1 figure. Minor corrections are made. Accepted for
publication in Int.J.Theor.Phy
Precision mass measurements of radioactive nuclei at JYFLTRAP
The Penning trap mass spectrometer JYFLTRAP was used to measure the atomic
masses of radioactive nuclei with an uncertainty better than 10 keV. The atomic
masses of the neutron-deficient nuclei around the N = Z line were measured to
improve the understanding of the rp-process path and the SbSnTe cycle.
Furthermore, the masses of the neutron-rich gallium (Z = 31) to palladium (Z =
46) nuclei have been measured. The physics impacts on the nuclear structure and
the r-process paths are reviewed. A better understanding of the nuclear
deformation is presented by studying the pairing energy around A = 100.Comment: 4 pages and 4 figures, RNB7 conf. pro
Fuzzy Logic Controller Design for Intelligent Air-Conditioning System
Inefficient air cooling systems may cause of wasting energy in a great amount specially in the urban area. Being the most popular cooling system, air-conditioners have been used in domestic usage as well as in industrial applications. However, the unintelligent nature of such cooling system gives rise to excess energy consumption which causes a huge problem in the current energy hungry world. In this paper, we present design of a fuzzy logic controller for the intelligent air-conditioning system. The performance of the controller is also simulated. The proposed controller has the adaptive nature to control fan and compressor speed which leads to reducing power consumption. Also, the system controls the operation mode to retain the healthy oxygen level and humid condition of the indoor environment
Synthesis, Molecular Structures and Electrochemical Investigations of [FeFe]-Hydrogenase Biomimics [Fe₂(CO)_{6-n}(EPh₃)_{n}(mu-edt)] (E = P, As, Sb; n = 1, 2)
A series of ethane‐dithiolate (edt = S(CH_{2})_{2}S) complexes [Fe_{2}(CO)_{5}(EPh_{3})(µ‐edt)] and [Fe_{2}(CO)4(EPh_{3})_{2}(µ‐edt)] (E = P, As, Sb), biomimics of the core of [FeFe]‐hydrogenases, have been prepared and structurally characterised. The introduced ligand(s) occupies apical sites lying trans to the iron‐iron bond. NMR studies reveal that while in the mono‐substituted complexes the Fe(CO)_{3} moiety undergoes facile trigonal rotation, the Fe(CO)2(PPh3) centres do not rotate on the NMR timescale. The reductive chemistry has been examined by cyclic voltammetry both in the presence and absence of CO and the observed behavior is found to be dependent upon the nature of the substituents. With L = CO or SbPh_{3} potential inversion is seen leading to a two‐electron reduction, while for others (L = PPh_{3}, AsPh_{3}) a quasi‐reversible one‐electron reduction is observed. Protonation studies reveal that [Fe_{2}(CO)_{5}(PPh_{3})(µ‐edt)] is only partially protonated by excess HBF_{4}·Et_{2}O, thus ruling complexes [Fe_{2}(CO)_{5}(EPh3)(µ‐edt)(µ‐H)]^{+} out as a catalytic intermediates, but [Fe_{2}(CO)_{4}(PPh_{3})_{2}(µ‐edt)] reacts readily with HBF_{4}·Et_{2}O to produce [Fe_{2}(CO)_{4}(PPh3)_{2}(µ‐edt)(µ‐H)]^{+}. While all new complexes are catalysts for the reduction of protons in MeCN, their poor stability and relatively high reduction potentials does not make them attractive in this respect
Bianchi Type III Anisotropic Dark Energy Models with Constant Deceleration Parameter
The Bianchi type III dark energy models with constant deceleration parameter
are investigated. The equation of state parameter is found to be time
dependent and its existing range for this model is consistent with the recent
observations of SN Ia data, SN Ia data (with CMBR anisotropy) and galaxy
clustering statistics. The physical aspect of the dark energy models are
discussed.Comment: 12 pages, 2 figures, Accepted version of IJT
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