96 research outputs found
Gravitation Interaction and Electromagnetic Interaction in the Relativistic Universe with Total Zero and Local Non-Zero Energy
In the model of flat expansive homogeneous and isotropic relativistic
universe with total zero and local non-zero energy the gravitation energy of
bodies and the elecromagnetic energy of charged bodies can be localised.Comment: LaTeX, 10 pages, 1 figur
<i>N,N</i>-bis-(dimethylfluorosilylmethyl)amides of <i>N</i>-organosulfonylproline and sarcosine: synthesis, structure, stereodynamic behaviour and <i>in silico</i> studies
(O→Si)-Chelate difluorides R3R2NCH(R1)C(O)N(CH2SiMe2F)2 (9a–c, R1R2 = (CH2)3, R3 = Ms (a), Ts (b); R1 = H, R2 = Me, R3 = Ms (c)), containing one penta- and one tetracoordinate silicon atoms were synthesized by silylmethylation of amides R3R2NCH(R1)C(O)NH2, subsequent hydrolysis of unstable intermediates R3R2NCH(R1)C(O)N(CH2SiMe2Cl)2 (7a–c) into 4-acyl-2,6-disilamorpholines R3R2NCH(R1)C(O)N(CH2SiMe2O)2 (8a–c) and the reaction of the latter compounds with BF3·Et2O. The structures of disilamorpholines 8a,c and difluoride 9a were confirmed by an X-ray diffraction study. According to the IR and NMR data, the O→Si coordination in solutions of these compounds was weaker than that in the solid state due to effective solvation of the Si–F bond. A permutational isomerisation involving an exchange of equatorial Me groups at the pentacoordinate Si atom in complexes 9a–c was detected, and its activational parameters were determined by 1H DNMR. In silico estimation of possible pharmacological effects and acute rat toxicity by PASS Online and GUSAR Online services showed a potential for their further pharmacological study
Mechanical Behavior of Osteoporotic Bone at Sub-Lamellar Length Scales
Osteoporosis is a disease known to promote bone fragility but the effect on the mechanical properties of bone material, which is independent of geometric effects, is particularly unclear. To address this problem, micro-beams of osteoporotic bone were prepared using focused ion beam microscopy and mechanically tested in compression using an atomic force microscope while observing them using in situ electron microscopy. This experimental approach was shown to be effective for measuring the subtle changes in the mechanical properties of bone material required to evaluate the effects of osteoporosis. Osteoporotic bone material was found to have lower elastic modulus and increased strain to failure when compared to healthy bone material, while the strength of osteoporotic and healthy bone was similar. Surprisingly, the increased strain to failure for osteoporotic bone material provided enhanced toughness relative to the control samples, suggesting that lowering of bone fragility due to osteoporosis is not defined by material performance. A mechanism is suggested based on these results and previous literature that indicates degradation of the organic material in osteoporosis bone is responsible for resultant mechanical properties
Structural orientation dependent sub-lamellar bone mechanics
The lamellar unit is a critical component in defining the overall mechanical properties of bone. In this paper, micro-beams of bone with dimensions comparable to the lamellar unit were fabricated using focused ion beam (FIB) microscopy and mechanically tested in bending to failure using atomic force microscopy (AFM). A variation in the mechanical properties, including elastic modulus, strength and work to fracture of the micro-beams was observed and related to the collagen fibril orientation inferred from back-scattered scanning electron microscopy (SEM) imaging. Established mechanical models were further applied to describe the relationship between collagen fibril orientation and mechanical behaviour of the lamellar unit. Our results highlight the ability to measure mechanical properties of discrete bone volumes directly and correlate with structural orientation of collagen fibrils
An Ap-Structure with Finslerian Flavor: I
A geometric structure (FAP-structure), having both absolute parallelism and
Finsler properties, is constructed. The building blocks of this structures are
assumed to be functions of position and direction. A non-linear connection
emerges naturally and is defined in terms of the building blocks of the
structure. Two linear connections, one of Berwald type and the other of the
Cartan type, are defined using the non-linear connection of the FAP. Both
linear connections are non-symmetric and consequently admit torsion. A metric
tensor is defined in terms of the building blocks of the structure. The
condition for this metric to be a Finslerian one is obtained. Also, the
condition for an FAP-space to be an AP-one is given.Comment: 13 pages, LaTeX file, typographical corrections. Part of a talk
presented at The International Conference on "Finsler Extensions of
Relativity Theory" held at Cairo, Egypt, November 4-10,200
The emergence of gravity as a retro-causal post-inflation macro-quantum-coherent holographic vacuum Higgs-Goldstone field
We present a model for the origin of gravity, dark energy and dark matter:
Dark energy and dark matter are residual pre-inflation false vacuum random zero
point energy (w=-1) of large-scale negative, and short-scale positive pressure,
respectively, corresponding to the "zero point" (incoherent) component of a
superfluid (supersolid) ground state. Gravity, in contrast, arises from the 2nd
order topological defects in the post-inflation virtual "condensate" (coherent)
component. We predict, as a consequence, that the LHC will never detect exotic
real on-mass-shell particles that can explain dark matter. We also point out
that the future holographic dark energy de Sitter horizon is a total absorber
(in the sense of retro-causal Wheeler-Feynman action-at-a-distance
electrodynamics) because it is an infinite redshift surface for static
detectors. Therefore, the advanced Hawking-Unruh thermal radiation from the
future de Sitter horizon is a candidate for the negative pressure dark vacuum
energy.Comment: 8 pages, no figures. To appear in Proc. DICE2008 From Quantum
Mechanics through Complexity to Spacetime: the role of emergent dynamical
structures. Castello Pasquini/Castiglioncello (Tuscany), September 22-26,
200
Bringing spacecraft into solar-oriented attitude by the measurements of a single-axis angular-rate sensor and an optical solar sensor
The algorithm of the turn of the spacecraft from an initial arbitrary angular position at an arbitrary angular rate to a solar-oriented attitude is investigated. Minimum essential equipment of the motion control system required for the purpose of ensuring maintenance of solar orientation is defined: a solar sensor, a single-axis angular-rate sensor, low-thrust liquid rocket engines. A solution of the problem of defining the spacecraft angular rate vector by the measurements of the deviation of the optical axis of the solar sensor from the sun vector and the single-axis angular-rate sensor is presented. The conditions under which control action on the rocket engines for the purpose of changing the value of the angular-rate vector for the Sun to get into the field of viewing of the solar sensor or for the spacecraft stabilization are defined. Mathematical modeling of the spacecraft attitude control system with the unknown initial state vector of motion is carried out. The results of mathematical modeling confirmed the efficiency of the proposed algorithm in terms of reducing propellant fuel consumption and high-speed performance. In comparison with the known methods of solving the problem of reducing angular speed (a lengthy process with the use of a magnetic system or a fast process with the use of a three-axis angular-rate sensor and rocket engines) the duration of the process of reducing angular speeds is the same as in normal operation, however, at the same time the problem of bringing spacecraft into the solar oriented attitude is solved
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