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Search Results: 1 - 10 of 468308 matches for " A. A. Ahmad "
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Extraction Timing of Heavily Destructed Upper First Permanent Molars  [PDF]
Ahmad A. Rahhal
Open Journal of Stomatology (OJST) , 2014, DOI: 10.4236/ojst.2014.43024
Abstract: The first permanent molar as the first permanent tooth in the mouth and with a general insufficient oral hygiene of the children, is commonly subject to significant compromise which may arise due to caries or endodontic complication, or from developmental anomalies such as hypoplasia. Compromised teeth with questionable prognosis may result in short- and long-term clinical dilemmas. The aim of this research is to highlight the factors that require careful consideration when a compromised UFPM is detected and the importance of timely UFPM extraction to ensure the mesial drift of the upper second permanent molar (USPM) to fulfill the space of the extracted UFPM without any orthodontic intervention. For this purpose 52 heavily destructed UFPMs were extracted at age of 10.5 years old, 44 (84.6%) USPMs erupted exactly distal to the second premolar while only 7 (13.4%) USPMs erupted 1 mm distal to the second premolar. Clinically it is recommended to extract the heavily destructed upper first molars at age of 10.5 years old to ensure the complete closure of the extraction space by the passive mesial drift of upper second permanent molar.
On the Ultimate Fate of Massive Neutron Stars in an Ever Expanding Universe  [PDF]
Ahmad A. Hujeirat
Journal of Modern Physics (JMP) , 2018, DOI: 10.4236/jmp.2018.91004
Abstract: General theory of relativity predicts the central densities of massive neutron stars (-MANs) to be much larger than the nuclear density. In the absence of energy production, the lifetimes of MANs should be shorter that their low-mass counterparts. Yet neither black holes nor neutron stars, whose masses are between two and five solar masses have ever been observed. Also, it is not clear what happened to the old MANs that were created through the collapse of first generation of stars shortly after the Big Bang. In this article, it is argued that MANs must end as completely invisible objects, whose cores are made of incompressible quark-gluon-superfluids and that their effective masses must have doubled through the injection of dark energy by a universal scalar field at the background of supranuclear density. It turns out that recent glitch observations of pulsars and young neutron star systems and data from particle collisions at the LHC and RHIC are in line with the present scenario.
Black Holes, the Big Bang and the Habitable Universe: Are They Really Compatible?  [PDF]
Ahmad A. Hujeirat
Journal of Modern Physics (JMP) , 2018, DOI: 10.4236/jmp.2018.91005
Abstract: Astronomical observations have confirmed the existence of BHs and the occurrence of the Big Bang event to beyond any reasonable doubt. While quantum field theory and general theory of relativity predict the mass-spectrum of BHs to be unlimited, both theories agree that their creation is irreversible. In this article, I argue that the recently-proposed SuSu-objects (objects that are made of incompressible superconducting gluon-quark superfluids) may not only entail the required properties to be excellent BH-candidates, but also encode a hidden connection to dark matter and dark energy in cosmology. If such connection indeed exists, then the inevitable consequence would be that our universe is infinite and subject to repeated Big Bang events of the second kind, which makes the habitability of the universe certain and our cosmic relevance insignificant and meaningless.
Evidence of Pulsars Metamorphism and Their Connection to Stellar Black Holes  [PDF]
Ahmad A. Hujeirat
Journal of Modern Physics (JMP) , 2018, DOI: 10.4236/jmp.2018.94037
Abstract: It is agreed that the progenitors of neutron stars (-NSs) and black holes (-BHs) should be massive stars with \"\". Yet none of these objects have ever been found with \"\". Moreover, numerical modelings show that NSs of reasonable masses can be obtained only if the corresponding central density is beyond the nuclear one: an unverifiable density-regime with unknown physics. Here I intend to clarify the reasons underlying the existence of this mass-gap and propose a new class of invisible ultra-compact objects: the end-stage in the cosmological evolution of pulsars and neutron stars in an ever expanding universe. The present study relies on theoretical and experimental considerations as well as on solution of the non-linear TOV equation modified to include a universal scalar field at the background of supranuclear densities. The computer-code is based on finite volume method using both the first-order Euler and fourth-order Rugge-Kutta integration methods. The inclusion of at zero-temperature is motivated by recent observations of the short-living pentaquarks at the LHC. Based on these studies, I argue that pulsars must be born with embryonic super-baryons (SBs) that form through merger of individual neutrons at their centers. The cores of SBs are made of purely incompressible superconducting gluon-quark superfluids (henceforth SuSu-fluids). Such quantum fluids have a uniform supranuclear density and governed by the critical EOSs for baryonic matter \"\"and for -induced dark energy \"\". The incompressibility here ensures that particles communicate at the shortest possible time scale, superfluidity and superconductivity enforce SBs to spin-down promptly as dictated by the Onsager-Feynman equation and to expel vortices and magnetic flux tubes, whereas their lowest energy state grants SBs lifetimes that are comparable to those of protons. These extra-ordinary long lifetimes suggest that conglomeration of SuSu-objects would evolve over several big bang events to possibly form dark matter halos that embed the galaxies in the observable universe. Pulsars and young neutron stars should
Glitches: The Exact Quantum Signatures of Pulsars Metamorphosis  [PDF]
Ahmad A. Hujeirat
Journal of Modern Physics (JMP) , 2018, DOI: 10.4236/jmp.2018.94038
Abstract: The observed recurrence of glitches in pulsars and neutron stars carries rich information about the evolution of their internal structures. In this article, I show that the glitch-events observed in pulsars are exact quantum signatures for their metamorphosis into dark super-baryons (SBs), whose interiors are made of purely incompressible superconducting gluon-quark superfluids. Here the quantum nuclear shell model is adopted to describe the permitted energy levels of the SB, which are assumed to be identical to the discrete spinning rates ΩSB that SBs are allowed to rotate with. Accordingly, a glitch-event corresponds to a prompt spin-down of the superconducting SB from one energy level to the next, thereby expelling a certain number of vortices, which in turn spins up the ambient medium. The process is provoked mainly by the negative torque of the ambient dissipative nuclear fluid and by a universal scalar field at the background of a supranuclear dense matter. As dictated by the Onsager-Feynman equation, the prompt spin-down must be associated with increase of the dimensions of the embryonic SB to finally convert the entire pulsar into SB-Objects on the scale of Gyrs. Based on our calculations, a Vela-like pulsar should display billions of glitches during its lifetime, before it metamorphoses entirely into a maximally compact SB-object and disappears from our observational windows. The present model predicts the mass of SBs and ΔΩ/Ω in young pulsars to be relatively lower than their older counterparts.
Heavy Metals Nickel and Chromiumin Sediments in the Juru River, Penang, Malaysia  [PDF]
A. A. Idriss, A. K. Ahmad
Journal of Environmental Protection (JEP) , 2013, DOI: 10.4236/jep.2013.411144
Abstract:

Study was conducted to determine the concentrations of (Ni) and (Cr) in sediment and to investigate the effect pH and organic matters on concentrations of nickel and chromium in sediment at Juru River, Penang, Malaysia. The sequential extraction procedure was used based on defined fractions: exchangeable, acid reduction, oxidation and residual. The concentrations of Ni and Cr in residual fraction were higher than the other fractions. In non-residual fractions, the concentration of heavy metals in organic matter fraction was much higher than other fractions (6.63 ± 3.90 μg/g-1 dry weight ) for nickel and (6.44 ± 2.10 μg/g-1 dry weight) for chromium. The pH of the sediment in all sites was acidic. The mean of total concentrations of Ni and Cr was 38.21 and 24.92 μg/g-1 dry weight, respectively. Results of organic matter analysis showed that the percentage of organic matter present in sediment samples varied throughout the river and all sites of sediments were ranged from 7.10% to 16.20%. Comparison between sampling sites using one-way analysis of variance showed that there were significant differences for Ni (P < 0.05) while there was no significant differences for Cr (P > 0.05) in changeable fraction. At acid reduction, oxidation and residual fractions, there were significant differences for the two metals (P < 0.05). For anthropogenic metals, Ni was varied significantly (P < 0.05) whereas Cr was not found significantly (P > 0.05). Analysis of pH and

Mechanical Properties of Fly Ash Filled High Density Polyethylene  [PDF]
Iftekhar Ahmad, Prakash A. Mahanwar
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2010, DOI: 10.4236/jmmce.2010.93016
Abstract: Effect of fly ash as filler in mechanical properties of HDPE is described in this study. Three different particle size of fly ash was used. Concentration of fly ash was varied up to 40 % by weight. The composites were prepared using twin screw extruder and then test specimens were prepared by injection molding. Tensile, flexural and impact properties were tested. The microstructure was investigated through scanning electron microscopy (SEM) of the fractured samples. Both tensile and flexural strengths and moduli were found to increase with fly ash addition. Tensile elongation drastically reduced at fly ash concentration greater than 10%. With increasing fly ash concentration impact resistance decreased up to about 15% fly ash concentration and then did not reduce significantly on further addition. Composites with smallest size fly ash particles proved to be better in enhancing strength and relative elongation. Modulus and impact resistance did not seem to depend much on particle size.
Another Perspective in Generating and Using Gray Code-word
A. Ahmad
Elektrika : Journal of Electrical Engineering , 2007,
Abstract: A newly innovated set of binary code-words of unitary Hamming distance is proposed. The design of generating the code using VHDL, hardware and algorithmic implementation procedures are embodied in this paper. Also, a comparison study is carried-out to demonstrate the edge-over improvement and added advantages over the binary Gray code-words.Further, since the existence of latches is the fact of any digital system design and by exploitation of these latches in generating the Gray type codes hence reduces the extra burden of hardware to generate the ‘true’ Gray code.
A Simulation Experiment on a Built-In Self Test Equipped with Pseudorandom Test Pattern Generator and Multi-Input Shift Register (MISR)
A. Ahmad
Computer Science , 2011,
Abstract: This paper investigates the impact of the changes of the characteristic polynomials and initial loadings, on behaviour of aliasing errors of parallel signature analyzer (Multi-Input Shift Register), used in an LFSR based digital circuit testing technique. The investigation is carried-out through an extensive simulation study of the effectiveness of the LFSR based digital circuit testing technique. The results of the study show that when the identical characteristic polynomials of order n are used in both pseudo-random test-pattern generator, as well as in Multi-Input Shift Register (MISR) signature analyzer (parallel type) then the probability of aliasing errors remains unchanged due to the changes in the initial loadings of the pseudo-random test-pattern generator.
Charge Fluctuations in pp and AA Collisions at RHIC and LHC Energies  [PDF]
Shakeel Ahmad, M. Zafar, M. Irfan, A. Ahmad
World Journal of Nuclear Science and Technology (WJNST) , 2012, DOI: 10.4236/wjnst.2012.24031
Abstract: Various measures of event-by-event net charge and charge ratio fluctuations in pp and AA collisions at RHIC and LHC energies are studied using the different Monte Carlo generators: URQMD, HIJING and HIJING/ and the results are compared with the predictions for the independent emission, hadron gas and QGP phase. Values of the D-measures are observed to exhibit significant energy dependence for both pp and AA data. Furthermore, there is essentially no significant difference in the values of the D-measures predicted by the various Monte Carlo codes used in the present study. A slight centrality dependence of the D-measures in terms of net charge fluctuations is observed in the case of Au-Au data at 200A GeV/c. These findings, thus, suggest that a difference in the D-measures for pp and AA collisions either the re-scattering effect plays a predominant role or there might be some new physics present in these collisions.
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